Abstract Details

Name: Priyanka Chaturvedi
Affiliation: Physical Research Laboratory
Conference ID: ASI2017_433
Title : Radial Velocity studies of Eclipsing Binary Systems
Authors and Co-Authors : Priyanka Chaturvedi (PRL)
Abstract Type : Thesis
Abstract Category : Thesis
Abstract : A vast majority of observations of M dwarfs for varying masses have reported a higher radius by 10-20% and a temperature lower by 5-10% than those predicted by the models (Torres and Ribas 2002, Lopez-Morales et al. 2007, Torres et al. 2010). The mismatch of the radii as seen in these stars is termed as the 'M dwarf radius problem' (Triaud et al. 2013). Studying M dwarfs or very low mass stars (VLMS) in Eclipsing Binaries (EBs) in the mass range of 0.08-0.4 M_sun with an aim to alleviate the M dwarf radius problem has been the motivation for the thesis work. This research work has contributed 12% more samples to the existing 26 samples with masses and radii measurements at accuracies ~ 10%. We shortlisted a collection of 10 potential EB candidates from the photometric catalogues of Kepler, STEREO, and Super-Wasp for the PRL EB programme led by me. The aim of the study was to look for single-lined EB, where VLMS occur as companions to F, G, K type primaries. Radial velocity (RV) data of these sources were obtained using the high-resolution spectrograph, Physical Research Laboratory Advanced Radial-velocity Abu-sky Search (PARAS) coupled with the 1.2 m telescope at Gurushikhar Observatory, Mount Abu, India. Wideband differential photometry with the help of a 10 inch telescope located at PRL's Mount Abu Observatory has also been performed to complement the spectroscopy. In addition, for a few sources, the archival photometry data have been analysed and included in our study. A software code, PARAS SPEC has been developed to determine the stellar properties of the host star (T_eff, [Fe/H] and log g), essential to determine the mass and radius of its companion, based on the synthetic spectral fitting and equivalent width methods. The basic principles and methodology utilized to develop this tool and results obtained when applied to some of the programme stars are discussed in thesis. My thesis has produced the first science results with PARAS by discerning the masses, radii and orbital parameters of four VLMS in single-lined detached EBs (M3 to M7 spectral type) i.e HD 213597, HD 23765, SAO 106989 and 1SWASP J2334318+295556. Orbital parameters and system properties such as period, RV semi-amplitude, semi-major axis, masses and radii of the components and inclination are studied as a part of this research work. We have detected three F+M EBs, wherein the M dwarfs have mass range close to the transition between radiative and convective zones (mass less than 0.3 M_sun). The fourth EB is a K+M EB, wherein the M dwarf is the second least massive star studied for its mass and radius at such high precisions.