BI 253

BI 253
Observation data
Epoch J2000      Equinox J2000
Constellation Dorado
Right ascension 05h 37m 34.461s[1]
Declination −69° 01′ 10.20″[1]
Apparent magnitude (V) 13.76[2]
Characteristics
Evolutionary stage Main Sequence[3]
Spectral type O2V-III(n)((f*))[3]
U−B color index −1.02[4]
B−V color index −0.13[4]
Astrometry
Proper motion (μ) RA: 2.3[1] mas/yr
Dec.: 3.1[1] mas/yr
Distance164,000 ly
(50,000[5] pc)
Absolute magnitude (MV)−5.7[3]
Details
Mass84[3] M☉
Radius10.7[2] R☉
Luminosity912,000[3] L☉
Surface gravity (log g)4.20[2] cgs
Temperature50,100[3] K
Rotational velocity (v sin i)200[3] km/s
Other designations
BI 253, VFTS 72, 2MASS J05373446-6901102, IRSF J05373446-6901102
Database references
SIMBADdata

BI 253 is an O2 V star in the Large Magellanic Cloud and is a primary standard of the O2 type. It is one of the hottest main sequence stars known and one of the most massive and most luminous stars known.

Discovery

BI 253 was first catalogued in 1975 as the 253rd of 272 likely O and early B stars in the Large Magellanic Cloud.[4] In 1995, the spectral type was analysed to be O3 V, the earliest type defined at that time.[6]

When the classification of the earliest type O stars was refined in 2002, the complete lack of neutral helium or doubly ionised nitrogen lines in the spectrum led to BI 253 being placed in a new O2 V class. It was given a ((f*)) qualifier because of the very weak emission lines of helium and nitrogen.[7] The most recent published data gives a spectral type of O2V-III(n)((f*)), although it is unclear whether this is due to higher quality spectra or an actual change in the spectrum.[3][8]

BI 253 has been proposed as a runaway star because of its relatively isolated position outside the main star-forming areas of 30 Doradus. However, it does not exhibit a particularly high space velocity or any other indicators such as a bow shock.[9][10]

Properties

BI 253 is one of the hottest, most massive, and most luminous known main sequence stars.[11] The temperature is around 50,000 K, the luminosity over 750,000 L☉, and the mass over 80 M☉, although it is less than 11 R☉. The rotation rate of at least 200 km/s is high, but this is common in the youngest and hottest stars, either due to spin-up during stellar formation or merger of a close binary system.

Evolution

BI 253 is still burning hydrogen in its core, but shows enrichment of nitrogen and helium at the surface due to strong rotational and convectional mixing and because of its strong stellar wind. It is very close to the expected ZAMS position for an 85 M☉ star. It is expected that stars more massive than BI 253 would show a giant or supergiant luminosity class even on the main sequence.[11]

See also

Stellar classification

References

  1. 1 2 3 4 Zacharias, N.; Urban, S. E.; Zacharias, M. I.; Wycoff, G. L.; Hall, D. M.; Germain, M. E.; Holdenried, E. R.; Winter, L. (2003). "VizieR Online Data Catalog: The Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2)". CDS/ADC Collection of Electronic Catalogues 1289. Bibcode:2003yCat.1289....0Z.
  2. 1 2 3 Rivero González, J. G.; Puls, J.; Najarro, F.; Brott, I. (2012). "Nitrogen line spectroscopy of O-stars. II. Surface nitrogen abundances for O-stars in the Large Magellanic Cloud". Astronomy & Astrophysics 537: A79. arXiv:1110.5148. Bibcode:2012A&A...537A..79R. doi:10.1051/0004-6361/201117790.
  3. 1 2 3 4 5 6 7 8 Bestenlehner, J. M.; Gräfener, G.; Vink, J. S.; Najarro, F.; De Koter, A.; Sana, H.; Evans, C. J.; Crowther, P. A.; Hénault-Brunet, V.; Herrero, A.; Langer, N.; Schneider, F. R. N.; Simón-Díaz, S.; Taylor, W. D.; Walborn, N. R. (2014). "The VLT-FLAMES Tarantula Survey. XVII. Physical and wind properties of massive stars at the top of the main sequence". Astronomy & Astrophysics 570: A38. arXiv:1407.1837. Bibcode:2014A&A...570A..38B. doi:10.1051/0004-6361/201423643.
  4. 1 2 3 Brunet, J. P.; Imbert, M.; Martin, N.; Mianes, P.; Prévot, L.; Rebeirot, E.; Rousseau, J. (1975). "Studies of the LMC stellar content. I. A catalogue of 272 new O-B2 stars". Astronomy and Astrophysics 21: 109. Bibcode:1975A&AS...21..109B.
  5. ↑ Evans, C. J.; Taylor, W. D.; Hénault-Brunet, V.; Sana, H.; De Koter, A.; Simón-Díaz, S.; Carraro, G.; Bagnoli, T.; Bastian, N.; Bestenlehner, J. M.; Bonanos, A. Z.; Bressert, E.; Brott, I.; Campbell, M. A.; Cantiello, M.; Clark, J. S.; Costa, E.; Crowther, P. A.; De Mink, S. E.; Doran, E.; Dufton, P. L.; Dunstall, P. R.; Friedrich, K.; Garcia, M.; Gieles, M.; Gräfener, G.; Herrero, A.; Howarth, I. D.; Izzard, R. G.; et al. (2011). "The VLT-FLAMES Tarantula Survey. I. Introduction and observational overview". Astronomy & Astrophysics 530: A108. arXiv:1103.5386. Bibcode:2011A&A...530A.108E. doi:10.1051/0004-6361/201116782.
  6. ↑ Massey, Philip; Lang, Cornelia C.; Degioia-Eastwood, Kathleen; Garmany, Catharine D. (1995). "Massive stars in the field and associations of the magellanic clouds: The upper mass limit, the initial mass function, and a critical test of main-sequence stellar evolutionary theory". Astrophysical Journal 438: 188. Bibcode:1995ApJ...438..188M. doi:10.1086/175064.
  7. ↑ Walborn, Nolan R.; Howarth, Ian D.; Lennon, Daniel J.; Massey, Philip; Oey, M. S.; Moffat, Anthony F. J.; Skalkowski, Gwen; Morrell, Nidia I.; Drissen, Laurent; Parker, Joel Wm. (2002). "A New Spectral Classification System for the Earliest O Stars: Definition of Type O2". The Astronomical Journal 123 (5): 2754. Bibcode:2002AJ....123.2754W. doi:10.1086/339831.
  8. ↑ Walborn, N. R.; Sana, H.; Simón-Díaz, S.; Maíz Apellániz, J.; Taylor, W. D.; Evans, C. J.; Markova, N.; Lennon, D. J.; De Koter, A. (2014). "The VLT-FLAMES Tarantula Survey. XIV. The O-type stellar content of 30 Doradus". Astronomy & Astrophysics 564: A40. arXiv:1402.6969. Bibcode:2014A&A...564A..40W. doi:10.1051/0004-6361/201323082.
  9. ↑ Gvaramadze, V. V.; Kroupa, P.; Pflamm-Altenburg, J. (2010). "Massive runaway stars in the Large Magellanic Cloud". Astronomy and Astrophysics 519: A33. arXiv:1006.0225. Bibcode:2010A&A...519A..33G. doi:10.1051/0004-6361/201014871.
  10. ↑ Evans, C. J.; Walborn, N. R.; Crowther, P. A.; Hénault-Brunet, V.; Massa, D.; Taylor, W. D.; Howarth, I. D.; Sana, H.; Lennon, D. J.; Van Loon, J. Th. (2010). "A Massive Runaway Star from 30 Doradus". The Astrophysical Journal Letters 715 (2): L74. arXiv:1004.5402. Bibcode:2010ApJ...715L..74E. doi:10.1088/2041-8205/715/2/L74.
  11. 1 2 Doran, Emile I.; Crowther, Paul A. (2011). "A VLT/UVES spectroscopy study of O2 stars in the LMC". Société Royale des Sciences de Liège 80: 129. Bibcode:2011BSRSL..80..129D.
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