Lambda Crucis
Star in the constellation Crux
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λ Crucis, Latinized as Lambda Crucis, is a single,[10] variable star in the southern constellation Crux, near the constellation border with Centaurus. It is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude that fluctuates around 4.62.[2] The star is located approximately 384 light-years distant from the Sun based on parallax, and is drifting further away with a radial velocity of +12 km/s.[5] It is a proper motion member of the Lower Centaurus–Crux sub-group in the Scorpius–Centaurus OB association, the nearest such association of co-moving massive stars to the Sun.[6]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Crux |
| Right ascension | 12h 54m 39.18258s[1] |
| Declination | −59° 08′ 48.1229″[1] |
| Apparent magnitude (V) | 4.62[2] |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | B4 Vne[3] |
| U−B color index | −0.60[4] |
| B−V color index | −0.15[4] |
| Variable type | β Cep?[2] |
| Astrometry | |
| Radial velocity (Rv) | +12.0±4.2[5] km/s |
| Proper motion (μ) | RA: −32.92[1] mas/yr Dec.: −14.60[1] mas/yr |
| Parallax (π) | 8.50±0.21 mas[1] |
| Distance | 384 ± 9 ly (118 ± 3 pc) |
| Absolute magnitude (MV) | −1.2[6] |
| Details | |
| Mass | 5.0±0.1[7] M☉ |
| Radius | 3.00[8] R☉ |
| Luminosity | 790[6] L☉ |
| Surface gravity (log g) | 3.01[8] cgs |
| Temperature | 16,500[8] K |
| Rotational velocity (v sin i) | 290[8] km/s |
| Age | 53.3±8.1[7] Myr |
| Other designations | |
| λ Cru, Lambda Cru, CD−58°4794, HD 112078, HIP 63007, HR 4897, SAO 240368[9] | |
| Database references | |
| SIMBAD | data |
λ Crucis is listed in the General Catalogue of Variable Stars as a possible β Cephei-type variable. Its brightness varies with an amplitude of 0m.02 over a period of 0.3951 days.[2] However, it is currently thought more likely to be a different type of variable,[12] possibly a λ Eridani variable or rotating ellipsoidal variable.[13][14]
This object is a B-type main-sequence star with a stellar classification of B4 Vne,[3] where the suffix notation indicates "nebulous" (broad) lines due to rapid rotation, along with emission lines from circumstellar material, making it a Be star.[13] It is around 53[7] million years old and is spinning rapidly with a projected rotational velocity of 341 km/s.[15] The star has five[7] times the mass of the Sun and about 3.0[8] times the Sun's radius. It is radiating 790[6] times the luminosity of the Sun from its photosphere at an effective temperature of 16,500 K.[8]