Ancient, eclipsing, tidally-locked: A blue lurker progenitor in the population of extreme-velocity star candidates
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arXiv
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| Auteurs principaux: | , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866911110803750912 |
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| author | Bhat, A. Dorsch, M. Geier, S. Heber, U. Dawson, H. Mattig, F. Benitez-Palacios, D. Fernandez-Schlosser, Pablo |
| author_facet | Bhat, A. Dorsch, M. Geier, S. Heber, U. Dawson, H. Mattig, F. Benitez-Palacios, D. Fernandez-Schlosser, Pablo |
| contents | Many extreme velocity candidate stars have been found based on \textit{Gaia} astrometry, but need spectroscopic confirmation. We select late-type hypervelocity star (HVS) candidates from the \textit{Gaia} DR3 catalog with a $1σ$ lower limit of the tangential velocity of 800 km\,s$^{-1}$. J1903-0023, one of the brightest targets, stands out as high priority candidate for follow-up spectroscopy using the X-shooter instrument at ESO-VLT. We determine its atmospheric parameters and abundances utilizing synthetic spectral grids and a global $χ^2-$minimization procedure, and its stellar parameters with the help of evolutionary tracks and the spectral energy distribution. The star shows variability in its light curve and follow-up spectroscopy confirms that the star is radial-velocity variable. The spectroscopic distance of J1903-0023 is lower than that based on the parallax, indicating that the star is not a hypervelocity binary star but bound to the Galaxy. The star turned out to be of spectral type F, very similar to the extreme-velocity star J0725-2351, which we analyse in the same way as the target. Apparently, both stars are very metal poor and old halo main-sequence (sdF) stars with masses slightly below the halo turn-off mass, and share the low metallicity ([Fe/H]=-2.3,-2.6) and strong alpha enhancement ([$α$/Fe]$\sim0.44$). While J0725-2351 is non-rotating ($v\sin\,i<3$\,km\,s$^{-1}$), J1903-0023 is a fast rotator ($v\sin i=42.3\pm2.0$ km\,s$^{-1}$). The Gaia, and ZTF light curves show an eclipse at a 1.179 day period, similar to the rotation period of J1903-0023. We therefore conclude that J1903-0023 is a high-velocity tidally-synchronised binary most likely with a metal-poor M dwarf companion. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_17101 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Ancient, eclipsing, tidally-locked: A blue lurker progenitor in the population of extreme-velocity star candidates Bhat, A. Dorsch, M. Geier, S. Heber, U. Dawson, H. Mattig, F. Benitez-Palacios, D. Fernandez-Schlosser, Pablo Solar and Stellar Astrophysics Astrophysics of Galaxies Many extreme velocity candidate stars have been found based on \textit{Gaia} astrometry, but need spectroscopic confirmation. We select late-type hypervelocity star (HVS) candidates from the \textit{Gaia} DR3 catalog with a $1σ$ lower limit of the tangential velocity of 800 km\,s$^{-1}$. J1903-0023, one of the brightest targets, stands out as high priority candidate for follow-up spectroscopy using the X-shooter instrument at ESO-VLT. We determine its atmospheric parameters and abundances utilizing synthetic spectral grids and a global $χ^2-$minimization procedure, and its stellar parameters with the help of evolutionary tracks and the spectral energy distribution. The star shows variability in its light curve and follow-up spectroscopy confirms that the star is radial-velocity variable. The spectroscopic distance of J1903-0023 is lower than that based on the parallax, indicating that the star is not a hypervelocity binary star but bound to the Galaxy. The star turned out to be of spectral type F, very similar to the extreme-velocity star J0725-2351, which we analyse in the same way as the target. Apparently, both stars are very metal poor and old halo main-sequence (sdF) stars with masses slightly below the halo turn-off mass, and share the low metallicity ([Fe/H]=-2.3,-2.6) and strong alpha enhancement ([$α$/Fe]$\sim0.44$). While J0725-2351 is non-rotating ($v\sin\,i<3$\,km\,s$^{-1}$), J1903-0023 is a fast rotator ($v\sin i=42.3\pm2.0$ km\,s$^{-1}$). The Gaia, and ZTF light curves show an eclipse at a 1.179 day period, similar to the rotation period of J1903-0023. We therefore conclude that J1903-0023 is a high-velocity tidally-synchronised binary most likely with a metal-poor M dwarf companion. |
| title | Ancient, eclipsing, tidally-locked: A blue lurker progenitor in the population of extreme-velocity star candidates |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.17101 |