Tau Librae
Star in the constellation Libra
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Tau Librae, Latinized from τ Librae, is a binary star system at the southern edge of the zodiac constellation of Libra. It can be seen with the naked eye, having an apparent visual magnitude of 3.68.[2] The distance to this system is around 367 light years, as determined from an annual parallax shift of 8.89 mas.[1]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Libra |
| Right ascension | 15h 38m 39.36950s[1] |
| Declination | −29° 46′ 39.8956″[1] |
| Apparent magnitude (V) | 3.68[2] |
| Characteristics | |
| Spectral type | B2.5 V[3] |
| U−B color index | −0.717[2] |
| B−V color index | −0.179[2] |
| Astrometry | |
| Radial velocity (Rv) | +33.3±2.3[4] km/s |
| Proper motion (μ) | RA: −22.08[1] mas/yr Dec.: −24.46[1] mas/yr |
| Parallax (π) | 8.89±0.20 mas[1] |
| Distance | 367 ± 8 ly (112 ± 3 pc) |
| Absolute magnitude (MV) | −1.59[5] |
| Orbit[6] | |
| Period (P) | 3.2907 d |
| Eccentricity (e) | 0.28 |
| Longitude of the node (Ω) | 114° |
| Periastron epoch (T) | 2439272.312 JD |
| Semi-amplitude (K1) (primary) | 75 km/s |
| Semi-amplitude (K2) (secondary) | 167 km/s |
| Details | |
| τ Lib A | |
| Mass | 7.25±0.49[7] M☉ |
| Radius | 3.2[8] R☉ |
| Luminosity (bolometric) | 2,705[7] L☉ |
| Surface gravity (log g) | 4.33[9] cgs |
| Temperature | 17,990[9] K |
| Metallicity [Fe/H] | +0.17[9] dex |
| Rotational velocity (v sin i) | 134[4] km/s |
| Age | 31.5±5.6[10] Myr |
| Other designations | |
| τ Lib, 40 Lib, CD−29°11837, HD 139365, HIP 76600, HR 5812, SAO 183649[11] | |
| Database references | |
| SIMBAD | data |
Judging by its motion through space and physical properties, this system is a member of the Upper Centaurus–Lupus group of the Scorpius–Centaurus association.[4] It is a double-lined spectroscopic binary[12] with an orbital period of just 3.3 days and an eccentricity of 0.28.[6] The primary, component A, is a B-type main sequence star with a stellar classification of B2.5 V.[3] It is estimated to hold more than seven times the mass of the Sun[7] and have over three times the Sun's radius.[8] It is only 31.5 million years old[10] and is spinning relatively rapidly with a projected rotational velocity of 134 km/s.[4] It is a heartbeat star system, with pulsations caused by tidal forces.[13]
The system is emitting an infrared excess, suggesting the presence of a circumstellar disk of material.[9]