R Crucis
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Crux |
| Right ascension | 12h 23m 37.68840s |
| Declination | −61° 37′ 44.8570″ |
| Apparent magnitude (V) | 6.89 |
| Characteristics | |
| Spectral type | F6-G2Ib-II or F7Ib/II |
| B−V color index | 0.67±0.02 |
| Variable type | δ Cep |
| Astrometry | |
| Radial velocity (Rv) | −13.5±3.0 km/s |
| Proper motion (μ) | RA: -9.404 mas/yr Dec.: −0.430 mas/yr |
| Parallax (π) | 1.98±0.54 mas |
| Distance | approx. 1,600 ly (approx. 500 pc) |
| Details | |
| Radius | 44.6 R☉ |
| Surface gravity (log g) | 1.65 cgs |
| Temperature | 5,812±22 K |
| Metallicity [Fe/H] | +0.06 dex |
| Other designations | |
| R Cru, AAVSO 1218-61, CD−60°4138, HD 107805, HIP 60455, SAO 251878 | |
| Database references | |
| SIMBAD | data |
R Crucis is a variable star in the southern constellation of Crux. It has a yellow-white hue and is often too faint to see with the naked eye, having an apparent visual magnitude that fluctuates around 6.89. This object is located at a distance of approximately 1,600 light years from the Sun based on parallax, but it is drifting closer with a radial velocity of −13.5 km/s.
This is a Classical Cepheid, or Delta Cephei variable, that ranges in brightness from visual magnitude 6.40 down to 7.23 with a period of 5.82575 days. It is a supergiant star with a stellar classification that varies over each pulsation cycle, giving it a class range of F6-G2Ib-II. The star has a mean radius 44.6 times the radius of the Sun (44.6 R☉), but the radius varies by 5 R☉ during each pulsation. It has a near solar metallicity and the atmospheric abundances indicate it is likely past first dredge-up.
A candidate companion star has been detected at an angular separation of 7.6″, which corresponds to a projected separation of 6,330 AU. The Hubble WFC3 shows a closer companion at a separation of 1.9″. The system is a source for X-ray emission but the contributing component is unclear.