Var 83

VHK 83 (Var 83 in the VHK survey[6]) is a luminous blue variable (LBV) in the constellation Triangulum, in the Triangulum Galaxy. With its bolometric luminosity of at least 2,240,000 times that of the Sun (4,500,000 in some estimates), it was described as "the brightest nonstable star in M33"[6] and is one of the most luminous stars known.

VHK 83
Observation data
Epoch J2000      Equinox J2000
Constellation Triangulum
Right ascension  01h 33m 50.02s[1]
Declination +30° 39′ 36.7″[1]
Apparent magnitude (V) 15.4-16.6[2]
Characteristics
Spectral type LBV
U−B color index ~−0.9[2]
B−V color index ~0.1[2]
Variable type LBV
Astrometry
Proper motion (μ) RA: 11.54[3] mas/yr
Dec.: -2.75[3] mas/yr
Distance~3,000,000 ly
(~900,000 pc)
Absolute magnitude (MV)−8.4- −9.5[2]
Details
Mass60[4] M☉
Radius50-80,[2] 150[5] R☉
Luminosity2,100,000-4,500,000[5] L☉
Temperature18,000-37,000[2][5] K
Other designations
M33 Var 83, VHK 83, 2MASS J01341090+3034373
Database references
SIMBADdata

The brightness varies slowly and unpredictably over a 1-2 magnitude visual range and can remain approximately constant for many years. These variations, combined with the high luminosity and temperature of the star, caused it to be grouped with the Hubble-Sandage variables even before the term "Luminous blue variable" was more than a simple description.[7] Despite widespread agreement that it is an LBV it has yet to be observed in outburst, although the temperature has been observed to change in tandem with the brightness variations.[2]

Temperature estimates for the star range from around 18,000K to well over 30,000K. The hotter temperatures found from fitting the spectral energy distribution (SED) are consistent with the calculated luminosity of an LBV in the quiescent stage, but the spectrum is that of a cooler star.[5]

References
  1. Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T.; Fowler, J.; Gizis, J.; Howard, E.; Huchra, J.; Jarrett, T.; Kopan, E. L.; Kirkpatrick, J. D.; Light, R. M.; Marsh, K. A.; McCallon, H.; Schneider, S.; Stiening, R.; Sykes, M.; Weinberg, M.; Wheaton, W. A.; Wheelock, S.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally Published in: 2003yCat.2246....0C. 2246: 0. Bibcode:2003yCat.2246....0C.
  2. Humphreys, R. M.; Blaha, C.; d'Odorico, S.; Gull, T. R.; Benvenuti, P. (1984). "IUE and ground-based observations of the Hubble-Sandage variables in M31 and M33". The Astrophysical Journal. 278: 124. Bibcode:1984ApJ...278..124H. doi:10.1086/161774.
  3. Khrutskaya, E. V.; Khovritchev, M. Yu.; Bronnikova, N. M. (2004). "The Pul-3 catalogue of 58483 stars in the Tycho-2 system". Astronomy and Astrophysics. 418: 357–362. Bibcode:2004A&A...418..357K. doi:10.1051/0004-6361:20034232.
  4. Burggraf, B.; Weis, K.; Bomans, D. J. (2006). "LBVs in M33: Their Environments and Ages". Stellar Evolution at Low Metallicity: Mass Loss. 353: 245. Bibcode:2006ASPC..353..245B.
  5. Valeev, A. F.; Sholukhova, O.; Fabrika, S. (2009). "A new luminous variable in M33". Monthly Notices of the Royal Astronomical Society: Letters. 396 (1): L21. arXiv:0903.5222. Bibcode:2009MNRAS.396L..21V. doi:10.1111/j.1745-3933.2009.00654.x.
  6. Van Den Bergh, S.; Herbst, E.; Kowal, C. T. (1975). "A survey of bright variable stars in M33". The Astrophysical Journal Supplement Series. 29: 303. Bibcode:1975ApJS...29..303V. doi:10.1086/190344.
  7. Humphreys, R. M. (1978). "Luminous variable stars in M31 and M33". The Astrophysical Journal. 219: 445. Bibcode:1978ApJ...219..445H. doi:10.1086/155797.

Further reading
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