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, having an apparent visual magnitude of 5.03.^[3] With an annual parallax shift of 10.54 mas,^[2] it is 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.^[7] It is 0.1 degree north of the ecliptic.

Lambda Librae

A light curve for Lambda Librae, adapted from Wraight et al. (2012)[1]
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Libra
Right ascension	15h 53m 20.05463s[2]
Declination	−20° 10′ 01.4177″[2]
Apparent magnitude (V)	5.03[3]
Characteristics
Spectral type	B3 V[4]
U−B color index	−0.584[3]
B−V color index	−0.023[3]
Variable type	Rotating ellipsoidal[5]
Astrometry
Radial velocity (Rv)	−2.0±0.5[6] km/s
Proper motion (μ)	RA: −9.81[2] mas/yr Dec.: −26.85[2] mas/yr
Parallax (π)	10.54±0.91 mas[2]
Distance	310 ± 30 ly (95 ± 8 pc)
Absolute magnitude (MV)	0.56[7]
Orbit[8]
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[9] M☉
Radius	3.9[10] R☉
Luminosity	743[9] L☉
Surface gravity (log g)	4.75 cgs
Temperature	18,700[9] K
Metallicity [Fe/H]	−0.27 dex
Rotational velocity (v sin i)	155[11] km/s
Age	282[7] Myr
Other designations
λ Lib, 45 Lib, BD−19°4249, FK5 1415, HD 142096, HIP 77811, HR 5902, SAO 183895.[12]
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.^[8] The visible component is a B-type main sequence star with a stellar classification of B3 V.^[4] It is a helium-weak chemically peculiar star^[13] and a rotating ellipsoidal variable.^[5] The star has an estimated 3.9^[10] times the radius of the Sun and five times the Sun's mass.^[9] This is a candidate Vega-like star, meaning that it shows an infrared excess characteristic of a circumstellar debris disk.^[14] The system is a source of X-ray emission.^[15]