Shanti Priya Devarapalli

arXiv2023

Multi-wavelength photometric study of five contact binaries in the field of globular cluster M4

Binary stars are believed to be key determinants in understanding globular cluster evolution. In this paper, we present the Multi-band photometric analyses of five variables in the nearest galactic globular cluster M4, from the observations of CASE, M4 Core Project with HST for four variables (V48, V49, V51, and V55) and the data collected from T40 and C18 Telescopes of Wise Observatory for one variable (NV4). The light curves of five binaries are analyzed using the Wilson-Devinney method (WD) and their fundamental parameters have been derived. A period variation study was carried out using times of minima obtained from the literature for four binaries and the nature of the variation observed is discussed. The evolutionary state of systems is evaluated using M-R diagram, correlating with that of a few well-studied close binaries in other globular clusters. Based on the data obtained from the Gaia DR3 database, a three-dimensional Vector-Point Diagrams (VPD) was built to evaluate the cluster membership of the variables, and two out of them (V49 and NV4) were found to be not cluster members.

astro-ph.SR↗

arXiv2023

The First Photometric and Spectroscopic Study of Contact Binary V2840 Cygni

The first photometric, spectroscopic, and period variation studies of neglected short-period eclipsing binary V2840 Cygni are presented. High Mass Ratio Contact Binaries, especially those in the weak-contact configuration are vital while probing into the evolutionary models of CBs using stellar parameters. The photometric solutions reveal the weak-contact nature of V2840 Cygni with a high mass ratio ($\sim1.36$), motivating us to investigate the nature of such binaries. The period variation study of V2840 Cygni spanning for 15 years shows a secular period decrease at a rate of $\sim5.5\times10^{-7}$d/yr indicating mass transfer between the components. The superimposed cyclic variation provides a basic understanding of the possible third body (P$_3$ $\sim8$ yr, m$_3$ $\sim0.51$M$_\odot$). Following the derived parameters, the evolution of the system is discussed based on Thermal Relaxation Oscillation (TRO) model. It is found that V2840 Cygni falls in a special category of HMRCBs, that validates TRO. To characterise the nature of HMRCBs, a catalog of 59 CBs with high mass ratios has been compiled along with their derived parameters from the literature. For all the HMRCBs in the study, a possible correlation between their contact configuration and observed period variations for relative log\emph{J$_{rel}$} is discussed. The spectroscopic study of V2840 Cygni provides evidence of the presence of magnetic activity in the system and the existence of ongoing mass transfer which is additionally deduced from the period variation study. The LAMOST spectra of 17 HMRCBs are collected to interpret the stellar magnetic activity in such systems.

astro-ph.SR↗