HD 124639 is a Be star in the southern constellation of Apus. It has an apparent visual magnitude of 6.42,[2] which makes it a challenge to view with the naked eye even under the best viewing conditions. Based upon an annual parallax shift of 3.41 mas as seen from Earth, it is 956 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction of 0.17 due to interstellar dust.[9] The star is moving further away with a heliocentric radial velocity of +27 km/s.[5]
This is a B-type main-sequence star with a stellar classification of B8 Ve.[3] The 'e' suffix indicates the presence of emission lines in the spectrum from ejected circumstellar material that is being heated by the host star. At the age of 126[3] million years, it has completed 96% of its lifespan on the main sequence.[7] Levenhagen and Leister (2006) class it as a B9 IVe star,[4] which would suggest it has already evolved into a subgiant star.
^ abcdJohnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
^ abcdefgLevenhagen, R. S.; Leister, N. V. (February 2004), "Physical Parameters of Southern B- and Be-Type Stars", The Astronomical Journal, 127 (2): 1176–1180, Bibcode:2004AJ....127.1176L, doi:10.1086/381063.
^ abKharchenko, N. V.; et al. (2007), "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations", Astronomische Nachrichten, 328 (9): 889–896, arXiv:0705.0878, Bibcode:2007AN....328..889K, doi:10.1002/asna.200710776, S2CID119323941.
^ abcdefZorec, J.; et al. (November 2016), "Critical study of the distribution of rotational velocities of Be stars. I. Deconvolution methods, effects due to gravity darkening, macroturbulence, and binarity", Astronomy & Astrophysics, 595: 26, Bibcode:2016A&A...595A.132Z, doi:10.1051/0004-6361/201628760.
