6 Geminorum

6 Geminorum is a variable star in the zodiac constellation of Gemini, located roughly 5,000 light years away from the Sun.[1] It has the variable star designation BU Geminorum; 6 Geminorum is the Flamsteed designation. At its brightest this reddish hued star is barely visible to the naked eye but is readily visible with binoculars, found southwest of M 35, below WY Geminorum. It is moving further from the Earth with a heliocentric radial velocity of +27 km/s.[5] The star is a member of the Gemini OB1 association.[12]

6 Geminorum
Location of 6 Geminorum (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Gemini
Right ascension  06h 12m 19.09889s[1]
Declination +22° 54′ 30.6580″[1]
Apparent magnitude (V) 5.74 - 8.10[2]
Characteristics
Spectral type M1-2 Ia-Iab[3]
U−B color index +1.93[4]
B−V color index +1.63[4]
Variable type LC[2]
Astrometry
Radial velocity (Rv)+27.16±0.42[5] km/s
Proper motion (μ) RA: +0.090[1] mas/yr
Dec.: −2.426[1] mas/yr
Parallax (π)0.7071 ± 0.2376[1] mas
Distanceapprox. 5,000 ly
(approx. 1,400 pc)
Absolute magnitude (MV)-6.32[6]
Details
Mass~20[7] M☉
Radius821+60
−27[8] R☉
Luminosity86,000[9] L☉
Surface gravity (log g)0.0[6] cgs
Temperature3,789[10] K
Other designations
6 Gem, BU Gem, BD+22°1220, GC 7896, HD 42543, HIP 29450, HR 2197, SAO 78098, TYC 1877-1719-1, 2MASS J06121911+2254305[11]
Database references
SIMBADdata

This is an evolved red supergiant with a stellar classification of M1-2 Ia-Iab.[3] It is a semiregular variable star, ranging from visual magnitude +5.7 down to +7.5 over a period of 325 days. It has been given the sub-classification of Lc, which means "Irregular variable supergiants of late spectral types having amplitudes of about 1 mag. in V.O".[13] The star has expanded to 821[8] times the Sun's radius and is radiating 86,000[9] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 3,789 K.[10]

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. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  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. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272.
  6. Levesque, Emily M. (2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, but Not As Cool As We Thought". The Astrophysical Journal. 628 (2): 973–985. arXiv:astro-ph/0504337. Bibcode:2005ApJ...628..973L. doi:10.1086/430901.
  7. "6 GEM". 2012. Retrieved 15 December 2016.
  8. Norris, Ryan P. (2019). Seeing Stars Like Never Before: A Long-term Interferometric Imaging Survey of Red Supergiants (PDF) (PhD). Georgia State University.
  9. Mauron, N; Josselin, E (2011). "The mass-loss rates of red supergiants and the de Jager prescription". Astronomy and Astrophysics. 526: A156. arXiv:1010.5369. Bibcode:2011A&A...526A.156M. doi:10.1051/0004-6361/201013993.
  10. Mármol-Queraltó, E; Cardiel, N; Cenarro, A. J; Vazdekis, A; Gorgas, J; Pedraz, S; Peletier, R. F; Sánchez-Blázquez, P (2008). "A new stellar library in the region of the CO index at 2.3 μm. New index definition and empirical fitting functions" (PDF). Astronomy and Astrophysics. 489 (2): 885–909. arXiv:0806.0581. Bibcode:2008A&A...489..885M. doi:10.1051/0004-6361:200810044.
  11. "6 Gem". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-04-24.
  12. Laur, Jaan; et al. (February 2017), "Variability survey of brightest stars in selected OB associations", Astronomy & Astrophysics, 598: 27, arXiv:1611.02452, Bibcode:2017A&A...598A.108L, doi:10.1051/0004-6361/201629395, A108.
  13. Variable Star Type Designations in VSX- Retrieved 2016-11-06
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