Tau Librae

Tau Librae
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]
Distance367 ± 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
Mass7.25±0.49[7] M☉
Radius3.2[8] R☉
Luminosity (bolometric)2,705[7] L☉
Surface gravity (log g)4.33[9] cgs
Temperature17,990[9] K
Metallicity [Fe/H]+0.17[9] dex
Rotational velocity (v sin i)134[4] km/s
Age31.5±5.6[10] Myr
Other designations
τ Lib, 40 Lib, CD−29° 11837, HD 139365, HIP 76600, HR 5812, SAO 183649.[11]
Database references
SIMBADdata

Tau Librae, Latinized from τ Librae, is the Bayer designation for 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]

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 double-lined[12] spectroscopic binary 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[7] times the mass of the Sun and have over three[8] times the Sun's radius. It is only 31.5[10] million years old 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]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference apjs15 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Hiltner2969 was invoked but never defined (see the help page).
  4. ^ a b c d Cite error: The named reference Jilinski2006 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Pourbaix2004 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference Hohle2010 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference PasinettiFracassini2001 was invoked but never defined (see the help page).
  9. ^ a b c d Cite error: The named reference Saffe2008 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Tetzlaff2011 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Strom2005 was invoked but never defined (see the help page).
  13. ^ Sharma, Awshesh N.; Bedding, Timothy R.; Saio, Hideyuki; White, Timothy R. (2022). "Pulsating B stars in the Scorpius–Centaurus Association with TESS". Monthly Notices of the Royal Astronomical Society. 515 (1): 828–840. arXiv:2203.02582. Bibcode:2022MNRAS.515..828S. doi:10.1093/mnras/stac1816.