Epsilon Equulei

Epsilon Equulei, Latinized from ε Equulei, is a star system of apparent magnitude +5.23[2] in the constellation of Equuleus. It is located 180 light years away from the Solar System, based on its parallax.[1]

Epsilon Equulei
Observation data
Epoch J2000      Equinox J2000
Constellation Equuleus
Right ascension  20h 59m 04.47539s[1]
Declination 04° 17′ 36.5211″[1]
Apparent magnitude (V) 5.23[2] (5.96 / 6.31)[3]
Characteristics
Spectral type F5(V) + F6(V)[4]
U−B color index +0.00[5]
B−V color index +0.47[5]
Astrometry
Radial velocity (Rv)8.20 ± 0.2[6] km/s
Proper motion (μ) RA: -115.75[1] mas/yr
Dec.: -151.70[1] mas/yr
Parallax (π)18.49 ± 1.35[1] mas
Distance180 ± 10 ly
(54 ± 4 pc)
Absolute magnitude (MV)+1.65[7]
Orbit[3]
Period (P)101.485 yr
Semi-major axis (a)0.6474″
Eccentricity (e)0.705
Inclination (i)92.17°
Longitude of the node (Ω)105.15°
Periastron epoch (T)1920.37
Argument of periastron (ω)
(secondary)		340.19°
Details
A
Mass1.74[8] M☉
Surface gravity (log g)3.87[9] cgs
Temperature6,223[9] K
B
Mass1.53[8] M☉
Surface gravity (log g)4.29[9] cgs
Temperature6,399[9] K
Age1.5[10] Gyr
Other designations
ε Equ, 1 Equulei, HD 199766, HIP 103569, HR 8034, SAO 126428, BD+03° 4473
Database references
SIMBADdata

Star system

Two stars make up the brighter part of the Epsilon Equulei star system. They are called Epsilon Equulei A and B and are main-sequence stars of spectral type of F5 and F6, respectively.[4] The orbital period of this binary is about 101.5 years. Although the average separation between the two stars is about 0.64″, the orbit is remarkably eccentric, at 0.705. The two stars passed their periastron in 1920.[3] Finally, it is thought that Epsilon Equulei A may be, in turn, a spectroscopic binary. The orbital period of the latter would be 2.03133 days.[11]

Approximately 10 arcseconds away from A and B is Epsilon Equulei C (HIP 103571), with an apparent magnitude of 7.35. It is another F-type main-sequence stars, and based on its similar distance and proper motion to A and B, it is assumed to be associated.[12]

The Epsilon Equulei system is thought to be approximately 1.5 billion years old.[13]

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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. "* eps Equ". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 8 July 2017.
  3. "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Retrieved 8 July 2017.
  4. Beavers, W. I.; Cook, D. B. (1980). "Scanner studies of composite spectra. I - Dwarfs". The Astrophysical Journal Supplement Series. 44: 489. Bibcode:1980ApJS...44..489B. doi:10.1086/190702.
  5. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data: 0. Bibcode:1986EgUBV........0M.
  6. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  7. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  8. "Multiple Star Catalog". Retrieved 2018-11-28.
  9. Luck, R. Earle (2015). "Abundances in the Local Region. I. G and K Giants". The Astronomical Journal. 150 (3): 88. arXiv:1507.01466. Bibcode:2015AJ....150...88L. doi:10.1088/0004-6256/150/3/88.
  10. Casagrande, L.; Schönrich, R.; Asplund, M.; Cassisi, S.; Ramírez, I.; Meléndez, J.; Bensby, T.; Feltzing, S. (2011). "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey". Astronomy and Astrophysics. 530: A138. arXiv:1103.4651. Bibcode:2011A&A...530A.138C. doi:10.1051/0004-6361/201016276.
  11. Abt, H. A.; Levy, S. G. (1976). "Multiplicity among solar-type stars". The Astrophysical Journal Supplement Series. 30: 273. Bibcode:1976ApJS...30..273A. doi:10.1086/190363.
  12. "* eps Equ C". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 31 July 2017.
  13. Casagrande, L.; Schönrich, R.; Asplund, M.; Cassisi, S.; Ramírez, I.; Meléndez, J.; Bensby, T.; Feltzing, S. (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. arXiv:1103.4651. Bibcode:2011A&A...530A.138C. doi:10.1051/0004-6361/201016276.
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