Westerlund 1-243
Westerlund 1 super star cluster. The location of Wd 1-243 is circled.
Credit: ESO
Observation data
Epoch J2000      Equinox J2000
Constellation Ara
Right ascension 16h 47m 7.5041s[1]
Declination −45° 52′ 29.123″[1]
Apparent magnitude (V) 15.807[2]
Characteristics
Spectral type A3Ia+[3]
Apparent magnitude (J) 6.407[4]
Apparent magnitude (H) 5.271[4]
Apparent magnitude (K) 4.632[4]
Astrometry
Proper motion (μ) RA: −1.574[1] mas/yr
Dec.: −4.036[1] mas/yr
Parallax (π)0.0119 ± 0.0812 mas[1]
Distance13,400 ly
(4,120[5] pc)
Details[3]
Mass40 M☉
Radius376.9 R☉
Luminosity730,000 L☉
Surface gravity (log g)~0.65 cgs
Temperature~8,500 K
Rotational velocity (v sin i)10 km/s
Age10.4+1.3
−1.2[5] Myr
Other designations
Westerlund 1 W 243, Westerlund 1 BKS G, 2MASS J16470749-4552290, Gaia DR3 5940105830990286208
Database references
SIMBADdata

Westerlund 1-243 or Wd 1-243 is a luminous blue variable (LBV) star undergoing an eruptive phase located within the outskirts of the super star cluster Westerlund 1.[6] Located about 13,400 ly (4,100 pc) from Earth,[5] it has a luminosity of 0.73 million L☉ making it one of the most luminous stars known.[3]

Observation

Westerlund 1-243 is the second brightest star in Westerlund 1, behind only Westerlund 1-4.[2] It is one of several different hypergiant stars in Westerlund 1. It may also have a companion star, possibly an O-type supergiant.[7]

Spectrum

Westerlund 1-243 displays a complex, time-varying spectrum with emission lines of hydrogen, helium and Lyman-α pumped metals, forbidden lines of nitrogen and iron, and a large number of absorption lines from neutral and singly-ionized metals. Many lines are complex emission/absorption blends, with significant spectral evolution occurring on timescales of just a few days.[3]

Properties

Westerlund 1-243 has a temperature of ~8,500 K determined from modelling the absorption line spectrum. It has expanded to a radius of 376.9 R☉, and a Rosseland radius of 450 R☉. It is radiating at a luminosity of 730,000 L☉. It is losing mass at a rate of 6.1×10−7 M☉/yr.[3]

Evolution

Westerlund 1-243 is believed to be either in an advanced pre-red supergiant LBV phase, or has evolved through the RSG phase and returned to the blue side of the HR diagram. In the future it is expected to evolve toward a WR phase. The K-band spectrum also implies a higher temperature than that of a typical yellow hypergiant and suggests that Westerlund 1-243 may be evolving back towards a hotter state.[3]

References

  1. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 Lim, Beomdu; Chun, Moo-Young; Sung, Hwankyung; Park, Byeong-Gon; Lee, Jae-Joon; Sohn, Sangmo T.; Hur, Hyeonoh; Bessell, Michael S. (February 2013). "The Starburst Cluster Westerlund 1: The Initial Mass Function and Mass Segregation". The Astronomical Journal. 145 (2): 46. arXiv:1211.5832. Bibcode:2013AJ....145...46L. doi:10.1088/0004-6256/145/2/46. ISSN 0004-6256. S2CID 56143904.
  3. 1 2 3 4 5 6 Ritchie, B. W.; Clark, J. S.; Negueruela, I.; Najarro, F. (December 2009). "Spectroscopic monitoring of the luminous blue variable Westerlund 1-243 from 2002 to 2009". Astronomy and Astrophysics. 507 (3): 1597–1611. arXiv:0910.0529. Bibcode:2009A&A...507.1597R. doi:10.1051/0004-6361/200912986. ISSN 0004-6361. S2CID 2004271.
  4. 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.
  5. 1 2 3 Beasor, Emma R.; Davies, Ben; Smith, Nathan; Gehrz, Robert D.; Figer, Donald F. (May 2021). "The Age of Westerlund 1 Revisited". The Astrophysical Journal. 2103 (1): arXiv:2103.02609. arXiv:2103.02609. Bibcode:2021ApJ...912...16B. doi:10.3847/1538-4357/abec44. S2CID 232110879.
  6. ↑ Clark, J. S.; Negueruela, I. (January 2004). "A newly identified Luminous Blue Variable in the galactic starburst cluster Westerlund 1". Astronomy and Astrophysics. 413 (2): L15–L18. arXiv:astro-ph/0312058. Bibcode:2004A&A...413L..15C. doi:10.1051/0004-6361:20031700. ISSN 0004-6361. S2CID 2033421.
  7. ↑ Ritchie, B. W.; Clark, J. S.; Negueruela, I.; Najarro, F. (2022). "A VLT/FLAMES survey for massive binaries in Westerlund 1. VIII. Binary systems and orbital parameters". Astronomy and Astrophysics. 660: A89. arXiv:2111.12463. Bibcode:2022A&A...660A..89R. doi:10.1051/0004-6361/202142405. S2CID 244866093.
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