Theta2 Crucis

Theta² Crucis, Latinized from θ² Crucis, is a spectroscopic binary star in the constellation Crux. This pair of stars complete an orbit every 3.4280 days and they have a low orbital eccentricity that is close to 0.0.^[12] Theta² Crucis is located at about 690 light-years from the Sun.

For other stars with the name θ Crucis, see Theta Crucis.

θ² Crucis

A light curve for Theta2 Crucis, plotted from TESS data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Crux
Right ascension	12h 04m 19.22008s[2]
Declination	−63° 09′ 56.5167″[2]
Apparent magnitude (V)	4.70 - 4.74[3]
Characteristics
Spectral type	B3 V[4]
U−B color index	−0.61[5]
B−V color index	−0.08[5]
Variable type	β Cep[3]
Astrometry
Radial velocity (Rv)	+16.3[6] km/s
Proper motion (μ)	RA: −18.467[2] mas/yr Dec.: +0.467[2] mas/yr
Parallax (π)	4.7314±0.1276 mas[2]
Distance	690 ± 20 ly (211 ± 6 pc)
Absolute magnitude (MV)	−2.35[7]
Orbit[8]
Period (P)	3.428 d
Eccentricity (e)	0.00
Periastron epoch (T)	2419604.367 JD
Semi-amplitude (K1) (primary)	51.3 km/s
Details
Mass	5.9[2] M☉
Radius	6.9[2] R☉
Luminosity	1,935[2] L☉
Surface gravity (log g)	3.55[2] cgs
Temperature	15,361[2] K
Metallicity [Fe/H]	+0.20[2] dex
Rotational velocity (v sin i)	23[9] km/s
Age	18.5[10] Myr
Other designations
θ2 Cru, CD−62°610, HD 104841, HIP 58867, HR 4603, SAO 251717[11]
Database references
SIMBAD	data

Since a member of the system is a β Cephei-type variable star, the magnitude is not fixed but varies slightly between +4.70 and +4.74. The period of this variability is 0.0889 days.^[3] The system is categorized as is a blue-white B-type main sequence star with a stellar classification of B3 V,^[4] although it has also been classified as a subgiant.^[13] Evolutionary models show it at a late stage of its main sequence life.^[2]