| Name: | Deepthi S. Prabhu |
| Affiliation: | Indian Institute of Astrophysics |
| Conference ID : | ASI2024_946 |
| Title : | Exploring Stellar Exotica in the Core-Collapsed Globular Cluster NGC 6397: Insights from AstroSat/UVIT |
| Authors : | Deepthi S. Prabhu (1), Annapurni Subramaniam (1), Snehalata Sahu (2) |
| Authors Affiliation: | (1) Indian Institute of Astrophysics, Bengaluru - 560034, India
(2) Department of Physics, University of Warwick, Coventry CV4 7AL, UK |
| Mode of Presentation: | Poster |
| Abstract Category : | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract : | Highly frequent dynamical interactions in the dense environments of globular clusters (GCs) result in several exotic sources like blue stragglers (BSs), helium-core white dwarfs (He-core WDs), cataclysmic variables, and so on. BSs are predicted to form mainly through stellar collisions leading to mergers or via mass transfer (MT) in binary systems. He-core WDs are speculated to develop mainly through binary evolution as very low-mass single stars cannot reach the end stages within the Hubble time unless an unusual amount of mass-loss occurs in the red-giant phase. Studying such sources in GCs thus contributes to our broader understanding of stellar evolution, binary interactions, and the dynamical processes at play. NGC 6397, a nearby core-collapsed globular cluster, is an interesting candidate that has been reported to host several stellar exotica. In this work, we studied this GC using AstroSat/UVIT FUV observations complemented by catalogs based on HST, Gaia, and ground-based telescopes. A total of 197 FUV-bright sources were detected, and their optical counterparts were identified. Among these, we found 29 BSs based on their positions on the UV-optical CMD and 3 He-core WD candidates by cross-matching with previous works. We also found a previously unreported extreme horizontal branch star. We constructed and fitted the spectral energy distributions (SEDs) of these sources to derive their fundamental parameters and thus determine their evolutionary status. The derived parameters of the He-WD candidates were found to fall within the range of low-mass He-WD models, although the presence of binary companions could not be confirmed. The SEDs of two BSs showed UV excess and required double-component models involving WDs for a satisfactory fit, implying that these could have formed via the MT scenario. I will present these and other results in detail. |
