| Name: | Anju Panthi |
| Affiliation: | Birla Institute of Technology and Science, Pilani |
| Conference ID : | ASI2023_91 |
| Title : | Search for hot companions in blue metal-poor stars using UVIT/AstroSat |
| Authors : | Anju Panthi , Kaushar Vaidya, Annapurni Subramaniam , Vikrant Jadhav , Sindhu Pandey , Snehalata Sahu , Sivarani T. , Sharmila Rani |
| Mode of Presentation: | Oral |
| Abstract Category : | Stars, ISM and Galaxy |
| Abstract : | Blue metal-poor (BMP) stars are main-sequence stars that appear bluer and more luminous than
normal turn-off stars of metal-poor globular clusters. They are metal deficient, with [Fe/H] < -1.
These stars are believed to be either field blue straggler stars (BSS) formed via post mass transfer mechanism or accreted from dwarf satellite galaxies of the Milky Way. A significant fraction of BMP stars are discovered to be binaries, typically with long periods and circular orbits, likely to have a compact companion. UVIT/AstroSat has observed 27 BMP stars in two FUV filters, F148W and F169M. We report the discovery of hot companions in 12 of them. The hot companions with estimated temperatures, Teff ∼ 10500 – 32000 K, are white dwarfs (WDs) of extremely low-mass (∼ 0.20 M⊙ ), low-mass ( ∼ 0.20 – 0.40 M⊙ ), normal mass ( ∼ 0.40 – 0.60 M⊙ ), and high-mass ( ∼ 0.8M⊙ ). Eight BMP stars with orbital periods < 100 days are found to have extremely low-mass and low-mass WDs as their hot companions. Our findings confirm Case-A/Case-B mass transfer as the possible formation mechanism of these BMP stars. Four BMP stars with long-periods > 100 days are found to have normal mass WDs as their companions. This supports Case-C mass transfer as the formation pathway for these 4 BMP stars. Our initial analysis suggests that Case-A, Case-B, and Case-C mass transfer channels play a major role in the formation of BMP stars and thus BMP stars are likely to be candidates of field BSS. |
