T Carinae

T Carinae is a star in the southern constellation of Carina. Although given a variable star designation, it is now thought to be constant;[5] the identifier HD 94776 from the Henry Draper catalogue may be used instead. It has an orange hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.93.[2] The distance to this object is approximately 285 light years based on parallax,[1] and it has an absolute magnitude of 1.08.[2] It is drifting closer to the Sun with a radial velocity of −26 km/s.[2]

This article is about the variable star. For t¹ Carinae, see HD 92063. For t² Carinae, see HD 92397.
T Carinae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Carina
Right ascension  10h 55m 17.22143s[1]
Declination −60° 31′ 01.1999″[1]
Apparent magnitude (V) 5.93[2]
Characteristics
Evolutionary stage Horizontal branch[3]
Spectral type K0III[4]
B−V color index +1.065±0.007[2]
Variable type Constant[5]
Astrometry
Radial velocity (Rv)−25.5±2.9[2] km/s
Proper motion (μ) RA: −34.858[1] mas/yr
Dec.: +85.164[1] mas/yr
Parallax (π)11.4593 ± 0.0762[1] mas
Distance285 ± 2 ly
(87.3 ± 0.6 pc)
Absolute magnitude (MV)1.08[2]
Details
Radius9.25+0.21
−0.86[1] R☉
Luminosity38.6±0.3[1] L☉
Temperature4,729+237
−52[1] K
Other designations
T Car, CD−59°3419, CPD−59°2840, GC 15026, HD 94776, HIP 53394, HR 4271, SAO 251178[6]
Database references
SIMBADdata

This is an aging giant star with a stellar classification of K0III,[4] which indicates it has exhausted the supply of hydrogen at its core and expanded off the main sequence. It is a red clump giant, which means it is on the horizontal branch and is undergoing core helium fusion.[3] At present it has nine times the Sun's radius and is radiating 39 times the luminosity of the Sun from its photosphere at an effective temperature of 4,729 K.[1]

When used as a comparison star for AG Carinae in 1914 by H. E. Wood,[7] this object was announced as a candidate variable star. A year later it was determined by R. Innis that it was AG Carinae that varied and this star is constant. Later, T Carinae became flagged as a low amplitude irregular variable.[8] It is now catalogued as a probable constant star.[5]

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. 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.
  3. Laney, C. D.; et al. (January 2012), "A new Large Magellanic Cloud K-band distance from precision measurements of nearby red clump stars", Monthly Notices of the Royal Astronomical Society, 419 (2): 1637–1641, arXiv:1109.4800, Bibcode:2012MNRAS.419.1637L, doi:10.1111/j.1365-2966.2011.19826.x.
  4. Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, 1, Ann Arbor, Michigan: Department of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  5. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085.
  6. "HD 94776". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-15.
  7. Wood, H. E. (June 1914), "Discovery of a variable star in Carina", Monthly Notices of the Royal Astronomical Society, 74: 698, Bibcode:1914MNRAS..74..698W, doi:10.1093/mnras/74.8.698.
  8. Mayall, Margaret W. (August 1969), "Variable Star Notes", Journal of the Royal Astronomical Society of Canada, 63: 221, Bibcode:1969JRASC..63..221M.
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