W Mensae

W Mensae (W Men) is an unusual yellow supergiant star in the Large Magellanic Cloud in the southern constellation Mensa. It is an R Coronae Borealis variable and periodically decreases in brightness by several magnitudes.

W Mensae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Mensa
Right ascension  05h 26m 24.516s[1]
Declination −71° 11′ 11.79″ [1]
Apparent magnitude (V) 13.90[2] (13.4pg - <18.3pg[3])
Characteristics
Spectral type F5Ipec[3]
Apparent magnitude (R) 13.700[1]
Apparent magnitude (J) 13.032[1]
Apparent magnitude (H) 12.831[1]
Apparent magnitude (K) 12.296[1]
U−B color index −0.24[2]
B−V color index +0.45[2]
J−H color index 0.201[1]
J−K color index 0.736[1]
Variable type R CrB[4]
Astrometry
Radial velocity (Rv)+260[5] km/s
Distance~168,000 ly
(~51,500 pc)
Absolute magnitude (MV)−4.8[6]
Details
Radius61[2] R☉
Luminosity7,700[2] L☉
Surface gravity (log g)0.5[7] cgs
Temperature6,700[7] K
Other designations
W Mensae, HV 966, RMC 102, 2MASS J05262451-7111117, AAVSO 0527-71, OGLE LMC-RCB-13
Database references
SIMBADdata

W Men is very distant, being located in the neighboring galaxy Large Magellanic Cloud, where it lies on the southern metal-deficient edge.[2] Despite its high luminosity, the star has a maximum apparent brightness of +13.8m,[4] too dim to be visible in a small telescope. Its radius has been calculated to be 61 times that of the Sun.[2]

The variability of W Men was discovered in 1927 by W. J. Luyten.[8] It belongs to the very rare R Coronae Borealis class of variables which are often called "inverse novae" since they experience occasional very large drops in brightness. At minimum brightness, W Men has a photographic (blue) magnitude less than +18.3, being undetectable on photographic plates at the time.[9] The drop in brightness is less pronounced at longer wavelengths, and the overall luminosity of the star is thought to be largely unchanged. The variations are caused by condensation of dust which temporarily obscures the star. Short wavelengths of light are absorbed and re-emitted as infra-red. Many R CrB variables show small amplitude pulsations and W Mensae has a pulsation period of approximately 67 days.[4]

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. Bibcode:2003yCat.2246....0C.
  2. Goldsmith, M. J.; Evans, A.; Albinson, J. S.; Bode, M. F. (1990). "Effective temperatures of RCB stars". Monthly Notices of the Royal Astronomical Society. 245 (1): 119–29. Bibcode:1990MNRAS.245..119G. ISSN 0035-8711.
  3. Milone, Luis A. (1990). "Identification charts for southern R Coronae Borealis-stars". Astrophysics and Space Science. 172: 263. Bibcode:1990Ap&SS.172..263M. doi:10.1007/BF00643318.
  4. Soszyński, I.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Wyrzykowski, Ł.; Szewczyk, O.; Ulaczyk, K.; Poleski, R. (2009). "The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. V. R Coronae Borealis Stars in the Large Magellanic Cloud". Acta Astronomica. 59: 335. arXiv:0912.2097. Bibcode:2009AcA....59..335S.
  5. Evans, D. S. (1967). "The Revision of the General Catalogue of Radial Velocities". Determination of Radial Velocities and their Applications. 30: 57. Bibcode:1967IAUS...30...57E.
  6. Sherwood, Vicki E. (1975). "Some Statistics of Southern R Coronae Borealis Variables (abstract)". Variable Stars and Stellar Evolution; Proceedings of the Symposium. 67: 147. Bibcode:1975IAUS...67..147S.
  7. Pollard, K. R.; Cottrell, P. L.; Lawson, W. A. (1994). "An Abundance Analysis of R-Coronae Stars in the Galaxy and the Large Magellanic Cloud". Monthly Notices of the Royal Astronomical Society. 268 (2): 544. Bibcode:1994MNRAS.268..544P. doi:10.1093/mnras/268.2.544.
  8. Luyten, W. J. (1927). "A New Irregular Variable of the R Coronae Type". Harvard College Observatory Bulletin. 846 (846): 31–33. Bibcode:1927BHarO.846...33L. 1927BHarO.846...33L.
  9. Milone, L. A. (1975). "A Note on V CrA and W Men". Information Bulletin on Variable Stars. 989: 1. Bibcode:1975IBVS..989....1M.
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