TYC 1337-1137-1 and TYC 3836-0854-1: Two Low-mass Ratio, Deep Overcontact Systems Near the End Evolutionary Stage of Contact Binaries

Abstract

New high-precision CCD photometric light curves of two contact binary stars, TYC 1337-1137-1 and TYC 3836-0854-1, are displayed and analyzed by using the Wilson-Devinney (W-D) program. The light curve solutions show that both of them are low-mass ratio, deep overcontact binary systems with a mass ratio of q=0.1716±0.0010 and a high fillout factor of f=76.0±2.9% for TYC 1337-1137-1, and q=0.1900±0.0032 and f=79.4±7.9% for TYC 3836-0854-1, respectively. These results indicate that they are near the end evolutionary stage of contact binaries. The absolute parameters were calculated by using the new method of mass-radius relationship (0.238 ± 0.009 M e and 1.386 ± 0.050 M e for TYC 1337-1137-1, 0.228 ± 0.014 M e and 1.20 ± 0.07 M e for TYC 3836-0854-1, respectively). The preliminary orbital period analysis suggests that long-term period increases exist for both of them, which may be interpreted in two possible ways. A first possibility is mass transfer conservation from the less massive component to the more massive one leading to an orbital period increase. In this case, when their orbital angular momentum is less than three times the total spin angular momentum, they may evolve into a rapidly rotating single star. A second possibility is that the parabolic variation in the (O − C) diagram is only a part of a long-period cyclic change caused by a potential third body. In future, more high-precision observations of these two binaries are needed to confirm the form of orbital period changes.

Two contact binaries with mass ratios close to the minimum mass ratio

“…Qian et al (2005a) firstly put forward the concept "deep (f ≥ 50.0%), low mass ratio (q ≤ 0.25) overcontact binaries" and proposed that this type of stars are likely to be the progenitors of blue stragglers/FK Com-type stars. At present, a lot of such type binaries have been analyzed (e.g., Yang et al 2009;Qian et al 2011;Liao et al 2017). However, there is only one target, V1309 Sco, whose merging progress has been observed (Tylenda et al 2011), and it is making a blue straggler (Ferreira et al 2019).…”

The first photometric investigation and spectroscopic analysis of two contact binaries: ASAS J124343+1531.7 and LINEAR 2323566

“…The two stars fill or over-fill their Roche lobes, and there exists a common convective envelope(CCE) (Lucy 1968a,b) around two components. Due to the existence of a CCE, there may be mass transfer and energy exchange between two components (eg., Li et al 2015;Liao et al 2017;Lee & Park 2018;Li 2018). The mass and angular momentum may also be lost from the binary system (eg., Van't Veer 1979;Rahunen 1981;van Hamme 1982;Qian 2001aQian ,b, 2003.…”

Photometric study of 61 totally eclipsing contact binaries from the ASAS, OGLE, HATNet, AST3 and TESS databases.

“…Eclipsing binaries in pre-contact and marginal contact phases are important systems to help understand close binary evolution from detached to contact stages. The contact binary systems with mass ratios < 0.25 and fillout factors > 50% are prominent sources of interest, as they are progenitors of some fascinating objects and related to several key astrophysical processes (Liao et al, 2017).…”