Abstract Details

Name: Keerthana S Narayan
Affiliation: Christ (Deemed to be University)
Conference ID: ASI2020_241
Title : Is the ratio of blue to red supergiants indicative of the metallicity of an open cluster ?
Authors and Co-Authors : Keerthana S Narayan, Blesson Mathew
Abstract Type : Poster
Abstract Category : Stars, ISM and Galaxy
Abstract : Every star in the night sky takes its birth, lives over a period of time and explodes as novae/supernovae. The intriguing aspect is to understand various stages in the evolution of a star after it leaves main sequence. Though lots of studies were done, stellar evolution still leaves mysteries and excitement to the astronomers. High mass stars (≥ 8Mʘ), in general, can evolve through various evolutionary phases such as Blue Supergiants, Red Supergiants, Luminous Blue Variables and Wolf-Rayet stars. The way massive stars populate in any of these evolutionary stages depends on its initial mass, chemical composition, metallicity and mass loss. Studies pertaining to blue and red supergiants is important since they are identified as progenitors to Type II supernovae. For the present work, we compiled a sample of 154 blue supergiants and 67 red supergiants, belonging to 60 open clusters. We assessed the stellar parameters and evaluated the membership probability of these evolved stars in open clusters using Gaia DR2 data. We found that, in most cases, the ratio of blue to red supergiants (B/R ratio) correlates with the mean metallicity of the open cluster. Also, when plotted with respect to galactocentric radius, the B/R ratio and metallicity is higher near the Galactic center and decreases towards the outer arms. This can also be identified in terms of active star formation rate in the Galactic center relative to the outer arms. We have identified a few clusters where the B/R ratio do not follow with the metallicity of the cluster, which demands more investigation.