Magnetic activities on low-mass stars and X-ray binaries

          In this seminar, I will discuss my proposal to carry out an in-depth study of low-mass stars and X-ray binary systems using X-ray, FUV, and NUV observations from ASTROSAT and other X-ray telescopes. Low-mass stars with a similar internal structure to that of the Sun, supposed to operate a similar type of dynamo mechanism. However, the observations of these stars have introduced a range of stellar rotation periods, gravities, masses, and ages, which put into the debate on the existing magnetic dynamo theory. In order to provide useful constraints for the dynamo theory, I intend to study the highly time-resolved correlation of photosphere, upper chromospheric and coronal activity indicators, the rotational modulation, surface inhomogeneity, surface differential rotations, and flaring events. Study of this observational evidence of magnetic activities will be very useful to yield insight into the nature of the associated magnetic dynamos. Simultaneous observations in UV and X-ray would give us the chromospheric and coronal features of the binary system. Whereas, the time-resolved spectral analysis will allow us to investigate origin and mechanism of the emission of radiation in this system. On the other hand, X-ray binaries show an excessive amount of spectral and timing properties which can be used to study the fundamental problems, such as probing the strong gravity and dense matter and understanding the accretion-ejection mechanism. Such spectral and timing properties and transitions are even poorly observed for the X-ray binaries having low accretion rates. The broadband X-ray spectral and fast timing capabilities of ASTROSAT would help us to advance our knowledge of the low accretion rate regime and will characterize the less studied source.