Volume 526, February 2011
|Number of page(s)||13|
|Section||Stellar structure and evolution|
|Published online||17 December 2010|
Massive unseen companions to hot faint underluminous stars from SDSS (MUCHFUSS)
Dr. Karl Remeis-Observatory & ECAP, Astronomical Institute,
Friedrich-Alexander University Erlangen-Nuremberg, Sternwartstr. 7, 96049
2 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
3 Centre of Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
4 Institute of Astronomy, K.U. Leuven, Celestijnenlaan 200D, 3001 Heverlee, Belgium
5 Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255, USA
6 Instituto de Astrofísica de Andalucía Glorieta de la Astronomía s/n 18008 Granada, Spain
7 Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
8 Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Santa Cruz de Tenerife, Spain
9 Department of Physics, University of Warwick, Conventry CV4 7AL, UK
Accepted: 15 November 2010
The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars with massive compact companions like massive white dwarfs (M > 1.0 M⊙), neutron stars or stellar mass black holes. The existence of such systems is predicted by binary evolution theory and recent discoveries indicate that they exist in our Galaxy. First results are presented for seven close binary sdBs with short orbital periods ranging from ≃0.21 d to 1.5 d. The atmospheric parameters of all objects are compatible with core helium-burning stars. The companions are most likely white dwarfs. In one case the companion could be shown to be a white dwarf by the absence of light-curve variations. However, in most cases late type main sequence stars cannot be firmly excluded. Comparing our small sample with the known population of close sdB binaries we show that our target selection method aiming at massive companions is efficient. The minimum companion masses of all binaries in our sample are high compared to the reference sample of known sdB binaries.
Key words: subdwarfs / binaries: spectroscopic / binaries: close / white dwarfs
Based on observations at the Paranal Observatory of the European Southern Observatory for programme number 081.D-0819. Based on observations at the La Silla Observatory of the European Southern Observatory for programmes number 082.D-0649 and 084.D-0348. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC). Based on observations with the William Herschel Telescope and the Isaac Newton Telescope operated both by the Isaac Newton Group at the Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias on the island of La Palma, Spain. Based on observations with the Southern Astrophysical Research (SOAR) telescope operated by the U.S. National Optical Astronomy Observatory (NOAO), the Ministerio da Ciłncia e Tecnologia of the Federal Republic of Brazil (MCT), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministerio da Ciłncia e Tecnologia (Brazil) and Ministerio de Ciłncia, Tecnologia e Innovacin Productiva (Argentina). This paper uses observations made at the South African Astronomical Observatory (SAAO).
Appendices are only available in electronic form at http://www.aanda.org
© ESO, 2010
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