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  • 1. Akiyama, E.
    et al.
    Muto, T.
    Kusakabe, N.
    Kataoka, A.
    Hashimoto, J.
    Tsukagoshi, T.
    Kwon, J.
    Kudo, T.
    Kandori, R.
    Grady, C. A.
    Takami, M.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Kuzuhara, M.
    Henning, T.
    Sitko, M. L.
    Carson, J. C.
    Mayama, S.
    Currie, T.
    Thalmann, C.
    Wisniewski, J.
    Momose, M.
    Ohashi, N.
    Abe, L.
    Brandner, W.
    Brandt, T. D.
    Egner, S.
    Feldt, M.
    Goto, M.
    Guyon, O.
    Hayano, Y.
    Hayashi, M.
    Hayashi, S.
    Hodapp, K. W.
    Ishi, M.
    Iye, M.
    Knapp, G. R.
    Matsuo, T.
    Mcelwain, M. W.
    Miyama, S.
    Morino, J. -I.
    Moro-Martin, A.
    Nishimura, T.
    Pyo, T. -S.
    Serabyn, G.
    Suenaga, T.
    Suto, H.
    Suzuki, R.
    Takahashi, Y. H.
    Takato, N.
    Terada, H.
    Tomono, D.
    Turner, E. L.
    Watanabe, M.
    Yamada, T.
    Takami, H.
    Usuda, T.
    Tamura, M.
    DISCOVERY OF A DISK GAP CANDIDATE AT 20 AU IN TW HYDRAE2015In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 802, no 2, article id L17Article in journal (Refereed)
    Abstract [en]

    We present a new Subaru/HiCIAO high-contrast H-band polarized intensity (PI) image of a nearby transitional disk associated with TW Hydrae. The scattered light from the disk was detected from 0 ''.2 to 1 ''.5 (11-81 AU) and the PI image shows a clear axisymmetric depression in PI at similar to 0 ''.4 (similar to 20 AU) from the central star, similar to the similar to 80 AU gap previously reported from Hubble Space Telescope images. The azimuthal PI profile also shows that the disk beyond 0 ''.2 is almost axisymmetric. We discuss two possible scenarios explaining the origin of the PI depression: (1) a gap structure may exist at similar to 20 AU from the central star because of a shallow slope seen in the PI profile, and (2) grain growth may be occurring in the inner region of the disk. Multi-band observations at near-infrared and millimeter/submillimeter wavelengths play a complementary role in investigating dust opacity and may help reveal the origin of the gap more precisely.

  • 2. Akiyama, Eiji
    et al.
    Hashimoto, Jun
    Liu, Hauyu Baobabu
    Li, Jennifer I-Hsiu
    Bonnefoy, Michael
    Dong, Ruobing
    Hasegawa, Yasuhiro
    Henning, Thomas
    Sitko, Michael L.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Feldt, Markus
    Wisniewski, John
    Kudo, Tomoyuki
    Kusakabe, Nobuhiko
    Tsukagoshi, Takashi
    Momose, Munetake
    Muto, Takayuki
    Taki, Tetsuo
    Kuzuhara, Masayuki
    Satoshi, Mayama
    Takami, Michihiro
    Ohashi, Nagayoshi
    Grady, Carol A.
    Kwon, Jungmi
    Thalmann, Christian
    Abe, Lyu
    Brandner, Wolfgang
    Brandt, Timothy D.
    Carson, Joseph C.
    Egner, Sebastian
    Goto, Miwa
    Guyon, Olivier
    Hayano, Yutaka
    Hayashi, Masahiko
    Hayashi, Saeko S.
    Hodapp, Klaus W.
    Ishii, Miki
    Iye, Masanori
    Knapp, Gillian R.
    Kandori, Ryo
    Matsuo, Taro
    Mcelwain, Michael W.
    Miyama, Shoken
    Morino, Jun-Ichi
    Moro-Martin, Amaya
    Nishimura, Tetsuo
    Pyo, Tae-Soo
    Serabyn, Eugene
    Suenaga, Takuya
    Suto, Hiroshi
    Suzuki, Ryuji
    Takahashi, Yasuhiro H.
    Takato, Naruhisa
    Terada, Hiroshi
    Tomono, Daigo
    Turner, Edwin L.
    Watanabe, Makoto
    Yamada, Toru
    Takami, Hideki
    Usuda, Tomonori
    Tamura, Motohide
    SPIRAL STRUCTURE AND DIFFERENTIAL DUST SIZE DISTRIBUTION IN THE LkH alpha 330 DISK2016In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 152, no 6, article id 222Article in journal (Refereed)
    Abstract [en]

    Dust trapping accelerates the coagulation of dust particles, and, thus, it represents an initial step toward the formation of planetesimals. We report H-band (1.6 mu m) linear polarimetric observations and 0.87 mm interferometric continuum observations toward a transitional disk around LkH alpha 330. As a. result, a pair of spiral arms were detected in the H-band emission, and an asymmetric (potentially arm-like) structure was detected in the 0.87 mm continuum emission. We discuss the origin of the spiral arm and the asymmetric structure. and suggest that a massive unseen planet is the most plausible explanation. The possibility of dust trapping and grain growth causing the asymmetric structure was also investigated through the opacity index (beta) by plotting the observed spectral energy distribution slope between 0.87 mm from our Submillimeter Array observation and 1.3 mm from literature. The results imply that grains are indistinguishable from interstellar medium-like dust in the east side (beta = 2.0 +/- 0.5) but are much smaller in the west side beta = 0.7(-0.4)(+0.5), indicating differential dust size distribution between the two sides of the disk. Combining the results of near-infrared and submillimeter observations, we conjecture that the spiral arms exist at the upper surface and an asymmetric structure resides in the disk interior. Future observations at centimeter wavelengths and differential polarization imaging in other bands (Y-K) with extreme AO imagers are required to understand how large dust grains form and to further explore the dust distribution in the disk.

  • 3.
    Asensio-Torres, Ruben
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bonavita, M.
    Desidera, S.
    Thalmann, C.
    Kuzuhara, M.
    Henning, Th.
    Marzari, F.
    Meyer, M. R.
    Calissendorff, Per
    Stockholm University, Faculty of Science, Department of Astronomy.
    Uyama, T.
    SPOTS: The Search for Planets Orbiting Two Stars III. Complete sample and statistical analysis2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 619, article id A43Article in journal (Refereed)
    Abstract [en]

    Binary stars constitute a large percentage of the stellar population, yet relatively little is known about the planetary systems orbiting them. Most constraints on circumbinary planets (CBPs) so far come from transit observations with the Kepler telescope, which is sensitive to close-in exoplanets but does not constrain planets on wider orbits. However, with continuous developments in high-contrast imaging techniques, this population can now be addressed through direct imaging. We present the full survey results of the Search for Planets Orbiting Two Stars (SPOTS) survey, which is the first direct imaging survey targeting CBPs. The SPOTS observational program comprises 62 tight binaries that are young and nearby, and thus suitable for direct imaging studies, with VLT/NaCo and VLT/SPHERE. Results from SPOTS include the resolved circumbinary disk around AK Sco, the discovery of a low-mass stellar companion in a triple packed system, the relative astrometry of up to 9 resolved binaries, and possible indications of non-background planetary-mass candidates around HIP 77911. We did not find any CBP within 300 AU, which implies a frequency upper limit on CBPs (1-15 M-Jup) of 6-10% between 30-300 AU. Coupling these observations with an archival dataset for a total of 163 stellar pairs, we find a best-fit CBP frequency of 1.9% (2-15 M-Jup) between 1 and 300 AU with a 10.5% upper limit at a 95% confidence level. This result is consistent with the distribution of companions around single stars.

  • 4.
    Asensio-Torres, Ruben
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hashimoto, J.
    Thalmann, C.
    Currie, T.
    Buenzli, E.
    Kudo, T.
    Kuzuhara, M.
    Kusakabe, N.
    Abe, L.
    Akiyama, E.
    Brandner, W.
    Brandt, T. D.
    Carson, J.
    Egner, S.
    Feldt, M.
    Goto, M.
    Grady, C.
    Guyon, O.
    Hayano, Y.
    Hayashi, M.
    Hayashi, S.
    Henning, T.
    Hodapp, K.
    Ishii, M.
    Iye, M.
    Kandori, R.
    Knapp, G.
    Kwon, J.
    Matsuo, T.
    McElwain, M.
    Mayama, S.
    Miyama, S.
    Morino, J.
    Moro-Martin, A.
    Nishimura, T.
    Pyo, T.
    Serabyn, E.
    Suenaga, T.
    Suto, H.
    Suzuki, R.
    Takahashi, Y.
    Takami, M.
    Takato, N.
    Terada, H.
    Turner, E.
    Watanabe, M.
    Wisniewski, J.
    Yamada, T.
    Takami, H.
    Usuda, T.
    Tamura, M.
    Polarimetry and flux distribution in the debris disk around HD 322972016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 593, article id A73Article in journal (Refereed)
    Abstract [en]

    We present high-contrast angular differential imaging (ADI) observations of the debris disk around HD32297 in H-band, as well as the first polarimetric images for this system in polarized differential imaging (PDI) mode with Subaru/HICIAO. In ADI, we detect the nearly edge-on disk at > 5 sigma levels from similar to 0.45 '' to similar to 1.7 '' (50-192AU) from the star and recover the spine deviation from the midplane already found in previous works. We also find for the first time imaging and surface brightness (SB) indications for the presence of a gapped structure on both sides of the disk at distances of similar to 0.75 '' (NE side) and similar to 0.65 '' (SW side). Global forward-modelling work delivers a best-fit model disk and well-fitting parameter intervals that essentially match previous results, with high-forward scattering grains and a ring located at 110AU. However, this single ring model cannot account for the gapped structure seen in our SB profiles. We create simple double ring models and achieve a satisfactory fit with two rings located at 60 and 95AU, respectively, low-forward scattering grains and very sharp inner slopes. In polarized light we retrieve the disk extending from similar to 0.25-1.6 '', although the central region is quite noisy and high S/N are only found in the range similar to 0.75-1.2 ''. The disk is polarized in the azimuthal direction, as expected, and the departure from the midplane is also clearly observed. Evidence for a gapped scenario is not found in the PDI data. We obtain a linear polarization degree of the grains that increases from similar to 10% at 0.55 '' to similar to 25% at 1.6 ''. The maximum is found at scattering angles of similar to 90 degrees, either from the main components of the disk or from dust grains blown out to larger radii.

  • 5.
    Asensio-Torres, Ruben
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Tamura, Motohide
    Isochronal age-mass discrepancy of young stars: SCExAO/CHARIS integral field spectroscopy of the HIP 79124 triple system2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 622, article id A42Article in journal (Refereed)
    Abstract [en]

    We present SCExAO/CHARIS 1.1--2.4 micron integral field direct spectroscopy of the young HIP 79124 triple system. HIP 79124 is a member of the Scorpius-Centaurus association, consisting of an A0V primary with two low-mass companions at a projected separation of <1 arcsecond. Thanks to the high quality wavefront corrections provided by SCExAO, both companions are decisively detected without the employment of any PSF-subtraction algorithm to eliminate quasi-static noise. The spectrum of the outer C object is very well matched by Upper Scorpius M4 pm 0.5 standard spectra, with a Teff = 2945 pm 100 and a mass of 350 MJup. HIP 79124 B is detected at a separation of only 180 mas in a highly-correlated noise regime, and it falls in the spectral range M6 pm 0.5 with Teff = 2840 pm 190 and 100 MJup. Previous studies of stellar populations in Sco-Cen have highlighted a discrepancy in isochronal ages between the lower-mass and higher-mass populations. This could be explained either by an age spread in the region, or by conventional isochronal models failing to reproduce the evolution of low-mass stars. The HIP 79124 system should be coeval, and therefore it provides an ideal laboratory to test these scenarios. We place the three components in a color-magnitude diagram and find that the models predict a younger age for the two low-mass companions (3 Myr) than for the primary star (6 Myr). These results imply that the omission of magnetic effects in conventional isochronal models inhibit them from reproducing early low-mass stellar evolution, which is further supported by the fact that new models that include such effects provide more consistent ages in the HIP 79124 system.

  • 6. Baron, Frédérique
    et al.
    Artigau, Étienne
    Rameau, Julien
    Lafrenière, David
    Gagné, Jonathan
    Malo, Lison
    Albert, Loïc
    Naud, Marie-Eve
    Doyon, René
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Delorme, Philippe
    Beichman, Charles
    WEIRD: Wide-orbit Exoplanet Search with InfraRed Direct Imaging2018In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 156, no 3, article id 137Article in journal (Refereed)
    Abstract [en]

    We report results from the Wide-orbit Exoplanet search with InfraRed Direct imaging, or WEIRD, a survey designed to search for Jupiter-like companions on very wide orbits (1000-5000 au) around young stars (<120 Myr) that are known members of moving groups in the solar neighborhood (<70 pc). Companions that share the same age, distance, and metallicity as their host while being on large enough orbits to be studied as isolated objects make prime targets for spectroscopic observations, and they are valuable benchmark objects for exoplanet atmosphere models. The search strategy is based on deep imaging in multiple bands across the near-infrared domain For all 177 objects of our sample, z(ab)', J, [3.6], and [4.5] images were obtained with CFHT/MegaCam, GEMINI/GMOS, CFHT/WIRCam, GEMINI/Flamingos-2, and Spitzer IIRAC. Using this set of four images per target, we searched for sources with red z(ab)' and [3.6]-[4.5] colors, typically reaching good completeness down to 2 M-J(up) companions, while going down to 1 M-J(up) for some targets, at separations of 1000-5000 au. The search yielded four candidate companions with the expected colors, but they were all rejected through follow-up proper motion observations. Our results constrain the occurrence of 1-13 M(J)(u)p planetary-mass companions on orbits with a semimajor axis between 1000 and 5000 au at less than 0.03, with a 95% confidence level.

  • 7. Bergfors, C.
    et al.
    Brandner, W.
    Bonnefoy, M.
    Schlieder, J.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Henning, Th.
    Chauvin, G.
    Characterization of close visual binaries from the AstraLux Large M Dwarf Survey2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 456, no 3, p. 2576-2585Article in journal (Refereed)
    Abstract [en]

    We present Very Large Telescope/Spectrograph for INtegral Field Observations in the Near Infrared (VLT/SINFONI) J, H + K spectra of seven close visual pairs in M dwarf binary/triple systems, discovered or observed by the AstraLux M dwarf survey. We determine the spectral types to within +/- 1.0 subclasses from comparison to template spectra and the strength of K-band water absorption, and derive effective temperatures. The results are compared to optical spectral types of the unresolved binary/multiple systems, and we confirm that our photometric method to derive spectral types in the AstraLux M dwarf survey is accurate. We look for signs of youth such as chromospheric activity and low surface gravity, and find an age in the range 0.25-1 Gyr for the GJ 852 system. Strong Li absorption is detected in optical spectra of the triple system J024902 obtained with the Fiberfed Extended Range Optical Spectrograph (FEROS) at the European Southern Observatory (ESO)-Max-Planck-Gesellschaft (MPG) 2.2 m telescope. The equivalent width of the absorption suggests an age consistent with the beta Pic moving group. However, further observations are needed to establish group membership. Ongoing orbital monitoring will provide dynamical masses and thus calibration of evolutionary models for low mass stars.

  • 8. Boccaletti, A.
    et al.
    Sezestre, E.
    Lagrange, A-M
    Thebault, P.
    Gratton, R.
    Langlois, M.
    Thalmann, C.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max-Planck-Institut für Astronomie, Germany.
    Delorme, P.
    Augereau, J-C
    Schneider, G.
    Milli, J.
    Grady, C.
    Debes, J.
    Kral, Q.
    Olofsson, J.
    Carson, J.
    Maire, A. L.
    Henning, T.
    Wisniewski, J.
    Schlieder, J.
    Dominik, C.
    Desidera, S.
    Ginski, C.
    Hines, D.
    Menard, F.
    Mouillet, D.
    Pawellek, N.
    Vigan, A.
    Lagadec, E.
    Avenhaus, H.
    Beuzit, J-L
    Biller, B.
    Bonavita, M.
    Bonnefoy, M.
    Brandner, W.
    Cantalloube, F.
    Chauvin, G.
    Cheetham, A.
    Cudel, M.
    Gry, C.
    Daemgen, S.
    Feldt, M.
    Galicher, R.
    Girard, J.
    Hagelberg, J.
    Janin-Potiron, P.
    Kasper, M.
    Le Coroller, H.
    Mesa, D.
    Peretti, S.
    Perrot, C.
    Samland, M.
    Sissa, E.
    Wildi, F.
    Zurlo, A.
    Rochat, S.
    Stadler, E.
    Gluck, L.
    Origne, A.
    Llored, M.
    Baudoz, P.
    Rousset, G.
    Martinez, P.
    Rigal, F.
    Observations of fast-moving features in the debris disk of AU Mic on a three-year timescale: Confirmation and new discoveries2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 614, article id A52Article in journal (Refereed)
    Abstract [en]

    Context. The nearby and young M star AU Mic is surrounded by a debris disk in which we previously identified a series of large-scale arch-like structures that have never been seen before in any other debris disk and that move outward at high velocities. Aims. We initiated a monitoring program with the following objectives: (1) track the location of the structures and better constrain their projected speeds, (2) search for new features emerging closer in, and ultimately (3) understand the mechanism responsible for the motion and production of the disk features. Methods. AU Mic was observed at 11 different epochs between August 2014 and October 2017 with the IR camera and spectrograph of SPHERE. These high-contrast imaging data were processed with a variety of angular, spectral, and polarimetric differential imaging techniques to reveal the faintest structures in the disk. We measured the projected separations of the features in a systematic way for all epochs. We also applied the very same measurements to older observations from the Hubble Space Telescope (HST) with the visible cameras STIS and ACS. Results. The main outcomes of this work are (1) the recovery of the five southeastern broad arch-like structures we identified in our first study, and confirmation of their fast motion (projected speed in the range 4-12 km s(-1) ); (2) the confirmation that the very first structures observed in 2004 with ACS are indeed connected to those observed later with STIS and now SPHERE; (3) the discovery of two new very compact structures at the northwest side of the disk (at 0.40 '' and 0.55 '' in May 2015) that move to the southeast at low speed; and (4) the identification of a new arch-like structure that might be emerging at the southeast side at about 0.4 from the star (as of May 2016). Conclusions. Although the exquisite sensitivity of SPHERE allows one to follow the evolution not only of the projected separation, but also of the specific morphology of each individual feature, it remains difficult to distinguish between possible dynamical scenarios that may explain the observations. Understanding the exact origin of these features, the way they are generated, and their evolution over time is certainly a significant challenge in the context of planetary system formation around M stars.

  • 9. Boccaletti, Anthony
    et al.
    Thalmann, Christian
    Lagrange, Anne-Marie
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Society, Germany.
    Augereau, Jean-Charles
    Schneider, Glenn
    Milli, Julien
    Grady, Carol
    Debes, John
    Langlois, Maud
    Mouillet, David
    Henning, Thomas
    Dominik, Carsten
    Maire, Anne-Lise
    Beuzit, Jean-Luc
    Carson, Joseph
    Dohlen, Kjetil
    Engler, Natalia
    Feldt, Markus
    Fusco, Thierry
    Ginski, Christian
    Girard, Julien H.
    Hines, Dean
    Kasper, Markus
    Mawet, Dimitri
    Menard, Franois
    Meyer, Michael R.
    Moutou, Claire
    Olofsson, Johan
    Rodigas, Timothy
    Sauvage, Jean-Francois
    Schlieder, Joshua
    Schmid, Hans Martin
    Turatto, Massimo
    Udry, Stephane
    Vakili, Farrokh
    Vigan, Arthur
    Wahhaj, Zahed
    Wisniewski, John
    Fast-moving features in the debris disk around AU Microscopii2015In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 526, no 7572, p. 230-+Article in journal (Refereed)
    Abstract [en]

    In the 1980s, excess infrared emission was discovered around main-sequence stars; subsequent direct-imaging observations revealed orbiting disks of cold dust to be the source(1). These 'debris disks' were thought to be by-products of planet formation because they often exhibited morphological and brightness asymmetries that may result from gravitational perturbation by planets. This was proved to be true for the beta Pictoris system, in which the known planet generates an observable warp in the disk(2-5). The nearby, young, unusually active late-type star AU Microscopii hosts a well-studied edge-on debris disk; earlier observations in the visible and near-infrared found asymmetric localized structures in the form of intensity variations along the midplane of the disk beyond a distance of 20 astronomical units(6-9). Here we report high-contrast imaging that reveals a series of five large-scale features in the southeast side of the disk, at projected separations of 10-60 astronomical units, persisting over intervals of 1-4 years. All these features appear to move away from the star at projected speeds of 4-10 kilometres per second, suggesting highly eccentric or unbound trajectories if they are associated with physical entities. The origin, localization, morphology and rapid evolution of these features are difficult to reconcile with current theories.

  • 10. Bonavita, M.
    et al.
    Desidera, S.
    Thalmann, C.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Vigan, A.
    Chauvin, G.
    Lannier, J.
    SPOTS: The Search for Planets Orbiting Two Stars II. First constraints on the frequency of sub-stellar companions on wide circumbinary orbits2016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 593, article id A38Article in journal (Refereed)
    Abstract [en]

    A large number of direct imaging surveys for exoplanets have been performed in recent years, yielding the first directly imaged planets and providing constraints on the prevalence and distribution of wide planetary systems. However, like most of the radial velocity ones, these generally focus on single stars, hence binaries and higher-order multiples have not been studied to the same level of scrutiny. This motivated the Search for Planets Orbiting Two Stars (SPOTS) survey, which is an ongoing direct imaging study of a large sample of close binaries, started with VLT / NACO and now continuing with VLT / SPHERE. To complement this survey, we have identified the close binary targets in 24 published direct imaging surveys. Here we present our statistical analysis of this combined body of data. We analysed a sample of 117 tight binary systems, using a combined Monte Carlo and Bayesian approach to derive the expected values of the frequency of companions, for different values of the companion's semi-major axis. Our analysis suggest that the frequency of sub-stellar companions in wide orbit is moderately low (less than or similar to 13% with a best value of 6% at 95% confidence level) and not significantly different between single stars and tight binaries. One implication of this result is that the very high frequency of circumbinary planets in wide orbits around post-common envelope binaries, implied by eclipse timing, cannot be uniquely due to planets formed before the common-envelope phase (first generation planets), supporting instead the second generation planet formation or a non-Keplerian origin of the timing variations.

  • 11. Bonavita, M.
    et al.
    D'Orazi, V.
    Mesa, D.
    Fontanive, C.
    Desidera, S.
    Messina, S.
    Daemgen, S.
    Gratton, R.
    Vigan, A.
    Bonnefoy, M.
    Zurlo, A.
    Antichi, J.
    Avenhaus, H.
    Baruffolo, A.
    Baudino, J. L.
    Beuzit, J. L.
    Boccaletti, A.
    Bruno, P.
    Buey, T.
    Carbillet, M.
    Cascone, E.
    Chauvin, G.
    Claudi, R. U.
    De Caprio, V.
    Fantinel, D.
    Farisato, G.
    Feldt, M.
    Galicher, R.
    Giro, E.
    Gry, C.
    Hagelberg, J.
    Incorvaia, S.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max-Planck Institute for Astronomy, Germany.
    Jaquet, M.
    Lagrange, A. M.
    Langlois, M.
    Lannier, J.
    Le Coroller, H.
    Lessio, L.
    Ligi, R.
    Maire, A. L.
    Meyer, M.
    Menard, F.
    Perrot, C.
    Peretti, S.
    Petit, C.
    Ramos, J.
    Roux, A.
    Salasnich, B.
    Salter, G.
    Samland, M.
    Scuderi, S.
    Schlieder, J.
    Surez, M.
    Turatto, M.
    Weber, L.
    Orbiting a binary SPHERE characterisation of the HD 284149 system2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 608, article id A106Article in journal (Refereed)
    Abstract [en]

    Aims. In this paper we present the results of the SPHERE observation of the HD 284149 system, aimed at a more detailed characterisation of both the primary and its brown dwarf companion.

    Methods. We observed HD 284149 in the near-infrared with SPHERE, using the imaging mode (IRDIS + IFS) and the long-slit spectroscopy mode (IRDIS-LSS). The data were reduced using the dedicated SPHERE pipeline, and algorithms such as PCA and TLOCI were applied to reduce the speckle pattern.

    Results. The IFS images revealed a previously unknown low-mass (similar to 0.16 M-circle dot) stellar companion (HD 294149 B) at similar to 0.1 '', compatible with previously observed radial velocity differences, as well as proper motion differences between Gaia and Tycho-2 measurements. The known brown dwarf companion (HD 284149 b) is clearly visible in the IRDIS images. This allowed us to refine both its photometry and astrometry. The analysis of the medium resolution IRDIS long slit spectra also allowed a refinement of temperature and spectral type estimates. A full reassessment of the age and distance of the system was also performed, leading to more precise values of both mass and semi-major axis.

    Conclusions. As a result of this study, HD 284149 ABb therefore becomes the latest addition to the (short) list of brown dwarfs on wide circumbinary orbits, providing new evidence to support recent claims that object in such configuration occur with a similar frequency to wide companions to single stars.

  • 12. Bonnefoy, M.
    et al.
    Perraut, K.
    Lagrange, A. -M.
    Delorme, P.
    Vigan, A.
    Line, M.
    Rodet, L.
    Ginski, C.
    Mourard, D.
    Marleau, G. -D.
    Samland, M.
    Tremblin, P.
    Ligi, R.
    Cantalloube, F.
    Molliere, P.
    Charnay, B.
    Kuzuhara, M.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Morley, C.
    Homeier, D.
    D'Orazi, V.
    Klahr, H.
    Mordasini, C.
    Lavie, B.
    Baudino, J. -L.
    Beust, H.
    Peretti, S.
    Bartucci, A. Musso
    Mesa, D.
    Bezard, B.
    Boccaletti, A.
    Galicher, R.
    Hagelberg, J.
    Desidera, S.
    Biller, B.
    Maire, A. -L.
    Allard, F.
    Borgniet, S.
    Lannier, J.
    Meunier, N.
    Desort, M.
    Alecian, E.
    Chauvin, G.
    Langlois, M.
    Henning, T.
    Mugnier, L.
    Mouillet, D.
    Gratton, R.
    Brandt, T.
    Mc Elwain, M.
    Beuzit, J. -L.
    Tamura, M.
    Hori, Y.
    Brandner, W.
    Buenzli, E.
    Cheetham, A.
    Cudel, M.
    Feldt, M.
    Kasper, M.
    Keppler, M.
    Kopytova, T.
    Meyer, M.
    Perrot, C.
    Rouan, D.
    Salter, G.
    Schmidt, T.
    Sissa, E.
    Zurlo, A.
    Wildi, F.
    Blanchard, P.
    De Caprio, V.
    Delboulbe, A.
    Maurel, D.
    Moulin, T.
    Pavlov, A.
    Rabou, P.
    Ramos, J.
    Roelfsema, R.
    Rousset, G.
    Stadler, E.
    Rigal, F.
    Weber, L.
    The GJ 504 system revisited Combining interferometric, radial velocity, and high contrast imaging data2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 618, article id A63Article in journal (Refereed)
    Abstract [en]

    Context. The G-type star GJ504A is known to host a 3-35 M-Jup companion whose temperature, mass, and projected separation all contribute to making it a test case for planet formation theories and atmospheric models of giant planets and light brown dwarfs. Aims. We aim at revisiting the system age, architecture, and companion physical and chemical properties using new complementary interferometric, radial-velocity, and high-contrast imaging data. Methods. We used the CHARA interferometer to measure GJ504A's angular diameter and obtained an estimation of its radius in combination with the HIPPARCOS parallax. The radius was compared to evolutionary tracks to infer a new independent age range for the system. We collected dual imaging data with IRDIS on VLT/SPHERE to sample the near-infrared (1.02-2.25 mu m) spectral energy distribution (SED) of the companion. The SED was compared to five independent grids of atmospheric models (petitCODE, Exo-REM, BT-SETTL, Morley et al., and ATMO) to infer the atmospheric parameters of GJ 504b and evaluate model-to-model systematic errors. In addition, we used a specific model grid exploring the effect of different C/O ratios. Contrast limits from 2011 to 2017 were combined with radial velocity data of the host star through the MESS2 tool to define upper limits on the mass of additional companions in the system from 0.01 to 100 au. We used an MCMC fitting tool to constrain the companion's orbital parameters based on the measured astrometry, and dedicated formation models to investigate its origin. Results. We report a radius of 1.35 +/- 0.04 R-circle dot for GJ504A. The radius yields isochronal ages of 21 +/- 2 Myr or 4.0 +/- 1.8 Gyr for the system and line-of-sight stellar rotation axis inclination of 162.4(-4.3)(+3.8) degrees or 18.6(-3.8)(+4.3) degrees. We re-detect the companion in the Y2, Y3, J3, H2, and K1 dual-band images. The complete 1-4 mu m SED shape of GJ504b is best reproduced by T8-T9.5 objects with intermediate ages (<= 1.5Gyr), and/or unusual dusty atmospheres and/or super-solar metallicities. All atmospheric models yield T-eff = 550 +/- 50 K for GJ504b and point toward a low surface gravity (3.5-4.0 dex). The accuracy on the metallicity value is limited by model-to-model systematics; it is not degenerate with the C/O ratio. We derive log L/L-circle dot = 6.15 +/- 0.15 dex for the companion from the empirical analysis and spectral synthesis. The luminosity and T-eff yield masses of M = 1.3(-0.3)(+0.6) M-Jup and M = 23(-9)(+10) M-Jup for the young and old age ranges, respectively. The semi-major axis (sma) is above 27.8 au and the eccentricity is lower than 0.55. The posterior on GJ 504b's orbital inclination suggests a misalignment with the rotation axis of GJ 504A. We exclude additional objects (90% prob.) more massive than 2.5 and 30 M-Jup with semi-major axes in the range 0.01-80 au for the young and old isochronal ages, respectively. Conclusions. The mass and semi-major axis of GJ 504b are marginally compatible with a formation by disk-instability if the system is 4 Gyr old. The companion is in the envelope of the population of planets synthesized with our core-accretion model. Additional deep imaging and spectroscopic data with SPHERE and JWST should help to confirm the possible spin-orbit misalignment and refine the estimates on the companion temperature, luminosity, and atmospheric composition.

  • 13. Bonnefoy, M.
    et al.
    Zurlo, A.
    Baudino, J. L.
    Lucas, P.
    Mesa, D.
    Maire, A. -L.
    Vigan, A.
    Galicher, R.
    Homeier, D.
    Marocco, F.
    Gratton, R.
    Chauvin, G.
    Allard, F.
    Desidera, S.
    Kasper, M.
    Moutou, C.
    Lagrange, A. -M.
    Antichi, J.
    Baruffolo, A.
    Baudrand, J.
    Beuzit, J. -L.
    Boccaletti, A.
    Cantalloube, F.
    Carbillet, M.
    Charton, J.
    Claudi, R. U.
    Costille, A.
    Dohlen, K.
    Dominik, C.
    Fantinel, D.
    Feautrier, P.
    Feldt, M.
    Fusco, T.
    Gigan, P.
    Girard, J. H.
    Gluck, L.
    Gry, C.
    Henning, T.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max-Planck-Institut für Astronomie, Germany.
    Langlois, M.
    Madec, F.
    Magnard, Y.
    Maurel, D.
    Mawet, D.
    Meyer, M. R.
    Milli, J.
    Moeller-Nilsson, O.
    Mouillet, D.
    Pavlov, A.
    Perret, D.
    Pujet, P.
    Quanz, S. P.
    Rochat, S.
    Rousset, G.
    Roux, A.
    Salasnich, B.
    Salter, G.
    Sauvage, J. -F.
    Schmid, H. M.
    Sevin, A.
    Soenke, C.
    Stadler, E.
    Turatto, M.
    Udry, S.
    Vakili, F.
    Wahhaj, Z.
    Wildi, F.
    First light of the VLT planet finder SPHERE IV. Physical and chemical properties of the planets around HR87992016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 587, article id A58Article in journal (Refereed)
    Abstract [en]

    Context. The system of four planets discovered around the intermediate-mass star HR8799 offers a unique opportunity to test planet formation theories at large orbital radii and to probe the physics and chemistry at play in the atmospheres of self-luminous young (similar to 30 Myr) planets. We recently obtained new photometry of the four planets and low-resolution (R similar to 30) spectra of HR8799 d and e with the SPHERE instrument (Paper III).

    Aims. In this paper (Paper IV), we aim to use these spectra and available photometry to determine how they compare to known objects, what the planet physical properties are, and how their atmospheres work.

    Methods. We compare the available spectra, photometry, and spectral energy distribution (SED) of the planets to field dwarfs and young companions. In addition, we use the extinction from corundum, silicate (enstatite and forsterite), or iron grains likely to form in the atmosphere of the planets to try to better understand empirically the peculiarity of their spectrophotometric properties. To conclude, we use three sets of atmospheric models (BT-SETTL14, Cloud-AE60, Exo-REM) to determine which ingredients are critically needed in the models to represent the SED of the objects, and to constrain their atmospheric parameters (T-eff, log g, M/H).

    Results. We find that HR8799d and e properties are well reproduced by those of L6-L8 dusty dwarfs discovered in the field, among which some are candidate members of young nearby associations. No known object reproduces well the properties of planets b and c. Nevertheless, we find that the spectra and WISE photometry of peculiar and/or young early-T dwarfs reddened by submicron grains made of corundum, iron, enstatite, or forsterite successfully reproduce the SED of these planets. Our analysis confirms that only the Exo-REM models with thick clouds fit (within 2 sigma) the whole set of spectrophotometric datapoints available for HR8799 d and e for T-eff = 1200 K, log g in the range 3.0-4.5, and M/H = +0.5. The models still fail to reproduce the SED of HR8799c and b. The determination of the metallicity, log g, and cloud thickness are degenerate.

    Conclusions. Our empirical analysis and atmospheric modelling show that an enhanced content in dust and decreased CIA of H-2 is certainly responsible for the deviation of the properties of the planet with respect to field dwarfs. The analysis suggests in addition that HR8799c and b have later spectral types than the two other planets, and therefore could both have lower masses.

  • 14.
    Calissendorff, Per
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Improving dynamical mass constraints for intermediate-period substellar companions using Gaia DR22018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 615, article id A149Article in journal (Refereed)
    Abstract [en]

    The relationship between luminosity and mass is of fundamental importance for direct imaging studies of brown dwarf and planetary companions to stars. In principle this can be inferred from theoretical mass-luminosity models; however, these relations have not yet been thoroughly calibrated, since there is a lack of substellar companions for which both the brightness and mass have been directly measured. One notable exception is GJ 758 B, a brown dwarf companion in a similar to 20 AU orbit around a nearby Sun-like star, which has been both directly imaged and dynamically detected through a radial velocity trend in the primary. This has enabled a mass constraint for GJ 758 B of 42(-7)(+19) M-Jup. Here, we note that Gaia is ideally suited for further constraining the mass of intermediate-separation companions such as GJ 758 B. A study of the differential proper motion, Delta mu, with regards to HIPPARCOS is particularly useful in this context, as it provides a long time baseline for orbital curvature to occur. By exploiting already determined orbital parameters, we show that the dynamical mass can be further constrained to 42.4(-5.0)(+5.6) M-Jup through the Gaia-HIPPARCOS Delta mu motion. We compare the new dynamical mass estimate with substellar evolutionary models and confirm previous indications that there is significant tension between the isochronal ages of the star and companion, with a preferred stellar age of <= 5 Gyr while the companion is only consistent with very old ages of >= 8 Gyr.

  • 15.
    Calissendorff, Per
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Asensio-Torres, Ruben
    Stockholm University, Faculty of Science, Department of Astronomy.
    Koehler, Rainer
    Spectral characterization of newly detected young substellar binaries with SINFONI2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 627, article id A167Article in journal (Refereed)
    Abstract [en]

    We observe 14 young low-mass substellar objects using the VLT/SINFONI integral field spectrograph with laser guide star adaptive optics to detect and characterize three candidate binary systems. All three binary candidates show strong signs of youth, with two of them likely belonging to young moving groups. Together with the adopted young-moving-group ages we employ isochrones from the BT-Settle CIFIST substellar evolutionary models to estimate individual masses for the binary components. We find 2MASS J15104786-2818174 to be part of the approximate to 30-50 Myr Argus moving group and to be composed of a 34-48 M-Jup primary brown dwarf with spectral type M9 gamma and a fainter 15 22 MJup companion, separated by approximate to 100 mas. 2MASS J22025794-5605087 is identified as an almost equal-mass binary in the AB Dor moving group, with a projected separation of approximate to 60 mas. Both components share spectral type M9 gamma/beta, which with the adopted age of 120 200 Myr yields masses in the range of 50 68 M-Jup for each component individually. The observations of 2MASS J15474719-2423493 are of lower quality and we obtain no spectral characterization for the target, but resolve two components separated by approximate to 170 mas which with the predicted young field age of 30 50 Myr yields individual masses below 20 M-Jup. Out of the three candidate binary systems, 2MASS J22025794-5605087 has unambiguous spectroscopic signs of being a bona-fide binary, while the other two will require second-epoch confirmation. The small projected separations between the binary components correspond to physical separations of approximate to 4-7AU, meaning that astrometric monitoring of just a few years would be adequate to generate constrained orbital fits and dynamical masses for the systems. In combination with their young ages, these binaries will prove to be excellent benchmarks for calibrating substellar evolutionary models down to a very low-mass regime.

  • 16.
    Calissendorff, Per
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Koehler, Rainer
    Durkan, Stephen
    Hippler, Stefan
    Dai, Xiaolin
    Brandner, Wolfgang
    Schlieder, Joshua
    Henning, Thomas
    The discrepancy between dynamical and theoretical mass in the triplet-system 2MASS J10364483+15213942017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 604, article id A82Article in journal (Refereed)
    Abstract [en]

    We combine new Lucky Imaging astrometry from New Technology Telescope /AstraLux Sur with already published astrometry from the AstraLux Large M-dwarf Multiplicity Survey to compute orbital elements and individual masses of the 2MASS J10364483 + 1521394 triple system belonging to the Ursa-Major moving group. The system consists of one primary low-mass M-dwarf orbited by two less massive companions, for which we determine a combined dynamical mass of MB+C = 0 : 48 +/- 0 : 14 M-circle dot. We show from the companions' relative motions that they are of equal mass (with a mass ratio of 1 : 00 +/- 0 : 03), thus 0 : 24 +/- 0 : 07 M-circle dot individually, with a separation of 3 : 2 +/- 0 : 3 AU, and we conclude that these masses are significantly higher (30%) than what is predicted by theoretical stellar evolutionary models. The biggest uncertainty remains the distance to the system, here adopted as 20 : 1 +/- 2 : 0 pc based on trigonometric parallax, whose ambiguity has a major impact on the result. With the new observational data we are able to conclude that the orbital period of the BC pair is 8.4(-0.021)(+0.04) yr.

  • 17. Chauvin, G.
    et al.
    Desidera, S.
    Lagrange, A. -M.
    Vigan, A.
    Gratton, R.
    Langlois, M.
    Bonnefoy, M.
    Beuzit, J. -L.
    Feldt, M.
    Mouillet, D.
    Meyer, M.
    Cheetham, A.
    Biller, B.
    Boccaletti, A.
    D'Orazi, V.
    Galicher, R.
    Hagelberg, J.
    Maire, A. -L.
    Mesa, D.
    Olofsson, J.
    Samland, M.
    Schmidt, T. O. B.
    Sissa, E.
    Bonavita, M.
    Charnay, B.
    Cudel, M.
    Daemgen, S.
    Delorme, P.
    Janin-Potiron, P.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany.
    Keppler, M.
    Le Coroller, H.
    Ligi, R.
    Marleau, G. D.
    Messina, S.
    Molliere, P.
    Mordasini, C.
    Müller, A.
    Peretti, S.
    Perrot, C.
    Rodet, L.
    Rouan, D.
    Zurlo, A.
    Dominik, C.
    Henning, T.
    Menard, F.
    Schmid, H. -M.
    Turatto, M.
    Udry, S.
    Vakili, F.
    Abe, L.
    Antichi, J.
    Baruffolo, A.
    Baudoz, P.
    Baudrand, J.
    Blanchard, P.
    Bazzon, A.
    Buey, T.
    Carbillet, M.
    Carle, M.
    Charton, J.
    Cascone, E.
    Claudi, R.
    Costille, A.
    Deboulbe, A.
    De Caprio, V.
    Dohlen, K.
    Fantinel, D.
    Feautrier, P.
    Fusco, T.
    Gigan, P.
    Giro, E.
    Gisler, D.
    Gluck, L.
    Hubin, N.
    Hugot, E.
    Jaquet, M.
    Kasper, M.
    Madec, F.
    Magnard, Y.
    Martinez, P.
    Maurel, D.
    Le Mignant, D.
    Moeller-Nilsson, O.
    Llored, M.
    Moulin, T.
    Origne, A.
    Pavlov, A.
    Perret, D.
    Petit, C.
    Pragt, J.
    Puget, P.
    Rabou, P.
    Ramos, J.
    Rigal, R.
    Rochat, S.
    Roelfsema, R.
    Rousset, G.
    Roux, A.
    Salasnich, B.
    Sauvage, J. -F.
    Sevin, A.
    Soenke, C.
    Stadler, E.
    Suarez, M.
    Weber, L.
    Wildi, F.
    Antoniucci, S.
    Augereau, J. -C.
    Baudino, J. -L.
    Brandner, W.
    Engler, N.
    Girard, J.
    Gry, C.
    Kral, Q.
    Kopytova, T.
    Lagadec, E.
    Milli, J.
    Moutou, C.
    Schlieder, J.
    Szulagyi, J.
    Thalmann, C.
    Wahhaj, Z.
    Discovery of a warm, dusty giant planet around HIP 654262017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 605, article id L9Article in journal (Refereed)
    Abstract [en]

    Aims. The SHINE program is a high-contrast near-infrared survey of 600 young, nearby stars aimed at searching for and characterizing new planetary systems using VLT/SPHERE's unprecedented high-contrast and high-angular-resolution imaging capabilities. It is also intended to place statistical constraints on the rate, mass and orbital distributions of the giant planet population at large orbits as a function of the stellar host mass and age to test planet-formation theories.

    Methods. We used the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-contrast coronagraphic differential near-infrared images and spectra of the young A2 star HIP 65426. It is a member of the similar to 17 Myr old Lower Centaurus-Crux association.

    Results. At a separation of 830 mas (92 au projected) from the star, we detect a faint red companion. Multi-epoch observations confirm that it shares common proper motion with HIP 65426. Spectro-photometric measurements extracted with IFS and IRDIS between 0.95 and 2.2 mu m indicate a warm, dusty atmosphere characteristic of young low-surface-gravity L5-L7 dwarfs. Hot-start evolutionary models predict a luminosity consistent with a 6-12 M-Jup, T-eff = 1300-1600K and R = 1.5 +/- 0.1 R-Jup giant planet. Finally, the comparison with Exo-REM and PHOENIX BT-Settl synthetic atmosphere models gives consistent effective temperatures but with slightly higher surface gravity solutions of log(g) = 4.0-5.0 with smaller radii (1.0-1.3 R-Jup).

    Conclusions. Given its physical and spectral properties, HIP 65426 b occupies a rather unique placement in terms of age, mass, and spectral-type among the currently known imaged planets. It represents a particularly interesting case to study the presence of clouds as a function of particle size, composition, and location in the atmosphere, to search for signatures of non-equilibrium chemistry, and finally to test the theory of planet formation and evolution.

  • 18. Chauvin, G.
    et al.
    Gratton, R.
    Bonnefoy, M.
    Lagrange, A. -M.
    de Boer, J.
    Vigan, A.
    Beust, H.
    Lazzoni, C.
    Boccaletti, A.
    Galicher, R.
    Desidera, S.
    Delorme, P.
    Keppler, M.
    Lannier, J.
    Maire, A. -L.
    Mesa, D.
    Meunier, N.
    Kral, Q.
    Henning, T.
    Menard, F.
    Moor, A.
    Avenhaus, H.
    Bazzon, A.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany.
    Beuzit, J. -L.
    Bhowmik, T.
    Bonavita, M.
    Borgniet, S.
    Brandner, W.
    Cheetham, A.
    Cudel, M.
    Feldt, M.
    Fontanive, C.
    Ginski, C.
    Hagelberg, J.
    Janin-Potiron, P.
    Lagadec, E.
    Langlois, M.
    Le Coroller, H.
    Messina, S.
    Meyer, M.
    Mouillet, D.
    Peretti, S.
    Perrot, C.
    Rodet, L.
    Samland, M.
    Sissa, E.
    Olofsson, J.
    Salter, G.
    Schmidt, T.
    Zurlo, A.
    Milli, J.
    van Boekel, R.
    Quanz, S.
    Feautrier, P.
    Le Mignant, D.
    Perret, D.
    Ramos, J.
    Rochat, S.
    Investigating the young solar system analog HD 95086 A combined HARPS and SPHERE exploration2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 617, article id A76Article in journal (Refereed)
    Abstract [en]

    Context. HD 95086 (A8V, 17 Myr) hosts a rare planetary system for which a multi-belt debris disk and a giant planet of 4-5 Mjup have been directly imaged.

    Aims. Our study aims to characterize the global architecture of this young system using the combination of radial velocity and direct imaging observations. We want to characterize the physical and orbital properties of HD 95086 b, search for additional planets at short and wide orbits and image the cold outer debris belt in scattered light.

    Methods. We used HARPS at the ESO 3.6 m telescope to monitor the radial velocity of HD 95086 over two years and investigate the existence of giant planets at less than 3 au orbital distance. With the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE at VLT, we imaged the faint circumstellar environment beyond 10 au at six epochs between 2015 and 2017.

    Results. We do not detect additional giant planets around HD 95086. We identify the nature (bound companion or background contaminant) of all point-like sources detected in the IRDIS field of view. None of them correspond to the ones recently discovered near the edge of the cold outer belt by ALMA. HD 95086 b is resolved for the first time in J-band with IFS. Its near-infrared spectral energy distribution is well fitted by a few dusty and/or young L7-L9 dwarf spectral templates. The extremely red 1-4 mu m spectral distribution is typical of low-gravity objects at the L/T spectral type transition. The planet's orbital motion is resolved between January 2015 and May 2017. Together with past NaCo measurements properly re-calibrated, our orbital fitting solutions favor a retrograde low to moderate-eccentricity orbit e = 0.2(-0.2)(+0.3), with a semi-major axis similar to 52 au corresponding to orbital periods of similar to 288 yr and an inclination that peaks at i = 141 degrees, which is compatible with a planet-disk coplanar configuration. Finally, we report the detection in polarimetric differential imaging of the cold outer debris belt between 100 and 300 au, consistent in radial extent with recent ALMA 1.3 mm resolved observations.

  • 19. Cheetham, A.
    et al.
    Bonnefoy, M.
    Desidera, S.
    Langlois, M.
    Vigan, A.
    Schmidt, T.
    Olofsson, J.
    Chauvin, G.
    Klahr, H.
    Gratton, R.
    D'Orazi, V.
    Henning, T.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany.
    Biller, B.
    Peretti, S.
    Hagelberg, J.
    Segransan, D.
    Udry, S.
    Mesa, D.
    Sissa, E.
    Kral, Q.
    Schlieder, J.
    Maire, A. -L.
    Mordasini, C.
    Menard, F.
    Zurlo, A.
    Beuzit, J. -L.
    Feldt, M.
    Mouillet, D.
    Meyer, M.
    Lagrange, A. -M.
    Boccaletti, A.
    Keppler, M.
    Kopytova, T.
    Ligi, R.
    Rouan, D.
    Le Coroller, H.
    Dominik, C.
    Lagadec, E.
    Turatto, M.
    Abe, L.
    Antichi, J.
    Baruffolo, A.
    Baudoz, P.
    Blanchard, P.
    Buey, T.
    Carbillet, M.
    Carle, M.
    Cascone, E.
    Claudi, R.
    Costille, A.
    Delboulbe, A.
    De Caprio, V.
    Dohlen, K.
    Fantinel, D.
    Feautrier, P.
    Fusco, T.
    Giro, E.
    Gluck, L.
    Hubin, N.
    Hugot, E.
    Jaquet, M.
    Kasper, M.
    Llored, M.
    Madec, F.
    Magnard, Y.
    Martinez, P.
    Maurel, D.
    Le Mignant, D.
    Moeller-Nilsson, O.
    Moulin, T.
    Origne, A.
    Pavlov, A.
    Perret, D.
    Petit, C.
    Pragt, J.
    Puget, P.
    Rabou, P.
    Ramos, J.
    Rigal, F.
    Rochat, S.
    Roelfsema, R.
    Rousset, G.
    Roux, A.
    Salasnich, B.
    Sauvage, J. -F.
    Sevin, A.
    Soenke, C.
    Stadler, E.
    Suarez, M.
    Weber, L.
    Wildi, F.
    Discovery of a brown dwarf companion to the star HIP 648922018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 615, article id A160Article in journal (Refereed)
    Abstract [en]

    We report the discovery of a bright, brown dwarf companion to the star HIP 64892, imaged with VLT/SPHERE during the SHINE exoplanet survey. The host is a B9.5V member of the Lower-Centaurus-Crux subgroup of the Scorpius Centaurus OB association. The measured angular separation of the companion (1.2705 +/- 0.0023) corresponds to a projected distance of 159 +/- 12AU. We observed the target with the dual-band imaging and long-slit spectroscopy modes of the IRDIS imager to obtain its spectral energy distribution (SED) and astrometry. In addition, we reprocessed archival NACO L-band data, from which we also recover the companion. Its SED is consistent with a young (<30 Myr), low surface gravity object with a spectral type of M9 gamma +/- 1. From comparison with the BT-Settl atmospheric models we estimate an effective temperature of T-eff = 2600 +/- 100 K, and comparison of the companion photometry to the COND evolutionary models yields a mass of similar to 29-37 M-J at the estimated age of 16(-7)(+15) Myr for the system. The star HIP 64892 is a rare example of an extreme-mass ratio system (q similar to 0.01) and will be useful for testing models relating to the formation and evolution of such low-mass objects.

  • 20. Cheetham, A. C.
    et al.
    Samland, M.
    Brems, S. S.
    Launhardt, R.
    Chauvin, G.
    Ségransan, D.
    Henning, T.
    Quirrenbach, A.
    Avenhaus, H.
    Cugno, G.
    Girard, J.
    Godoy, N.
    Kennedy, G. M.
    Maire, A-L
    Metchev, S.
    Müller, A.
    Barcucci, A. Musso
    Olofsson, J.
    Pepe, F.
    Quanz, S. P.
    Queloz, D.
    Reffert, S.
    Rickman, E.
    Van Boekel, R.
    Boccaletti, A.
    Bonnefoy, M.
    Cantalloube, F.
    Charnay, B.
    Delorme, P.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany.
    Keppler, M.
    Lagrange, A-M
    Langlois, M.
    Lazzoni, C.
    Menard, F.
    Mesa, D.
    Meyer, M.
    Schmidt, T.
    Sissa, E.
    Udry, S.
    Zurlo, A.
    Spectral and orbital characterisation of the directly imaged giant planet HIP 65426 b2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 622, article id A80Article in journal (Refereed)
    Abstract [en]

    HIP 65426 b is a recently discovered exoplanet imaged during the course of the SPHERE-SHINE survey. Here we present new L' and M' observations of the planet from the NACO instrument at the VLT from the NACO-ISPY survey, as well as a new Y-H spectrum and K-band photometry from SPHERE-SHINE. Using these data, we confirm the nature of the companion as a warm, dusty planet with a mid-L spectral type. From comparison of its SED with the BT-Settl atmospheric models, we derive a best-fit effective temperature of T-eff = 1618 +/- 7 K, surface gravity log g = 3 : 78(-0.03)(+0.04) and radius R = 1.17 +/- 0.04 R-J (statistical uncertainties only). Using the DUSTY and COND isochrones we estimate a mass of 8 +/- 1 MJ. Combining the astrometric measurements from our new datasets and from the literature, we show the first indications of orbital motion of the companion (2.6 sigma significance) and derive preliminary orbital constraints. We find a highly inclined orbit (i = 107(+13)(-10) deg) with an orbital period of 800(+1200)(-400) yr. We also report SPHERE sparse aperture masking observations that investigate the possibility that HIP 65426 b was scattered onto its current orbit by an additional companion at a smaller orbital separation. From this data we rule out the presence of brown dwarf companions with masses greater than 16 M-J at separations larger than 3AU, significantly narrowing the parameter space for such a companion.

  • 21. Claudi, R.
    et al.
    Maire, A. -L.
    Mesa, D.
    Cheetham, A.
    Fontanive, C.
    Gratton, R.
    Zurlo, A.
    Avenhaus, H.
    Bhowmik, T.
    Biller, B.
    Boccaletti, A.
    Bonavita, M.
    Bonnefoy, M.
    Cascone, E.
    Chauvin, G.
    Delboulbe, A.
    Desidera, S.
    D'Orazi, V.
    Feautrier, P.
    Feldt, M.
    Dotti, F. Flammini
    Girard, J. H.
    Giro, E.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany .
    Hagelberg, J.
    Keppler, M.
    Kopytova, T.
    Lacour, S.
    Lagrange, A. -M.
    Langlois, M.
    Lannier, J.
    Le Coroller, H.
    Menard, F.
    Messina, S.
    Meyer, M.
    Millward, M.
    Olofsson, J.
    Pavlov, A.
    Peretti, S.
    Perrot, C.
    Pinte, C.
    Pragt, J.
    Ramos, J.
    Rochat, S.
    Rodet, L.
    Roelfsema, R.
    Rouan, D.
    Salter, G.
    Schmidt, T.
    Sissa, E.
    Thebault, P.
    Udry, S.
    Vigan, A.
    SPHERE dynamical and spectroscopic characterization of HD142527B2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 622, article id A96Article in journal (Refereed)
    Abstract [en]

    Aims. HD142527 is one of the most frequently studied Herbig Ae/Be stars with a transitional disk that hosts a large cavity that is up to about 100 au in radius. For this reason, it has been included in the guaranteed time observation (GTO) SpHere INfrared survey for Exoplanets (SHINE) as part of the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) at the Very Large Telescope (VLT) in order to search for low-mass companions that might explain the presence of the gap. SHINE is a large survey within about 600 young nearby stars are observed with SPHERE with the aim to constrain the occurrence and orbital properties of the giant planet population at large (>5 au) orbital separation around young stars. Methods. We used the IRDIFS observing mode of SPHERE (IRDIS short for infrared dual imaging and spectrograph plus IFS or integral field spectrograph) without any coronagraph in order to search for and characterize companions as close as 30 mas of the star. Furthermore, we present the first observations that ever used the sparse aperture mask (SAM) for SPHERE both in IRDIFS and IRDIFS_EXT modes. All the data were reduced using the dedicated SPHERE pipeline and dedicated algorithms that make use of the principal component analysis (PCA) and reference differential imaging (RDI) techniques. Results. We detect the accreting low-mass companion HD142527B at a separation of 73 mas (11.4 au) from the star. No other companions with mass greater than 10 M-J are visible in the field of view of IFS (similar to 100 au centered on the star) or in the IRDIS field of view (similar to 400 au centered on the star). Measurements from IFS, SAM IFS, and IRDIS suggest an M6 spectral type for HD142527B, with an uncertainty of one spectral subtype, compatible with an object of M = 0.11 +/- 0.06 M-circle dot and R = 0.15 +/- 0.07 R-circle dot. The determination of the mass remains a challenge using contemporary evolutionary models, as they do not account for the energy input due to accretion from infalling material. We consider that the spectral type of the secondary may also be earlier than the type we derived from IFS spectra. From dynamical considerations, we further constrain the mass to 0.26(-0.14)(+0.16) , which is consistent with both our spectroscopic analysis and the values reported in the literature. Following previous methods, the lower and upper dynamical mass values correspond to a spectral type between M2.5 and M5.5 for the companion. By fitting the astrometric points, we find the following orbital parameters: a period of P = 35 137 yr; an inclination of i = 121 130 degrees, a value of Omega = 124 135 degrees for the longitude of node, and an 68% confidence interval of similar to 18-57 au for the separation at periapsis. Eccentricity and time at periapsis passage exhibit two groups of values: similar to 0.2-0.45 and similar to 0.45-0.7 for e, and similar to 2015-2020 and similar to 2020-2022 for T-0. While these orbital parameters might at first suggest that HD142527B is not the companion responsible for the outer disk truncation, a previous hydrodynamical analysis of this system showed that they are compatible with a companion that is able to produce the large cavity and other observed features.

  • 22. Cugno, G.
    et al.
    Quanz, S. P.
    Hunziker, S.
    Stolker, T.
    Schmid, H. M.
    Avenhaus, H.
    Baudoz, P.
    Bohn, A. J.
    Bonnefoy, M.
    Buenzli, E.
    Chauvin, G.
    Cheetham, A.
    Desidera, S.
    Dominik, C.
    Feautrier, P.
    Feldt, M.
    Ginski, C.
    Girard, J. H.
    Gratton, R.
    Hagelberg, J.
    Hugot, E.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lagrange, A. -M.
    Langlois, M.
    Magnard, Y.
    Maire, A. -L.
    Menard, F.
    Meyer, M.
    Milli, J.
    Mordasini, C.
    Pinte, C.
    Pragt, J.
    Roelfsema, R.
    Rigal, F.
    Szulagyi, J.
    van Boekel, R.
    van der Plas, G.
    Vigan, A.
    Wahhaj, Z.
    Zurlo, A.
    A search for accreting young companions embedded in circumstellar disks High-contrast H alpha imaging with VLT/SPHERE2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 622, article id A156Article in journal (Refereed)
    Abstract [en]

    Context. In recent years, our understanding of giant planet formation progressed substantially. There have even been detections of a few young protoplanet candidates still embedded in the circumstellar disks of their host stars. The exact physics that describes the accretion of material from the circumstellar disk onto the suspected circumplanetary disk and eventually onto the young, forming planet is still an open question.

    Aims. We seek to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets.

    Methods. We analyzed observations of six young stars (age 3.5-10 Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the H alpha filter (656 nm) and a nearby continuum filter (644.9 nm). We applied several point spread function (PSF) subtraction techniques to reach the highest possible contrast near the primary star, specifically investigating regions where forming companions were claimed or have been suggested based on observed disk morphology.

    Results. We redetect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both H alpha and the continuum. We derive new astrometry (r = 62.8(-2.7)(+2.1)mas and PA = (98.7 +/- 1.8)degrees) and photometry (Delta N_Ha = 6.3-(+0.2)(0.3) mag, Delta B_Ha = 6.7 +/- 0.2 mag and Delta Cnt_Ha= 7.3(-0.2)(+0.3) mag) for the companion in agreement with previous studies, and estimate its mass accretion rate (M approximate to 1-2 x 10(-10) M-circle dot yr(-1)). A faint point-like source around HD135344 B (SA0206462) is also investigated, but a second deeper observation is required to reveal its nature. No other companions are detected. In the framework of our assumptions we estimate detection limits at the locations of companion candidates around HD100546, HD169142, and MWC 758 and calculate that processes involving Ha fluxes larger than similar to 8 x 10(-14)-10(-15) erg s(-1) cm(-2) (M > 10(-10)-10(-12) M-circle dot yr(-1)) can be excluded. Furthermore, flux upper limits of similar to 10(-14)-10(-15)erg s(-1) cm(-2) (M < 10(-11) -10(-12)M(circle dot )yr(-1)) are estimated within the gaps identified in the disks surrounding HD135344 B and TW Hya. The derived luminosity limits exclude H alpha signatures at levels similar to those previously detected for the accreting planet candidate LkCa15 b.

  • 23. Currie, Thayne
    et al.
    Brandt, Timothy D.
    Uyama, Taichi
    Nielsen, Eric L.
    Blunt, Sarah
    Guyon, Olivier
    Tamura, Motohide
    Marois, Christian
    Mede, Kyle
    Kuzuhara, Masayuki
    Groff, Tyler D.
    Jovanovic, Nemanja
    Kasdin, N. Jeremy
    Lozi, Julien
    Hodapp, Klaus
    Chilcote, Jeffrey
    Carson, Joseph
    Martinache, Frantz
    Goebel, Sean
    Grady, Carol
    McElwain, Michael
    Akiyama, Eiji
    Asensio-Torres, Ruben
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hayashi, Masa
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Knapp, Gillian R.
    Kwon, Jungmi
    Nishikawa, Jun
    Oh, Daehyeon
    Schlieder, Joshua
    Serabyn, Eugene
    Sitko, Michael
    Skaf, Nour
    SCExAO/CHARIS Near-infrared Direct Imaging, Spectroscopy, and Forward-Modeling of kappa And b: A Likely Young, Low-gravity Superjovian Companion2018In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 156, no 6, article id 291Article in journal (Refereed)
    Abstract [en]

    We present SCExAO/CHARIS high-contrast imaging/JHK integral field spectroscopy of kappa And b, a directly imaged low-mass companion orbiting a nearby B9V star. We detect kappa And b at a high signal-to-noise ratio and extract high-precision spectrophotometry using a new forward-modeling algorithm for (A-)LOCI complementary to KLIP-FM developed by Pueyo et al. kappa And b's spectrum best resembles that of a low-gravity LO-L1 dwarf (L0-L1 gamma). Its spectrum and luminosity are very well matched by 2MASS J0141-4633 and several other 12.5-15 M-J free-floating members of the 40 Myr old Tuc-Hor Association, consistent with a system age derived from recent interferometric results for the primary, a companion mass at/near the deuterium-burning limit (13(-2)(+12) M-J), and a companion-to-primary mass ratio characteristic of other directly imaged planets (q similar to 0.0051(-0.001)(+0.005)). We did not unambiguously identify additional, more closely orbiting companions brighter and more massive than kappa And b down to p similar to 0.'' 3 (15 au). SCExAO/CHARIS and complementary Keck/NIRC2 astrometric points reveal clockwise orbital motion. Modeling points toward a likely eccentric orbit: a subset of acceptable orbits include those that are aligned with the star's rotation axis. However, kappa And b's semimajor axis is plausibly larger than 55 au and in a region where disk instability could form massive companions. Deeper high-contrast imaging of kappa And and low-resolution spectroscopy from extreme adaptive optics systems such as SCExAO/CHARIS and higher-resolution spectroscopy from Keck/OSIRIS or, later, IRIS on the Thirty Meter Telescope could help to clarify kappa And b's chemistry and whether its spectrum provides an insight into its formation environment.

  • 24. Currie, Thayne
    et al.
    Guyon, Olivier
    Tamura, Motohide
    Kudo, Tomoyuki
    Jovanovic, Nemanja
    Lozi, Julien
    Schlieder, Joshua E.
    Brandt, Timothy D.
    Kuhn, Jonas
    Serabyn, Eugene
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Carson, Joseph
    Groff, Tyler
    Kasdin, N. Jeremy
    McElwain, Michael W.
    Singh, Garima
    Uyama, Taichi
    Kuzuhara, Masayuki
    Akiyama, Eiji
    Grady, Carol
    Hayashi, Saeko
    Knapp, Gillian
    Kwon, Jung-mi
    Oh, Daehyeon
    Wisniewski, John
    Sitko, Michael
    Yang, Yi
    Subaru/SCExAO First-light Direct Imaging of a Young Debris Disk around HD 365462017In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 836, no 1, article id L15Article in journal (Refereed)
    Abstract [en]

    We present H-band scattered light imaging of a bright debris disk around the A0 star HD 36546 obtained from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system with data recorded by the HiCIAO camera using the vector vortex coronagraph. SCExAO traces the disk from r similar to 0.3 to r similar to 1 (34-114 au). The disk is oriented in a near east-west direction (PA similar to 75 degrees), is inclined by i similar to 70 degrees-75 degrees, and is strongly forward-scattering (g > 0.5). It is an extended disk rather than a sharp ring; a second, diffuse dust population extends from the disk's eastern side. While HD 36546 intrinsic properties are consistent with a wide age range (t similar to 1-250 Myr), its kinematics and analysis of coeval stars suggest a young age (3-10 Myr) and a possible connection to Taurus-Auriga's star formation history. SCExAO's planet-to-star contrast ratios are comparable to the first-light Gemini Planet Imager contrasts; for an age of 10 Myr, we rule out planets with masses comparable to HR 8799 b beyond a projected separation of 23 au. A massive icy planetesimal disk or an unseen super-Jovian planet at r > 20 au may explain the disk's visibility. The HD 36546 debris disk may be the youngest debris disk yet imaged, is the first newly identified object from the now-operational SCExAO extreme AO system, is ideally suited for spectroscopic follow-up with SCExAO/CHARIS in 2017, and may be a key probe of icy planet formation and planet-disk interactions.

  • 25. Currie, Thayne
    et al.
    Muto, Takayuki
    Kudo, Tomoyuki
    Honda, Mitsuhiko
    Brandt, Timothy D.
    Grady, Carol
    Fukagawa, Misato
    Burrows, Adam
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Kuzuhara, Masayuki
    McElwain, Michael W.
    Follette, Katherine
    Hashimoto, Jun
    Henning, Thomas
    Kandori, Ryo
    Kusakabe, Nobuhiko
    Kwon, Jungmi
    Mede, Kyle
    Morino, Jun-ichi
    Nishikawa, Jun
    Pyo, Tae-Soo
    Serabyn, Gene
    Suenaga, Takuya
    Takahashi, Yasuhiro
    Wisniewski, John
    Tamura, Motohide
    RECOVERY OF THE CANDIDATE PROTOPLANET HD 100546 b WITH GEMINI/NICI AND DETECTION OF ADDITIONAL (PLANET-INDUCED ?) DISK STRUCTURE AT SMALL SEPARATIONS2014In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 796, no 2, p. L30-Article in journal (Refereed)
    Abstract [en]

    We report the first independent, second epoch (re-) detection of a directly imaged protoplanet candidate. Using L' high-contrast imaging of HD 100546 taken with the Near-Infrared Coronagraph and Imager on Gemini South, we recover HD 100546 b with a position and brightness consistent with the original Very Large Telescope/NAos-COnica detection from Quanz et al., although data obtained after 2013 will be required to decisively demonstrate common proper motion. HD 100546 b may be spatially resolved, up to approximate to 12-13 AU in diameter, and is embedded in a finger of thermal IR-bright, polarized emission extending inward to at least 0 ''.3. Standard hot-start models imply a mass of approximate to 15 M-J. However, if HD 100546 b is newly formed or made visible by a circumplanetary disk, both of which are plausible, its mass is significantly lower (e.g., 1-7 M-J). Additionally, we discover a thermal IR-bright disk feature, possibly a spiral density wave, at roughly the same angular separation as HD 100546 b but 90 degrees. away. Our interpretation of this feature as a spiral arm is not decisive, but modeling analyses using spiral density wave theory implies a wave launching point exterior to approximate to 0 ''.45 embedded within the visible disk structure: plausibly evidence for a second, hitherto unseen, wide-separation planet. With one confirmed protoplanet candidate and evidence for one to two others, HD 100546 is an important evolutionary precursor to intermediate-mass stars with multiple super-Jovian planets at moderate/wide separations like HR 8799.

  • 26. Daemgen, Sebastian
    et al.
    Bonavita, Mariangela
    Jayawardhana, Ray
    Lafreniere, David
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    SUB-STELLAR COMPANIONS AND STELLAR MULTIPLICITY IN THE TAURUS STAR-FORMING REGION2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 799, no 2, article id 155Article in journal (Refereed)
    Abstract [en]

    We present results from a large, high- spatial- resolution near- infrared imaging search for stellar and sub- stellar companions in the Taurus- Auriga star- forming region. The sample covers 64 stars with masses between those of the most massive Taurus members at 3 M-circle dot and low-mass stars at 0.2 M-circle dot. We detected 74 companion candidates, 34 of these reported for the first time. Twenty- five companions are likely physically bound, partly confirmed by follow- up observations. Four candidate companions are likely unrelated field stars. Assuming physical association with their host star, estimated companion masses are as low as 2M(Jup.) The inferred multiplicity frequency within our sensitivity limits between 10-1500 AU is 26.3(-4.9)(+ 6.6)% - 4.9%. Applying a completeness correction, 62% 14% of all Taurus stars between 0.7 and 1.4 M appear to be multiple. Higher order multiples were found in 1.8+ 4.2 - 1.5 % of the cases, in agreement with previous observations of the field. We estimate a sub- stellar companion frequency of 3.5%- 8.8% within our sensitivity limits from the discovery of two likely bound and three other tentative very low- mass companions. This frequency appears to be in agreement with what is expected from the tail of the stellar companion mass ratio distribution, suggesting that stellar and brown dwarf companions share the same dominant formation mechanism. Further, we find evidence for possible evolution of binary parameters between two identified sub- populations in Taurus with ages of 2 Myr and 20 Myr, respectively.

  • 27. de Boer, J.
    et al.
    Salter, G.
    Benisty, M.
    Vigan, A.
    Boccaletti, A.
    Pinilla, P.
    Ginski, C.
    Juhasz, A.
    Maire, A. -L.
    Messina, S.
    Desidera, S.
    Cheetham, A.
    Girard, J. H.
    Wahhaj, Z.
    Langlois, M.
    Bonnefoy, M.
    Beuzit, J. -L.
    Buenzli, E.
    Chauvin, G.
    Dominik, C.
    Feldt, M.
    Gratton, R.
    Hagelberg, J.
    Isella, A.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Keller, C. U.
    Lagrange, A. -M.
    Lannier, J.
    Menard, F.
    Mesa, D.
    Mouillet, D.
    Mugrauer, M.
    Peretti, S.
    Perrot, C.
    Sissa, E.
    Snik, F.
    Vogt, N.
    Zurlo, A.
    Multiple rings in the transition disk and companion candidates around RX J1615.3-3255 High contrast imaging with VLT/SPHERE2016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 595, article id A114Article in journal (Refereed)
    Abstract [en]

    Context. The effects of a planet sculpting the disk from which it formed are most likely to be found in disks that are in transition between being classical protoplanetary and debris disks. Recent direct imaging of transition disks has revealed structures such as dust rings, gaps, and spiral arms, but an unambiguous link between these structures and sculpting planets is yet to be found. Aims. We aim to find signs of ongoing planet-disk interaction and study the distribution of small grains at the surface of the transition disk around RXJ1615.3-3255 (RX J1615). Methods. We observed RXJ1615 with VLT/SPHERE. From these observations, we obtained polarimetric imaging with ZIMPOL (R'-band) and IRDIS (J), and IRDIS (H2H3) dual-band imaging with simultaneous spatially resolved spectra with the IFS (YJ). Results. We image the disk for the first time in scattered light and detect two arcs, two rings, a gap and an inner disk with marginal evidence for an inner cavity. The shapes of the arcs suggest that they are probably segments of full rings. Ellipse fitting for the two rings and inner disk yield a disk inclination i = 47 +/- 2 degrees and find semi-major axes of 1.50 +/- 0.01 '' (278 au), 1.06 +/- 0.01 '' (196 au) and 0.30 +/- 0.01 '' (56 au), respectively. We determine the scattering surface height above the midplane, based on the projected ring center offsets. Nine point sources are detected between 2.1 '' and 8.0 '' separation and considered as companion candidates. With NACO data we recover four of the nine point sources, which we determine to be not co-moving, and therefore unbound to the system. Conclusions. We present the first detection of the transition disk of RXJ1615 in scattered light. The height of the rings indicate limited flaring of the disk surface, which enables partial self-shadowing in the disk. The outermost arc either traces the bottom of the disk or it is another ring with semi-major axis greater than or similar to 2.35 '' (435 au). We explore both scenarios, extrapolating the complete shape of the feature, which will allow us to distinguish between the two in future observations. The most attractive scenario, where the arc traces the bottom of the outer ring, requires the disk to be truncated at r approximate to 360 au. If the closest companion candidate is indeed orbiting the disk at 540 au, then it would be the most likely cause for such truncation. This companion candidate, as well as the remaining four, all require follow up observations to determine if they are bound to the system.

  • 28. de Leon, Jerome
    et al.
    Takami, Michihiro
    Karr, Jennifer L.
    Hashimoto, Jun
    Kudo, Tomoyuki
    Sitko, Michael
    Mayama, Satoshi
    Kusakabe, Nobuyuki
    Akiyama, Eiji
    Liu, Hauyu Baobab
    Usuda, Tomonori
    Abe, Lyu
    Brandner, Wolfgang
    Brandt, Timothy D.
    Carson, Joseph
    Currie, Thayne
    Egner, Sebastian E.
    Feldt, Markus
    Follette, Katherine
    Grady, Carol A.
    Goto, Miwa
    Guyon, Olivier
    Hayano, Yutaka
    Hayashi, Masahiko
    Hayashi, Saeko
    Henning, Thomas
    Hodapp, Klaus W.
    Ishii, Miki
    Iye, Masanori
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Kandori, Ryo
    Knapp, Gillian R.
    Kuzuhara, Masayuki
    Kwon, Jungmi
    Matsuo, Taro
    McElwain, Michael W.
    Miyama, Shoken
    Morino, Jun-Ichi
    Moro-Martin, Amaya
    Nishimura, Tetsuo
    Pyo, Tae-Soo
    Serabyn, Eugene
    Suenaga, Takuya
    Suto, Hiroshi
    Suzuki, Ryuji
    Takahashi, Yasuhiro
    Takato, Naruhisa
    Terada, Hiroshi
    Thalmann, Christian
    Tomono, Daigo
    Turner, Edwin L.
    Watanabe, Makoto
    Wisniewski, John P.
    Yamada, Toru
    Takami, Hideki
    Tamura, Motohide
    NEAR-IR HIGH-RESOLUTION IMAGING POLARIMETRY OF THE SU Aur DISK: CLUES FOR TIDAL TAILS?2015In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 806, no 1, article id L10Article in journal (Refereed)
    Abstract [en]

    We present new high-resolution (similar to 0.09) H-band imaging observations of the circumstellar disk around the T Tauri star SU Aur. Our observations with Subaru-HiCIAO have revealed the presence of scattered light as close as 0.15 (similar to 20 AU) to the star. Within our image, we identify bright emission associated with a disk with a minimum radius of similar to 90 AU, an inclination of similar to 35 degrees from the plane of the sky, and an approximate PA of 15 degrees for the major axis. We find a brightness asymmetry between the northern and southern sides of the disk due to a non-axisymmetric disk structure. We also identify a pair of asymmetric tail structures extending east and west from the disk. The western tail extends at least 2.5 (350 AU) from the star, and is probably associated with a reflection nebula previously observed at optical and near-IR wavelengths. The eastern tail extends at least 1. (140 AU) at the present signal-to-noise. These tails are likely due to an encounter with an unseen brown dwarf, but our results do not exclude the explanation that these tails are outflow cavities or jets.

  • 29. D'Orazi, V.
    et al.
    Desidera, S.
    Gratton, R. G.
    Lanza, A. F.
    Messina, S.
    Andrievsky, S. M.
    Korotin, S.
    Benatti, S.
    Bonnefoy, M.
    Covino, E.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    A critical reassessment of the fundamental properties of GJ 504: chemical composition and age2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 598, article id A19Article in journal (Refereed)
    Abstract [en]

    Context. The recent development of brand new observational techniques and theoretical models have greatly advanced the exoplanet research field. Despite significant achievements, which have allowed the detection of thousands extrasolar systems, a comprehensive understanding of planetary formation and evolution mechanisms is still desired. One relevant limitation is given by the accuracy in the measurements of planet-host star ages. The star GJ 504 has been found to host a substellar companion whose nature is strongly debated. There has been a recent difference of opinion in the literature owing to the uncertainty on the age of the system: a young age of similar to 160 Myr would imply a giant planet as a companion, but a recent revision pointing to a solar age (similar to 4 Gyr) instead suggests a brown dwarf.

    Aims. With the aim of shedding light on this debated topic, we have carried out a high-resolution spectroscopic study of GJ 504 to derive stellar parameters, metallicity, and abundances of both light and heavy elements, providing a full chemical characterisation. The main objective is to infer clues on the evolutionary stage (hence the age) of this system.

    Methods. We performed a strictly differential (line-by-line) analysis of GJ 504 with respect to two reference stars, that is the planethost dwarf (l)Hor and the subgiant HIP 84827. The former is crucial in this context because its stellar parameters (hence the evolutionary stage) is well constrained from asteroseismic observations. Regardless of the zero point off sets, our differential approach allows us to put tight constraints on the age of GJ 504 with respect to (l)Hor, thereby minimising the internal uncertainties.

    Results. We found that the surface gravity of GJ 504 is 0.2 +/- 0.07 dex lower than that of the main-sequence star (l)Hor, suggesting a past turn-off evolution for our target. The isochrone comparison provides us with an age range between 1.8 and 3.5 Gyr, with a most probable age of approximate to 2.5 Gyr. Thus, our findings support an old age for the system; further evidence comes from the barium abundance, which is compatible with a solar pattern and not enhanced as observed in young stars.

    Conclusions. We envisaged a possible engulfment scenario to reconcile all the age indicators (spectroscopy, isochrones, rotation, and activity); this engulfment could have occurred very recently and could be responsible for the enhanced levels of rotation and chromospheric activity, as previously suggested. We tested this hypothesis, exploiting a tidal evolution code and finding that the engulfment of a hot Jupiter, with mass not larger than approximate to 3 M-j and initially located at approximate to 0.03 AU, seems to be a very likely scenario.

  • 30. D'Orazi, V.
    et al.
    Gratton, R.
    Desidera, S.
    Avenhaus, H.
    Mesa, D.
    Stolker, T.
    Giro, E.
    Benatti, S.
    Jang-Condell, H.
    Rigliaco, E.
    Sissa, E.
    Scatolin, T.
    Benisty, M.
    Bhowmik, T.
    Boccaletti, A.
    Bonnefoy, M.
    Brandner, W.
    Buenzli, E.
    Chauvin, G.
    Daemgen, S.
    Damasso, M.
    Feldt, M.
    Galicher, R.
    Girard, J.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hagelberg, J.
    Mouillet, D.
    Kral, Q.
    Lanniers, J.
    Lagrange, A-M
    La Nglois, M.
    Maire, A-L
    Menard, F.
    Moeller-Nilsson, O.
    Perrot, C.
    Peretti, S.
    Rabou, P.
    Ramos, J.
    Rodet, L.
    Roelfsema, R.
    Roux, A.
    Salter, G.
    Schlieder, J. E.
    Schmidt, T.
    Szulagyi, J.
    Thalmann, C.
    Thebault, P.
    van der Plas, G.
    Vigan, A.
    Zurlo, A.
    Mapping of shadows cast on a protoplanetary disk by a close binary system2019In: Nature astronomy, ISSN 2397-3366, Vol. 3, no 2, p. 167-172Article in journal (Refereed)
    Abstract [en]

    For a comprehensive understanding of planetary formation and evolution, we need to investigate the environment in which planets form: circumstellar disks. Here we present high-contrast imaging observations of V4046 Sagittarii, a 20-Myr-old close binary known to host a circumbinary disk. We have discovered the presence of rotating shadows in the disk, caused by mutual occultations of the central binary. Shadow-like features are often observed in disks(1,2), but those found thus far have not been due to eclipsing phenomena. We have used the phase difference due to light travel time to measure the flaring of the disk and the geometrical distance of the system. We calculate a distance that is in very good agreement with the value obtained from the Gaia mission's Data Release 2 (DR2), and flaring angles of alpha = (6.2 +/- 0.6)degrees and alpha = (8.5 +/- 1.0)degrees for the inner and outer disk rings, respectively. Our technique opens up a path to explore other binary systems, providing an independent estimate of distance and the flaring angle, a crucial parameter for disk modelling.

  • 31. Durkan, Stephen
    et al.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Carson, Joseph C.
    HIGH CONTRAST IMAGING WITH SPITZER: CONSTRAINING THE FREQUENCY OF GIANT PLANETS OUT TO 1000 au SEPARATIONS2016In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 824, no 1, article id 58Article in journal (Refereed)
    Abstract [en]

    We report results of a re-analysis of archival Spitzer IRAC direct imaging surveys encompassing a variety of nearby stars. Our sample is generated from the combined observations of 73 young stars (median age, distance, spectral type = 85 Myr, 23.3 pc, G5) and 48 known exoplanet host stars with unconstrained ages (median distance, spectral type = 22.6 pc, G5). While the small size of Spitzer provides a lower resolution than 8 m class AO-assisted ground-based telescopes, which have been used for constraining the frequency of 0.5-13 M-J planets at separations of 10-10(2) au, its exquisite infrared sensitivity provides the ability to place unmatched constraints on the planetary populations at wider separations. Here we apply sophisticated high-contrast techniques to our sample in order to remove the stellar point-spread function and to open up sensitivity to planetary mass companions down to 5. separations. This enables sensitivity to 0.5-13 M-J planets at physical separations on the order of 10(2)-10(3) au, allowing us to probe a parameter space that has not previously been systematically explored to any similar degree of sensitivity. Based on a color and proper motion analysis, we do not record any planetary detections. Exploiting this enhanced survey sensitivity, employing Monte Carlo simulations with a Bayesian approach, and assuming a mass distribution of dn/dm alpha m(-1.31), we constrain (at 95% confidence) a population of 0.5-13 M-J planets at separations of 100-1000 au with an upper frequency limit of 9%.

  • 32.
    Durkan, Stephen
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Queens University Belfast, UK.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Ciceri, Simona
    Stockholm University, Faculty of Science, Department of Astronomy.
    Brandner, Wolfgang
    Schlieder, Joshua
    Henning, Thomas
    Bonnefoy, Mickaël
    Kankare, Juliet
    Watson, Christopher A.
    Radial velocity survey of spatially resolved young, low-mass binaries2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 618, article id A5Article in journal (Refereed)
    Abstract [en]

    The identification and characterisation of low-mass binaries is of importance for a range of astrophysical investigations. Low-mass binaries in young (similar to 10-100 Myr) moving groups (YMGs) in the solar neighborhood are of particular significance as they provide unique opportunities to calibrate stellar models and evaluate the ages and coevality of the groups themselves. Low-mass M-dwarfs have pre-main sequence life times on the order of similar to 100 Myr and therefore are continually evolving along a mass-luminosity track throughout the YMG phase, providing ideal laboratories for precise isochronal dating, if a model-independent dynamical mass can be measured. AstraLux lucky imaging multiplicity surveys have recently identified hundreds of new YMG low-mass binaries, where a subsample of M-dwarf multiples have estimated orbital periods less than 50 yr. We have conducted a radial velocity survey of a sample of 29 such targets to complement the astrometric data. This will allow enhanced orbital determinations and precise dynamical masses to be derived in a shorter timeframe than possible with astrometric monitoring alone, and allow for a more reliable isochronal analysis. Here we present radial velocity measurements derived for our sample over several epochs. We report the detection of the three-component spectroscopic multiple 2MASS J05301858-5358483, for which the C component is a new discovery, and forms a tight pair with the B component. Originally identified as a YMG member, we find that this system is a likely old field interloper, whose high chromospheric activity level is caused by tidal spin-up of the tight BC pair. Two other triple systems with a tight pair exist in the sample, 2MASS J04244260-0647313 (previously known) and 2MASS J20163382-0711456, but for the rest of the targets we find that additional tidally synchronized companions are highly unlikely, providing further evidence that their high chromospheric activity levels are generally signatures of youth.

  • 33. Engler, N.
    et al.
    Schmid, H. M.
    Thalmann, Ch.
    Boccaletti, A.
    Bazzon, A.
    Baruffolo, A.
    Beuzit, J. L.
    Claudi, R.
    Costille, A.
    Desidera, S.
    Dohlen, K.
    Dominik, C.
    Feldt, M.
    Fusco, T.
    Ginski, C.
    Gisler, D.
    Girard, J. H.
    Gratton, R.
    Henning, T.
    Hubin, N.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max-Planck-Institut für Astronomie, Germany.
    Kasper, M.
    Kral, Q.
    Langlois, M.
    Lagadec, E.
    Menard, F.
    Meyer, M. R.
    Milli, J.
    Mouillet, D.
    Olofsson, J.
    Pavlov, A.
    Pragt, J.
    Puget, P.
    Quanz, S. P.
    Roelfsema, R.
    Salasnich, B.
    Siebenmorgen, R.
    Sissa, E.
    Suarez, M.
    Szulagyi, J.
    Turatto, M.
    Udry, S.
    Wildi, F.
    The HIP 79977 debris disk in polarized light2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 607, article id A90Article in journal (Refereed)
    Abstract [en]

    Context. Debris disks are observed around 10 to 20% of FGK main-sequence stars as infrared excess emission. They are important signposts for the presence of colliding planetesimals and therefore provide important information about the evolution of planetary systems. Direct imaging of such disks reveals their geometric structure and constrains their dust-particle properties. Aims. We present observations of the known edge-on debris disk around HIP 79977 (HD 146897) taken with the ZIMPOL differential polarimeter of the SPHERE instrument. We measure the observed polarization signal and investigate the diagnostic potential of such data with model simulations. Methods. SPHERE-ZIMPOL polarimetric data of the 15 Myr-old F star HIP 79977 (Upper Sco, 123 pc) were taken in the Very Broad Band (VBB) filter (lambda(c) = 735 nm, Delta lambda = 290 nm) with a spatial resolution of about 25 mas. Imaging polarimetry efficiently suppresses the residual speckle noise from the AO system and provides a differential signal with relatively small systematic measuring uncertainties. We measure the polarization flux along and perpendicular to the disk spine of the highly inclined disk for projected separations between 0 : 200 (25 AU) and 1 : 600 (200 AU). We perform model calculations for the polarized flux of an optically thin debris disk which are used to determine or constrain the disk parameters of HIP 79977. Results. We measure a polarized flux contrast ratio for the disk of (F-pol) disk/F-* = (5 : 5 +/- 0 : 9) x 10(-4) in the VBB filter. The surface brightness of the polarized flux reaches a maximum of SBmax = 16.2 mag arcsec(-2) at a separation of 0 : 200 -0 : 500 along the disk spine with a maximum surface brightness contrast of 7 : 64 mag arcsec(-2). The polarized flux has a minimum near the star < 0 : 200 because no or only little polarization is produced by forward or backward scattering in the disk section lying in front of or behind the star. The width of the disk perpendicular to the spine shows a systematic increase in FWHM from 0 : 1 (12 AU) to 0 : 3 -0.5, when going from a separation of 0 : 2 to > 1. This can be explained by a radial blow-out of small grains. The data are modelled as a circular dust belt with a well defined disk inclination i = 85(+/- 1 : 5)degrees and a radius between r(0) = 60 and 90 AU. The radial density dependence is described by (r/r(0))alpha with a steep (positive) power law index alpha = 5 inside r(0) and a more shallow (negative) index alpha = -2 : 5 outside r(0). The scattering asymmetry factor lies between g = 0.2 and 0.6 (forward scattering) adopting a scattering-angle dependence for the fractional polarization such as that for Rayleigh scattering. Conclusions. Polarimetric imaging with SPHERE-ZIMPOL of the edge-on debris disk around HIP 79977 provides accurate profiles for the polarized flux. Our data are qualitatively very similar to the case of AU Mic and they confirm that edge-on debris disks have a polarization minimum at a position near the star and a maximum near the projected separation of the main debris belt. The comparison of the polarized flux contrast ratio (F-pol)(disk)/F* with the fractional infrared excess provides strong constraints on the scattering albedo of the dust.

  • 34. Follette, Katherine B.
    et al.
    Grady, Carol A.
    Swearingen, Jeremy R.
    Sitko, Michael L.
    Champney, Elizabeth H.
    van der Marel, Nienke
    Takami, Michihiro
    Kuchner, Marc J.
    Close, Laird M.
    Muto, Takayuki
    Mayama, Satoshi
    McElwain, Michael W.
    Fukagawa, Misato
    Maaskant, Koen
    Min, Michiel
    Russell, Ray W.
    Kudo, Tomoyuki
    Kusakabe, Nobuhiko
    Hashimoto, Jun
    Abe, Lyu
    Akiyama, Eiji
    Brandner, Wolfgang
    Brandt, Timothy D.
    Carson, Joseph
    Currie, Thayne
    Egner, Sebastian E.
    Feldt, Markus
    Goto, Miwa
    Guyon, Olivier
    Hayano, Yutaka
    Hayashi, Masahiko
    Hayashi, Saeko
    Henning, Thomas
    Hodapp, Klaus
    Ishii, Miki
    Iye, Masanori
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Kandori, Ryo
    Knapp, Gillian R.
    Kuzuhara, Masayuki
    Kwon, Jungmi
    Matsuo, Taro
    Miyama, Shoken
    Morino, Jun-Ichi
    Moro-Martin, Amaya
    Nishimura, Tetsuo
    Pyo, Tae-Soo
    Serabyn, Eugene
    Suenaga, Takuya
    Suto, Hiroshi
    Suzuki, Ryuji
    Takahashi, Yasuhiro
    Takato, Naruhisa
    Terada, Hiroshi
    Thalmann, Christian
    Tomono, Daigo
    Turner, Edwin L.
    Watanabe, Makoto
    Wisniewski, John P.
    Yamada, Toru
    Takami, Hideki
    Usuda, Tomonori
    Tamura, Motohide
    SEEDS ADAPTIVE OPTICS IMAGING OF THE ASYMMETRIC TRANSITION DISK OPH IRS 48 IN SCATTERED LIGHT2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 798, no 2, article id 132Article in journal (Refereed)
    Abstract [en]

    We present the first resolved near-infrared imagery of the transition disk Oph IRS 48 (WLY 2-48), which was recently observed with ALMA to have a strongly asymmetric submillimeter flux distribution. H-band polarized intensity images show a similar to 60 AU radius scattered light cavity with two pronounced arcs of emission, one from northeast to southeast and one smaller, fainter, and more distant arc in the northwest. K-band scattered light imagery reveals a similar morphology, but with a clear third arc along the southwestern rim of the disk cavity. This arc meets the northwestern arc at nearly a right angle, revealing the presence of a spiral arm or local surface brightness deficit in the disk, and explaining the east-west brightness asymmetry in the H-band data. We also present 0.8-5.4 mu m IRTF SpeX spectra of this object, which allow us to constrain the spectral class to A0 +/- 1 and measure a low mass accretion rate of 10(-8.5) M-circle dot yr(-1), both consistent with previous estimates. We investigate a variety of reddening laws in order to fit the multiwavelength spectral energy distribution of Oph IRS 48 and find a best fit consistent with a younger, higher luminosity star than previous estimates.

  • 35. Galicher, R.
    et al.
    Boccaletti, A.
    Mesa, D.
    Delorme, P.
    Gratton, R.
    Langlois, M.
    Lagrange, A. -M.
    Maire, A. -L.
    Le Coroller, H.
    Chauvin, G.
    Biller, B.
    Cantalloube, F.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lagadec, E.
    Meunier, N.
    Vigan, A.
    Hagelberg, J.
    Bonnefoy, M.
    Zurlo, A.
    Rocha, S.
    Maurel, D.
    Jaquet, M.
    Buey, T.
    Weber, L.
    Astrometric and photometric accuracies in high contrast imaging: The SPHERE speckle calibration tool (SpeCal)2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 615, article id A92Article in journal (Refereed)
    Abstract [en]

    Context. The consortium of the Spectro-Polarimetric High-contrast Exoplanet REsearch installed at the Very Large Telescope (SPHERE/VLT) has been operating its guaranteed observation time (260 nights over five years) since February 2015. The main part of this time (200 nights) is dedicated to the detection and characterization of young and giant exoplanets on wide orbits. Aims. The large amount of data must be uniformly processed so that accurate and homogeneous measurements of photometry and astrometry can be obtained for any source in the field. Methods. To complement the European Southern Observatory pipeline, the SPHERE consortium developed a dedicated piece of software to process the data. First, the software corrects for instrumental artifacts. Then, it uses the speckle calibration tool (SpeCal) to minimize the stellar light halo that prevents us from detecting faint sources like exoplanets or circumstellar disks. SpeCal is meant to extract the astrometry and photometry of detected point-like sources (exoplanets, brown dwarfs, or background sources). SpeCal was intensively tested to ensure the consistency of all reduced images (cADI, Loci, TLoci, PCA, and others) for any SPHERE observing strategy (ADI, SDI, ASDI as well as the accuracy of the astrometry and photometry of detected point-like sources. Results. SpeCal is robust, user friendly, and efficient at detecting and characterizing point-like sources in high contrast images. It is used to process all SPHERE data systematically, and its outputs have been used for most of the SPHERE consortium papers to date. SpeCal is also a useful framework to compare different algorithms using various sets of data (different observing modes and conditions). Finally, our tests show that the extracted astrometry and photometry are accurate and not biased.

  • 36. Garcia, E. Victor
    et al.
    Currie, Thayne
    Guyon, Olivier
    Stassun, Keivan G.
    Jovanovic, Nemanja
    Lozi, Julien
    Kudo, Tomoyuki
    Doughty, Danielle
    Schlieder, Josh
    Kwon, J.
    Uyama, T.
    Kuzuhara, M.
    Carson, J. C.
    Nakagawa, T.
    Hashimoto, J.
    Kusakabe, N.
    Abe, L.
    Brandner, W.
    Brandt, T. D.
    Feldt, M.
    Goto, M.
    Grady, C. A.
    Hayano, Y.
    Hayashi, M.
    Hayashi, S. S.
    Henning, T.
    Hodapp, K. W.
    Ishii, M.
    Iye, M.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Kandori, R.
    Knapp, G. R.
    Matsuo, T.
    McElwain, M. W.
    Miyama, S.
    Morino, J. -I.
    Moro-Martin, A.
    Nishimura, T.
    Pyo, T. -S.
    Serabyn, E.
    Suenaga, T.
    Suto, H.
    Suzuki, R.
    Takahashi, Y. H.
    Takami, H.
    Takami, M.
    Takato, N.
    Terada, H.
    Thalmann, C.
    Turner, E. L.
    Watanabe, M.
    Wisniewski, J.
    Yamada, T.
    Usuda, T.
    Tamura, M.
    SCExAO AND GPI Y JH BAND PHOTOMETRY AND INTEGRAL FIELD SPECTROSCOPY OF THE YOUNG BROWN DWARF COMPANION TO HD 11602017In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 834, no 2, article id 162Article in journal (Refereed)
    Abstract [en]

    We present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957-1.120 mu m) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5(-0.5)(+1.0), where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000-3100 K, a surface gravity of log g - 4-4.5, a radius of. 1.55 +/- 0.10 R-J, and a luminosity of log L/L circle dot - 2.76 +/- 0.05. Neither the primary's Hertzspring-Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a subsolar metallicity. Interpretation of the HD 1160 B spectroscopy depends on which stellar system components are used to estimate the age. Considering HD 1160 A, B and C jointly, we derive an age of 80-125 Myr, implying that HD 1160 B straddles the hydrogen-burning limit (70-90 M-J) If we consider HD 1160 A alone, younger ages (20-125 Myr) and a brown dwarf-like mass (35-90 M-J) are possible. Interferometric measurements of the primary, a precise Gaia parallax, and moderate-resolution spectroscopy can better constrain the system's age and how HD 1160 B fits within the context of (sub) stellar evolution.

  • 37. Garufi, A.
    et al.
    Quanz, S. P.
    Schmid, H. M.
    Mulders, G. D.
    Avenhaus, H.
    Boccaletti, A.
    Ginski, C.
    Langlois, M.
    Stolker, T.
    Augereau, J. -C.
    Benisty, M.
    Lopez, B.
    Dominik, C.
    Gratton, R.
    Henning, T.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany.
    Menard, F.
    Meyer, M. R.
    Pinte, C.
    Sissa, E.
    Vigan, A.
    Zurlo, A.
    Bazzon, A.
    Buenzli, E.
    Bonnefoy, M.
    Brandner, W.
    Chauvin, G.
    Cheetham, A.
    Cudel, M.
    Desidera, S.
    Feldt, M.
    Galicher, R.
    Kasper, M.
    Lagrange, A. -M.
    Lannier, J.
    Maire, A. L.
    Mesa, D.
    Mouillet, D.
    Peretti, S.
    Perrot, C.
    Salter, G.
    Wildi, F.
    The SPHERE view of the planet-forming disk around HD 1005462016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 588, article id A8Article in journal (Refereed)
    Abstract [en]

    Context. The mechanisms governing planet formation are not fully understood. A new era of high-resolution imaging of protoplanetary disks has recently started, thanks to new instruments such as SPHERE, GPI, and ALMA. The planet formation process can now be directly studied by imaging both planetary companions embedded in disks and their e ff ect on disk morphology. Aims. We image disk features that could be potential signs of planet-disk interaction with unprecedented spatial resolution and sensitivity. Two companion candidates have been claimed in the disk around the young Herbig Ae /Be star HD 100546. Thus, this object serves as an excellent target for our investigation of the natal environment of giant planets. Methods. We exploit the power of extreme adaptive optics operating in conjunction with the new high-contrast imager SPHERE to image HD 100546 in scattered light. We obtained the first polarized light observations of this source in the visible (with resolution as fine as 2 AU) and new H and K band total intensity images that we analyzed with the p y n p o i n t package. Results. The disk shows a complex azimuthal morphology, where multiple scattering of photons most likely plays an important role. High brightness contrasts and arm-like structures are ubiquitous in the disk. A double-wing structure (partly due to angular di ff erential imaging processing) resembles a morphology newly observed in inclined disks. Given the cavity size in the visible (11 AU), the CO emission associated to the planet candidate c might arise from within the circumstellar disk. We find an extended emission in the K band at the expected location of b. The surrounding large-scale region is the brightest in scattered light. There is no sign of any disk gap associated to b.

  • 38. Grady, C.
    et al.
    Fukagawa, M.
    Maruta, Y.
    Ohta, Y.
    Wisniewski, J.
    Hashimoto, J.
    Okamoto, Y.
    Momose, M.
    Currie, T.
    McElwain, M.
    Muto, T.
    Kotani, T.
    Kusakabe, N.
    Feldt, M.
    Sitko, M.
    Follette, K.
    Bonnefoy, M.
    Henning, T.
    Takami, M.
    Karr, J.
    Kwon, J.
    Kudo, T.
    Abe, L.
    Brandner, W.
    Brandt, T.
    Carson, J.
    Egner, S.
    Goto, M.
    Guyon, O.
    Hayano, Y.
    Hayashi, M.
    Hayashi, S.
    Hodapp, K.
    Ishii, M.
    Iye, M.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Kandori, R.
    Knapp, G.
    Kuzuhara, M.
    Matsuo, T.
    Miyama, S.
    Morino, J. -I
    Moro-Martin, A.
    Nishimura, T.
    Pyo, T. -S
    Serabyn, E.
    Suenaga, T.
    Suto, H.
    Suzuki, R.
    Takahashi, Y. H.
    Takato, N.
    Terada, H.
    Thalmann, C.
    Tomono, D.
    Turner, E. L.
    Watanabe, M.
    Yamada, T.
    Takami, H.
    Usuda, T.
    Tamura, M.
    The outer disks of Herbig stars from the UV to NIR2015In: Astrophysics and Space Science, ISSN 0004-640X, E-ISSN 1572-946X, Vol. 355, no 2, p. 253-266Article, review/survey (Refereed)
    Abstract [en]

    Spatially-resolved imaging of Herbig stars and related objects began with HST, but intensified with commissioning of high-contrast imagers on 8-m class telescopes. The bulk of the data taken from the ground have been polarized intensity imagery at H-band, with the majority of the sources observed as part of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) survey. Sufficiently many systems have been imaged that we discuss disk properties in scattered, polarized light in terms of groups defined by the IR spectral energy distribution. We find novel phenomena in many of the disks, including spiral density waves, and discuss the disks in terms of clearing mechanisms. Some of the disks have sufficient data to map the dust and gas components, including water ice dissociation products.

  • 39. Grandjean, A.
    et al.
    Lagrange, A-M
    Beust, H.
    Rodet, L.
    Milli, J.
    Rubini, P.
    Babusiaux, C.
    Meunier, N.
    Delorme, P.
    Aigrain, S.
    Zicher, N.
    Bonnefoy, M.
    Biller, B. A.
    Baudino, J-L
    Bonavita, M.
    Boccaletti, A.
    Cheetham, A.
    Girard, J. H.
    Hagelberg, J.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lannier, J.
    Lazzoni, C.
    Ligi, R.
    Maire, A-L
    Mesa, D.
    Perrot, C.
    Rouan, D.
    Zurlo, A.
    Constraining the properties of HD 206893 B A combination of radial velocity, direct imaging, and astrometry data2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 627, article id L9Article in journal (Refereed)
    Abstract [en]

    Context. High contrast imaging enables the determination of orbital parameters for substellar companions (planets, brown dwarfs) from the observed relative astrometry and the estimation of model and age-dependent masses from their observed magnitudes or spectra. Combining astrometric positions with radial velocity gives direct constraints on the orbit and on the dynamical masses of companions. A brown dwarf was discovered with the VLT/SPHERE instrument at the Very Large Telescope (VLT) in 2017, which orbits at similar to 11 au around HD 206893. Its mass was estimated between 12 and 50 M-J from evolutionary models and its photometry. However, given the significant uncertainty on the age of the system and the peculiar spectrophotometric properties of the companion, this mass is not well constrained. Aims. We aim at constraining the orbit and dynamical mass of HD 206893 B. Methods. We combined radial velocity data obtained with HARPS spectra and astrometric data obtained with the high contrast imaging VLT/SPHERE and VLT/NaCo instruments, with a time baseline less than three years. We then combined those data with astrometry data obtained by HIPPARCOS and Gaia with a time baseline of 24 yr. We used a Markov chain Monte Carlo approach to estimate the orbital parameters and dynamical mass of the brown dwarf from those data. Results. We infer a period between 21 and 33 yr and an inclination in the range 20-41 degrees from pole-on from HD 206893 B relative astrometry. The RV data show a significant RV drift over 1.6 yr. We show that HD 206893 B cannot be the source of this observed RV drift as it would lead to a dynamical mass inconsistent with its photometry and spectra and with HIPPARCOS and Gaia data. An additional inner (semimajor axis in the range 1.4-2.6 au) and massive (similar to 15 M-J) companion is needed to explain the RV drift, which is compatible with the available astrometric data of the star, as well as with the VLT/SPHERE and VLT/NaCo nondetection.

  • 40. Gratton, R.
    et al.
    Ligi, R.
    Sissa, E.
    Desidera, S.
    Mesa, D.
    Bonnefoy, M.
    Chauvin, G.
    Cheetham, A.
    Feldt, M.
    Lagrange, A. M.
    Langlois, M.
    Meyer, M.
    Vigan, A.
    Boccaletti, A.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany.
    Lazzoni, C.
    Zurlo, A.
    De Boer, J.
    Henning, T.
    D'Orazi, V
    Gluck, L.
    Madec, F.
    Jaquet, M.
    Baudoz, P.
    Fantinel, D.
    Pavlov, A.
    Wildi, F.
    Blobs, spiral arms, and a possible planet around HD 1691422019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 623, article id A140Article in journal (Refereed)
    Abstract [en]

    Context. Young planets are expected to cause cavities, spirals, and kinematic perturbations in protostellar disks that may be used to infer their presence. However, a clear detection of still-forming planets embedded within gas-rich disks is still rare.

    Aims. HD169142 is a very young Herbig Ae-Be star surrounded by a pre-transitional disk, composed of at least three rings. While claims of sub-stellar objects around this star have been made previously, follow-up studies remain inconclusive. The complex structure of this disk is not yet well understood.

    Methods. We used the high contrast imager SPHERE at ESO Very large Telescope to obtain a sequence of high-resolution, high-contrast images of the immediate surroundings of this star over about three years in the wavelength range 0.95-2.25 mu m. This enables a photometric and astrometric analysis of the structures in the disk.

    Results. While we were unable to definitively confirm the previous claims of a massive sub-stellar object at 0.1-0.15 arcsec from the star, we found both spirals and blobs within the disk. The spiral pattern may be explained as due to the presence of a primary, a secondary, and a tertiary arm excited by a planet of a few Jupiter masses lying along the primary arm, likely in the cavities between the rings. The blobs orbit the star consistently with Keplerian motion, allowing a dynamical determination of the mass of the star. While most of these blobs are located within the rings, we found that one of them lies in the cavity between the rings, along the primary arm of the spiral design.

    Conclusions. This blob might be due to a planet that might also be responsible for the spiral pattern observed within the rings and for the cavity between the two rings. The planet itself is not detected at short wavelengths, where we only see a dust cloud illuminated by stellar light, but the planetary photosphere might be responsible for the emission observed in the K1 and K2 bands. The mass of this putative planet may be constrained using photometric and dynamical arguments. While uncertainties are large, the mass should be between 1 and 4 Jupiter masses. The brightest blobs are found at the 1:2 resonance with this putative planet.

  • 41. Helminiak, K. G.
    et al.
    Kuzuhara, M.
    Mede, K.
    Brandt, T. D.
    Kandori, R.
    Suenaga, T.
    Kusakabe, N.
    Narita, N.
    Carson, J. C.
    Currie, T.
    Kudo, T.
    Hashimoto, J.
    Abe, L.
    Akiyama, E.
    Brandner, W.
    Feldt, M.
    Goto, M.
    Grady, C. A.
    Guyon, O.
    Hayano, Y.
    Hayashi, M.
    Hayashi, S. S.
    Henning, T.
    Hodapp, K. W.
    Ishii, M.
    Iye, M.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Knapp, G. R.
    Kwon, J.
    Matsuo, T.
    McElwain, M. W.
    Miyama, S.
    Morino, J. -I.
    Moro-Martin, A.
    Nishimura, T.
    Ryu, T.
    Pyo, T. -S.
    Serabyn, E.
    Suto, H.
    Suzuki, R.
    Takahashi, Y. H.
    Takami, M.
    Takato, N.
    Terada, H.
    Thalmann, C.
    Turner, E. L.
    Watanabe, M.
    Wisniewski, J.
    Yamada, T.
    Takami, H.
    Usuda, T.
    Tamura, M.
    SEEDS DIRECT IMAGING OF THE RV-DETECTED COMPANION TO V450 ANDROMEDAE, AND CHARACTERIZATION OF THE SYSTEM2016In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 832, no 1, article id 33Article in journal (Refereed)
    Abstract [en]

    We report the direct imaging detection of a low-mass companion to a young, moderately active star V450. And, that was previously identified with the radial velocity (RV) method. The companion was found in high-contrast images obtained with the Subaru Telescope equipped with the HiCIAO camera and AO188 adaptive optics system. From the public ELODIE and SOPHIE archives we extracted available high-resolution spectra and RV measurements, along with RVs from the Lick planet search program. We combined our multi-epoch astrometry with these archival, partially unpublished RVs, and found that the companion is a low-mass star, not a brown dwarf, as previously suggested. We found the best-fitting dynamical masses to be m(1) = 1.141(-0.091)(+0.037)and m(2) = 0.279(-0.020)(+0.023) M-circle dot. We also performed spectral analysis of the SOPHIE spectra with the iSpec code. Hipparcos time-series photometry shows a periodicity of P = 5.743 day, which is also seen in the SOPHIE spectra as an RV modulation of the star A. We interpret it as being caused by spots on the stellar surface, and the star to be rotating with the given period. From the rotation and level of activity, we found that the system is 380(-100)(+220) Myr old, consistent with an isochrone analysis (220(-90)(+2120) Myr). This work may serve as a test case for future studies of low-mass stars, brown dwarfs, and exoplanets by combination of RV and direct imaging data.

  • 42.
    Janson, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Asensio-Torres, Ruben
    Stockholm University, Faculty of Science, Department of Astronomy.
    André, Damien
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bonnefoy, Mickaël
    Delorme, Philippe
    Reffert, Sabine
    Desidera, Silvano
    Langlois, Maud
    Chauvin, Gaël
    Gratton, Raffaele
    Bohn, Alexander J.
    Eriksson, Simon C.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Marleau, Gabriel-Dominique
    Mamajek, Eric E.
    Vigan, Arthur
    Carson, Joseph C.
    The B-Star Exoplanet Abundance Study: a co-moving 16-25 M-Jup companion to the young binary system HIP 790982019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 626, article id A99Article in journal (Refereed)
    Abstract [en]

    Wide low-mass substellar companions are known to be very rare among low-mass stars, but appear to become increasingly common with increasing stellar mass. However, B-type stars, which are the most massive stars within similar to 150 pc of the Sun, have not yet been examined to the same extent as AFGKM-type stars in that regard. In order to address this issue, we launched the ongoing B-star Exoplanet Abundance Study (BEAST) to examine the frequency and properties of planets, brown dwarfs, and disks around B-type stars in the Scorpius-Centaurus (Sco-Cen) association; we also analyzed archival data of B-type stars in Sco-Cen. During this process, we identified a candidate substellar companion to the B9-type spectroscopic binary HIP 79098 AB, which we refer to as HIP 79098 (AB)b. The candidate had been previously reported in the literature, but was classified as a background contaminant on the basis of its peculiar colors. Here we demonstrate that the colors of HIP 79098 (AB)b are consistent with several recently discovered young and low-mass brown dwarfs, including other companions to stars in Sco-Cen. Furthermore, we show unambiguous common proper motion over a 15-yr baseline, robustly identifying HIP 79098 (AB)b as a bona fide substellar circumbinary companion at a 345 +/- 6 AU projected separation to the B9-type stellar pair. With a model-dependent mass of 16-25 M-Jup yielding a mass ratio of <1%, HIP 79098 (AB)b joins a growing number of substellar companions with planet-like mass ratios around massive stars. Our observations underline the importance of common proper motion analysis in the identification of physical companionship, and imply that additional companions could potentially remain hidden in the archives of purely photometric surveys.

  • 43.
    Janson, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany; Queen's University Belfast, United Kingdom .
    Bergfors, Carolina
    Brandner, Wolfgang
    Bonnefoy, Mickael
    Schlieder, Joshua
    Koehler, Rainer
    Hormuth, Felix
    Henning, Thomas
    Hippler, Stefan
    ORBITAL MONITORING OF THE ASTRALUX LARGE M-DWARF MULTIPLICITY SAMPLE2014In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 214, no 2, p. 17-Article in journal (Refereed)
    Abstract [en]

    Orbital monitoring of M-type binaries is essential for constraining their fundamental properties. This is particularly useful in young systems, where the extended pre-main-sequence evolution can allow for precise isochronal dating. Here, we present the continued astrometric monitoring of the more than 200 binaries of the AstraLux Large Multiplicity Survey, building both on our previous work, archival data, and new astrometric data spanning the range of 2010-2012. The sample is very young overall-all included stars have known X-ray emission, and a significant fraction (18%) of them have recently also been identified as members of young moving groups in the solar neighborhood. We identify similar to 30 targets that both have indications of being young and for which an orbit either has been closed or appears possible to close in a reasonable time frame (a few years to a few decades). One of these cases, GJ 4326, is, however, identified as probably being substantially older than has been implied from its apparent moving group membership, based on astrometric and isochronal arguments. With further astrometric monitoring, these targets will provide a set of empirical isochrones, against which theoretical isochrones can be calibrated, and which can be used to evaluate the precise ages of nearby young moving groups.

  • 44.
    Janson, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Durkan, Stephen
    Stockholm University, Faculty of Science, Department of Astronomy. Queens University Belfast, UK.
    Bonnefoy, Mickaël
    Rodet, Laetitia
    Köhler, Rainer
    Lacour, Sylvestre
    Brandner, Wolfgang
    Henning, Thomas
    Girard, Julien
    Dynamical masses of M-dwarf binaries in young moving groups II. Toward empirical mass-luminosity isochrones2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 620, article id A33Article in journal (Refereed)
    Abstract [en]

    Low-mass stars exhibit substantial pre-main sequence evolution during the first similar to 100 Myr of their lives. Thus, young M-type stars are prime targets for isochronal dating, especially in young moving groups (YMGs), which contain large amounts of stars in this mass and age range. If the mass and luminosity of a star can both be directly determined, this allows for a particularly robust isochronal analysis. This motivates in-depth studies of low-mass binaries with spatially resolvable orbits, where dynamical masses can be derived. Here we present the results of an observing campaign dedicated to orbital monitoring of AB Dor Ba/Bb, which is a close M-dwarf pair within the quadruple AB Dor system. We have acquired eight astrometric epochs with the SPHERE /ZIMPOL and NACO instruments, which we combine with literature data to improve the robustness and precision for the orbital characterization of the pair. We find a system mass 0.66(-0.12)(+0.12) M-circle dot and bolometric luminosities in log L/L-circle dot of 2 .02 +/- 0.02 and 2 .11 +/- 0.02 for AB Dor Ba and Bb, respectively. These measurements are combined with other YMG pairs in the literature to start building a framework of empirical isochrones in mass-luminosity space. This can be used to calibrate theoretical isochrones and to provide a model-free basis for assessing relative stellar ages. We note a tentative emerging trend where the youngest moving group members are largely consistent with theoretical expectations, while stars in older associations such as the AB Dor moving group appear to be systematically underluminous relative to isochronal expectations.

  • 45.
    Janson, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Durkan, Stephen
    Hippler, Stefan
    Dai, Xiaolin
    Brandner, Wolfgang
    Schlieder, Joshua
    Bonnefoy, Mickael
    Henning, Thomas
    Binaries among low-mass stars in nearby young moving groups2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 599, article id A70Article in journal (Refereed)
    Abstract [en]

    The solar galactic neighborhood contains a number of young co-moving associations of stars (known as young moving groups) with ages of similar to 10-150 Myr, which are prime targets for a range of scientific studies, including direct imaging planet searches. The latetype stellar populations of such groups still remain in their pre-main sequence phase, and are thus well suited for purposes such as isochronal dating. Close binaries are particularly useful in this regard since they allow for a model-independent dynamical mass determination. Here we present a dedicated e ff ort to identify new close binaries in nearby young moving groups, through highresolution imaging with the AstraLux Sur Lucky Imaging camera. We surveyed 181 targets, resulting in the detection of 61 companions or candidates, of which 38 are new discoveries. An interesting example of such a case is 2MASS J00302572-6236015 AB, which is a high-probability member of the Tucana-Horologium moving group, and has an estimated orbital period of less than 10 yr. Among the previously known objects is a serendipitous detection of the deuterium burning boundary circumbinary companion 2MASS J01033563-5515561 (AB)b in the z' band, thereby extending the spectral coverage for this object down to near-visible wavelengths.

  • 46.
    Janson, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Quanz, Sascha P.
    Carson, Joseph C.
    Thalmann, Christian
    Lafreniere, David
    Amara, Adam
    High-contrast imaging with Spitzer: deep observations of Vega, Fomalhaut, and is an element of Eridani2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 574, article id A120Article in journal (Refereed)
    Abstract [en]

    Stars with debris disks are intriguing targets for direct imaging exoplanet searches, owing both to previous detections of wide planets in debris disk systems. and to commonly existing morphological features in the disks themselves that may be indicative of a planetary influence. Here we present observations of three of the most nearby young stars, which are also known to host massive debris disks: Vega. Fomalhaut, and c Fri. The Spitzer Space Telescope is used at a range of orientation angles for each star to supply a deep conumst through angular differential imaging combined with high contrast algorithms. The observations provide the opportunity to probe substantially colder bound planets (120-330 I() than is possible with any other technique or instrument. For Vega, sonic apparently very red candidate point sources detected in the 4.5 pm image remain to be tested for common proper motion. The images are sensitive to similar to 2 M-JUP companions at 150 AU in this system. The observations presented here represent the first search for planets around Vega using Spitzer. The upper 4.5 mu m flux limit on Fomalhaut b could be further constrained relative to previous data ln the case of is an element of Ed, planets below both the effective temperature and the mass of Jupiter could be probed from 80 AU and outward, although no such planets were found. The data sensitively probe the regions around the edges of the debris rings in the systems where planets can be expected to reside. These observations validate previous results showing that more than an order of magnitude improvement in performance in the contrast -limited regime can be acquired with respect to conventional methods by applying sophisticated high contrast techniques to space based telescopes, thanks to the high degree of PSF stability provided in this environment.

  • 47.
    Janson, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Thalmann, Christian
    Boccaletti, Anthony
    Maire, Anne-Lise
    Zurlo, Alice
    Marzari, Francesco
    Meyer, Michael R.
    Carson, Joseph C.
    Augereau, Jean-Charles
    Garufi, Antonio
    Henning, Thomas
    Desidera, Silvano
    Asensio-Torres, Ruben
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pohl, Adriana
    DETECTION OF SHARP SYMMETRIC FEATURES IN THE CIRCUMBINARY DISK AROUND AK Sco2016In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 816, no 1, article id L1Article in journal (Refereed)
    Abstract [en]

    The Search for Planets Orbiting Two Stars survey aims to study the formation and distribution of planets in binary systems by detecting and characterizing circumbinary planets and their formation environments through direct imaging. With the SPHERE Extreme Adaptive Optics instrument, a good contrast can be achieved even at small (< 300 mas) separations from bright stars, which enables studies of planets and disks in a separation range that was previously inaccessible. Here, we report the discovery of resolved scattered light emission from the circumbinary disk around the well-studied young double star AK. Sco, at projected separations in the similar to 13-40 AU range. The sharp morphology of the imaged feature is surprising, given the smooth appearance of the disk in its spectral energy distribution. We show that the observed morphology can be represented either as a highly eccentric ring around AK Sco, or as two separate spiral arms in the disk, wound in opposite directions. The relative merits of these interpretations are discussed, as well as whether these features may have been caused by one or several circumbinary planets interacting with the disk.

  • 48. Keppler, M.
    et al.
    Benisty, M.
    Mueller, A.
    Henning, Th.
    van Boekel, R.
    Cantalloube, F.
    Ginski, C.
    van Holstein, R. G.
    Maire, A. -L.
    Pohl, A.
    Samland, M.
    Avenhaus, H.
    Baudino, J. -L.
    Boccaletti, A.
    de Boer, J.
    Bonnefoy, M.
    Chauvin, G.
    Desidera, S.
    Langlois, M.
    Lazzoni, C.
    Marleau, G. -D.
    Mordasini, C.
    Pawellek, N.
    Stolker, T.
    Vigan, A.
    Zurlo, A.
    Birnstiel, T.
    Brandner, W.
    Feldt, M.
    Flock, M.
    Girard, J.
    Gratton, R.
    Hagelberg, J.
    Isella, A.
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Max Planck Institute for Astronomy, Germany.
    Juhasz, A.
    Kemmer, J.
    Kral, Q.
    Lagrange, A. -M.
    Launhardt, R.
    Matter, A.
    Menard, F.
    Milli, J.
    Molliere, P.
    Olofsson, J.
    Perez, L.
    Pinilla, P.
    Pinte, C.
    Quanz, S. P.
    Schmidt, T.
    Udry, S.
    Wahhaj, Z.
    Williams, J. P.
    Buenzli, E.
    Cudel, M.
    Dominik, C.
    Galicher, R.
    Kasper, M.
    Lannier, J.
    Mesa, D.
    Mouillet, D.
    Peretti, S.
    Perrot, C.
    Salter, G.
    Sissa, E.
    Wildi, F.
    Abe, L.
    Antichi, J.
    Augereau, J. -C.
    Baruffolo, A.
    Baudoz, P.
    Bazzon, A.
    Beuzit, J. -L.
    Blanchard, P.
    Brems, S. S.
    Buey, T.
    De Caprio, V.
    Carbillet, M.
    Carle, M.
    Cascone, E.
    Cheetham, A.
    Claudi, R.
    Costille, A.
    Delboulbe, A.
    Dohlen, K.
    Fantinel, D.
    Feautrier, P.
    Fusco, T.
    Giro, E.
    Gluck, L.
    Gry, C.
    Hubin, N.
    Hugot, E.
    Jaquet, M.
    Le Mignant, D.
    Llored, M.
    Madec, F.
    Magnard, Y.
    Martinez, P.
    Maurel, D.
    Meyer, M.
    Moeller-Nilsson, O.
    Moulin, T.
    Mugnier, L.
    Origne, A.
    Pavlov, A.
    Perret, D.
    Petit, C.
    Pragt, J.
    Puget, P.
    Rabou, P.
    Ramose, J.
    Rigal, F.
    Rochat, S.
    Roelfsema, R.
    Rousset, G.
    Roux, A.
    Salasnich, B.
    Sauvage, J. -F.
    Sevin, A.
    Soenke, C.
    Stadler, E.
    Suarez, M.
    Turatto, M.
    Weber, L.
    Discovery of a planetary-mass companion within the gap of the transition disk around PDS 702018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 617, article id A44Article in journal (Refereed)
    Abstract [en]

    Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features.

    Aims. In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of an embedded young planet and search for disk structures that may be the result of disk-planet interactions and other evolutionary processes.

    Methods. We analyse new and archival near-infrared images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo, and Gemini/NICI instruments in polarimetric differential imaging and angular differential imaging modes.

    Results. We detect a point source within the gap of the disk at about 195 mas (similar to 22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. The luminosity of the detected object is consistent with that of an L-type dwarf, but its IR colours are redder, possibly indicating the presence of warm surrounding material. Further, we confirm the detection of a large gap of similar to 54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than similar to 17 au in radius, and its position angle is consistent with that of the outer disk. The images of the outer disk show evidence of a complex azimuthal brightness distribution which is different at different wavelengths and may in part be explained by Rayleigh scattering from very small grains.

    Conclusions. The detection of a young protoplanet within the gap of the transition disk around PDS 70 opens the door to a so far observationally unexplored parameter space of planetary formation and evolution. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet-disk interactions, planetary atmospheres, and evolutionary models.

  • 49. Konishi, Mihoko
    et al.
    Matsuo, Taro
    Yamamoto, Kodai
    Samland, Matthias
    Sudo, Jun
    Shibai, Hiroshi
    Itoh, Yoichi
    Fukagawa, Misato
    Sumi, Takahiro
    Kudo, Tomoyuki
    Hashimoto, Jun
    Kuzuhara, Masayuki
    Kusakabe, Nobuhiko
    Abe, Lyu
    Akiyama, Eiji
    Brandner, Wolfgang
    Brandt, Timothy D.
    Carson, Joseph C.
    Feldt, Markus
    Goto, Miwa
    Grady, Carol A.
    Guyon, Olivier
    Hayano, Yutaka
    Hayashi, Masahiko
    Hayashi, Saeko S.
    Henning, Thomas
    Hodapp, Klaus W.
    Ishii, Miki
    Iye, Masanori
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Kandori, Ryo
    Knapp, Gillian R.
    Kwon, Jungmi
    McElwain, Michael W.
    Mede, Kyle
    Miyama, Shoken
    Morino, Jun-Ichi
    Moro-Martin, Amaya
    Nishimura, Tetsuo
    Oh, Daehyeon
    Pyo, Tae-Soo
    Serabyn, Eugene
    Schlieder, Joshua E.
    Suenaga, Takuya
    Suto, Hiroshi
    Suzuki, Ryuji
    Takahashi, Yasuhiro H.
    Takami, Michihiro
    Takato, Naruhisa
    Terada, Hiroshi
    Thalmann, Christian
    Turner, Edwin L.
    Watanabe, Makoto
    Wisniewski, John P.
    Yamada, Toru
    Takami, Hideki
    Usuda, Tomonori
    Tamura, Motohide
    A substellar companion to Pleiades HII 34412016In: Publications of the Astronomical Society of Japan, ISSN 0004-6264, Vol. 68, no 6, article id 92Article in journal (Refereed)
    Abstract [en]

    We find a new substellar companion to the Pleiades member star, Pleiades HII 3441, using the Subaru telescope with adaptive optics. The discovery is made as part of the high-contrast imaging survey to search for planetary-mass and substellar companions in the Pleiades and young moving groups. The companion has a projected separation of 0.'' 49 +/- 0.'' 02 (66 +/- 2 au) and a mass of 68 +/- 5 M-J based on three observations in the J-, H-, and K-s-bands. The spectral type is estimated to be M7 (similar to 2700 K), and thus no methane absorption is detected in the H band. Our Pleiades observations result in the detection of two substellar companions including one previously reported among 20 observed Pleiades stars, and indicate that the fraction of substellar companions in the Pleiades is about 10.0(-8.8)(+26.1)%. This is consistent with multiplicity studies of both the Pleiades stars and other open clusters.

  • 50. Kooistra, Robin
    et al.
    Kamp, Inga
    Fukagawa, Misato
    Menard, Franois
    Momose, Munetake
    Tsukagoshi, Takashi
    Kudo, Tomoyuki
    Kusakabe, Nobuhiko
    Hashimoto, Jun
    Abe, Lyu
    Brandner, Wolfgang
    Brandt, Timothy D.
    Carson, Joseph C.
    Egner, Sebastian E.
    Feldt, Markus
    Goto, Miwa
    Grady, Carol A.
    Guyon, Olivier
    Hayano, Yutaka
    Hayashi, Masahiko
    Hayashi, Saeko S.
    Henning, Thomas
    Hodapp, Klaus W.
    Ishii, Miki
    Iye, Masanori
    Janson, Markus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Kandori, Ryo
    Knapp, Gillian R.
    Kuzuhara, Masayuki
    Kwon, Jungmi
    Matsuo, Taro
    McElwain, Michael W.
    Miyama, Shoken
    Morino, Jun-Ichi
    Moro-Martin, Amaya
    Nishimura, Tetsuo
    Pyo, Tae-Soo
    Serabyn, Eugene
    Suenaga, Takuya
    Suto, Hiroshi
    Suzuki, Ryuji
    Takahashi, Yasuhiro H.
    Takami, Michihiro
    Takato, Naruhisa
    Terada, Hiroshi
    Thalmann, Christian
    Tomono, Daigo
    Turner, Edwin L.
    Watanabe, Makoto
    Wisniewski, John
    Yamada, Toru
    Takami, Hideki
    Usuda, Tomonori
    Tamura, Motohide
    Currie, Thayne
    Akiyama, Eiji
    Mayama, Satoshi
    Follette, Katherine B.
    Nakagawa, Takao
    Radial decoupling of small and large dust grains in the transitional disk RX J1615.3-32552017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 597, article id A132Article in journal (Refereed)
    Abstract [en]

    We present H-band (1.6 mu m) scattered light observations of the transitional disk RX J1615.3-3255, located in the similar to 1 Myr old Lupus association. From a polarized intensity image, taken with the HiCIAO instrument of the Subaru Telescope, we deduce the position angle and the inclination angle of the disk. The disk is found to extend out to 68 +/- 12 AU in scattered light and no clear structure is observed. Our inner working angle of 24 AU does not allow us to detect a central decrease in intensity similar to that seen at 30 AU in the 880 mu m continuum observations. We compare the observations with multiple disk models based on the spectral energy distribution (SED) and submm interferometry and find that an inner rim of the outer disk at 30 AU containing small silicate grains produces a polarized intensity signal which is an order of magnitude larger than observed. We show that a model in which the small dust grains extend smoothly into the cavity found for large grains is closer to the actual H-band observations. A comparison of models with di ff erent dust size distributions suggests that the dust in the disk might have undergone significant processing compared to the interstellar medium.

12 1 - 50 of 91
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