Hidden Companions to Intermediate-mass Stars. Upgraded Multiplicity 2 → 3. XXIII. Discovery of a 0.94M _⊙, 9.2 au Companion to the Ap Star Gamma Piscis Austrini A*

Abstract Gamma Piscis Austrini is a nearby ρ = 4.″1 ↔ 284 au visual binary consisting of an A0Vp primary (A) and an F5V secondary (B). Here we report that the primary is actually a closer binary based on a VLTI/GRAVITY interferometric observation. The newly discovered companion Ab has a K band flux ratio 4.8% ± 0.2% and a projected separation ρ = 143.50 mas ↔ 9.2 au relative to Aa. We estimate isochrone masses M Aa = 2.65 M ⊙ , M Ab = 0.94 M ⊙ and M B = 1.20 M ⊙ . γ PsA will become a triple white dwarf system within a Hubble time, with a low enough hierarchy for possibly interesting dynamical effects with a timescale P KL ∼ 200 kyr.