BVR_CI_C Observations, Analysis, and Spectra of The Most Extreme Mass Ratio (Totally Eclipsing) W UMa Binary, V1187 Herculis

Abstract

CCD, BVRI primary light curves of V1187 Her were taken in 2017 May and 2018 May at the Dark Sky Observatory in North Carolina with the 0.81-m reflector of Appalachian State University. A spectrum was taken earlier at Dominion Astrophysical Observatory (DAO) with the 1.8 m telescope. The spectral type is F(8.5 ± 1)V, resulting in a surface temperature of 6250±125 K (Cox 2000), so solar-type activity is expected. V1187 Her was previously identified as a low-amplitude, short-period, over-contact eclipsing binary (EW) with an orbital period of 0.310726 d. Strikingly, despite its low amplitude (∼0.15 mag), the early light curves show a total eclipse (eclipse duration: 31.5 minutes). This can only occur (in the absence of a strong third light) if the binary is an exceptionally extreme mass ratio binary, perhaps the most extreme known. Eight instances of minimum light were calculated. A 12-year period study reveals a secular period decrease in the orbital period with good confidence. The rate of period change is dP/dt=−1.5×10 −07 d/yr, probably due to magnetic braking. Its Roche Lobe fill-out is found to be a hefty 84% along with a mass ratio of only ∼0.044; indeed, the most extreme known among solar-type (i.e., W UMa) binaries. It has a cool spot region. The secondary component has a temperature of »6680 K, which makes it a W-subtype binary (the less massive component is hotter). The inclination is only ∼67°despite its total eclipses. A q-search was conducted, which showed the 0.044 value was the best fit to the light curves. Additionally, followup observations were taken on 2018 May 4, which confirmed the mass ratio found from the earlier curves.

ZZ Piscis Austrinus (ZZ PsA): a bright red nova progenitor and the instability mass ratio of contact binary stars

“…Preliminary analysis of amateur red band photometry by Wadhwa (2017) suggested a W-Type star with mass ratio 0.059 and only marginal fill-out of 20%. Multi-band photometry analysis (Caton et al 2019), however, yielded a system with an extremely low mass ratio of 0.044 and fill-out exceeding 80%. Although no component masses were givenn, the spectrum is reported to be F8.5, corresponding to a primary mass of 1.1 𝑀 (Cox 2000).…”

Extremely Low Mass Ratio Contact Binaries. I. The First Photometric and Spectroscopic Investigations of Ten Systems

“…Extremely low mass ratio contact binaries (ELMRCBs) were defined as contact binaries with mass ratios less than 0.15. At present, only a few ELMRCBs were discovered, such as V1187 Her (q ∼ 0.044; Caton et al 2019), VSX J082700.8+462850 (q ∼ 0.055; Li et al 2021a), V857 Her (q ∼ 0.065; Qian et al 2005b), and ASAS J083241+2332.4 (q ∼ 0.068; Sriram et al 2016). We carried out a project on the analysis of ELMRCBs.…”

CoBiToM Project -- I. Contact Binaries Towards Merging

“…There are a few targets under investigation in this regime. The systems V1187 Her (q = 0.044, Caton et al 2019), V857 Her (q = 0.065, Qian et al 2005a,b), ASAS J083241+2332.4 (q = 0.068, Sriram et al 2016) and AW UMa (q = 0.099, Rucinski 2015) are a few examples of this rare class of contact binaries, where the secondary component is extremely small in size and mass. Wadhwa et al (2020) studied the contact binary system ZZ PsA and found a very small mass ratio of 0.078(2) and an orbital period of 0.37405(3) d. They concluded that the extreme mass ratio is accompanied by rapid mass transfer between the two components.…”