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  • 1. Biver, Nicolas
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Radio observations of Comet 9P/Tempel 1 before and after Deep Impact2007In: Icarus, Vol. 187, no 1, p. 253-271Article in journal (Refereed)
  • 2. Biver, Nicolas
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Radio observations of Comet 9P/Tempel 1 before and after Deep Impact2007In: Icarus (Supplement), Vol. 191, no 2, p. 494-512Article in journal (Refereed)
  • 3. Biver, Nicolas
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    Submillimetre observations of comets with Odin: 2001 20052007In: Planetary and Space Science, Vol. 55, no 9, p. 1058-1068Article in journal (Refereed)
    Abstract [en]

    The Odin satellite, launched in February 2001, is equipped with a 1.1-m submillimetre telescope. Odin was used to observe the 557 GHz line of water with high spectral resolution in 12 comets between 2001 and 2005. Line shapes and spatial mapping provide information on the anisotropy of the outgassing and constraints on water excitation, enabling accurate measurements of the water production rate. Five comets were regularly observed over periods of more than one month to monitor the variation of their water outgassing rate with heliocentric distance. Observing campaigns have been generally coordinated with ground-based observations of molecular lines at Nançay, CSO or IRAM 30-m telescopes to obtain molecular abundances relative to water. Thanks to Odin's frequency coverage, it was also possible to detect the H218O 548 GHz line, first in comet 153P/Ikeya Zhang in April 2002 [Lecacheux, A., Biver, N., Crovisier, J. et al., 2003, Observations of water in comets with Odin. Astron. Astrophys. 402, L55 L58.] and then in comets C/2002 T7 (LINEAR), C/2001 Q4 (NEAT) and C/2004 Q2 (Machholz). The 16O/18O isotopic ratio (≈450) is consistent with the terrestrial value. Ammonia has been searched for in three comets through its J=1 0 line at 572 GHz and was tentatively detected in C/2001 Q4 and C/2002 T7. The derived abundances of NH3 relative to water are 0.5% and 0.3%, respectively, similar to values obtained in other comets with different techniques.

  • 4. Chauvin, M.
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Friis, M.
    Jackson, M.
    Kamae, T.
    Kataoka, J.
    Kawano, T.
    Kiss, M.
    Mikhalev, V.
    Mizuno, T.
    Ohashi, N.
    Stana, T.
    Tajima, H.
    Takahashi, H.
    Uchida, N.
    Pearce, M.
    Shedding new light on the Crab with polarized X-rays2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 7816Article in journal (Refereed)
    Abstract [en]

    Strong magnetic fields, synchrotron emission, and Compton scattering are omnipresent in compact celestial X-ray sources. Emissions in the X-ray energy band are consequently expected to be linearly polarized. X-ray polarimetry provides a unique diagnostic to study the location and fundamental mechanisms behind emission processes. The polarization of emissions from a bright celestial X-ray source, the Crab, is reported here for the first time in the hard X-ray band (similar to 20-160 keV). The Crab is a complex system consisting of a central pulsar, a diffuse pulsar wind nebula, as well as structures in the inner nebula including a jet and torus. Measurements are made by a purpose-built and calibrated polarimeter, PoGO+. The polarization vector is found to be aligned with the spin axis of the pulsar for a polarization fraction, PF = (20.9 +/- 5.0)%. This is higher than that of the optical diffuse nebula, implying a more compact emission site, though not as compact as, e.g., the synchrotron knot. Contrary to measurements at higher energies, no significant temporal evolution of phase-integrated polarisation parameters is observed. The polarization parameters for the pulsar itself are measured for the first time in the X-ray energy band and are consistent with observations at optical wavelengths.

  • 5. Chauvin, M.
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Jackson, M.
    Kamae, T.
    Kawano, T.
    Kiss, M.
    Kole, M.
    Mikhalev, V.
    Moretti, E.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Rydström, S.
    Takahashi, H.
    Iyudin, A.
    Arimoto, M.
    Fukazawa, Y.
    Kataoka, J.
    Kawai, N.
    Mizuno, T.
    Ryde, F.
    Tajima, H.
    Takahashi, T.
    Pearce, M.
    Observation of polarized hard X-ray emission from the Crab by the PoGOLite Pathfinder2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 456, no 1, p. l84-L88Article in journal (Refereed)
    Abstract [en]

    We have measured the linear polarization of hard X-ray emission from the Crab in a previously unexplored energy interval, 20-120 keV. The introduction of two new observational parameters, the polarization fraction and angle stands to disentangle geometrical and physical effects, thereby providing information on the pulsar wind geometry and magnetic field environment. Measurements are conducted using the PoGOLite Pathfinder - a balloon-borne polarimeter. Polarization is determined by measuring the azimuthal Compton scattering angle of incident X-rays in an array of plastic scintillators housed in an anticoincidence well. The polarimetric response has been characterized prior to flight using both polarized and unpolarized calibration sources. We address possible systematic effects through observations of a background field. The measured polarization fraction for the integrated Crab light curve is 18.4(-10.6)(+9.8) per cent, corresponding to an upper limit (99 per cent credibility) of 42.4 per cent, for a polarization angle of (149.2 +/- 16.0)degrees.

  • 6. Chauvin, M.
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Jackson, M.
    Kamae, T.
    Kawano, T.
    Kiss, M.
    Kole, M.
    Mikhalev, V.
    Moretti, E.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Rydström, S.
    Takahashi, H.
    Lind, J.
    Strömberg, J. -E.
    Welin, O.
    Iyudin, A.
    Shifrin, D.
    Pearce, M.
    The design and flight performance of the PoGOLite Pathfinder balloon-borne hard X-ray polarimeter2016In: Experimental astronomy (Print), ISSN 0922-6435, E-ISSN 1572-9508, Vol. 41, no 1, p. 17-41Article in journal (Refereed)
    Abstract [en]

    In the 50 years since the advent of X-ray astronomy there have been many scientific advances due to the development of new experimental techniques for detecting and characterising X-rays. Observations of X-ray polarisation have, however, not undergone a similar development. This is a shortcoming since a plethora of open questions related to the nature of X-ray sources could be resolved through measurements of the linear polarisation of emitted X-rays. The PoGOLite Pathfinder is a balloon-borne hard X-ray polarimeter operating in the 25-240 keV energy band from a stabilised observation platform. Polarisation is determined using coincident energy deposits in a segmented array of plastic scintillators surrounded by a BGO anticoincidence system and a polyethylene neutron shield. The PoGOLite Pathfinder was launched from the SSC Esrange Space Centre in July 2013. A near-circumpolar flight was achieved with a duration of approximately two weeks. The flight performance of the Pathfinder design is discussed for the three Crab observations conducted. The signal-to-background ratio for the observations is shown to be 0.25 +/- 0.03 and the Minimum Detectable Polarisation (99 % C.L.) is (28.4 +/- 2.2) %. A strategy for the continuation of the PoGOLite programme is outlined based on experience gained during the 2013 maiden flight.

  • 7. Djupvik, A. A.
    et al.
    André, Philippe
    Bontemps, Sylvain
    Motte, F.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Gålfalk, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    A multi-wavelength census of star formation activity in the young embedded cluster around Serpens/G3-G62006In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 458, no 3, p. 789-803Article in journal (Refereed)
    Abstract [en]

    Aims.The aim of this paper is to characterise the star formation activity in the poorly studied embedded cluster Serpens/G3-G6, located ~45 arcmin (3 pc) to the south of the Serpens Cloud Core, and to determine the luminosity and mass functions of its population of Young Stellar Objects (YSOs).

    Methods: .Multi-wavelength broadband photometry was obtained to sample the near and mid-IR spectral energy distributions to separate YSOs from field stars and classify the YSO evolutionary stage. ISOCAM mapping in the two filters LW2 (5-8.5 μm) and LW3 (12-18 μm) of a 19 arcmin × 16 arcmin field was combined with JHKS data from 2MASS, KS data from Arnica/NOT, and L arcmin data from SIRCA/NOT. Continuum emission at 1.3 mm (IRAM) and 3.6 cm (VLA) was mapped to study the cloud structure and the coldest/youngest sources. Deep narrow band imaging at the 2.12 μm S(1) line of H2 from NOTCam/NOT was obtained to search for signs of bipolar outflows.

    Results: .We have strong evidence for a stellar population of 31 Class II sources, 5 flat-spectrum sources, 5 Class I sources, and two Class 0 sources. Our method does not sample the Class III sources. The cloud is composed of two main dense clumps aligned along a ridge over ~0.5 pc plus a starless core coinciding with absorption features seen in the ISOCAM maps. We find two S-shaped bipolar collimated flows embedded in the NE clump, and propose the two driving sources to be a Class 0 candidate (MMS3) and a double Class I (MMS2). For the Class II population we find a best age of ~2 Myr and compatibility with recent Initial Mass Functions (IMFs) by comparing the observed Class II luminosity function (LF), which is complete to 0.08 Lȯ, to various model LFs with different star formation scenarios and input IMFs.

  • 8. Hjalmarson, Å.
    et al.
    Frisk, U.
    Olberg, M.
    Bergman, P.
    Bernath, P.
    Biver, N.
    Black, J. H.
    Booth, R. S.
    Buat, V.
    Crovisier, J.
    Curry, C. L.
    Dahlgren, M.
    Encrenaz, P. J.
    Falgarone, E.
    Feldman, P. A.
    Fich, M.
    Florén, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fredrixon, M.
    Gerin, M.
    Gregersen, E. M.
    Hagström, M.
    Harju, J.
    Hasegawa, T.
    Horellou, C.
    Johansson, L. E. B.
    Kyrölä, E.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljeström, T.
    Lindqvist, M.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Llewellyn, E. J.
    Mattila, K.
    Mégie, G.
    Mitchell, G. F.
    Murtagh, D.
    Nyman, L.-Å.
    Nordh, H. L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, A. O. H.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Persson, G.
    Plume, R.
    Rickman, H.
    Ristorcelli, I.
    Rydbeck, G.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Schéele, F.
    Serra, G.
    Torchinsky, S.
    Tothill, N. F.
    Volk, K.
    Wiklind, T.
    Wilson, C. D.
    Winnberg, A.
    Witt, G.
    Highlights from the first year of Odin observations2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L39-L46Article in journal (Refereed)
    Abstract [en]

    Key Odin operational and instrumental features and highlights from our sub-millimetre and millimetre wave observations of H2O, H218O, NH3, 15NH3 and O2 are presented, with some insights into accompanying Odin Letters in this A&A issue. We focus on new results where Odin's high angular resolution, high frequency resolution, large spectrometer bandwidths, high sensitivity or/and frequency tuning capability are crucial: H2O mapping of the Orion KL, W3, DR21, S140 regions, and four comets; H2O observations of Galactic Centre sources, of shock enhanced H2O towards the SNR IC443, and of the candidate infall source IRAS 16293-2422; H218O detections in Orion KL and in comet Ikeya-Zhang; sub-mm detections of NH3 in Orion KL (outflow, ambient cloud and bar) and ρ Oph, and very recently, of 15NH3 in~Orion KL. Simultaneous sensitive searches for the 119 GHz line of O2 have resulted in very low abundance limits, which are difficult to accomodate in chemical models. We also demonstrate, by means of a quantitative comparison of Orion KL H2O results, that the Odin and SWAS observational data sets are very consistently calibrated. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'études Spatiales (CNES, France). The Swedish Space Corporation (SSC) has been the prime industrial contractor, and is also responsible for the satellite operation from its Odin Mission Control Centre at SSC in Solna and its Odin Control Centre at ESRANGE near Kiruna in northern Sweden. See also the SNSB Odin web page: http://www.snsb.se/eng_odin_intro.shtml

  • 9. Hjalmarson, Åke
    et al.
    Bergman, Per
    Biver, Nicolas
    Florén, H.-G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, Urban
    Hasegawa, Tatsuhiko
    Justtanont, Kay
    Stockholm University, Faculty of Science, Department of Astronomy.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lundin, Stefan
    Olberg, Michael
    Olofsson, Henrik
    Persson, Glenn
    Rydbeck, Gustaf
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    The Odin Team,
    Recent astronomy highlights from the Odin satellite2005In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 36, p. 1031-1047Article in journal (Refereed)
    Abstract [en]

    Astronomy highlights, mainly from the third year of Odin observations time shared 50/50% with aeronomy are presented: the very low O2 abundance limits achieved, the highly pressure broadened absorption lines of H2O, H218O, and CO (5 → 4) in the atmosphere of Mars, the high precision H2O and H218O observations of comets, the detections of NH3 and H2O around the C-rich star IRC+10216 (CW Leo) and of H2O around the O-rich star W Hya, NH3 and H2O observations of infall/outflow interactions, observations of H2O, H218O, H217O as well as NH3 and 15NH3 in multiple absorptions towards Sgr B2, and in emission towards Orion KL, the H2O detection of several new outflows in the DR21 W75S region. We also discuss the results of deconvolution of high S/N H2O, CO and 13CO (5 → 4) maps of the Orion KL region to 40″ resolution (the beam size of the Herschel telescope) and the first results from our ongoing “spectral scan” of Orion KL in bands around 555 and 570 GHz. Finally, a search for primordial molecules is presented.

  • 10. Hjalmarson, Åke
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    On the progress in Odin’s hunt for molecules2007In: Advances in Space Research, Vol. 40, no 5, p. 630-638Article in journal (Refereed)
  • 11. Kiss, M.
    et al.
    Larsson, Stefan
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, Department of Astronomy.
    Bettolo, C.
    Bogaert, G.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, Department of Astronomy.
    Fukazawa, Y.
    Gunji, S.
    Hjalmarsdotter, Linnea
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, Department of Astronomy.
    Kamae, T.
    Kanai, Y.
    Kataoka, J.
    Kawai, N.
    Klamra, W.
    Kurita, K.
    Madejski, G.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, Department of Astronomy.
    Pearce, Mark
    Ryde, Felix
    Rydström, S.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Ueno, M.
    Umeki, Y.
    Varner, G.
    Yoshida, H.
    The PoGOLite balloon-borne soft gamma-ray polarimeter2008In: COOL DISCS, HOT FLOWS: The Varying Faces of Accreting Compact Objects, 2008, p. 225-232Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Linearly polarized radiation in the hard X-ray/soft gamma-ray band is expected from a large variety of astronomical sources. We discuss the importance of polarimetric studies for several classes of sources-pulsars, accreting black holes, magnetic neutron stars and jets from active galaxies-and then describe PoGOLite, a balloon-borne instrument which is currently under construction and will be able to measure the polarization of electromagnetic radiation from such extra-solar objects in the energy range 25-80 keV.

  • 12.
    Larsson, B.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Bernath, P.
    Black, J. H.
    Booth, R. S.
    Buat, V.
    Curry, C. L.
    Encrenaz, P.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Florén, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E. M.
    Harju, J.
    Hasegawa, T.
    Johansson, L. E. B.
    Kwok, S.
    Lecacheux, A.
    Liljeström, T.
    Mattila, K.
    Mitchell, G. F.
    Nordh, L. H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Schéele, F. v.
    Tothill, N. F. H.
    Volk, K.
    Wilson, C. D.
    Hjalmarson, Å.
    First NH3 detection of the Orion Bar2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L69-L72Article in journal (Refereed)
    Abstract [en]

    Odin has successfully observed three regions in the Orion A cloud, i.e. Ori KL, Ori S and the Orion Bar, in the 572.5 GHz rotational ground state line of ammonia, ortho-NH3 (J,K) = (1,0) -> (0,0), and the result for the Orion Bar represents the first detection in an ammonia line. Several velocity components are present in the data. Specifically, the observed line profile from the Orion Bar can be decomposed into two components, which are in agreement with observations in high-J CO lines by Wilson et al. (\cite{wilson01}). Using the source model for the Orion Bar by these authors, our Odin observation implies a total ammonia abundance of NH3/H2 = 5x 10-9. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor.

  • 13.
    Larsson, Bengt
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Liseau, Rene
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, Laurent
    Bergman, Per
    Bernath, Peter
    Biver, Nicolas
    Black, John
    Booth, Roy
    Buat, Veronique
    Crovisier, Jacques
    Curry, Charles
    Dahlgren, Magnus
    Encrenaz, Pierre
    Falgarone, Edith
    Feldman, Paul
    Fish, Michel
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Fredrixon,
    Frisk, Urban
    Gahm, Gösta
    Stockholm University, Faculty of Science, Department of Astronomy.
    Gerin, Maryvonne
    Hagström, Magne
    Harju, Jorma
    Hasegawa, Tatsuhiko
    Hjalmarsson, Åke
    Johansson, Lars
    Justtanout, Kay
    Stockholm University, Faculty of Science, Department of Astronomy.
    Klotz, Alain
    Kytölä, Erikii
    Kwok, Sun
    Lecacheux, Alain
    Liljeström, Tarja
    Llewellyn, Edward
    Lundin, Stefan
    Mégie, Gérard
    Mitchell, Gary
    Murtagh, Donal
    Nordh, Lennart
    Nyman, Lars-Åke
    Olberg, Michael
    Olofsson, Henrik
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olofsson, Hans
    Stockholm University, Faculty of Science, Department of Astronomy.
    Persson, Glen
    Plume, Rene
    Rickman, Hans
    Ristorcelli, Isabelle
    Rydbeck, Gustaf
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Scheele, Fredrik
    Serra, Guy
    Torchinsky, Steve
    Tothill, Nick
    Volk, Kevin
    Wiklind, Tommy
    Wilson, Christine
    Winnberg, Anders
    Witt, George
    Department of Meteorology.
    Molecular oxygen in the rho Ophiuchi cloud2007In: Astronomy & Astrophysics, ISSN 0004-6361, Vol. 466, no 3, p. 5-Article in journal (Refereed)
    Abstract [en]

    Context: Molecular oxygen, O2, has been expected historically to be an abundant component of the chemical species in molecular clouds and, as such, an important coolant of the dense interstellar medium. However, a number of attempts from both ground and from space have failed to detect O2 emission.

    Aims: The work described here uses heterodyne spectroscopy from space to search for molecular oxygen in the interstellar medium. Methods: The Odin satellite carries a 1.1 m sub-millimeter dish and a dedicated 119 GHz receiver for the ground state line of O2. Starting in 2002, the star forming molecular cloud core ρ Oph A was observed with Odin for 34 days during several observing runs.

    Results: We detect a spectral line at v_LSR =+3.5 km s-1 with Δ v_FWHM=1.5 km s-1, parameters which are also common to other species associated with ρ Oph A. This feature is identified as the O2 (NJ = 11 - 1_0) transition at 118 750.343 MHz.

    Conclusions: The abundance of molecular oxygen, relative to H{2} , is 5 × 10-8 averaged over the Odin beam. This abundance is consistently lower than previously reported upper limits.

    Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Étude Spatiale (CNES). The Swedish Space Corporation has been the industrial prime contractor and also is operating the satellite. Appendix A is only available in electronic form at http://www.aanda.org

  • 14.
    Liseau, R.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Brandeker, A.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Bernath, P.
    Black, J. H.
    Booth, R.
    Buat, V.
    Curry, C.
    Encrenaz, P.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Florén, H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E.
    Harju, J.
    Hasegawa, T.
    Hjalmarson, Å.
    Johansson, L.
    Kwok, S.
    Lecacheux, A.
    Liljeström, T.
    Mattila, K.
    Mitchell, G.
    Nordh, L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Schéele, F. v.
    Serra, G.
    Tothill, N.
    Volk, K.
    Wilson, C.
    First detection of NH3 (10 -> 00) from a low mass cloud core. On the low ammonia abundance of the rho Oph A core2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L73-L76Article in journal (Refereed)
    Abstract [en]

    Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH3OH)= 3 x 10-9. Unless NH3 is not entirely segregated from C17O and CH3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH3) = 8 x 10-10. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor. and based on observations collected with the Swedish ESO Submillimeter Telescope, SEST, in La Silla, Chile.

  • 15. Maercker, M.
    et al.
    Ramstedt, S.
    Leal-Ferreira, M. L.
    Olofsson, Göran
    Stockholm University, Faculty of Science, Department of Astronomy.
    Floren, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    The detached dust shells around the carbon AGB stars R Sculptoris and V644 Scorpii2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 570, p. A101-Article in journal (Refereed)
    Abstract [en]

    Context. The morphology of the circumstellar envelopes (CSE) around asymptotic giant branch (AGB) stars gives information on the mass-loss process from the star, its evolution and wind, and on the effect of binary interaction. However, determining the distribution of dust in the circumstellar envelopes is difficult. Observations of polarised, dust-scattered stellar light in the optical have produced images with high-spatial resolution of the envelopes around evolved stars. For sources with detached shells in particular, this method has proven extremely successful. Detached shells are believed to be created during a thermal pulse, and studying them can constrain the time scales and physical properties of one of the main drivers of late stellar evolution. Aims. We aim at determining the morphology of the detached shells around the carbon AGB stars R Scl and V644 Sco. In particular, we attempt to constrain the radii and widths of the detached dust shells around the stars and compare them to observations of the detached gas shells. Methods. We observed the polarised, dust-scattered stellar light around the carbon AGB stars R Scl and V644 Sco using the PolCor instrument mounted on the ESO 3.6 m telescope. Observations were done with a coronographic mask to block out the direct stellar light. The polarised images clearly show the detached shells around R Scl and V644 Sco. Using a dust radiative transfer code to model the dust-scattered polarised light, we constrained the radii and widths of the shells. Results. We determine radii of 19 ''.5 and 9 ''.4 for the detached dust shells around R Scl and V644 Sco, respectively. Both shells have an overall spherical symmetry and widths of approximate to 2 ''. For R Scl, we can compare the observed dust emission directly with high spatialresolution maps of CO(3-2) emission from the shell observed with ALMA. We find that the dust and gas coincide almost exactly, indicating a common evolution. The data presented here for R Scl are the most detailed observations of the entire dusty detached shell to date. For V644 Sco, these are the first direct measurements of the detached shell. Also here we find that the dust most likely coincides with the gas shell. Conclusions. The observations are consistent with a scenario where the detached shells are created during a thermal pulse. The determined radii and widths will constrain hydrodynamical models describing the pre-pulse mass loss, the thermal pulse, and postpulse evolution of the star.

  • 16. Meech, K.J.
    et al.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Sandqvist, Aage
    Stockholm University, Faculty of Science, Department of Astronomy.
    EPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 734, no L1, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO2-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production.

  • 17. Olofsson, A. O. H.
    et al.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Hjalmarson, Å.
    Bergman, P.
    Black, J. H.
    Booth, R. S.
    Buat, V.
    Curry, C. L.
    Encrenaz, P. J.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Florén, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E. M.
    Harju, J.
    Hasegawa, T.
    Johansson, L. E. B.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljeström, T.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Mattila, K.
    Mitchell, G. F.
    Nordh, H. L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Rydbeck, G.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Schéele, F.
    Serra, G.
    Tothill, N. F.
    Volk, K.
    Wilson, C. D.
    Odin water mapping in the Orion KL region2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L47-L54Article in journal (Refereed)
    Abstract [en]

    New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1\arcmin beam size at 557 GHz), are presented. The ortho-H2O \jkktrans{1}{1}{0}{1}{0}{1} ground state transition was observed in a 7arcminx 7arcmin rectangular grid with a spacing of 1\arcmin, while the same line of H218O was measured in two positions, Orion KL itself and 2\arcmin south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60\arcsec-110\arcsec. The H2O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near (or ``blue'') part of the outflow (and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL H218O outflow emission emanates from the compact (size ~ 15\arcsec) low-velocity flow and here estimate an H2O abundance of circa 10-5 compared to all H2 in the flow - an order of magnitude below earlier estimates of the H2O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. H218O is detected for the first time in the southern position at a level of ~ 0.15 K and we here estimate an H2O abundance of (1-8) x 10-8. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'Études Spatiales (CNES, France). The Swedish Space Corporation (SSC) was the industrial prime contractor and is also responsible for the satellite operation.

  • 18.
    Olofsson, Göran
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Nilsson, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Djupvik, A.
    Aberasturi, M.
    Polarimetric coronagraphy of BD+31 degrees 6432012In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 544, p. A43-Article in journal (Refereed)
    Abstract [en]

    Context. The binary B5V star BD+ 31 degrees 643 exhibits a disk-like structure detected at optical wavelengths. Even though the feature is well centered on the star, it has been argued, based on Spitzer observations, that the feature is a filament not directly associated to the binary star. Aims. The purpose of the present paper is to investigate whether polarization imaging may provide evidence either for or against the disk hypothesis. In addition, we aim at clarifying whether there might be any additional close companion to the binary star. Methods. We used the coronagraph PolCor in its polarization mode in combination with an EMCCD camera allowing short unit exposure times. As a result of shift-and-add and frame selection, the spatial resolution is improved compared to traditional CCD imaging. In order to possibly reveal an additional stellar companion, we used high resolution spectroscopy in the optical and high spatial resolution imaging in the near-IR. Results. The disk/filament is much better seen in polarization; it is narrow and a line drawn along the ridge passes within a second of arc from the star. The degree of polarization is high (approximate to 50% after correction for the extended component of the reflection nebula) which means that the disk/filament must be approximately at the same distance as the star. Although we confirm that the feature is much brighter south-east than north-west of the star, the evidence that the feature is physically connected to the star is strengthened and suggests that we are witnessing the destruction process of an accretion disk. Our spectroscopy shows that at least one of the stars is a spectroscopic binary. We were, however, not able to spatially resolve any stellar component in addition to the two well separated stars.

  • 19.
    Olofsson, Göran
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Nilsson, Ricky
    Stockholm University, Faculty of Science, Department of Astronomy.
    Florén, Hans-Gustav
    Stockholm University, Faculty of Science, Department of Astronomy.
    Djupvik, Amanda
    Aberasturi, M.
    Polarimetric coronagraphy of BD+31°643Article in journal (Refereed)
  • 20. Pagani, L.
    et al.
    Olofsson, A. O. H.
    Bergman, P.
    Bernath, P.
    Black, J. H.
    Booth, R. S.
    Buat, V.
    Crovisier, J.
    Curry, C. L.
    Encrenaz, P. J.
    Falgarone, E.
    Feldman, P. A.
    Fich, M.
    Floren, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E. M.
    Harju, J.
    Hasegawa, T.
    Hjalmarson, Å.
    Johansson, L. E. B.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljeström, T.
    Lindqvist, M.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Mattila, K.
    Mitchell, G. F.
    Nordh, L. H.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Ristorcelli, I.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Scheele, F.
    Serra, G.
    Tothill, N. F.
    Volk, K.
    Wiklind, T.
    Wilson, C. D.
    Low upper limits on the O2 abundance from the Odin satellite2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L77-L81Article in journal (Refereed)
    Abstract [en]

    For the first time, a search has been conducted in our Galaxy for the 119 GHz transition connecting to the ground state of O2, using the Odin satellite. Equipped with a sensitive 3 mm receiver (Tsys(SSB) = 600 K), Odin has reached unprecedented upper limits on the abundance of O2, especially in cold dark clouds where the excited state levels involved in the 487 GHz transition are not expected to be significantly populated. Here we report upper limits for a dozen sources. In cold dark clouds we improve upon the published SWAS upper limits by more than an order of magnitude, reaching N(O2)/N(H2) <= 10-7 in half of the sources. While standard chemical models are definitively ruled out by these new limits, our results are compatible with several recent studies that derive lower O2 abundances. Goldsmith et al. (\cite{SWAS2002}) recently reported a SWAS tentative detection of the 487 GHz transition of O2 in an outflow wing towards rho Oph A in a combination of 7 beams covering approximately 10arcmin x 14arcmin . In a brief (1.3 hour integration time) and partial covering of the SWAS region (~65% if we exclude their central position), we did not detect the corresponding 119 GHz line. Our 3 sigma upper limit on the O2 column density is 7.3x 1015 cm-2. We presently cannot exclude the possibility that the SWAS signal lies mostly outside of the 9\arcmin Odin beam and has escaped our sensitive detector. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation was the industrial prime contractor and is operating Odin.

  • 21.
    Sandqvist, Aa.
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bergman, P.
    Black, J. H.
    Booth, R.
    Buat, V.
    Curry, C. L.
    Encrenaz, P.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Floren, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Gregersen, E. M.
    Harju, J.
    Hasegawa, T.
    Hjalmarson, Å.
    Johansson, L. E. B.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljeström, T.
    Lindqvist, M.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Mattila, K.
    Mitchell, G. F.
    Nordh, L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, A. O. H.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Schéele, F. v.
    Serra, G.
    Tothill, N. F. H.
    Volk, K.
    Wilson, C. D.
    Winnberg, A.
    Odin observations of H2O in the Galactic Centre2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L63-L67Article in journal (Refereed)
    Abstract [en]

    The Odin satellite has been used to detect emission and absorption in the 557-GHz H216O line in the Galactic Centre towards the Sgr Astar Circumnuclear Disk (CND), and the Sgr A +20 km s-1 and +50 km s-1 molecular clouds. Strong broad H2O emission lines have been detected in all three objects. Narrow H2O absorption lines are present at all three positions and originate along the lines of sight in the 3-kpc Spiral Arm, the -30 km s-1 Spiral Arm and the Local Sgr Spiral Arm. Broad H2O absorption lines near -130 km s-1 are also observed, originating in the Expanding Molecular Ring. A new molecular feature (the ``High Positive Velocity Gas'' - HPVG) has been identified in the positive velocity range of ~+120 to +220 km s-1, seen definitely in absorption against the stronger dust continuum emission from the +20 km s-1 and +50 km s-1 clouds and possibly in emission towards the position of Sgr Astar CND. The 548-GHz H218O isotope line towards the CND is not detected at the 0.02 K (rms) level. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation was the industrial prime contractor and is also responsible for the satellite operation.

  • 22. Wilson, C. D.
    et al.
    Mason, A.
    Gregersen, E.
    Olofsson, A. O. H.
    Bergman, P.
    Booth, R.
    Boudet, N.
    Buat, V.
    Curry, C. L.
    Encrenaz, P.
    Falgarone, E.
    Feldman, P.
    Fich, M.
    Floren, H. G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Frisk, U.
    Gerin, M.
    Harju, J.
    Hasegawa, T.
    Hjalmarson, Å.
    Juvela, M.
    Kwok, S.
    Larsson, B.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lecacheux, A.
    Liljestrom, T.
    Liseau, R.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Mattila, K.
    Mitchell, G.
    Nordh, L.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Olberg, M.
    Olofsson, G.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Pagani, L.
    Plume, R.
    Ristorcelli, I.
    Sandqvist, Aa.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Serra, G.
    Tothill, N.
    Volk, K.
    von Scheele, F.
    Submillimeter emission from water in the W3 region2003In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 402, p. L59-L62Article in journal (Refereed)
    Abstract [en]

    Using the Odin satellite, we have mapped the submillimeter emission from the 110-101 transition of ortho-water in the W3 star-forming region. A 5arcminx 5arcmin map of the W3 IRS4 and W3 IRS5 region reveals strong water lines at half the positions in the map. The relative strength of the Odin lines compared to previous observations by SWAS suggests that we are seeing water emission from an extended region. Across much of the map the lines are double-peaked, with an absorption feature at -39 km s-1; however, some positions in the map show a single strong line at -43 km s-1. We interpret the double-peaked lines as arising from optically thick, self-absorbed water emission near the W3 IRS5, while the narrower blue-shifted lines originate in emission near W3 IRS4. In this model, the unusual appearance of the spectral lines across the map results from a coincidental agreement in velocity between the emission near W3 IRS4 and the blue peak of the more complex lines near W3 IRS5. The strength of the water lines near W3 IRS4 suggests we may be seeing water emission enhanced in a photon-dominated region. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation was the industrial prime contractor and is also responsible for the satellite operation.

1 - 22 of 22
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