Astronomy and Astrophysics Seminars

High-resolution spectroscopy study of stars with PARAS

by Dr. Priyanka Chaturvedi (Physical Research Laboratory, Ahmedabad)

Wednesday, October 26, 2016 from to (Asia/Kolkata)
at TIFR ( A269 )
Description
Despite copious number of M dwarfs present in our galaxy, masses and radii for such stars are still not determined at higher accuracies, primarily due to their fainter magnitudes in visible band. Radii for stars less massive than Sun are known to be 10% smaller theoretically than observed and temperatures are 5% higher. It is suggested that strong magnetic fields inhibit convection, which causes these stars to inflate. We have made radial velocity observations of few M dwarfs in eclipsing binary systems as companions to brighter stars as part of my thesis work. The instrument used is PRL's indigenous high-resolution optical fiber-fed spectrograph PARAS (Physical Research Laboratory Advanced Radial-velocity Abu-sky Search) coupled with the 1.2 m telescope at Mt. Abu. I will be discussing the techniques and some preliminary results obtained after studying these systems. In the Radial Velocity technique, we determine the mass and radius of the secondary star (or a planet) as a function of the mass and radius of the primary host star. Thus, accurate determination of host star properties is important in proper estimation of mass and age of the companion. We, as a team of PARAS, have also developed an indigenous package, PARAS-SPEC, to determine the stellar properties of the primary host star. The basic principles and methodology used for designing this tool will be discussed in the talk. A few results when applied to known and unknown stars shall be discussed along.