Y Centauri or Y Cen (HD 127233, HIP 70969) is a semiregular variable star in the constellation of Centaurus.
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Centaurus |
Right ascension | 14h 30m 58.61656s[2] |
Declination | −30° 05′ 51.8706″[2] |
Apparent magnitude (V) | 8.0 - 9.1[3] |
Characteristics | |
Spectral type | M4e - M7[3] |
U−B color index | +0.72[4] |
B−V color index | +1.44[4] |
Variable type | SRb[3] |
Astrometry | |
Radial velocity (Rv) | −6.00[5] km/s |
Proper motion (μ) | RA: −38.874[6] mas/yr Dec.: −25.867[6] mas/yr |
Parallax (π) | 4.4510 ± 0.2738 mas[6] |
Distance | 730 ± 50 ly (220 ± 10 pc) |
Details | |
Radius | 48[6] R☉ |
Luminosity | 330[6] L☉ |
Surface gravity (log g) | −0.315[7] cgs |
Temperature | 3,557[6] K |
Other designations | |
Database references | |
SIMBAD | data |
The variability in the star was discovered by Williamina Fleming in 1895 and published in the Third Catalogue of Variable Stars. The photographic magnitude range was given as 7.7 - 8.8, but the variability was described as "somewhat doubtful".[8] It was later given the designation HV 52 in the Harvard Catalogue of Variable Stars.[9] The General Catalogue of Variable Stars lists it as a semiregular variable star with a period of 180 days and a visual magnitude range of 8.0 - 9.1.[3] A study of Hipparcos satellite photometry found a small amplitude range of 0.2 magnitudes at a visual magnitude of 8.53.[10]
The distance of the star is poorly known. The revised Hipparcos annual parallax of 3.50 mas gives a distance of 900 light years.[2] A study taking into account the variability of the star found a parallax of 5.57 mas, corresponding to a distance of 585 light years.[11] Both estimates have a margin of error over 20%. The Gaia Data Release 2 parallax lies between these two values and appears more accurate with a margin of error around 5%, but with a large value for astrometric noise.[6] Gaia EDR3 does not list a parallax for this star.[12]
Y Centauri is an asymptotic giant branch[13] star 330 times as luminous as the sun. Its spectral type varies between M4 and M7 as it pulsates.[3]
The star has been observed to produce 22 GHz water maser emission,[14] although later searches did not find any maser emission.[13]