A new reference catalogue for the very metal-poor Universe: +150 OB stars in Sextans A

ABSTRACT Local Group (LG) very metal-poor massive stars are the best proxy for First Stars of Universe and fundamental to modelling evolution early galaxies. These may follow new evolutionary pathways restricted low metallicities, such as chemically homogeneous (CHE). However, given great distance leap needed reach galaxies LG vicinity, no comprehensive spectroscopic studies have been carried out at metallicities lower than Small Magellanic Cloud (SMC; Z = 1/5 Z⊙) until now. After five observing campaigns 10.4-m Gran Telescopio Canarias, we assembled a low-resolution (R ∼ 1000) collection more 150 OB in 1/10 Z⊙ galaxy Sextans A, increasing by an order magnitude number known this galaxy. The catalogue includes 38 BA-type supergiants, four red first candidate binary systems, CHE sources systems hosting stripped stars. sample mainly overlap higher concentrations neutral gas A. find some H i column-density regions. colour–magnitude diagram presents large dispersion, which suggests uneven, internal extinction This is largest OB-type ever produced sub-SMC metallicities. constitutes step unveiling fates stars, analyzing dependence radiation-driven winds with metallicity, studying environment analogue Universe.