Orbital period investigations of two short-period early-type overcontact binaries BH Cen and V701 Sco in two extremely young galactic clusters IC 2944 and NGC 6383 |
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| Institution: | 1. National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming, Yunnan Province 650011, PR China;2. Mt. Suhora Observatory, Cracow Pedagogical University ul. Podchorazych 2 30-084 Krakow, Poland;1. Massachusetts Institute of Technology, Haystack Observatory, 99 Millstone Hill Road, Westford, MA 01886, USA;2. Wellesley College, Whitin Observatory, Wellesley, MA 02482, USA;3. National Radio Astronomy Observatory Jansky Fellow, USA;1. International Institute for Applied Systems Analysis (IIASA), Ecosystem Services and Management Program, Schlossplatz 1, A-2361 Laxenburg, Austria;2. Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 10081, China;3. Joint Global Change Research Institute, Pacific Northwest National Laboratory and University of Maryland, College Park, MD 20740, USA;4. Institute on the Environment, University of Minnesota, St. Paul, MN 55108, USA;5. Faculty of Natural Sciences, Comenius University in Bratislava, 842 15 Bratislava, Slovak Republic;6. Soil Science and Conservation Research Institute, 827 13 Bratislava, Slovak Republic;1. Department of Physics & Astronomy, Wayne State University, 666 W. Hancock Street, Detroit, MI 48201, USA;2. Department of Physics & Astronomy, Georgia State University, Atlanta, GA 30303, USA;3. MIT Kavli Institute for Astrophysics and Space Research, Cambridge, MA 02139, USA;1. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan;2. Atmospheric Physics Laboratory, Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK;3. The Centre for Planetary Sciences at UCL/Birkbeck, Gower Street, London, WC1E 6BT, UK;4. Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS, UK;5. Laboratoire AIM, Université Paris Diderot/CEA/CNRS, 91191 Gif-sur-Yvette Cedex, France;6. Institut Universitaire de France, 103 Boulevard Saint Michel, 75005 Paris, France;7. ONERA – The French Aerospace Lab, 92322 Châtillon, France;8. Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK;9. Atmospheric, Oceanic & Planetary Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK;10. LESIA, Observatoire de Paris, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, Meudon, France;11. Dipartimento di Fisica, Università di Padova, Via Marzolo 8, 35131 Padova, Italy;12. Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA;13. Departamento de Geodinámica, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid, 28040 Madrid, Spain;14. Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK;15. IRAP, CNRS, University Paul Sabatier Toulouse, Toulouse, France;p. Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695022, India;q. Planetary Science Institute, Tucson, AZ 85719, USA;r. Department of Geophysics and Planetary Science, Tel Aviv University, Tel Aviv 69978, Israel;s. Institut für Raumfahrtsysteme, Universität Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany;t. MS 169-237, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA;u. Laboratoire Kastler Brossel (LKB), ENS, UPMC, CNRS, Campus Jussieu, F-75252 Paris Cedex 05, France;v. Office of Space Research and Technology, Academy of Athens, Soranou Efesiou 4, 1527 Athens, Greece;w. Space Research Institute, Austrian Academy of Sciences, Schmiedlstraße 6, 8042 Graz, Austria;1. College of Geoscience and Surveying Engineering, China University of Mining & Technology, Beijing 100083, China;2. The Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;3. University of Chinese Academy of Sciences, Beijing 100101, China;4. Department of Geography and Planning, University of Toronto, 100 St. George St., Toronto, ON M5S 3G3, Canada |
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| Abstract: | Both V701 Sco and BH Cen are two early-type short-period overcontact systems (P = 0.d762 and P = 0.d792, respectively). V701 Sco is a member of the young galactic cluster NGC 6383, while BH Cen is a component of a younger galactic cluster IC 2944 where star formation is in process. They provide good opportunity to understand the formation and evolution of binary stars. In the present paper, orbital period changes of the two binaries are investigated. It is discovered that the orbital period of BH Cen shows a long-term increase with a rate of dP/dt = +1.70(±0.39) × 10−7 days/year while it undergoes a cyclic oscillation with a period of 44.6 years and an amplitude of A3 = 0.d0216. For V701 Sco, its O-C curve reveals a periodic change with a period of 41.2 years and amplitude of A3 = 0.d0158. The mass ratio of BH Cen is 0.84, but V701 Sco contains twin B1-1.5V type stars with a mass ratio of unit. The continuous period increase of BH Cen is caused by the mass transfer from the less massive component to the more massive one at a rate of dM2/dt = 3.5 × 10−6 days/year.The cyclic period changes of both systems can be plausibly explained as the results of light-travel time effects suggesting that they are triple systems. The astrophysical parameters of the unseen tertiary components in the two systems have been determined. We think that the invisible tertiary components in both binaries played an important role in the formations and evolutions of the overcontact configurations by bringing angular momentum out from the central systems. For BH Cen, this process created the initial short period and will support its evolution into an overcontact configuration via a Case A mass transfer within the life time of the extremely young cluster IC 2944. For V701 Sco, two identical zero-age main-sequence components in an overcontact configuration suggest that it may have been formed by fission, possibly by the fission of the third body. The fact that no long-term continuous period variations were found for V701 Sco may suggest that an overcontact binary with the mass ratio of unity can be in an equilibrium revealing that the original configuration of the binary was overcontact as is its present state. It has been reported that faint stars in the two extremely young clusters are relatively scare. From the present study, it is shown that faint stars in young clusters are usually formed as companions of OB stars (including binaries). It is very difficult to detect them because of their low luminosity when compared with the more luminous OB stars. |
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