WR 25

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WR 25
Image of the WR 25 binary.jpg
Image of the WR 25 star system. WR 25 is the brightest star in the image. Picture was captured in 2008.
Credit: Hubble Space Telescope
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Carina
Right ascension 10h 44m 10.337s[1]
Declination −59° 43′ 11.41″[1]
Apparent magnitude (V) 8.80[2]
Evolutionary stage Wolf-Rayet star
Spectral type O2.5If*/WN6[3]
Proper motion (μ) RA: -16.6[1] mas/yr
Dec.: -4.0[1] mas/yr
Absolute magnitude (MV) -6.6[4]
Absolute bolometric
Mass 110[5]/? M
Radius 33[5]/? R
Luminosity (bolometric) 6,300,000[5]/? L
Temperature 50,100[5]/? K
Age Myr
Other designations
HD 93162, 2MASS J10441038-5943111,WR 25, ALS 1833, XMMU J104410.3-594311, CD-59 3282, PPM 339385, SAO 238408, [ESK2003] 28, Trumpler 16 177, GSC 08626-01989, UBV 9882, IRS 61CPD-59 2561, Hen 3-478, UBV M 40364
Database references
WR 25 is the brightest star in the image (optical and IR image from Hubble Space Telescope)

WR 25 (HD 93162) is a Wolf-Rayet star in the turbulent star forming region Carina Nebula, about 7,500 light-years from Earth. It has a companion and resides in the Trumpler 16 cluster.

The primary star is notable for being the most luminous known star in the Milky Way Galaxy, substantially brighter than its nearby neighbor Eta Carinae, although it is unclear what contribution is from the companion. It is approximately 6.3 million times brighter than the Sun and illuminates the far southern end of the Trumpler 16 cluster. The model used to derive the stellar parameters is unsuitable for use in binary systems with the authors noting that the companion contributes more than 15% of the system luminosity, so the luminosity is highly uncertain. Earlier estimates based on measurements of the ionising flux produced values around 1.5 million times the sun, with correspondingly lower estimates for other physical data.[6]

The companion is assumed to be a young hot massive star, similar to other known WR+O or WR+WR binaries, where colliding stellar winds produce the hard X-rays[7] that led to suspicion about the binary status long before the 208 day orbital period was detected.[8]

Although very luminous it is beyond naked-eye visibility due to heavy dust extinction of clouds in the nebula. Despite this, it can be observed in X-rays and infra-red.[7][9]

WR 25 lies at the far southern tip of the Trumpler 16 star cluster, part of Carina OB1, one of the largest stellar associations in the Milky Way Galaxy. Because of its extreme luminosity it greatly affects its stellar environment, seen in the thin long arcs and filaments moving away from the star.

Carina Nebula with position of WR 25 annotated

See also[edit]


  1. ^ a b c d Roeser, S.; Bastian, U. (1988). "A new star catalogue of SAO type". Astronomy and Astrophysics Supplement Series 74: 449. Bibcode:1988A&AS...74..449R. ISSN 0365-0138. 
  2. ^ Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues 2237: 0. Bibcode:2002yCat.2237....0D. 
  3. ^ Roman-Lopes, A.; Barba, R. H.; Morrell, N. I. (2011). "Two O2 If*/WN6 stars possibly ejected from the massive young Galactic cluster Westerlund 2". Monthly Notices of the Royal Astronomical Society 416: 501. arXiv:1107.5001. Bibcode:2011MNRAS.416..501R. doi:10.1111/j.1365-2966.2011.19062.x. 
  4. ^ Levato, H.; Malaroda, S. (1982). "Spectral morphology in Trumpler 16". Astronomical Society of the Pacific 94: 807. Bibcode:1982PASP...94..807L. doi:10.1086/131067. 
  5. ^ a b c d e Hamann, W. -R.; Gräfener, G.; Liermann, A. (2006). "The Galactic WN stars". Astronomy and Astrophysics 457 (3): 1015. arXiv:astro-ph/0608078. Bibcode:2006A&A...457.1015H. doi:10.1051/0004-6361:20065052. 
  6. ^ Crowther, P. A.; Dessart, L. (1998). "Quantitative spectroscopy of Wolf--Rayet stars in HD 97950 and R136a -- the cores of giant H II regions". Monthly Notices of the Royal Astronomical Society 296 (3): 622. doi:10.1046/j.1365-8711.1998.01400.x. 
  7. ^ a b Pandey, J. C.; Pandey, S. B.; Karmakar, S. (2014). "Phase-Resolvedxmm-Newtonandswiftobservations of Wr 25". The Astrophysical Journal 788: 84. doi:10.1088/0004-637X/788/1/84. 
  8. ^ Gamen, R.; Gosset, E.; Morrell, N.; Niemela, V.; Sana, H.; Nazé, Y.; Rauw, G.; Barbá, R.; Solivella, G. (2006). "The first orbital solution for the massive colliding-wind binary HD 93162 (≡WR 25)". Astronomy and Astrophysics 460 (3): 777. doi:10.1051/0004-6361:20065618. 
  9. ^ Sanchawala, K.; Chen, W. P.; Lee, H. T.; Chu, Y. H.; Nakajima, Y.; Tamura, M.; Baba, D.; Sato, S. (2007). "An X‐Ray and Near‐Infrared Study of Young Stars in the Carina Nebula". The Astrophysical Journal 656: 462. doi:10.1086/510184.