Astronomy:BI 253
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| 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 |
| Distance | 164,000 ly |
| Absolute magnitude (MV) | −5.7[3] |
| Details | |
| Mass | 97.6 M☉ |
| Radius | 13.9 R☉ |
| Luminosity | 1,175,000 L☉ |
| Surface gravity (log g) | 4.02 cgs |
| Temperature | 54,000 K |
| Rotational velocity (v sin i) | 185 km/s |
| Age | 0.4+0.8 −0.4 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
BI 253 is an O2V 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.[5]
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.[6] 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][7]
BI 253 has been identified as a runaway star because of its relatively isolated position outside the main star-forming areas of 30 Doradus,[8][9] and because of its high space velocity. It was potentially ejected from the R136 cluster about a million years ago.[10]
Properties
BI 253 is one of the hottest, most massive, and most luminous known main sequence stars.[11] The temperature is around 54,000 K, the luminosity over a million L☉, and the mass of nearly 100 M☉, although its radius is less than 14 R☉. The rotation rate of around 185 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]
References
- ↑ 1.0 1.1 1.2 1.3 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.
- ↑ 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. doi:10.1051/0004-6361/201117790. Bibcode: 2012A&A...537A..79R.
- ↑ 3.0 3.1 3.2 3.3 Bestenlehner, J. M.; Gräfener, G.; Vink, J. S.; Najarro, F.; De Koter, A.; Sana, H.; Evans, C. J.; Crowther, P. A. et al. (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. doi:10.1051/0004-6361/201423643. Bibcode: 2014A&A...570A..38B.
- ↑ 4.0 4.1 4.2 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.
- ↑ 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. doi:10.1086/175064. Bibcode: 1995ApJ...438..188M.
- ↑ Walborn, Nolan R.; Howarth, Ian D.; Lennon, Daniel J.; Massey, Philip; Oey, M. S.; Moffat, Anthony F. J.; Skalkowski, Gwen; Morrell, Nidia I. et al. (2002). "A New Spectral Classification System for the Earliest O Stars: Definition of Type O2". The Astronomical Journal 123 (5): 2754. doi:10.1086/339831. Bibcode: 2002AJ....123.2754W.
- ↑ Walborn, N. R.; Sana, H.; Simón-Díaz, S.; Maíz Apellániz, J.; Taylor, W. D.; Evans, C. J.; Markova, N.; Lennon, D. J. et al. (2014). "The VLT-FLAMES Tarantula Survey. XIV. The O-type stellar content of 30 Doradus". Astronomy & Astrophysics 564: A40. doi:10.1051/0004-6361/201323082. Bibcode: 2014A&A...564A..40W.
- ↑ Gvaramadze, V. V.; Kroupa, P.; Pflamm-Altenburg, J. (2010). "Massive runaway stars in the Large Magellanic Cloud". Astronomy and Astrophysics 519: A33. doi:10.1051/0004-6361/201014871. Bibcode: 2010A&A...519A..33G.
- ↑ Evans, C. J.; Walborn, N. R.; Crowther, P. A.; Hénault-Brunet, V.; Massa, D.; Taylor, W. D.; Howarth, I. D.; Sana, H. et al. (2010). "A Massive Runaway Star from 30 Doradus". The Astrophysical Journal Letters 715 (2): L74. doi:10.1088/2041-8205/715/2/L74. Bibcode: 2010ApJ...715L..74E.
- ↑ Lennon, D. J.; Evans, C. J.; Van Der Marel, R. P.; Anderson, J.; Platais, I.; Herrero, A.; De Mink, S. E.; Sana, H. et al. (2018). "Gaia DR2 reveals a very massive runaway star ejected from R136". Astronomy and Astrophysics 619: A78. doi:10.1051/0004-6361/201833465. Bibcode: 2018A&A...619A..78L.
- ↑ 11.0 11.1 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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