2 Equulei

2 Equulei is a double star system in the constellation of Equuleus.

2 Equulei
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Equuleus
Right ascension  21h 02m 12.50262s[1]
Declination +07° 10′ 47.1545″[1]
Apparent magnitude (V) 6.698[2] (7.41 + 7.64)[3]
Characteristics
Spectral type F6V[4]
Astrometry
Radial velocity (Rv)−4.8±1.6[5] km/s
Proper motion (μ) RA: −8.14[1] mas/yr
Dec.: −14.79[1] mas/yr
Parallax (π)12.35 ± 1.04[1] mas
Distance260 ± 20 ly
(81 ± 7 pc)
Absolute magnitude (MV)2.16±0.18[2]
Details
2 Equ A
Mass1.73[5] M☉
Radius3.37[6] R☉
Luminosity13.087[6] L☉
Surface gravity (log g)4.05[5] cgs
Temperature6,561±80[5] K
Metallicity [Fe/H]0.17[5] dex
Age1.6[5] Gyr
2 Equ B
Radius2.74[7] R☉
Luminosity10.828 L☉
Temperature6,330[7] K
Other designations
λ Equ, 2 Equulei, BD+06° 4731, HD 200256, HIP 103813, LTT 16227, SAO 126643[8]
Database references
SIMBADdata

The primary component of the 2 Equ pair is an F-type main sequence star. As of 2015, the secondary had an angular separation of 2.90 arc seconds along a position angle of 213° from the primary.[3] They form a common proper motion pair, two stars at approximately the same distance and moving in the same direction.[4] Gaia Data Release 2 gives them parallaxes of 8.6247″±0.1052″ and 8.5102″±0.0702″ respectively, although they are flagged as dubious.[6][7] These parallaxes correspond to a distance of around 380 ly, in contrast to the Hipparcos distance of 260±20 ly for the two stars as a pair.[1]

References
  1. van Leeuwen, F. (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. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191.
  3. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22
  4. Abt, Helmut A. (2008). "Visual Multiples. IX. MK Spectral Types". The Astrophysical Journal Supplement Series. 176 (1): 216. Bibcode:2008ApJS..176..216A. doi:10.1086/525529.
  5. Casagrande, L.; et al. (2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy & Astrophysics, 530 (A138): 21, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276.
  6. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  8. "2 Equ -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-02-17.
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