Hidden Companions to Intermediate-mass Stars. VII. Discovery of a 0.76 M ⊙, 39 au Companion to the Ap Star HIP 88866 = π Pavonis* *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.

Abstract

HIP 88866 = π Pavonis is a nearby chemically peculiar Ap star. Here we report the discovery of a companion with an H band contrast ΔH = 3.63 at a projected separation ρ = 959 mas ↔ 39 au based on the acquisition camera image of a VLTI/GRAVITY observation. Isochrone fitting yields masses M A = 1.80 M ⊙ and M B = 0.76 M ⊙ and an age of 1.4 Gyr. However, even for a face-on orbit the companion cannot fully account for the GaiaDR3-Hipparcos proper motion change of π Pav. We present constraints on the nature and location of a putative additional closer companion based on the lack of its detection in the interferometric data.