Lambda Tauri

λ Tauri
Location of λ Tauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Taurus
Right ascension 04h 00m 40.81572s[1]
Declination +12° 29′ 25.2259″[1]
Apparent magnitude (V) +3.37 (- 3.54) - 3.91[2]
Characteristics
Spectral type B3 V + A4 IV[3]
U−B color index −0.62[4]
B−V color index −0.12[4]
Variable type Algol[2]
Astrometry
Radial velocity (Rv)+17.8[5] km/s
Proper motion (μ) RA: −8.02[1] mas/yr
Dec.: −14.42[1] mas/yr
Parallax (π)6.74 ± 0.17 mas[1]
Distance480 ± 10 ly
(148 ± 4 pc)
Absolute magnitude (MV)−2.45[6]
Orbit[7]
Primaryλ Tau A
Companionλ Tau B
Period (P)3.9529552 days
Semi-major axis (a)21.91 R☉[8]
Eccentricity (e)0.025±0.015
Inclination (i)76[9]°
Periastron epoch (T)2,444,667.3±2.1 HJD
Semi-amplitude (K1)
(primary)		56.9±0.6 km/s
Semi-amplitude (K2)
(secondary)		215.6±0.7 km/s
Details
λ Tau A
Mass7.18[9] M☉
Radius6.40[9] R☉
Luminosity5,801[3] L☉
Surface gravity (log g)3.38[10] cgs
Temperature18,700[3] K
Rotational velocity (v sin i)85[8] km/s
Age33.2±3.9[11] Myr
λ Tau B
Mass1.89[9] M☉
Radius5.30[9] R☉
Luminosity128[3] L☉
Temperature8,405[3] K
Rotational velocity (v sin i)76[8] km/s
Other designations
35 Tauri, BD+12 539, FK5 150, HD 25204, HIP 18724, HR 1239, SAO 93719.[12]
Database references
SIMBADdata

Lambda Tauri (λ Tau, λ Tauri) is a triple star system in the constellation Taurus. In the Calendarium of Al Achsasi Al Mouakket, this star was designated Sadr al Tauri, which was translated into Latin as Pectus Tauri, meaning "the bull chest".[13] In 1848, the light from this system was found to vary periodically and it was determined to be an eclipsing binary system—the third such discovered.[7] The components of this system have a combined apparent visual magnitude of +3.37 at its brightest, making it one of the brighter members of the constellation. Based upon parallax measurements from the Hipparcos mission, the distance to this system is approximately 480 light-years (150 parsecs).[1]

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