Westerhout 49-2

Westerhout 49-2

Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	19^h 10^m 21.858^s[1]
Declination	09° 05′ 02.53″[1]
Characteristics
Spectral type	O2-3.5If^*[2]
Astrometry
Distance	36,200 ly (11,100[2] pc)
Details[2]
Mass	130 – 370 M☉
Radius	55.29[a] R☉
Luminosity	4,365,000 L☉
Temperature	35,500 K
Other designations
TIC 202340617, 2MASS J19102185+0905025
Database references
SIMBAD	data

Westerhout 49-2 (W49-2) is a very massive and luminous star in the H II region Westerhout 49. At a mass of 250 solar masses (although with significant uncertainty) and a luminosity of over 4 million L_☉, it is one of the most massive and most luminous known stars.[2]

Properties

Westerhout 49-2 is located within the H II region Westerhout 49, about 11.1 kiloparsecs from the Sun. The star is heavily reddened, by nearly 5 magnitudes in the K band, the most of any star in the region. Westerhout 49-2 is classified as an evolved slash star, with a spectral type of O2-3.5If^*. The star is one of the most luminous stars known, with a luminosity of 4,365,000 L_☉, and has a temperature of about 35,500 K, corresponding to a radius of over 55 times that of the Sun.[2][a]

Uncertainties

There is significant uncertainty about Westerhout 49-2's properties. One estimate using mass-luminosity relations finds a mass between 90 and 240 M_☉. Its mass is likely higher than the theoretical upper limit of 150 M☉, which means it could be a binary, if x-rays are detected. Westerhout 49-1, 49-2 and 49-12 are all bright x-ray sources, which means they could all be binary stars and their masses would be lower than the predicted mass if they were single stars.[2]

Notes

1. Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:

   ${\displaystyle {\sqrt {(5772/35,500)^{4}*4,365,000}}=55.29\ R\odot }$

References

1. 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.
2. Wu, Shi-Wei; Bik, Arjan; Bestenlehner, Joachim M.; Henning, Thomas; Pasquali, Anna; Brandner, Wolfgang; Stolte, Andrea (2016-05-01). "The massive stellar population of W49: A spectroscopic survey". Astronomy and Astrophysics. 589: A16. arXiv:1602.05190. Bibcode:2016A&A...589A..16W. doi:10.1051/0004-6361/201527823. ISSN 0004-6361. S2CID 59425112.