Discovery of a hot post-AGB star in Galactic globular cluster E3
| Autor: | Kumar, R., Moharana, A., Piridi, S., Pradhan, A. C., Hełminiak, K. G., Ikonnikova, N., Dodin, A., Szczerba, R., Giersz, M., Ojha, D. K., Samal, M. R. |
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| Rok vydání: | 2024 |
| Předmět: | |
| Zdroj: | A&A 685, L6 (2024) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1051/0004-6361/202449777 |
| Popis: | We report a new hot post-asymptotic giant branch (PAGB) star in the Galactic globular cluster (GC) E3, which is one of the first of the identified PAGB stars in a GC to show a binary signature. The star stands out as the brightest source in E3 in the \mbox{{\em Astrosat}}/UVIT images. We confirmed its membership with the cluster E3 using Gaia DR3 kinematics and parallax measurements. We supplemented the photometric observations with radial velocities (RVs) from high-resolution spectroscopic observations at two epochs and with ground- and space-based photometric observations from 0.13 $\mu$m to 22 $\mu$m. We find that the RVs vary over $\sim$6 \kms\ between the two epochs. This is an indication of the star being in a binary orbit. A simulation of possible binary systems with the observed RVs suggests a binary period of either 39.12 days or 17.83 days with mass ratio q$\geq$1.0. The [Fe/H] derived using the high-resolution spectra is $\sim -$0.7 dex, which closely matches the cluster metallicity. The spectroscopic and photometric measurements suggest \Teff\ and $\log g$ of the star as 17\,500$\pm$1\,000~K and 2.37$\pm$0.20~dex, respectively. Various PAGB evolutionary tracks on the Hertzsprung--Russell (H-R) diagram suggest a current mass of the star in the range 0.51$-$0.55 \Msun. The star is enriched with C and O abundances, showing similar CNO abundances compared to the other PAGB stars in GCs with the evidence of the third dredge-up on the AGB phase. Comment: Published in A&A Letters, Published Version |
| Databáze: | arXiv |
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