Westerlund 1-237

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Westerlund 1-237
Surprise Cloud Around Vast Star.jpg
Red circle.svg
Westerlund 1 super star cluster. The location of Wd 1-237 is circled.
Credit: ESO
Observation data
Epoch J2000       Equinox J2000
Constellation Ara
Right ascension 16h 47m 03.1075s
Declination −45° 52′ 18.9572″
Apparent magnitude  (V)19.008 [1]
Characteristics
Evolutionary stage either a red supergiant or a foreground giant [2]
Spectral type M3Ia [3] or M6+ III [4]
Apparent magnitude  (B)22.8[ citation needed ]
Apparent magnitude  (R)13.634 [1]
Apparent magnitude  (G)11.259 [5]
Apparent magnitude  (J)5.075 [6]
Apparent magnitude  (H)3.01 [6]
Apparent magnitude  (K)2.18 [6]
Astrometry
Proper motion (μ)RA: -3.09±0.15 [5]   mas/yr
Dec.: -4.12±0.12 [5]   mas/yr
Parallax (π)0.3370 ± 0.1235  mas [5]
Distance 3,000 [7] or 623 [8]   pc
Absolute magnitude  (MV)–6.96 [9]
Details
if a supergiant
Radius 1,241±70 [9]   R☉
Luminosity 219,000±26,000 [9]   L☉
Temperature 3,550 [9] - 3,605 [8]   K
Age 7.9 [9]   Myr
if a foreground giant
Radius 216 [8]   R☉
Luminosity1,000 [2] or 7,178 – 7,379 [8]   L☉
Temperature 3,605 [8]   K
Other designations
Westerlund 1 W237, Westerlund 1 BKS B, 2MASS J16470309-4552189, Gaia EDR3 5940105904023386752
Database references
SIMBAD data

Westerlund 1-237 (commonly abbreviated to Wd 1-237) or Westerlund 1 BKS B is a possible red supergiant (RSG) in the constellation of Ara. It is one out of four known red supergiants in the Westerlund 1 super star cluster, although its outlying position, spectrum, and parallax, suggest it could be a foreground giant. [10] As a red supergiant, it would be one of the largest known stars and one of the most luminous of its type. [7]

Contents

Physical characteristics

Westerlund 1-237 compared to the other 3 RSGs (Red Supergiants) in the Westerlund 1 star cluster. Comparison of Radii of RSGs located in the Westerlund 1 star cluster.png
Westerlund 1-237 compared to the other 3 RSGs (Red Supergiants) in the Westerlund 1 star cluster.

Westerlund 1-237 is classified as a luminous cool supergiant emitting most of its energy in the infrared spectrum. [11] It is surrounded by a radio nebula which is similar in mass to those of Westerlund 1-20 and Westerlund 1 W26, and moreover directly comparable to that of VY Canis Majoris. The elliptical structure of this nebula however indicates that it has been less affected by the cluster wind of Westerlund 1 (W20 and W26 have pronounced cometary shaped nebulae). The outflow velocity for the RSG wind is assumed to be around 30 km/s. The nebula itself seems to have a mass of 0.07 M☉ and a radius of about 0.11 parsecs. This results in a kinematic age around 3,600 years and a time averaged mass loss rate of 2×10−5  M☉ per year. [12]

The star occupies the upper right corner of the Hertzsprung-Russell diagram. With an effective temperature of 3,550 K and a bolometric luminosity of 219,000 L☉, the radius of Westerlund 1-237 would be 1,241 times the solar radius (R☉), making it larger than the orbit of Jupiter. The initial mass of W237 has been calculated from its position relative to theoretical stellar evolutionary tracks to be around 28 M☉ or 32 M☉ for a non-rotating star. [9]

Distance

The distance of Westerlund 1-237 is assumed to be around 8,500+2,000
−1,300  light years or 2,600+600
−400  parsecs [13] based on it being commonly thought of as a member of the Westerlund 1 star cluster (the elliptical shape of its nebula indicates that it might not be near the center of W1, while other RSGs like W20 and W26 are). [12] Another but older source suggests a similar distance of 3,000±500 parsecs. [7]

Westerlund's 1987 analysis assigned a spectral type of M6+ III to W1-237 and considered it to be a foreground giant with a luminosity only around 1,000 L☉. [2] Gaia Data Release 2 gives a parallax of 1.64±0.2608  mas for W1-237, implying a distance of 623+139
−96  pc and a luminosity of 7,178–7,379 L☉ with a corresponding radius of 216 R☉. [14] [8] In 2020, the parallax was revised to the much smaller value of 0.3370±0.1235 mas. [5]

See also

Related Research Articles

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<span class="mw-page-title-main">Westerlund 1-20</span> Red supergiant star located in the Westerlund 1 super star cluster

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<span class="mw-page-title-main">Westerlund 1-75</span> Red supergiant in the Westerlund 1 super star cluster

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References

  1. 1 2 Bonanos, Alceste Z. (2007). "Variability of Young Massive Stars in the Galactic Super Star Cluster Westerlund 1". The Astronomical Journal. 133 (6): 2696–2708. arXiv: astro-ph/0702614 . Bibcode:2007AJ....133.2696B. doi:10.1086/518093. S2CID   119074868.
  2. 1 2 3 Westerlund, B. E. (1987). "Photometry and spectroscopy of stars in the region of a highly reddened cluster in ARA". Astronomy and Astrophysics. Supplement. 70 (3): 311–324. Bibcode:1987A&AS...70..311W. ISSN   0365-0138.
  3. ↑ Clark, J. S.; Ritchie, B. W.; Negueruela, I. (2010). "A serendipitous survey for variability amongst the massive stellar population of Westerlund 1". Astronomy and Astrophysics. 514: A87. arXiv: 1003.5107 . Bibcode:2010A&A...514A..87C. doi:10.1051/0004-6361/200913820. S2CID   14780809.
  4. ↑ Bonanos, Alceste Z. (2007). "Variability of Young Massive Stars in the Galactic Super Star Cluster Westerlund 1". The Astronomical Journal. 133 (6): 2696–2708. arXiv: astro-ph/0702614 . Bibcode:2007AJ....133.2696B. doi:10.1086/518093. S2CID   119074868.
  5. 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657 . S2CID   227254300. (Erratum:  doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  6. 1 2 3 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
  7. 1 2 3 Fok, Thomas K. T.; Nakashima, Jun-Ichi; Yung, Bosco H. K.; Hsia, Chih-Hao; Deguchi, Shuji (2012). "Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters". The Astrophysical Journal. 760 (1): 65. arXiv: 1209.6427 . Bibcode:2012ApJ...760...65F. doi:10.1088/0004-637X/760/1/65. S2CID   53393926.
  8. 1 2 3 4 5 6 Messineo, M.; Brown, A. G. A. (2019). "A Catalog of Known Galactic K-M Stars of Class I Candidate Red Supergiants in Gaia DR2". The Astronomical Journal. 158 (1): 20. arXiv: 1905.03744 . Bibcode:2019AJ....158...20M. doi: 10.3847/1538-3881/ab1cbd . S2CID   148571616.
  9. 1 2 3 4 5 6 Arévalo, Aura (2019). The Red Supergiants in the Supermassive Stellar Cluster Westerlund 1 (Thesis). doi: 10.11606/D.14.2019.tde-12092018-161841 .
  10. ↑ "APOD: 2017 June 20 - The Massive Stars in Westerlund 1". apod.nasa.gov. Retrieved 2020-06-21.
  11. ↑ "Cl* Westerlund 1 W 237". Simbad.
  12. 1 2 Dougherty, S. M.; Clark, J. S.; Negueruela, I.; Johnson, T.; Chapman, J. M. (2010-02-01). "Radio emission from the massive stars in the galactic super star cluster Westerlund 1". Astronomy & Astrophysics. 511: A58. arXiv: 0912.4165 . Bibcode:2010A&A...511A..58D. doi:10.1051/0004-6361/200913505. ISSN   0004-6361. S2CID   9792700.
  13. ↑ Aghakhanloo, Mojgan; Murphy, Jeremiah W.; Smith, Nathan; Parejko, John; Díaz-Rodríguez, Mariangelly; Drout, Maria R.; Groh, Jose H.; Guzman, Joseph; Stassun, Keivan G. (2020-02-21). "Inferring the parallax of Westerlund 1 from Gaia DR2". Monthly Notices of the Royal Astronomical Society. 492 (2): 2497–2509. arXiv: 1901.06582 . Bibcode:2020MNRAS.492.2497A. doi:10.1093/mnras/stz3628. ISSN   0035-8711. S2CID   119465620.
  14. ↑ Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Mantelet, G.; Andrae, R. (2018). "Estimating Distance from Parallaxes. IV. Distances to 1.33 Billion Stars in Gaia Data Release 2". The Astronomical Journal. 156 (2): 58. arXiv: 1804.10121 . Bibcode:2018AJ....156...58B. doi: 10.3847/1538-3881/aacb21 . S2CID   119289017.
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