Astronomy:Westerlund 1-243
Coordinates: 
16h 47m 7.503s, −45° 52′ 29.152″
  Credit: ESO | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Ara[1] |
| Right ascension | 16h 47m 7.5041s[2] |
| Declination | −45° 52′ 29.123″[2] |
| Apparent magnitude (V) | 15.807[3] |
| Characteristics | |
| Spectral type | A3Ia+[4] |
| Apparent magnitude (J) | 6.407[5] |
| Apparent magnitude (H) | 5.271[5] |
| Apparent magnitude (K) | 4.632[5] |
| Astrometry | |
| Proper motion (μ) | RA: −1.574[2] mas/yr Dec.: −4.036[2] mas/yr |
| Parallax (π) | 0.0119 ± 0.0812[2] mas |
| Distance | 13,400 ly (4,120[6] pc) |
| Details[4] | |
| Mass | 40 M☉ |
| Radius | 376.9 R☉ |
| Luminosity | 730,000 L☉ |
| Surface gravity (log g) | ~0.65 cgs |
| Temperature | ~8,500 K |
| Rotational velocity (v sin i) | 10 km/s |
| Age | 10.4+1.3 −1.2[6] Myr |
| Other designations | |
Westerlund 1 W 243, Westerlund 1 BKS G, 2MASS J16470749-4552290, Gaia DR3 5940105830990286208 | |
| Database references | |
| SIMBAD | data |
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.[7] Located about 13,400 ly (4,100 pc) from Earth,[6] it has a luminosity of 0.73 million L☉ making it one of the most luminous stars known.[4]
Observation
Westerlund 1-243 is the second brightest star in Westerlund 1, behind only Westerlund 1-4.[3] It is one of several different hypergiant stars in Westerlund 1. It may also have a companion star, possibly an O-type supergiant.[8]
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.[4]
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.[4]
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.[4]
References
- ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific 99 (617): 695. doi:10.1086/132034. Bibcode: 1987PASP...99..695R Constellation record for this object at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 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. doi:10.1088/0004-6256/145/2/46. ISSN 0004-6256. Bibcode: 2013AJ....145...46L.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 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. doi:10.1051/0004-6361/200912986. ISSN 0004-6361. Bibcode: 2009A&A...507.1597R.
- ↑ 5.0 5.1 5.2 Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E. et al. (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. http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=II/246.
- ↑ 6.0 6.1 6.2 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. doi:10.3847/1538-4357/abec44. Bibcode: 2021ApJ...912...16B.
- ↑ 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. doi:10.1051/0004-6361:20031700. ISSN 0004-6361. Bibcode: 2004A&A...413L..15C.
- ↑ 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. doi:10.1051/0004-6361/202142405. Bibcode: 2022A&A...660A..89R.
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