| Name: | ARVIND DATTATREY |
| Affiliation: | Aryabhatta Research Institute of Observational Sciences |
| Conference ID : | ASI2024_571 |
| Title : | UVIT/AstroSat detection of extremely low mass white dwarf companions to blue straggler stars in NGC 362 |
| Authors : | Arvind K. Dattatrey(1,2), R.K.S. Yadav1, Sharmila Rani3, Annapurni Subramaniam3, Gaurav Singh3,
Snehalata Sahu4, and Ravi S. Singh2 |
| Authors Affiliation: | 1 Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263002, India.
2 Deen Dayal Upadhyay Gorakhpur University, Gorakhpur, Uttar Pradesh 273009,India.
3 Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India.
4 University of Warwick, Coventry CV4 7AL, United Kingdom |
| Mode of Presentation: | Oral |
| Abstract Category : | Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Abstract : | We present discovery of extremely low-mass white dwarf stars (ELM WDs) coexisting with blue straggler stars (BSSs) within the NGC 362 Galactic globular cluster. Our investigation leverages data acquired through the Ultra Violet Imaging Telescope (UVIT) on AstroSat, and it involves the generation of Spectral Energy Distributions (SEDs) for 26 BSSs, incorporating information from UVIT, UVOT, Gaia Early Data Release 3 (EDR3), and the 2.2 m ESO/MPI telescope.
Our analysis reveals that 14 of these BSSs exhibit single-SED fits, while the remaining 12 exhibit double-SED fits, unveiling ELM WDs as binary companions. These ELM WDs demonstrate a broad range of characteristics, including effective temperature (Teff) values spanning from 9750 to 18000 K, radii (R) ranging from 0.1 to 0.4 times the solar radius (R⊙), luminosities (L) spanning from 0.4 to 3.3 times the solar luminosity (L⊙), and masses (M) between 0.16 and 0.20 times the solar mass (M⊙). This observation suggests that these 12 BSSs have evolved through a Case A/B mass transfer process, resulting in the formation of ELM WDs as their companions.
Significantly, this represents the inaugural identification of ELM WDs as companions to BSSs within globular clusters. The NGC 362 cluster is known for hosting a binary BSS sequence, and our findings indicate that the 12 binary BSSs, along with the 14 single BSSs categorized by their SEDs, follow the mass transfer and collisional sequence of BSSs within the color-magnitude diagram.
The cooling ages of nine of these ELM WDs are determined to be less than 500 million years, shedding light on their relatively recent formation. While it remains possible that the binary BSSs formed during the core-collapse event approximately 200 million years ago or as a result of the cluster's dynamical evolution, they provide valuable insights into the dynamic processes at play within this particular cluster. |
