CPD-20 1123 (Albus 1) is a bright He-B Subdwarf

Abstract

Based on photometric and astrometric data it has been proposed that Albus 1 (also known as CPD-20 1123) might be a hot white dwarf similar to G191-B2B or, alternatively, a hot subdwarf. We obtained a series of optical spectra showing that CPD-20 1123 is a bright He-B subdwarf. We analyzed the HI Balmer and HeI line spectra and measured T_eff = 19800+/-400 K, log g = 4.55+/-0.10, and log N(He)/N(H) = 0.15+/-0.15. This peculiar object belongs to a family of evolved helium-rich stars that may be the products of double-degenerate mergers, or, alternatively, the products of post horizontal- or giant-branch evolution.