31 Pegasi is a single[9] star in the northern constellation of Pegasus. It is visible to the naked eye as a dim, blue-white hued point of light with a baseline apparent visual magnitude of 4.99.[2] It is located approximately 1,600 light years away from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −5.3 km/s.[4]

31 Pegasi

Location of 31 Pegasi (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Pegasus
Right ascension	22h 21m 31.07511s[1]
Declination	12° 12′ 18.6628″[1]
Apparent magnitude (V)	4.99[2]
Characteristics
Spectral type	B2IV-Ve[3]
U−B color index	-0.81[2]
B−V color index	-0.10[2]
Variable type	γ Cas
Astrometry
Radial velocity (Rv)	−5.30[4] km/s
Proper motion (μ)	RA: +6.32[1] mas/yr Dec.: +4.80[1] mas/yr
Parallax (π)	2.01 ± 0.28 mas[1]
Distance	approx. 1,600 ly (approx. 500 pc)
Absolute magnitude (MV)	−3.61[5]
Details[6]
Mass	12.5±0.7 M☉
Luminosity (bolometric)	27,925+4,360 −3,770 L☉
Surface gravity (log g)	3.71±0.15 cgs
Temperature	23,890±740 K
Rotational velocity (v sin i)	98±8 km/s
Age	15.4±1.3[7] Myr
Other designations
31 Peg, IN Peg, BD+11°4784, FK5 843, GC 31255, HD 212076, HIP 110386, HR 8520, SAO 107854[8]
Database references
SIMBAD	data

This is a massive Be star with a stellar classification of B2IV-V.[11] It is a γ Cas variable; a type of shell star with a circumstellar disc of gas surrounding the star at the equator, and ranges from 5.05 up to 4.85 in visual magnitude.[12] It is spinning with a projected rotational velocity of 98 km/s, with the pole being inclined by an estimated angle of 26°±9° to the line of sight from the Earth.[6] The star is 15.4[7] million years old with 12.5[6] times the mass of the Sun. It is radiating around 28,000 times the luminosity of the Sun from its photosphere at an effective temperature of 23,890 K.[6]

References