22 Vulpeculae

22 Vulpeculae is a binary star[3] system in the northern constellation Vulpecula. Based on its parallax, it is located some 1,900 light-years away,[1] and it has an apparent magnitude of about 5.176,[2] making it visible to the naked eye. The system is moving closer to the Earth with a heliocentric radial velocity of −23 km/s.[5]

22 Vulpeculae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Vulpecula
Right ascension  20h 15m 30.23914s[1]
Declination +23° 30′ 32.0567″[1]
Apparent magnitude (V) 5.176[2]
Characteristics
Spectral type G2II + B8.5V[3]
U−B color index +1.03[4]
B−V color index +0.68[4]
Variable type Algol
Astrometry
Radial velocity (Rv)−22.8±0.9[5] km/s
Proper motion (μ) RA: 2.92[1] mas/yr
Dec.: −7.29[1] mas/yr
Parallax (π)1.70 ± 0.34[1] mas
Distanceapprox. 1,900 ly
(approx. 600 pc)
Absolute magnitude (MV)−3.67[6]
(−3.5 / −0.1)[7]
Orbit[8]
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[7]
22 Vul A
Mass5.4 M☉
Radius77 R☉
Temperature4700 K
22 Vul B
Mass3.4 M☉
Radius3.3 R☉
Temperature10900 K
Other designations
QS Vul, BD+23 3944, HD 192713, HIP 99853, HR 7741, SAO 88416[9]
Database references
SIMBADdata

The pair have an orbital period of 0.68 yr in what is assumed to be a circular orbit.[8] 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.[7] The stars have an orbit that are oriented in such a way that they periodically eclipse each other, blocking the other star's light. For that, it has been given the variable star designation QS Vulpeculae;[9] 22 Vulpeculae is the Flamsteed designation.

References
  1. van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
  3. Weaver, Wm. Bruce (2000). "Spectral Classification of Unresolved Binary Stars with Artificial Neural Networks". The Astrophysical Journal. 541: 298. Bibcode:2000ApJ...541..298W. doi:10.1086/309425.
  4. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
  6. Gray, David F.; Pugh, Teznie (2012). "The Third Signature of Granulation in Bright-Giant and Supergiant Stars". The Astronomical Journal. 143 (4): 92. Bibcode:2012AJ....143...92G. doi:10.1088/0004-6256/143/4/92.
  7. Schroeder, K.-P.; Griffin, R. E. M.; Hunsch, M. (1994). "Optical spectra of zeta Aurigae binary systems. 6: The chromosphere of 22 Vulpeculae". Astronomy and Astrophysics. 288 (1): 273–281. Bibcode:1994A&A...288..273S.
  8. Griffin, R. E. M.; et al. (July 1993). "Optical spectra of dzeta Aurigae binary systems. V. The 1988 eclipse of 22 Vulpeculae". Astronomy and Astrophysics. 274: 225. Bibcode:1993A&A...274..225G.
  9. "* 22 Vul". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 13 May 2017.
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