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15 Eridani
Observation data; Epoch J2000 Equinox J2000
Constellation	Eridanus
Right ascension	03h 18m 22.10504s
Declination	−22° 30′ 40.0191″
Apparent magnitude (V)	4.875; (6.57 / 5.32)
Characteristics
Evolutionary stage	horizontal branch
Spectral type	K0III
B−V color index	+0.90
Astrometry
Radial velocity (Rv)	23.90±0.5 km/s
Proper motion (μ)	RA: 13.08 mas/yr ; Dec.: 13.33 mas/yr
Parallax (π)	12.77 ± 1.17 mas
Distance	260 ± 20 ly ; (78 ± 7 pc)
Absolute magnitude (MV)	+0.85
Orbit
Period (P)	118.16 yr
Semi-major axis (a)	0.340″
Eccentricity (e)	0.030
Inclination (i)	66.6°
Longitude of the node (Ω)	271.6°
Periastron epoch (T)	1934.24
Argument of periastron (ω); (secondary)	333.5°
Details
15 Eri A
Mass	2.32 M☉
Luminosity	72.4 L☉
Temperature	4,960±31 K
Rotational velocity (v sin i)	4.5±0.2 km/s
Age	1.44 Gyr
Other designations
	15 Eri, CD−22°1146, HD 20610, HIP 15382, HR 994, SAO 168452, WDS J03184-2231
Database references
SIMBAD	data

15 Eridani is a binary star^[3] system in the equatorial constellation of Eridanus. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.875.^[2] Based upon parallax measurements, the system is located around 260 light years away from the Sun.^[1] It is moving further from the Earth with a heliocentric radial velocity of 24 km/s.^[6]

This system has an orbital period of 118.16 years with an eccentricity of 0.030 and a semimajor axis of 0.340″.^[3] The primary member, designated component A, is a magnitude 5.32^[9] giant star with a stellar classification of K0 III.^[4] It is a red clump giant,^[10] which means it is on the horizontal branch and is generating energy through helium fusion at its core. This star has 1.44 billion years old with 2.32 times the mass of the Sun. It is radiating 72.4 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,960 K.^[8] The companion, component B, has a magnitude of 6.57.^[9]

References

^ ^a ^b ^c ^d ^e ^f 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. S2CID 18759600.
^ ^a ^b 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.
^ ^a ^b ^c ^d "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 11 August 2017.
^ ^a ^b Houk, N.; Smith-Moore, M. (1988). "Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°.0". Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. 4. Bibcode:1988mcts.book.....H.
^ Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99. Bibcode:1966CoLPL...4...99J.
^ ^a ^b Kharchenko, N. V.; et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
^ ^a ^b Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics, 542: A116, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
^ ^a ^b ^c ^d ^e Luck, R. Earle (2015). "Abundances in the Local Region. I. G and K Giants". Astronomical Journal. 150 (3). 88. arXiv:1507.01466. Bibcode:2015AJ....150...88L. doi:10.1088/0004-6256/150/3/88. S2CID 118505114.
^ ^a ^b 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.
^ Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, arXiv:astro-ph/0003329, Bibcode:2000ApJ...539..732A, doi:10.1086/309278, S2CID 16673121