CH Crucis

Location of CH Crucis (circled in red)
Observation data Epoch J2000      Equinox ICRS
Constellation	Crux[1]
Right ascension	12h 41m 56.56918s[2]
Declination	−59° 41′ 08.9544″[2]
Apparent magnitude (V)	4.91[1]
Characteristics
Evolutionary stage	subgiant[2]
Spectral type	B5III[3] or B6IV[4]
U−B color index	−0.37[5]
B−V color index	−0.044±0.03[1]
Variable type	γ Cas[6]
Astrometry
Radial velocity (Rv)	+12.5±2.8[1] km/s
Proper motion (μ)	RA: -24.464[2] mas/yr Dec.: -4.226[2] mas/yr
Parallax (π)	3.8643±0.0811 mas[2]
Distance	840 ± 20 ly (259 ± 5 pc)
Absolute magnitude (MV)	−2.41[1]
Details
Mass	5.30±0.27[7] M☉
Radius	11.20±0.22[8] R☉
Luminosity	1,073[1] L☉
Surface gravity (log g)	2.90±0.03[8] cgs
Temperature	10,600±106[8] K
Rotational velocity (v sin i)	240[9] km/s
Age	120[10][better source needed] Myr
Other designations
Lumbung, 39 Crucis[11], CH Cru, CPD−59°4393, HD 110335, HIP 61966, HR 4823, SAO 240161[12]
Database references
SIMBAD	data

CH Crucis (39 Crucis), also named Lumbung,^[13] is a solitary^[14] variable star in the southern constellation of Crux. It has the Gould designation 39 G. Crucis.^[11] 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.^[1] The star is located 844.02 light years distant from the Sun based on parallax, with an uncertainty of −17.35/+18.09 light years.^[15] and is drifting further away with a radial velocity of about +12.5 km/s.^[1] It is a member of the nearby Sco OB2 association.^[16]

This is a conventional shell star, which is understood to be a Be star that is being viewed edge-on.^[18] Houk (1975) found a stellar classification of B5III,^[3] while Hiltner et al. assigned it to B6IV;^[4] suggesting it is a B-type star that is evolving off the main sequence.^[7]Later literature has also listed the star as B6IVe+sh (Yudin 2001)^[19] and B8IV (Arcos et al. 2018),^[20] while an older source, Buscombe & Morris (1960) ^[21]classified it as B7IV and identified it as a spectroscopic binary. indicating some variation in its spectral classification in the literature.

Samus et al. (2017) have tentatively classified it as a Gamma Cassiopeiae variable with a brightness range of 4.88–5.7 mag in the Johnson B band.^[6]

CH Crucis has 5.3^[7] times the mass of the Sun and 11.2^[8] times the Sun's radius. It is radiating 1,073^[1] times the luminosity of the Sun from its photosphere at an effective temperature of 10,600 K.^[8] It is spinning rapidly with estimates of the projected rotational velocity ranging up to 240 or 250 km/s.^[18][9] This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius.^[9]

The IAU Working Group on Star Names approved the name Lumbung for this star on 22 February 2026.^[13] Lumbung is a constellation from Bali (Indonesia), corresponding to Crux. The term is inherited from Malay, Proto-Malayo-Polynesian, meaning a rice barn or granary. The constellation of Lumbung is attested for ~1300 years in the cultural calendar and associated with Wednesday and the third day of an Oceanic market cycle.^[22]

References