J01020100-7122208: an accreted evolved blue straggler that was not ejected from a supermassive black hole

J01020100-7122208 is a star whose origin and nature still challenges us. It was first believed to be a yellow supergiant ejected from the Small Magellanic Cloud, hut it was more recently claimed to be a red giant accelerated by the Milky Way's central black hole. In order to unveil its nature, we analysed photometric, astrometric, and high-resolution spectroscopic observations to estimate the orbit, age, and 16 elemental abundances. Our results show that this star has a retrograde and highly-eccentric orbit, e = 0.914(-0.020)(+0.016). Correspondingly, it likely crossed the Galactic disc at 550 pc from the Galactic Centre. We obtained a spectroscopic mass and age of 1.09 +/- 0.10 M-circle dot and 4.51 +/- 1.44 Gyr, respectively. Its chemical composition is similar to the abundance of other retrograde halo stars. We found that the star is enriched in europium, having (Eu/Fe] = 0.93 +/- 0.24, and is more metal-poor than reported in the literature, with [Fe/H] = -1.30 +/- 0.10. This information was used to conclude that J01020100-7122208 is likely not a star ejected from the central black of the Milky Way or from the Small Magellanic Cloud. Instead, we propose that it is simply a halo star that was likely accreted by the Milky Way in the distant past, but its mass and age suggest it is probably an evolved blue straggler.

Automated summary

Our study reveals that J01020100-7122208 is a star with a retrograde and highly-eccentric orbit, likely accreted by the Milky Way in the distant past. Its mass and age suggest it is probably an evolved blue straggler.