Hidden Companions to Intermediate-mass Stars. XVII. Uncovering a 0.72 M ⊙, 0.35 au Companion in the Spectroscopic Binary Sigma Sculptoris*

Abstract

Abstract Sigma Sculptoris is a nearby star that was suspected of being a rotating Ap variable. It was recently found not to be an Ap star but rather a 47 days single-lined spectroscopic binary. Here we report on the direct detection of the companion with a K band flux ratio of 5.5% at a projected separation of 5.16 mas based on a VLTI/GRAVITY observation. We estimate isochrone masses M A  = 1.95M ⊙ and M B  = 0.72M ⊙, a semimajor axis a = 0.35 au and an orbital inclination i = 27° (or 153°). The large rotational velocity of the primary (assuming spin–orbit alignment) is consistent with the lack of prominent chemical peculiarities.