NSVS 7051868: A system in a key evolutionary stage. First multi-color photometric study
Institution:
1. Via Molinetto 35, 26845 Triulza di Codogno (LO), Italy;2. Via Don G. Minzoni 26/D, 20020 Magnago (MI), Italy;3. Via Zoncada 51, 26845 Codogno (LO), Italy;1. Florida Institute of Technology, Physics and Space Sciences Department, Melbourne, Florida, 32901, USA;2. Florida Institute of Technology, Systems Engineering Department, Melbourne, Florida, 32901, USA;1. Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V. (BAV), Berlin, Germany;2. American Association of Variable Star Observers (AAVSO), Cambridge, USA;3. Vereniging Voor Sterrenkunde (VVS), Brugge, Belgium;4. Astrolab IRIS, Ieper, Belgium;5. Department of Physics, University of Warwick, Coventry, United Kingdom;6. Center for Plasma Astrophysics, University of Leuven, Belgium;1. Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011, China;2. Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China;3. Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road,Beijing 100049, China;4. University of Chinese Academy of Sciences, Beijing 100049, China;1. Department of Physics, University of Central Florida, Orlando, FL 32816, United States;2. Sternberg Astronomical Institute, Moscow State University, Universitetskij prospect 13, Moscow 119992, Russian Federation;3. University of Dallas, 1845 E Northgate Drive, Irving, TX 75062, United States
Abstract:
The first CCD photometric complete light curves of the eclipsing binary NSVS 7051868 were obtained during six nights in January 2016 in the B, V and Ic bands using the 0.25 m telescope of the Stazione Astronomica Betelgeuse in Magnago, Italy.These observations confirm the short period (P = 0.517 days) variation found by Shaw and collaborators in their online list (http://www.physast.uga.edu/~jss/nsvs/) of periodic variable stars found in the Northern Sky Variability Survey.The light curves were modelled using the Wilson–Devinney code and the elements obtained from this analysis are used to compute the physical parameters of the system in order to study its evolutionary status.A grid of solutions for several fixed values of mass ratio was calculated.A reasonable fit of the synthetic light curves of the data indicate that NSVS 7051868 is an A-subtype W Ursae Majoris contact binary system, with a low mass ratio of q = 0.22, a degree of contact factor f = 35.5% and inclination i = 85°. Our light curves shows a time of constant light in the secondary eclipse of approximately 0.1 in phase. The light curve solution reveals a component temperature difference of about 700 K. Both the value of the fill-out factor and the temperature difference suggests that NSVS 7051868 is a system in a key evolutionary stage of the Thermal Relaxation Oscillation theory.The distance to NSVS 7051868 was calculated as 180 pc from this analysis, taking into account interstellar extinction.
