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Paper: Search for Close Binary Stars during Different Key Stages of the Evolutionary Track from Detached to Overcontact Configurations
Volume: 362, The Seventh Pacific Rim Conference on Stellar Astrophysics
Page: 63
Authors: Qian, S.-B.; Soonthornthum, B.; Zhu, L.-Y; He, J.-J.; Yuan, J.-Z.; Dai, Z.-B.; Liu, L.; Zhang, J.; Liao, W.-P.
Abstract: Search for and detailed studies of close binary stars during key evolutionary stages, e.g., semidetached with a lobe-filing primary, marginal contact, and newly formed overcontact systems, are very important to understand the formation and dynamical evolution of overcontact binary stars. We have started a series of photometric studies of those kinds of systems. New observations of 14 sample stars have been obtained. Here, we report preliminary results for several sample stars - GSC3658-0076, HL Aur, BL And, GW Tau, DM Del and RV Psc. Five systems - HL Aur, BL And, GW Tau, DM Del and RV Psc - have shown a continuous period decrease. Photometric solutions indicate that BL And and DM Del are semidetached system where the primary components are filling the critical Roche Lobe, while RV Psc and GW Tau are marginal contact systems. The long-time period decreases, the geometrical structures, and the astrophysical parameters of those binary systems all suggest that they are evolving from semidetached (e.g., DM Del and BL And) to marginal contact (already achieved by RV Psc and GW Tau). The period variations of HL Aur suggest that it may be a pre-contact system with a solar-mass companion. Though the times of light minimum of GSC3658-0076 are insufficient to reveal any period changes, our solution indicates that it is at the beginning of mass transfer.
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