R Geminorum

The visual band light curve of R Geminorum, from AAVSO data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Gemini
Right ascension 07h 07m 21.271s[2]
Declination +22° 42′ 12.75″[2]
Apparent magnitude (V) 6.0 - 14.0[3]
Characteristics
Evolutionary stage AGB
Spectral type S2,9e-S8,9e(Tc)[3]
Variable type mira[3]
Astrometry
Radial velocity (Rv)−45.2[4] km/s
Proper motion (μ) RA: −8.765[2] mas/yr
Dec.: 0.665[2] mas/yr
Parallax (π)1.1795 ± 0.0960 mas[2]
Distance2,800 ± 200 ly
(850 ± 70 pc)
Details
Radius431[5] R☉
Luminosity5,500[5] L☉
Temperature2,400[5] K
Other designations
BD+22 1577, HD 53791, HIP 34356, HR 2671, SAO 79070[6]
Database references
SIMBADdata

R Geminorum (R Gem) is a Mira variable and technetium star in the constellation Gemini. It is located approximately 850 parsecs (2,800 ly) away.

R Geminorum pulsates with an average period of 369.9 days, varying by up to eight magnitudes at visual wavelengths.[3] When at maximum light its apparent visual magnitude is usually between 6 and 7, while at minimum light it is typically near magnitude 14.[7]

R Geminorum is one of the brightest known examples of an S-type star, a type that is similar to M-type star, but whose spectra shows zirconium oxide, yttrium oxide and technetium.[8] These exotic elements are formed in the star's core. Technetium has a half-life of just 4.2 million years, so it must have been brought up from the core relatively recently. R Gem has an unusual amount of it, even for an S-type star.[8]

References

  1. ^ "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  2. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. ^ a b c d 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: B/gcvs. Bibcode:2009yCat....102025S.
  4. ^ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  5. ^ a b c Ramstedt, S.; Schöier, F. L.; Olofsson, H. (2009). "Circumstellar molecular line emission from S-type AGB stars: Mass-loss rates and SiO abundances". Astronomy & Astrophysics. 499 (2): 515–527. arXiv:0903.1672. Bibcode:2009A&A...499..515R. doi:10.1051/0004-6361/200911730. S2CID 17942939.
  6. ^ "R Geminorum". SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg. Retrieved 20 January 2014.
  7. ^ "Light Curve Generator". American Association of Variable Star Observers. Archived from the original on February 17, 2015. Retrieved 17 February 2015.
  8. ^ a b MacRobert, Alan (January 2015). "Weird R Gem Climbs to Maximum". Sky & Telescope. 129 (1): 51. Bibcode:2015S&T...129a..51M.
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