Hidden Companions to Intermediate-mass Stars. Upgraded Multiplicity 2 → 3. XXX. Discovery of a 0.79M ⊙, 7.5 au Outer Companion to the 0.20 au HgMn Binary Chi Lupi*
Year: 2025
Type: article
Abstract: Chi Lupi (χ Lup) is a nearby a = 0.20 au, 2.8M ⊙ + 1.9M ⊙ close binary and the prototype for the class of chemically peculiar mercury–manganese (HgMn) stars. There has been evidence for the presence of a third, outer companion based on variations of the systemic velocity of the inner binary but up to now it had evaded detection. Here we report on a VLTI/GRAVITY observation in which we detected an M C = 0.79M ⊙ red dwarf companion at a projected separation ρ ≃ 120 mas ↔ 7.5 au from the close binary, confirming χ Lup as a very compact triple system. The outer companion explains the eROSITA X-ray emission of χ Lup and hints that the inner binary was probably hardened by interacting with a circumbinary disk from which the outer companion also formed.
Source: Research Notes of the AAS
Authors: Idel Waisberg, Ygal Klein, Boaz Katz
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4413375710