V391 Pegasi
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 22h 04m 12.1045s |
| Declination | +26° 25′ 07.819″ |
| Apparent magnitude (V) | +14.61 |
| Characteristics | |
| Evolutionary stage | subdwarf B |
| Spectral type | sdB |
| Variable type | V361 Hydrae (sdBVr) |
| Astrometry | |
| Proper motion (μ) | RA: −4.906(40) mas/yr Dec.: −3.703(34) mas/yr |
| Parallax (π) | 0.7388±0.0327 mas |
| Distance | 4,400 ± 200 ly (1,350 ± 60 pc) |
| Absolute magnitude (MV) | +3.88 |
| Details | |
| Mass | 0.47 M☉ |
| Radius | 0.23 R☉ |
| Luminosity | 34 L☉ |
| Surface gravity (log g) | 5.4±0.1 cgs |
| Temperature | 29,300±500 K |
| Age | >10 Gyr |
| Other designations | |
| HS 2201+2610, 2MASS J22041211+2625078 | |
| Database references | |
| SIMBAD | data |
V391 Pegasi, also catalogued as HS 2201+2610, is a blue-white subdwarf star approximately 4,400 light-years away in the constellation of Pegasus. The star is classified as an "extreme horizontal branch star". It is small, with only half the mass and a bit less than one quarter the diameter of the Sun. It has luminosity 34 times that of the Sun. It could be quite old, perhaps in excess of 10 Gyr. It is believed that the star's mass when it was still on the main sequence was between 0.8 and 0.9 times that of the Sun.
In 2001, Roy Østensen et al. announced that the star, then called HS 2201+2610, is a variable star. It was given its variable star designation, V391 Pegasi, in 2003. It is a pulsating variable star of the V361 Hydrae type (or also called sdBVr type).