S Crateris
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| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Crater |
| Right ascension | 11h 52m 45.098s[1] |
| Declination | −07° 35′ 48.08″[1] |
| Apparent magnitude (V) | 8.64 - 9.51[2] |
| Characteristics | |
| Evolutionary stage | AGB[1] |
| Spectral type | M6e–M7e[3] |
| B−V color index | 1.078[4] |
| Variable type | SRb[3] |
| Astrometry | |
| Radial velocity (Rv) | 43.55[1] km/s |
| Proper motion (μ) | RA: −3.52[1] mas/yr Dec.: −5.08[1] mas/yr |
| Parallax (π) | 2.33±0.13 mas[5] |
| Distance | 430[5] pc |
| Details | |
| Radius | 260[5] R☉ |
| Luminosity | 5970[5] L☉ |
| Temperature | 3097[5] K |
| Other designations | |
| HD 103154, HIP 57917, SAO 138457, AFGL 4830S, IRAS 11501−0719, IRC −10259, 2MASS J11524508−0735482[1] | |
| Database references | |
| SIMBAD | data |
S Crateris (also designated S Crt, HD 103154, HIP 57917) is a semiregular variable star of subtype SRb[3][1] located in the Crater constellation. It is an asymptotic giant branch (AGB) star[1] with a spectral type of M6e-M7e.[3] The star was discovered to vary in brightness by Williamina Fleming in 1906.[3]
S Crateris is situated at right ascension 11h 52m 45.098s, declination −07° 35′ 48.08″ (J2000.0).[1] Its apparent magnitude in the V band varies between approximately 8.64 and 9.51, giving an amplitude of about 0.87 mag.[3] In the infrared, the star is considerably brighter: the 2MASS catalog lists magnitudes of J = 2.055, H = 1.127, and K = 0.786.[1][3]
Variability
S Crateris is classified as a semiregular variable of type SRb in both the General Catalogue of Variable Stars[5] and the AAVSO Variable Star Index.[3] Its pulsation period is 155 days.[3][5] The optical light curve in the V band exhibits a variation of approximately 0.8 magnitudes.[5] The reference epoch is HJD 2452284.2 (9 January 2002).[3]
Distance
The distance to S Crateris has been the subject of several independent measurements that yielded notably inconsistent results prior to modern VLBI observations. Early estimates based on the period-luminosity relation of Mira variables placed the star at distances of 285 and 420 pc.[5] The original Hipparcos Catalogue measured a parallax of 2.04±1.31 mas, corresponding to a distance of approximately 490 pc, but with a large uncertainty.[5] The revised Hipparcos reduction by van Leeuwen (2007) yielded a parallax of 1.26±0.92 mas,[4] corresponding to a distance of roughly 794 pc.
