Iota Eridani

Iota Eridani (ι Eri) is a solitary star in the constellation Eridanus. It is visible to the naked eye with an apparent magnitude of 4.11.^[2] With an annual parallax shift of 0.02165 arcseconds,^[1] it lies at an estimated distance of about 151 light years.

ι Eridani

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	02h 40m 40.03501s[1]
Declination	−39° 51′ 19.3541″[1]
Apparent magnitude (V)	4.11[2]
Characteristics
Evolutionary stage	Red clump[3]
Spectral type	K0 III[4]
U−B color index	+0.74[2]
B−V color index	+1.02[2]
Astrometry
Radial velocity (Rv)	−9.30±0.70[5] km/s
Proper motion (μ)	RA: +135.92[1] mas/yr Dec.: −27.53[1] mas/yr
Parallax (π)	21.65 ± 0.18 mas[1]
Distance	151 ± 1 ly (46.2 ± 0.4 pc)
Absolute magnitude (MV)	0.877[3]
Details[6]
Mass	1.29±0.01 M☉
Radius	11.17±0.06 R☉
Luminosity	54.7±0.5 L☉
Surface gravity (log g)	2.65±0.10 cgs
Temperature	4,700±30 K
Metallicity [Fe/H]	−0.34±0.02 dex
Age	3.55±0.12 Gyr
Other designations
ι Eri, CD−40° 689, FK5 1075, HD 16815, HIP 12486, HR 794, SAO 215999.[7]
Database references
SIMBAD	data

This is an evolved giant star with a stellar classification of K0 III.^[4] The measured angular diameter, after correcting for limb darkening, is 2.248±0.014 mas. This star is 3.55 billion years old, sufficient to have exhausted the hydrogen at its core and reached a red clump stage. It is only around 29% more massive than the Sun, but is eleven times larger. It radiates 54.7 times the solar luminosity from its outer atmosphere at an effective temperature of 4,700 K.^[6]

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, S2CID 18759600.
2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
3. Liu, Y. J.; et al. (2007), "The abundances of nearby red clump giants", Monthly Notices of the Royal Astronomical Society, 382 (2): 553–66, Bibcode:2007MNRAS.382..553L, doi:10.1111/j.1365-2966.2007.11852.x
4. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
5. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
6. Gallenne, A.; Pietrzyński, G.; Graczyk, D.; Nardetto, N.; Mérand, A.; Kervella, P.; Gieren, W.; Villanova, S.; Mennickent, R. E.; Pilecki, B. (2018-08-01), "Fundamental properties of red-clump stars from long-baseline H-band interferometry", Astronomy & Astrophysics, 616: A68, arXiv:1806.09572, doi:10.1051/0004-6361/201833341, ISSN 0004-6361
7. "iot Eri". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-29.{{cite web}}: CS1 maint: postscript (link)