Hidden Companions to Intermediate-mass Stars. X. Solving for the Mass Ratio in the Spectroscopic Binary Zubenelgenubi = α 2 Librae

• Published in: Research notes of the AAS Vol. 7; no. 8; p. 180
• Main Authors: Waisberg, Idel, Klein, Ygal, Katz, Boaz
• Format: Journal Article
• Language: English
• Published: 23.08.2023
• ISSN: 2515-5172; 2515-5172
• DOI: 10.3847/2515-5172/acf28f

Zubenelgenubi  =  α 2 Librae is a nearby double-lined spectroscopic binary that forms a quadruple system with α 1 Librae. The radial velocity amplitude for the rapidly rotating primary is subject to a systematic uncertainty and as a result only a lower limit q  = 0.81 to the mass ratio has been previously reported. Here we present a VLTI/GRAVITY interferometric observation of Zubenelgenubi in which we measured a K band flux ratio of 74.7%, resulting in isochrone masses M Aa  = 1.95  M ⊙ and M Ab  = 1.79  M ⊙ ( q  = 0.92). The fact that the projected rotational velocities differ by a factor of three despite the similar masses suggests that the stellar spin axes are significantly misaligned in spite of the small semimajor axis a  = 0.52 au or alternatively that the primary is a merger product.