Epsilon Sagittae

Epsilon Sagittae (ε Sagittae) is a solitary,[7] yellow-hued star in the northern constellation of Sagitta. With an apparent visual magnitude of +5.64 to +5.67,[2] it is faintly visible to the naked eye on a dark night. It is a variable star with a small amplitude of 0.03 magnitudes. Based upon an annual parallax shift of 5.60 mas as seen from Earth,[8] it is located roughly 580 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.1 due to interstellar dust.[3]

Epsilon Sagittae
Location of ε Sagittae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Sagitta
Right ascension  19h 37m 17.39324s[1]
Declination +16° 27′ 46.0871″[1]
Apparent magnitude (V) +5.64 to +5.67[2]
Characteristics
Spectral type G8 IIIvar[3]
U−B color index +0.83[4]
B−V color index +1.00[4]
Astrometry
Radial velocity (Rv)−32.49±0.18[1] km/s
Proper motion (μ) RA: +16.382±0.164[1] mas/yr
Dec.: +14.364±0.135[1] mas/yr
Parallax (π)5.6067 ± 0.1173[1] mas
Distance580 ± 10 ly
(178 ± 4 pc)
Absolute magnitude (MV)−0.84±0.03[1]
Details[5]
Mass3.09 M☉
Radius18.37+0.65
−0.88[1] R☉
Luminosity184.9±4.6[1] L☉
Surface gravity (log g)2.44 cgs
Temperature4966+124
−85[1] K
Metallicity [Fe/H]+0.03 dex
Rotational velocity (v sin i)3.2 km/s
Age331 Myr
Other designations
ε Sge, 4 Sge, BD+16° 3918, HD 185194, HIP 96516, HR 7463, WDS J19373+1628A[6]
Database references
SIMBADdata

This is an evolved, G-type giant star with a stellar classification of G8 IIIvar,[3] where the 'var' suffix indicates a variable spectral feature. The star is about 331 million years old with three times the mass of the Sun.[5] It is radiating 185 times the Sun's luminosity from its photosphere at an effective temperature of 4,966 K.[1]

Epsilon Sagittae is an optical binary, with a companion of magnitude 8.35 at an angular separation of 87.3 arc seconds along a position angle of 82°, as of 2013.[9] The companion is actually a more distant giant star approximately 7,000 light-years from Earth, with a luminosity 1,800 times that of the Sun.[10]

References
  1. 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.
  2. Details for NSV 12213, The International Variable Star Index, 17 December 2005, retrieved 14 September 2018
  3. Takeda, Yoichi; et al. (August 2008), "Stellar Parameters and Elemental Abundances of Late-G Giants", Publications of the Astronomical Society of Japan, 60 (4): 781–802, arXiv:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781.
  4. Argue, A. N. (1966), "UBV photometry of 550 F, G and K type stars", Monthly Notices of the Royal Astronomical Society, 133: 475–493, Bibcode:1966MNRAS.133..475A, doi:10.1093/mnras/133.4.475.
  5. Takeda, Yoichi; Tajitsu, Akito (2014), "Spectroscopic study on the beryllium abundances of red giant stars", Publications of the Astronomical Society of Japan, 66 (5): 91, arXiv:1406.7066, Bibcode:2014PASJ...66...91T, doi:10.1093/pasj/psu066.
  6. "eps Sge". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-07-14.
  7. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  8. 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.
  9. Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
  10. 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.
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