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Janson, M., Gratton, R., Rodet, L., Vigan, A., Bonnefoy, M., Delorme, P., . . . Carson, J. C. (2021). A wide-orbit giant planet in the high-mass b Centauri binary system. Nature, 600(7888)
Open this publication in new window or tab >>A wide-orbit giant planet in the high-mass b Centauri binary system
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2021 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 600, no 7888Article in journal (Refereed) Published
Abstract [en]

Planet formation occurs around a wide range of stellar masses and stellar system architectures1. An improved understanding of the formation process can be achieved by studying it across the full parameter space, particularly towards the extremes. Earlier studies of planets in close-in orbits around high-mass stars have revealed an increase in giant planet frequency with increasing stellar mass2 until a turnover point at 1.9 solar masses (M), above which the frequency rapidly decreases3. This could potentially imply that planet formation is impeded around more massive stars, and that giant planets around stars exceeding 3 M may be rare or non-existent. However, the methods used to detect planets in small orbits are insensitive to planets in wide orbits. Here we demonstrate the existence of a planet at 560 times the Sun–Earth distance from the 6- to 10-M binary b Centauri through direct imaging. The planet-to-star mass ratio of 0.10–0.17% is similar to the Jupiter–Sun ratio, but the separation of the detected planet is about 100 times wider than that of Jupiter. Our results show that planets can reside in much more massive stellar systems than what would be expected from extrapolation of previous results. The planet is unlikely to have formed in situ through the conventional core accretion mechanism4, but might have formed elsewhere and arrived to its present location through dynamical interactions, or might have formed via gravitational instability.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-201402 (URN)10.1038/s41586-021-04124-8 (DOI)000728238900014 ()34880428 (PubMedID)
Available from: 2022-02-08 Created: 2022-02-08 Last updated: 2022-02-25Bibliographically approved
D'Orazi, V., Gratton, R., Desidera, S., Avenhaus, H., Mesa, D., Stolker, T., . . . Zurlo, A. (2019). Mapping of shadows cast on a protoplanetary disk by a close binary system. Nature Astronomy, 3(2), 167-172
Open this publication in new window or tab >>Mapping of shadows cast on a protoplanetary disk by a close binary system
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2019 (English)In: Nature Astronomy, E-ISSN 2397-3366, Vol. 3, no 2, p. 167-172Article in journal (Refereed) Published
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.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-166744 (URN)10.1038/s41550-018-0626-6 (DOI)000458038800021 ()
Available from: 2019-03-18 Created: 2019-03-18 Last updated: 2022-02-26Bibliographically approved
Peretti, S., Segransan, D., Lavie, B., Desidera, S., Maire, A.-L., D'Orazi, V., . . . Wildi, F. (2019). Orbital and spectral analysis of the benchmark brown dwarf HD 4747B. Astronomy and Astrophysics, 631, Article ID A107.
Open this publication in new window or tab >>Orbital and spectral analysis of the benchmark brown dwarf HD 4747B
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2019 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 631, article id A107Article in journal (Refereed) Published
Abstract [en]

Context. The study of high-contrast imaged brown dwarfs and exoplanets depends strongly on evolutionary models. To estimate the mass of a directly imaged substellar object, its extracted photometry or spectrum is used and adjusted with model spectra together with the estimated age of the system. These models still need to be properly tested and constrained. HD 4747B is a brown dwarf close to the H burning mass limit, orbiting a nearby (d = 19.25 +/- 0.58 pc), solar-type star (G9V); it has been observed with the radial velocity method for over almost two decades. Its companion was also recently detected by direct imaging, allowing a complete study of this particular object.

Aims. We aim to fully characterize HD 4747B by combining a well-constrained dynamical mass and a study of its observed spectral features in order to test evolutionary models for substellar objects and to characterize its atmosphere.

Methods. We combined the radial velocity measurements of High Resolution Echelle Spectrometer (HIRES) and CORALIE taken over two decades and high-contrast imaging of several epochs from NACO, NIRC2, and SPHERE to obtain a dynamical mass. From the SPHERE data we obtained a low-resolution spectrum of the companion from Y to H band, and two narrow band-width photometric measurements in the K band. A study of the primary star also allowed us to constrain the age of the system and its distance.

Results. Thanks to the new SPHERE epoch and NACO archival data combined with previous imaging data and high-precision radial velocity measurements, we were able to derive a well-constrained orbit. The high eccentricity (e = 0.7362 +/- 0.0025) of HD 4747B is confirmed, and the inclination and the semi-major axis are derived (i = 47.3 +/- 1.6 degrees, a = 10.01 +/- 0.21 au). We derive a dynamical mass of m(B) = 70.0 +/- 1.6 M-Jup, which is higher than a previous study but in better agreement with the models. By comparing the object with known brown dwarfs spectra, we derive a spectral type of L9 and an effective temperature of 1350 +/- 50 K. With a retrieval analysis we constrain the oxygen and carbon abundances and compare them with the values from the HR 8799 planets.

Keywords
binaries: general, binaries: spectroscopic, binaries: visual, brown dwarfs, planets and satellites: atmospheres, techniques: high angular resolution
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-180673 (URN)10.1051/0004-6361/201732454 (DOI)000515095800001 ()
Available from: 2020-04-06 Created: 2020-04-06 Last updated: 2022-02-26Bibliographically approved
Mesa, D., Keppler, M., Cantalloube, F., Rodet, L., Charnay, B., Gratton, R., . . . Wildi, F. (2019). VLT/SPHERE exploration of the young multiplanetary system PDS70. Astronomy and Astrophysics, 632, Article ID A25.
Open this publication in new window or tab >>VLT/SPHERE exploration of the young multiplanetary system PDS70
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2019 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 632, article id A25Article in journal (Refereed) Published
Abstract [en]

Context. PDS 70 is a young (5.4 Myr), nearby (similar to 113 pc) star hosting a known transition disk with a large gap. Recent observations with SPHERE and NACO in the near-infrared (NIR) allowed us to detect a planetary mass companion, PDS 70 b, within the disk cavity. Moreover, observations in H-alpha with MagAO and MUSE revealed emission associated to PDS 70 b and to another new companion candidate, PDS 70 c, at a larger separation from the star. PDS 70 is the only multiple planetary system at its formation stage detected so far through direct imaging.

Aims. Our aim is to confirm the discovery of the second planet PDS 70 c using SPHERE at VLT, to further characterize its physical properties, and search for additional point sources in this young planetary system.

Methods. We re-analyzed archival SPHERE NIR observations and obtained new data in Y, J, H and K spectral bands for a total of four different epochs. The data were reduced using the data reduction and handling pipeline and the SPHERE data center. We then applied custom routines (e.g., ANDROMEDA and PACO) to subtract the starlight.

Results. We re-detect both PDS 70 b and c and confirm that PDS 70 c is gravitationally bound to the star. We estimate this second planet to be less massive than 5 M-Jup and with a T-eff around 900 K. Also, it has a low gravity with log g between 3.0 and 3.5 dex. In addition, a third object has been identified at short separation (similar to 0.12 '') from the star and gravitationally bound to the star. Its spectrum is however very blue, meaning that we are probably seeing stellar light reflected by dust and our analysis seems to demonstrate that it is a feature of the inner disk. We cannot however completely exclude the possibility that it is a planetary mass object enshrouded by a dust envelope. In this latter case, its mass should be of the order of a few tens of M-circle plus. Moreover, we propose a possible structure for the planetary system based on our data, and find that this structure cannot be stable on a long timescale.

Keywords
instrumentation: spectrographs, methods: data analysis, techniques: imaging spectroscopy, planetary systems, stars: individual: PDS70
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-180678 (URN)10.1051/0004-6361/201936764 (DOI)000515111200001 ()
Available from: 2020-04-06 Created: 2020-04-06 Last updated: 2022-02-26Bibliographically approved
Keppler, M., Benisty, M., Mueller, A., Henning, T., van Boekel, R., Cantalloube, F., . . . Weber, L. (2018). Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70. Astronomy and Astrophysics, 617, Article ID A44.
Open this publication in new window or tab >>Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70
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2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 617, article id A44Article in journal (Refereed) Published
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.

Keywords
stars: individual: PDS 70, techniques: high angular resolution, protoplanetary disks, scattering, radiative transfer, planets and satellites: detection
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-161084 (URN)10.1051/0004-6361/201832957 (DOI)000444604000003 ()
Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2022-02-26Bibliographically approved
Chauvin, G., Gratton, R., Bonnefoy, M., Lagrange, A.-M. -., de Boer, J., Vigan, A., . . . Rochat, S. (2018). Investigating the young solar system analog HD 95086 A combined HARPS and SPHERE exploration. Astronomy and Astrophysics, 617, Article ID A76.
Open this publication in new window or tab >>Investigating the young solar system analog HD 95086 A combined HARPS and SPHERE exploration
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2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 617, article id A76Article in journal (Refereed) Published
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.

Keywords
instrumentation: adaptive optics, instrumentation: high angular resolution, methods: observational, stars:individual: HD 95086, planet-disk interactions
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-161068 (URN)10.1051/0004-6361/201732077 (DOI)000444935300001 ()
Available from: 2018-11-05 Created: 2018-11-05 Last updated: 2022-02-26Bibliographically approved
Ligi, R., Vigan, A., Gratton, R., de Boer, J., Benisty, M., Boccaletti, A., . . . Weber, L. (2018). Investigation of the inner structures around HD 169142 with VLT/SPHERE. Monthly notices of the Royal Astronomical Society, 473(2), 1774-1783
Open this publication in new window or tab >>Investigation of the inner structures around HD 169142 with VLT/SPHERE
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2018 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 2, p. 1774-1783Article in journal (Refereed) Published
Abstract [en]

We present observations of the Herbig Ae star HD 169142 with the VLT/SPHERE instruments InfraRed Dual-band Imager and Spectrograph (IRDIS) (K1K2 and H2H3 bands) and the Integral Field Spectrograph (IFS) (Y, J and H bands). We detect several bright blobs at similar to 180 mas separation from the star, and a faint arc-like structure in the IFS data. Our reference differential imaging (RDI) data analysis also finds a bright ring at the same separation. We show, using a simulation based on polarized light data, that these blobs are actually part of the ring at 180 mas. These results demonstrate that the earlier detections of blobs in the H and K-S bands at these separations in Biller et al. as potential planet/substellar companions are actually tracing a bright ring with a Keplerian motion. Moreover, we detect in the images an additional bright structure at similar to 93 mas separation and position angle of 355 degrees, at a location very close to previous detections. It appears point-like in the YJ and K bands but is more extended in the H band. We also marginally detect an inner ring in the RDI data at similar to 100 mas. Follow-up observations are necessary to confirm the detection and the nature of this source and structure.

Keywords
Stars: individual: HD169142, Planets and satellites: detection, formation, Techniques: high angular resolution, Protoplanetary disc
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-153890 (URN)10.1093/mnras/stx2318 (DOI)000423731200027 ()
Available from: 2018-03-07 Created: 2018-03-07 Last updated: 2022-02-28Bibliographically approved
Mueller, A., Keppler, M., Henning, T., Samland, M., Chauvin, G., Beust, H., . . . Zurlo, A. (2018). Orbital and atmospheric characterization of the planet within the gap of the PDS70 transition disk. Astronomy and Astrophysics, 617, Article ID L2.
Open this publication in new window or tab >>Orbital and atmospheric characterization of the planet within the gap of the PDS70 transition disk
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2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 617, article id L2Article in journal (Refereed) Published
Abstract [en]

Context. The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. This discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation.

Aims. We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in the course of the SHINE survey with SPHERE, the extreme adaptive-optics instrument at the VLT.

Methods. We obtained new deep SPHERE/IRDIS imaging and SPHERE/IFS spectroscopic observations of PDS 70 b. The astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. For the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96-3.8 mu m). We use different atmospheric models covering a large parameter space in temperature, log g, chemical composition, and cloud properties to characterize the properties of the atmosphere of PDS 70 b.

Results. PDS 70 b is most likely orbiting the star on a circular and disk coplanar orbit at similar to 22 au inside the gap of the disk. We find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000-1600 K and log g no larger than 3.5 dex. The planet radius covers a relatively large range between 1.4 and 3.7 R-J with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 Myr.

Conclusions. This study provides a comprehensive data set on the orbital motion of PDS 70 b, indicating a circular orbit and a motion coplanar with the disk. The first detailed spectral energy distribution of PDS 70 b indicates a temperature typical of young giant planets. The detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux.

Keywords
planets and satellites: atmospheres, planets and satellites: individual: PDS 70, techniques: spectroscopic, astrometry, methods: observational
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-161082 (URN)10.1051/0004-6361/201833584 (DOI)000444602500002 ()
Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2022-02-26Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5902-7828

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