Lambda Librae

λ Librae (Latinised as Lambda Librae) is the Bayer designation for a binary star system in the zodiac constellation of Libra. It can be faintly seen with the naked eye on a dark night, having an apparent visual magnitude of 5.03.[2] With an annual parallax shift of 10.54 mas,[1] it is located roughly 310 light years from the Sun. At that distance, the visual magnitude of this system is diminished by an extinction factor of 0.22 due to interstellar dust.[6]

Lambda Librae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Libra
Right ascension	15^h 53^m 20.05463^s[1]
Declination	−20° 10′ 01.4177″[1]
Apparent magnitude (V)	5.03[2]
Characteristics
Spectral type	B3 V[3]
U−B color index	−0.584[2]
B−V color index	−0.023[2]
Variable type	Rotating ellipsoidal[4]
Astrometry
Radial velocity (Rv)	−2.0±0.5[5] km/s
Proper motion (μ)	RA: −9.81[1] mas/yr Dec.: −26.85[1] mas/yr
Parallax (π)	10.54 ± 0.91[1] mas
Distance	310 ± 30 ly (95 ± 8 pc)
Absolute magnitude (MV)	0.56[6]
Orbit[7]
Period (P)	14.4829±0.0004 d
Eccentricity (e)	0.27±0.09
Periastron epoch (T)	2435172.380 ± 0.664 JD
Argument of periastron (ω) (secondary)	217±17°
Semi-amplitude (K1) (primary)	28.5±3.3 km/s
Details
Mass	5.01±0.26[8] M☉
Radius	3.9[9] R☉
Luminosity	743[8] L☉
Surface gravity (log g)	4.75 cgs
Temperature	18,700[8] K
Metallicity [Fe/H]	−0.27 dex
Rotational velocity (v sin i)	155[10] km/s
Age	282[6] Myr
Other designations
λ Lib, 45 Lib, BD−19°4249, FK5 1415, HD 142096, HIP 77811, HR 5902, SAO 183895.[11]
Database references
SIMBAD	data

This is a single-lined spectroscopic binary star system with an orbital period of 14.48 days and an eccentricity of 0.27.[7] The visible component is a B-type main sequence star with a stellar classification of B3 V.[3] It is a helium-weak chemically peculiar star[12] and a rotating ellipsoidal variable.[4] The star has an estimated 3.9[9] times the radius of the Sun and five times the Sun's mass.[8] This is a candidate Vega-like star, meaning that it shows an infrared excess characteristic of a circumstellar debris disk.[13] The system is a source of X-ray emission.[14]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
2. Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168.
3. Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
4. Hoffleit, Dorrit (1996), "A Catalogue of Correlations Between Eclipsing Binaries and Other Categories of Double Stars", The Journal of the American Association of Variable Star Observers, 24 (2): 105–116, Bibcode:1996JAVSO..24..105H.
5. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
6. Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035.
7. Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I.; et al. (2004), "S_B⁹: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics, 424 (2): 727, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213.
8. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355.
9. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) – Third edition – Comments and statistics", Astronomy and Astrophysics, 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
10. Abt, Helmut A.; et al. (2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573: 359, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
11. "lam Lib -- Spectroscopic binary", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-01-30.
12. Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars" (PDF), Astronomy and Astrophysics, 498 (3): 961–966, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788.
13. Saffe, C.; Gómez, M.; Pintado, O.; González, E. (October 2008), "Spectroscopic metallicities of Vega-like stars", Astronomy and Astrophysics, 490 (1): 297–305, arXiv:0805.3936, Bibcode:2008A&A...490..297S, doi:10.1051/0004-6361:200810260.
14. Berghoefer, T. W.; Schmitt, J. H. M. M.; Cassinelli, J. P. (September 1996), "The ROSAT all-sky survey catalogue of optically bright OB-type stars", Astronomy and Astrophysics Supplement, 118: 481–494, Bibcode:1996A&AS..118..481B.