CH Crucis

CH Crucis is a solitary^[14] variable star in the southern constellation of Crux. It has the Gould designation 39 G. Crucis.^[12] The object is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude that fluctuates around 4.91.^[3] The star is located approximately 780 light years distant from the Sun based on parallax,^[2] and is drifting further away with a radial velocity of about +12.5 km/s.^[3] It is a member of the nearby Sco OB2 association.^[15]

CH Crucis

A blue band light curve for CH Crucis, plotted from data published by Balona et al. (1992)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Crux
Right ascension	12h 41m 56.56824s[2]
Declination	−59° 41′ 08.9564″[2]
Apparent magnitude (V)	4.91[3]
Characteristics
Spectral type	B5III[4] or B6IV[5]
U−B color index	−0.37[6]
B−V color index	−0.044±0.03[3]
Variable type	γ Cas?[7]
Astrometry
Radial velocity (Rv)	+12.5±2.8[3] km/s
Proper motion (μ)	RA: -23.987[2] mas/yr Dec.: -4.110[2] mas/yr
Parallax (π)	4.2068±0.1651 mas[2]
Distance	780 ± 30 ly (238 ± 9 pc)
Absolute magnitude (MV)	−2.41[3]
Details
Mass	5.30±0.27[8] M☉
Radius	11.20±0.22[9] R☉
Luminosity	1,073[3] L☉
Surface gravity (log g)	2.90±0.03[9] cgs
Temperature	10,600±106[9] K
Rotational velocity (v sin i)	240[10] km/s
Age	120[11][better source needed] Myr
Other designations
CH Cru, CPD−59° 4393, HD 110335, HIP 61966, HR 4823, SAO 240161, G 39 Crucis[12][13]
Database references
SIMBAD	data

This is a conventional shell star, which is understood to be a Be star that is being viewed edge-on.^[16] Houk (1975) found a stellar classification of B5III,^[4] while Hiltner et al. assigned it to B6IV;^[5] suggesting it is a B-type star that is evolving off the main sequence.^[8] Samus et al. (2017) have tentatively classified it as a Gamma Cassiopeiae variable that ranges in brightness from magnitude 4.88 down to 5.7.^[7]

CH Crucis has 5.3^[8] times the mass of the Sun and 11.2^[9] times the Sun's radius. It is radiating 1,073^[3] times the luminosity of the Sun from its photosphere at an effective temperature of 10,600 K.^[9] It is spinning rapidly with estimates of the projected rotational velocity ranging up to 240 or 250 km/s.^[16][10] This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius.^[10]