Photometric and H-alpha studies of two extreme mass-ratio short period contact binaries in the direction of open cluster Praesepe

TL;DR

This study conducts photometric and spectroscopic analyses of two extreme mass-ratio short period contact binaries near Praesepe, revealing their physical parameters, chromospheric activity, and potential merger mechanisms.

Contribution

It provides detailed photometric and H-alpha spectroscopic characterization of two rare low and high mass-ratio contact binaries, highlighting their activity and evolutionary implications.

Findings

V1 is a low mass-ratio A-type over-contact binary with 72% fill-out.

V2 is a marginal contact W-type binary with 11% fill-out.

H-alpha line variations indicate chromospheric activity and flares.

Abstract

We present the high precession photometric studies in V band and spectroscopic studies centered around H-alpha line for two extreme mass-ratio short period contact binaries ASAS J082243+1927.0 (V1) and ASAS J085710+1856.8 (V2). The variables in study are in the direction of open cluster Praesepe. From the light curve analysis V1 was found to be a low mass-ratio over-contact binary of A-type, with a mass ratio q 0.121 and fill-out factor f 72%, and V2 was found to be a low mass contact binary of W-type, with a mass-ratio q 1.29 and fill-out factor f 11% (marginal contact). The study of H-alpha absorption line profile of both the variables shows variation in equivalent widths (EWs) with orbital phases. The mean EWs of the H-alpha line were obtained as 1.6+or-0.13 A and 1.18+or-0.12 A for V1 and V2 respectively. The variation of H-alpha absorption with respect to phase is explained to be due to chromospheric activity in V1, as evident from the O Connell effect and that due to chromospheric flares, winds or photospheric source in V2. The parameters for both the binaries are also studied with respect to the large sample of well-studied contact binaries and possible mechanisms for merger in contact binaries of both low and high mass ratios emphasized.