When lettering Bayer designations to Scorpius, Johann Bayer accidentally gave the designation Phi Scorpii to what is now known to be 49 Librae and 48 Librae. That designation is no longer in use.[8]
Characteristics
This is a single-lined spectroscopic binary system, first spotted to have a variable radial velocity by W. S. Adams in 1924. Both stars take 3.128 years to orbit around the system's center of mass and have a rather low an eccentricity of 0.11.[4]
The primary component has a stellar classification of F8 V or F9 V,[4] which at first would indicate it is an F-type main-sequence star. Such star would have an age around 2.3 billion years, consistent with a Population I star. However, the space velocity and chemical composition of this star is inconsistent with that of a Pop I star, indicating it is a much older (over 12 billion years) Population II star. To account for its evolutionary stage, which is too young for such age, it has been proposed 49 Lib A is a blue straggler that was once smaller but gained mass after interacting gravitationally with the secondary.[3]
The secondary is a white dwarf with half the mass of the Sun.[3] The system is a source for radio and X-ray emissions, which may be coming from the secondary companion.[9]
Evolution
Initially both components were G-type main-sequence stars separated by 1.50 AU. The primary had a mass of 1.00±0.03 M☉, while the secondary had 1.05±0.02 M☉. [3]
The stars then started to evolve, becoming red giants. Mass transfer between components started to happen. The end product was the secondary becoming the current white dwarf with half of its original mass, and the primary gaining 0.55 M☉ and becoming a F-type star.[3]
Within 500 million years, the primary will evolve and 49 Librae may become a double white dwarf system. However, if the secondary accrete sufficient mass during the proccess, the system may instead undergo a Type Ia supernova.[3]
^ abcdNicolet, B. (October 1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
^ abcdNordström, B.; et al. (November 2007), "The Geneva-Copenhagen survey of the Solar neighbourhood. II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk", Astronomy & Astrophysics, 475 (2): 519–537, arXiv:0707.1891, Bibcode:2007A&A...475..519H, doi:10.1051/0004-6361:20077221, S2CID119054949.
