Is NSVS 5066754 a Near-Contact or a Marginal Contact Binary?

Abstract

BVR c I c light curves of NSVS 5066754 were taken on 2014 May at Dark Sky Observatory in North Carolina. This variable is a solar-type eclipsing binary (T1 ∼ 5750 K) with a period of only 0.3751689(1) days. It appeared to be one of the shortest periods in Shaw’s list of near-contact binaries. The Binary Maker fits and our Wilson–Devinney solutions show that the binary could have both semidetached and marginal contact binary configurations. Five new times of minimum light were calculated, along with two minima determined from archived All Sky Automated Survey observations. From these minima and the discovery epoch, a quadratic ephemeris was determined. Thus, a magnetic braking scenario is possible. Both semidetached and contact models were explored. A marginal contact solution had the best sum of square residuals. It gave a mass ratio of ∼0.5, and a component temperature difference of ∼360 K, albeit somewhat large for a contact binary. Two substantial cool spots were determined in this solution with 37° and 28° radii and t-factors or 0.94 and 0.78 respectively. The fill-out is very shallow, ∼106%. It may have recently achieved contact.

V505 Cyg: A Mass-transferring Marginal Contact Binary

“…505 Cyg is a progenitor of an overcontact binary. Now, it may lie in the broken-contact stage predicted by the TRO theory like UU Lyn (Zhu et al 2007), BL And, GW Tau ), V473 Cas, II Per (Zhu et al 2009), IR Cas (Li et al 2014), IZ Mon (Yang et al 2016), CN And (Cai et al 2019), NSVS 5066754 (Samec et al 2016) and DD Com (Zhu et al 2010). As pointed out by the TRO theory, W UMa binaries must go through oscillations about the state of marginal contact.…”