Asteroseismology of pulsating subdwarf B stars using space data
Sumanta Kumar Sahoo
Date & Time :
Subdwarf B (sdB) stars are horizontal branch stars located on their blue extension, consisting of a convective helium-burning core, helium shell, and a thin (in mass) hydrogen envelope. The formation of sdBs is not clear as most of the hydrogen must be stripped off before the helium flash occurs. There are two most probable evolutionary paths are there for sdBs. Binarity is one as over 70 % of sdBs are found in binaries. Two white dwarfs merger event is the second one, which also explains single sdBs. Hundreds of sdBs are found to pulsate (sdBV), which opens the opportunity to study their interiors employing asteroseismology. Unprecedented data delivery by the space missions Kepler and K2 led to a series of new sdBVs discoveries, which was not possible from ground-based observations. TESS mission being the perfect successor of Kepler continues to discover new sdBs all over the sky. We have utilized both the short (SC) and ultra-short (USC) cadences and have detected around 60 sdBVs with very rich pulsation spectra. We made additional discoveries of variable sdBs using TESS Full Frame Images sampled at 30minutes. We used two techniques for mode identification and identified their pulsation mode geometries. We are also continuing our effort to obtain follow–up spectroscopic observations. Using Gaia parallaxes and spectral energy distributions, we calculated stellar parameters like radii, masses, and luminosities. These analyses will provide constraints for asteroseismic modeling that we have just entered, and the results will be derived within the coming months. Our results will surely help us to understand the enigmatic evolution of sdBs
About Speaker :
The speaker is a Ph.D. student at Nicolaus Copernicus Astronomical Center (CAMK-PAN), Warsaw, Poland. This seminar is a part of the activities commemorating "75 years of India's Independence: Azadi ka Amrit Mahotsav" at ARIES.