Tau1 Arietis

For other stars with this Bayer designation, see τ Arietis.
τ1 Arietis
Location of τ1 Arietis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aries
Right ascension 03h 21m 13.62462s[1]
Declination +21° 08′ 49.4390″[1]
Apparent magnitude (V) 5.27[2]
Characteristics
Spectral type B5 IV[3]
U−B color index −0.53[2]
B−V color index −0.06[2]
Astrometry
Radial velocity (Rv)+14[4] km/s
Proper motion (μ) RA: +25.651[1] mas/yr
Dec.: −19.850[1] mas/yr
Parallax (π)6.1786 ± 0.2066 mas[1]
Distance530 ± 20 ly
(162 ± 5 pc)
Absolute magnitude (MV)−0.66[5]
Details
Mass5.0±0.1[6] M☉
Radius4.45[1] R☉
Luminosity234[5] L☉
Surface gravity (log g)3.68[1] cgs
Temperature12,606[1] K
Metallicity [Fe/H]−0.63[1] dex
Rotational velocity (v sin i)30[7] km/s
Age54.8±5.4[6] Myr
Other designations
τ1 Ari, 61 Arietis, BD+20 543, FK5 1094, HD 20756, HIP 15627, HR 1005, SAO 75886.[8]
Database references
SIMBADdata

Tau1 Arietis, Latinized from τ1 Arietis, is the Bayer designation for a triple star system[9] in the northern constellation of Aries. Based upon an annual parallax shift of 6.1786 mas, it is approximately 530 light-years (162 parsecs) distant from Earth. The combined apparent visual magnitude is 5.27,[2] making it faintly visible to the naked eye.

A light curve for Tau1 Arietis, plotted from TESS data[10]

The Tau1 Arietis system contains three stars. The inner pair form an eclipsing binary system, with the brightness of the pair decreasing by 0.06 in magnitude during an eclipse of the primary.[11] Its period is 2.20356 days.[12] The third component is located at an angular separation of 0.810 arcseconds and has a magnitude of 8.17.[9] The primary component is a subgiant star with a stellar classification of B5 IV.[3] It has five times the mass of the Sun[6] with about four times the Sun's radius.[1]

This system is a member of the Cas-Tau OB association of stars that share a common motion through space.[13]

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