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Membership analysis of galactic carbon stars in open clusters and analysis of frequency by mass using GAIA data

Presentation #139.13 in the session Galaxy Clusters/Large Scale Structure, Cosmic Distance — iPoster Session.

Published onJun 29, 2022
Membership analysis of galactic carbon stars in open clusters and analysis of frequency by mass using GAIA data

Carbon stars (C stars) are evolved from intermediate mass stars at the tip of the asymptotic giant branch (AGB) in the course of their evolution. These are typically called classical C stars. Their carbon to oxygen number density ratio exceeds one and their spectra feature carbon bearing molecules (like CO, CN etc.). C stars can be extremely luminous and contribute to the integrated light of a stellar population. We have some idea about the masses of C stars in Magellanic Cloud (MC) but it has not previously been possible to assign individual masses to these type of stars in the Milky Way (MW). GAIA DR2 provides us with extremely accurate parallax, proper motion and color (in G, BP and RP bands) information for about 1.3 billion galactic stars. We cross correlated catalogues of galactic C stars with catalogues of open clusters (OCs) to check if any of the C stars are members of the OC. We identified 12 such candidate C stars which are possible members of 12 different OCs. We then went on to analyse the membership probability using GAIA DR2 data in α–δ, μα–μδ and π spaces. We also use color-magnitude diagram (using GAIA BP and RP color bands) to assess if the star in question is really a classical C star. The result of this analysis led us to discard 3 C stars which are most probably not members of their respective clusters. We computed the number per unit luminosity (in V-band and GAIA-RP band) as a function of turn off mass for the remaining 9 C stars. We find good agreement with the statistics with MC C stars till m ≈ 1.38M and do not find any galactic classical C star below this mass. We also find an ambiguous C star candidate at ~ 7M. The identified OCs with C stars have different metallicities but we do not find evidence for strong metallicity effect on C star production.

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