Upsilon Capricorni

Upsilon Capricorni, Latinized from υ Capricorni, is a solitary^[7] star in the southern constellation of Capricornus. It has a reddish hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.17.^[2] The star is about 730 light years from the Sun based on parallax,^[1] but is drifting closer with a radial velocity of −12 km/s.^[4] It is 0.22 degree north of the ecliptic, so is subject to lunar occultations.^[8][9]

Upsilon Capricorni

Location of υ Capricorni (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Capricornus
Right ascension	20h 40m 02.94518s[1]
Declination	−18° 08′ 19.1664″[1]
Apparent magnitude (V)	5.17[2]
Characteristics
Spectral type	M1 III[3]
B−V color index	+1.65[2]
Astrometry
Radial velocity (Rv)	−12.3±1.6[4] km/s
Proper motion (μ)	RA: −23.503[1] mas/yr Dec.: −22.157[1] mas/yr
Parallax (π)	4.4702 ± 0.2352 mas[1]
Distance	730 ± 40 ly (220 ± 10 pc)
Absolute magnitude (MV)	−1.09[5]
Details
Radius	76.36+8.05 −14.16[1] R☉
Luminosity	1,283.0±76.5[1] L☉
Temperature	3,953+427 −193[1] K
Metallicity [Fe/H]	−0.08[5] dex
Other designations
υ Cap, 15 Capricorni, NSV 25208, BD−18°5738, FK5 773, HD 196777, HIP 101984, HR 7900, SAO 163779[6]
Database references
SIMBAD	data

This is an aging red giant star on the asymptotic giant branch^[10] with a stellar classification of M1 III,^[3] a star that has exhausted the supply of hydrogen at its core then cooled and expanded. At present it has 76^[1] times the radius of the Sun. It is a suspected variable star of unknown type with a brightness that has been measured ranging from a peak of 5.19 down to 5.24.^[11] The star is radiating 1,283^[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 3,953 K.^[1]

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. Barnes, T. G.; et al. (May 1978), "Stellar angular diameters and visual surface brightness. III - an improved definition of the relationship", Monthly Notices of the Royal Astronomical Society, 183 (3): 285–304, Bibcode:1978MNRAS.183..285B, doi:10.1093/mnras/183.3.285.
3. Houk, N.; Smith-Moore, M. (1988), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars, vol. 4, Bibcode:1988mcts.book.....H.
4. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
5. 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, S2CID 119257644.
6. "* ups Cap". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-05-12.
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, S2CID 14878976.
8. White, Nathaniel M.; Feierman, Barry H. (September 1987), "A Catalog of Stellar Angular Diameters Measured by Lunar Occultation", Astronomical Journal, 94: 751, Bibcode:1987AJ.....94..751W, doi:10.1086/114513.
9. Dunham, D. W.; Evans, D. S.; Silverberg, E. C.; Wiant, J. R. (March 1973), "The angular diameter of Upsilon Capricorni and an occultation of SAO 118655.", Astronomical Journal, 78: 199–201, Bibcode:1973AJ.....78..199D, doi:10.1086/111398.
10. Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun", Astronomical Journal, 104 (1): 275–313, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
11. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.