22 Vulpeculae is a binary star[4] system in the northern constellation Vulpecula. Based on its parallax, it is located some 1,490 light-years away,[2] and it has an apparent magnitude of about 5.176,[3] making it visible to the naked eye. The system is moving closer to the Earth with a heliocentric radial velocity of −23 km/s.[6]

22 Vulpeculae

A blue band light curve for QS Vulpeculae, adapted from Eaton and Shaw (2007)[1]
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Vulpecula
Right ascension	20h 15m 30.2386s[2]
Declination	+23° 30′ 32.051″[2]
Apparent magnitude (V)	5.176[3]
Characteristics
Spectral type	G2II + B8.5V[4]
U−B color index	+1.03[5]
B−V color index	+0.68[5]
Variable type	Algol
Astrometry
Radial velocity (Rv)	−22.8±0.9[6] km/s
Proper motion (μ)	RA: 2.852±0.067[2] mas/yr Dec.: −7.278±0.071[2] mas/yr
Parallax (π)	2.1872 ± 0.0850 mas[2]
Distance	1,490 ± 60 ly (460 ± 20 pc)
Absolute magnitude (MV)	−3.67[7] (−3.5 / −0.1)[8]
Orbit[9]
Period (P)	249.1310±0.0060 d
Eccentricity (e)	0 (assumed)
Argument of periastron (ω) (secondary)	0 (assumed)°
Semi-amplitude (K1) (primary)	27.03±0.14 km/s
Details[8]
22 Vul A
Mass	5.4 M☉
Radius	77 R☉
Temperature	4,700 K
22 Vul B
Mass	3.4 M☉
Radius	3.3 R☉
Temperature	10,900 K
Other designations
QS Vul, BD+23 3944, HD 192713, HIP 99853, HR 7741, SAO 88416[10]
Database references
SIMBAD	data

The pair have an orbital period of 0.68 yr in what is assumed to be a circular orbit.[9] The primary component is a G-type bright giant. It is over five times as massive as the Sun, and over 77 times as wide. Its companion is a B-type main-sequence star, 3.4 times as massive as the Sun.[8] The stars have an orbit that is oriented in such a way that they periodically eclipse each other, each star alternately blocking the light of the other. For that, it has been given the variable star designation QS Vulpeculae;[10] 22 Vulpeculae is the Flamsteed designation.

References