HD 30187 B and HD 39927 B: two suspected nearby hot subdwarfs in resolved binaries

Abstract

In doing a B_T, V_T photometric solution for close Hipparcos double stars, based on the observations with the Tycho instrument of the Hipparcos satellite, we discovered two very blue subluminous components of HD 30187 and HD 39927. The position of the components on an observational HR diagram implies their being sdO or sdB hot subdwarfs. The only previously known sdO component of a visual binary, HD 113001 B, is also confirmed by our photometric data. The two new candidate hot subdwarfs have parallaxes 8.25 and 10.17 mas, respectively, and with angular separations of about 0.35 arcsec, the orbital periods must be of the order of 100 years. This should make it possible to determine their masses from observation. Based on observations made with the ESA Hipparcos satellite.