Sher 25 and Sanduleak -69 202

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Sher 25 and Sanduleak -69 202 are two Wolf-Rayet stars that scientists believe are following the same path in stellar evolution. They are both blue supergiant stars and are related closely to supernovae.

Sher 25[edit]


Sher 25
NGC 3603b.jpg
HST image of NGC 3603. Sher 25 is the bright star at the 1 o'clock position relative to the center of the cluster, between two patches of nebula and with a faint ring surrounding it.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Carina
Right ascension 11h 15m 7.649s[1]
Declination −61° 15′ 17.59″[1]
Apparent magnitude (V) 12.23[1]
Characteristics
Spectral type B1Iab[1]
U−B color index 0.13[2]
B−V color index 1.42[2]
Variable type cLBV[3]
Astrometry
Distance25,000[1] ly
(7,600[1] pc)
Absolute magnitude (MV)-7.8[1]
Details
Mass40 ± 5[4] M
Radius54[1] R
Diameter54[1] D
Luminosity (bolometric)608,000[1] L
Surface gravity (log g)2.6[4] cgs
Temperature22,000[1][4] K
Rotational velocity (v sin i)65[3] km/s
Age4[1] Myr
Other designations
Sher 25, NGC 3603-25, NGC 3603 MTT 13, NGC 3603 MDS 5
Database references
SIMBADdata

Sher 25 is a blue supergiant star in the constellation Carina, located approximately 25,000 light years from the Sun in the H II region NGC 3603 of the Milky Way.[5] It is a spectral type B1Iab star with an apparent magnitude of 12.2.[6] Its initial main sequence mass is calculated at 60 times the mass of our Sun, but a star of this type will have already lost a substantial fraction of that mass. It is unclear whether Sher 25 has been through a red supergiant phase or has just evolved from the main sequence, so the current mass is very uncertain.[4]

The name derives from the original cataloguing of stars in NGC 3603 by David Sher. This catalogue entry is more properly referred to as NGC 3603 Sher 25 to distinguish it from stars numbered 25 by Sher in other clusters. The same star was numbered 13 by Melnick, Tapia, and Terlevich[2] (NGC 3603 MTT 13) and 5 in a Hubble Space Telescope survey by Moffat, Drissen, and Shara[7] (NGC 3603 MDS 5).

It is speculated that Sher 25 is near the point of going supernova, as it has recently thrown off matter in a pattern similar to that of supernova 1987A in the Large Magellanic Cloud, with a circumstellar ring and bipolar outflow filaments.[3]

Regular variations in the doppler shift of the star's spectral lines with a period of a few days have suggested orbital motion about a companion star, but pulsations are a more likely explanation.[8]

Sanduleak -69 202[edit]


Sher 25 and Sanduleak -69 202
Supernova-1987a.jpg
SN 1987A was caused by the explosion of Sanduleak -69 202.
Observation data
Epoch J2000      Equinox J2000
Constellation Dorado
Right ascension 05h 35m 27.92s[9]
Declination −69° 16′ 11.1″[9]
Characteristics
Spectral type B2 Ia[10]
Astrometry
Distance168,000 ly
(51,400[9] pc)
Details
Mass26[10] M
Luminosity400,000[10] L
Temperature21,000[10] K
Other designations
Sk -69 202, GSC 09162-00821
Database references
SIMBADdata

Sanduleak -69 202 (Sk -69 202, also known as GSC 09162-00821) was a magnitude 12 blue supergiant star, located on the outskirts of the Tarantula Nebula in the Large Magellanic Cloud. It is notable as the progenitor of supernova 1987A.

The star was originally charted by the Romanian-American astronomer Nicholas Sanduleak in 1970, but remained just a number in a catalogue until identified as the star that exploded in the first naked eye supernova since the invention of the telescope.[9]

The discovery that a blue supergiant was a supernova progenitor contradicted all known theories at the time and produced a flurry of new ideas about how such a thing might happen,[11] but it is now accepted that blue supergiants are a normal progenitor for some supernovae.[12]

The candidate luminous blue variable (LBV) HD 168625 possesses a bipolar nebula that is a close twin of that around Sk -69 202. It is speculated that Sk -69 202 may have been an LBV in the recent past, although it was apparently a normal luminous supergiant at the time it exploded.[10]

References[edit]

  1. 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Melena, N. W.; Massey, P.; Morrell, N. I.; Zangari, A. M. (2008). "The Massive Star Content of Ngc 3603". The Astronomical Journal 135 (3): 878. arXiv:0712.2621. Bibcode 2008AJ....135..878M. doi:10.1088/0004-6256/135/3/878.
  2. 2.0 2.1 2.2 Melnick, J.; Tapia, M.; Terlevich, R. (1989). "The galactic giant H II region NGC 3603". Astronomy and Astrophysics 213: 89. Bibcode 1989A&A...213...89M.
  3. 3.0 3.1 3.2 Smartt, S. J.; Lennon, D. J.; Kudritzki, R. P.; Rosales, F.; Ryans, R. S. I.; Wright, N. (2002). "The evolutionary status of Sher 25 - implications for blue supergiants and the progenitor of SN 1987A". Astronomy and Astrophysics 391 (3): 979. arXiv:astro-ph/0205242. Bibcode 2002A&A...391..979S. doi:10.1051/0004-6361:20020829.
  4. 4.0 4.1 4.2 4.3 Hendry, M. A.; Smartt, S. J.; Skillman, E. D.; Evans, C. J.; Trundle, C.; Lennon, D. J.; Crowther, P. A.; Hunter, I. (2008). "The blue supergiant Sher 25 and its intriguing hourglass nebula". Monthly Notices of the Royal Astronomical Society 388 (3): 1127. arXiv:0803.4262. Bibcode 2008MNRAS.388.1127H. doi:10.1111/j.1365-2966.2008.13347.x.
  5. Sher, D. (1965). "Distances of Five Open Cluster Near Eta Carinae". Monthly Notices of the Royal Astronomical Society 129 (3): 237–262. Bibcode 1965MNRAS.129..237S. doi:10.1093/mnras/129.3.237. ISSN 0035-8711.
  6. Brandner, Wolfgang; Grebel, Eva K.; Chu, You-Hua; Weis, Kerstin (January 1997). "Ring Nebula and Bipolar Outflows Associated with the B1.5 Supergiant Sher 25 in NGC 3603". Astrophysical Journal Letters 475: L45. arXiv:astro-ph/9611046. Bibcode 1997ApJ...475L..45B. doi:10.1086/310460.
  7. Moffat, A. F. J.; Drissen, L.; Shara, M. M. (1994). "NGC 3603 and its Wolf-Rayet stars: Galactic clone of R136 at the core of 30 Doradus, but without the massive surrounding cluster halo". The Astrophysical Journal 436: 183. Bibcode 1994ApJ...436..183M. doi:10.1086/174891.
  8. Taylor, W. D.; Evans, C. J.; Simon-Diaz, S.; Sana, H.; Langer, N.; Smith, N.; Smartt, S. J. (2014). "Sher 25: pulsating but apparently alone". Monthly Notices of the Royal Astronomical Society 442 (2): 1483–1490. arXiv:1405.2101. Bibcode 2014MNRAS.442.1483T. doi:10.1093/mnras/stu925. ISSN 0035-8711.
  9. 9.0 9.1 9.2 9.3 Sanduleak, N. (1970). "A deep objective-prism survey for Large Magellanic Cloud members". Contribution 89. Bibcode 1970CoTol..89.....S.
  10. 10.0 10.1 10.2 10.3 10.4 Smith, N. (2007). "Discovery of a Nearby Twin of SN 1987A's Nebula around the Luminous Blue Variable HD 168625: Was Sk -69 202 an LBV?". The Astronomical Journal 133 (3): 1034–1538. arXiv:astro-ph/0611544. Bibcode 2007AJ....133.1034S. doi:10.1086/510838.
  11. Podsiadlowski, P. (1992). "The progenitor of SN 1987 A". Publications of the Astronomical Society of the Pacific 104: 717. Bibcode 1992PASP..104..717P. doi:10.1086/133043.
  12. Georgy, C.; Meynet, G.; Walder, R.; Folini, D.; Maeder, A. (2009). "The different progenitors of type Ib, Ic SNe, and of GRB". Astronomy and Astrophysics 502 (2): 611. arXiv:0906.2284. Bibcode 2009A&A...502..611G. doi:10.1051/0004-6361/200811339.


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