Sigma1 Tauri

Sigma¹ Tauri (σ¹ Tauri) is the Bayer designation for a white-hued star in the zodiac constellation of Taurus. It has an apparent visual magnitude of +5.07,^[2] which indicates it is visible to the naked eye. Based upon parallax measurements, σ¹ Tauri is about 147 light-years from the Sun.

Sigma1 Tauri

Location of σ1 Tauri (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Taurus
Right ascension	04h 39m 09.22247s[1]
Declination	+15° 47′ 59.5345″[1]
Apparent magnitude (V)	5.07[2]
Characteristics
Spectral type	A4m[3]
U−B color index	0.190[2]
B−V color index	0.146[2]
Astrometry
Radial velocity (Rv)	+26.1±10.0[4] km/s
Proper motion (μ)	RA: +41.91[1] mas/yr Dec.: −66.88[1] mas/yr
Parallax (π)	22.18±0.93 mas[1]
Distance	147 ± 6 ly (45 ± 2 pc)
Absolute magnitude (MV)	1.73[2]
Orbit[5]
Primary	σ1 Tau A
Companion	σ1 Tau B
Period (P)	38.951 d
Eccentricity (e)	0.15
Longitude of the node (Ω)	82°
Periastron epoch (T)	2443094.319 JD
Semi-amplitude (K1) (primary)	7.9 km/s
Details
Mass	1.94[2] M☉
Luminosity	14.7[6] L☉
Surface gravity (log g)	4.08[2] cgs
Temperature	8,470[2] K
Rotational velocity (v sin i)	56.5±7.1[7] km/s
Other designations
91 Tauri, BD+15°665, HD 29479, HIP 21673, HR 1478, SAO 94051, WDS J04393+1555B[8]
Database references
SIMBAD	data

σ¹ Tauri is a single-lined spectroscopic binary star system with an orbital period of 38.951 days and an eccentricity of 0.15. The visible component is an Am star with a stellar classification of A4m,^[3] indicating it is chemically peculiar A-type star. It is spinning with a projected rotational velocity of 56.5 km/s.^[7] The star has 1.9^[2] times the mass of the Sun and is radiating 14.7^[6] times the Sun's luminosity from its photosphere at an effective temperature of 8,470 K.^[2] Although it lies in the general direction of the Hyades cluster, based on parallax measurements it has been excluded from the list of candidate members.^[2]