The Gaia Data Release 2 provides a parallax of 0.734+/-0.073 mas for SDSS J102915+172927, currently the most metal-poor known object. This parallax implies that it is dwarf star, ruling out the scenario that it is a subgiant. The subgiant scenario had as a corollary that the star had been formed in a medium highly enriched in C, thus making line cooling efficient during the collapse, that was also highly enriched in Fe by Type Ia SNe. This scenario can also now be ruled out for this star, reinforcing the need of dust cooling and fragmentation to explain its formation.
@article{arxiv.1804.10419,
title = {Gaia confirms that SDSS J102915+172927 is a dwarf star},
author = {P. Bonifacio and E. Caffau and M. Spite and F. Spite and P. François and S. Zaggia and F. Arenou and R. Haigron and N. Leclerc and O. Marchal and P. Panuzzo and G. Plum and P. Sartoretti},
journal= {arXiv preprint arXiv:1804.10419},
year = {2018}
}
Comments
Accepted for publication in Research Notes of the AAS