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Name: Sharmila Rani Affiliation: SRF, IIA Conference ID: ASI2020_134 Title : Study of UV bright stellar populations in Galactic Globular Cluster NGC 1261 Authors and Co-Authors : Sharmila Rani, Gajendra Pandey, Annapurni Subramaniam Abstract Type : Poster Abstract Category : Stars, ISM and Galaxy Abstract : A globular cluster (GC) is a collection of several thousand to one million stars distributed in a spherical, gravitationally-bound system. GCs are well studied in optical wavebands but ultraviolet studies are relatively sparse. Some evolved populations in globular clusters are brighter in ultraviolet (UV) region than in optical, such as horizontal branch (HB), blue straggler stars (BSSs), post-asymptotic giant branch (PAGB) stars and white dwarfs (WDs). We plan to study the hot UV bright stellar populations in GCs to understand their formation and evolution. We have observed NGC 1261 in four near-UV and two far-UV filters of the ultraviolet imaging telescope (UVIT) on board Astrosat. By performing PSF photometry on science ready images, we have created different UV colour-magnitude diagrams (CMDs). We detected the full HB in NUV CMDs and identified 2 EHB stars for the first time. HB stars have a tight sequence in UV-Optical CMDs which is more or less aligned with Padova isochrones. Effective temperature (Teff), luminosity and radius of bright HB stars estimated using spectral energy distribution suggest that the EHB stars have Teff around 30000 K, are unlikely to be evolved from HB but are an extension of HB. The comparison of the radial distribution of the 70 BSS stars with 220 HB stars indicates that BSSs are more centrally concentrated, suggesting that the cluster is dynamically old. |