2 Lupi

2 Lupi is a single[7] star in the southern constellation of Lupus,[6] located 326 light years away from the Sun.[1] It has the Bayer designation f Lupi; 2 Lupi is the Flamsteed designation. This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.33.[2] It is moving closer to the Earth with a heliocentric radial velocity of −3 km/s.[5]

2 Lupi
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Lupus
Right ascension  15h 17m 49.83809s[1]
Declination −30° 08′ 55.2165″[1]
Apparent magnitude (V) 4.33[2]
Characteristics
Evolutionary stage giant
Spectral type K0 IIIa CH-1[3]
B−V color index 1.100±0.004[4]
Astrometry
Radial velocity (Rv)−2.91±0.15[5] km/s
Proper motion (μ) RA: −10.16[1] mas/yr
Dec.: −3.66[1] mas/yr
Parallax (π)10.01 ± 0.21[1] mas
Distance326 ± 7 ly
(100 ± 2 pc)
Absolute magnitude (MV)−0.65[4]
Details
Radius11.0+0.7
−0.8[5] R☉
Luminosity65.6±0.8[5] L☉
Surface gravity (log g)2.84[2] cgs
Temperature4,953+197
−148[5] K
Metallicity [Fe/H]0.11[2] dex
Other designations
f Lupi, 2 Lup, NSV 7012, CD−29°11630, FK5 3207, HD 135758, HIP 74857, HR 5686, SAO 183346[6]
Database references
SIMBADdata

This is an aging giant star with a stellar classification of K0 IIIa CH-1.[3] The suffix notation indicates abnormally weak lines of carbyne. Having exhausted the hydrogen at its core, the star evolved away from the main sequence by expanding to 11[5] times the Sun's radius. The star is radiating 65.6[5] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,953 K.[5] It is a suspected variable star of unknown type.[8]

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. McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527
  3. Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373
  4. 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.
  5. 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.
  6. "2 Boo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-04-06.
  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. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S.
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