Many extreme velocity candidate stars have been found based on Gaia astrometry, but need spectroscopic confirmation. We selected late-type hypervelocity star (HVS) candidates from the Gaia DR3 catalogue with a 1σ lower limit of the tangential velocity of 800 km, s^-1. one of the brightest targets, stands out as a high-priority candidate for follow-up spectroscopy using the X-shooter instrument at ESO-VLT. We determined its atmospheric parameters and abundances utilising synthetic spectral grids and a global ̧hi²-minimisation 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 is lower than that based on the parallax, indicating that the star is not a hypervelocity binary star, but is bound to the Galaxy. The star turned out to be of spectral type F, very similar to the extreme-velocity star which we analysed in the same way as the target. Apparently, both are very metal-poor and old halo main-sequence (sdF) stars with masses slightly below the halo turn-off mass, and they both show low metallicity (Fe/H =-2. 3, -2. 6) and strong alpha enhancement (α/Fe ∼0. 44). is non-rotating (v instead is a fast rotator (v i=42. 3±2. 0 km, s^-1). The and ZTF light curves show an eclipse at a 1. 179-day period, similar to the rotation period of We therefore conclude that is a high-velocity tidally synchronised binary, most likely with a metal-poor M-dwarf companion.
Bhat et al. (Mon,) studied this question.