Rho2 Eridani

Rho2 Eridani is a star located in the constellation Eridanus. It forms an asterism with Rho1 and Rho3 Eridani, south of Cetus, in the upper north east portion of Eridanus. The star has an apparent visual magnitude of 5.32,[2] which indicates it is visible to the naked eye on a clear, dark night. Based upon parallax measurements made with the Hipparcos satellite, this star is roughly 260 light years away from the Sun.

For other star systems with this Bayer designation, see Rho Eridani.
ρ2 Eridani
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension  03h 02m 42.28856s[1]
Declination −07° 41′ 07.7165″[1]
Apparent magnitude (V) 5.32[2]
Characteristics
Spectral type K0 III[3]
U−B color index +0.73[2]
B−V color index +0.94[2]
Astrometry
Radial velocity (Rv)26.38±0.23[4] km/s
Proper motion (μ) RA: +49.30[1] mas/yr
Dec.: −5.42[1] mas/yr
Parallax (π)12.32 ± 1.23[1] mas
Distance260 ± 30 ly
(81 ± 8 pc)
Absolute magnitude (MV)0.830[5]
Details
Mass2.53[5] M☉
Radius9[4] R☉
Luminosity45.7[4] L☉
Surface gravity (log g)2.6[4] cgs
Temperature4,864[4] K
Metallicity [Fe/H]0.19[5] dex
Rotational velocity (v sin i)0.0[4] km/s
Other designations
ρ2 Eridani, ρ2 Eri, 9 Eridani, BD-08° 568, HD 18953, HIP 14168, HR 917, SAO 130254.[6]
Database references
SIMBADdata

This is an evolved K-type giant star with a stellar classification of K0 III.[3] It is a red clump giant on the horizontal branch of the Hertzsprung–Russell diagram, indicating that is it now generating energy through the thermonuclear fusion of helium at its core.[5] The star has 2.5 times the mass of the Sun and has expanded to 9 times the Sun's radius. As such, it is radiating nearly 46 times the solar luminosity from its outer atmosphere at an effective temperature of 4,864 K.[4]

There is a magnitude 9.7 companion star at an angular separation of 1.8″. Most likely the pair form a binary star system.[7] At least one of the stars appears to be a source of X-ray emission.[8] The X-ray band flux is 3.65×10−15 W·m−2.[9]

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.
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
  4. Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  5. Zhao, G.; et al. (2001), "High-Resolution Spectroscopic Observations of Hipparcos Red Clump Giants: Metallicity and Mass Determinations", The Astrophysical Journal, 551: L85, Bibcode:2001ApJ...551L..85Z, doi:10.1086/319832.
  6. "rho02 Eri". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-12.
  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.
  8. Haakonsen, Christian Bernt; Rutledge, Robert E. (September 2009), "XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources", The Astrophysical Journal Supplement, 184 (1): 138–151, arXiv:0910.3229, Bibcode:2009ApJS..184..138H, doi:10.1088/0067-0049/184/1/138.
  9. Schwope, A.; et al. (2000), "The ROSAT Bright Survey: II. Catalogue of all high-galactic latitude RASS sources with PSPC countrate CR > 0.2 s−1", Astronomische Nachrichten, 321 (1): 1–52, arXiv:astro-ph/0003039, Bibcode:2000AN....321....1S, doi:10.1002/(SICI)1521-3994(200003)321:1<1::AID-ASNA1>3.0.CO;2-C.
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