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Star in the constellation of Scorpius From Wikipedia, the free encyclopedia
HD 151932, also known as WR 78, is a Wolf-Rayet star located in the constellation Scorpius, close to the galactic plane. Its distance is around 1,300 parsecs (4,200 lightyears) away from the Earth.[10] Despite being a blue-colored Wolf-Rayet star, it is extremely reddened by interstellar extinction, so its apparent magnitude is brighter for longer-wavelength passbands.[4] HD 151932 lies about 22′ west of the open cluster NGC 6231, the center of the OB association Scorpius OB1; it is not clear whether it is a part of the association or not.[8] With an apparent magnitude of about 6.5,[4] it is one of the few Wolf-Rayet stars that can be seen with the naked eye (although it can only be seen with the naked eye under excellent viewing conditions).
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Scorpius |
Right ascension | 16h 52m 19.24769s[1] |
Declination | −41° 51′ 16.2631″[1] |
Apparent magnitude (V) | 6.45 - 6.61[2] |
Characteristics | |
Spectral type | WN7h[3] |
U−B color index | -0.63[4] |
B−V color index | +0.27[4] |
Variable type | WR[2] |
Astrometry | |
Radial velocity (Rv) | −25.00[5] km/s |
Proper motion (μ) | RA: −1.914±0.169[6] mas/yr Dec.: −2.402±0.097[6] mas/yr |
Parallax (π) | 0.7679 ± 0.0649 mas[6] |
Distance | 1,250+150 −120[7] pc |
Absolute magnitude (MV) | –5.83[3] |
Details | |
Mass | 22[3] M☉ |
Radius | 10.14[3] R☉ |
Luminosity (bolometric) | 630,000[3] L☉ |
Surface gravity (log g) | 3.5[8] cgs |
Temperature | 50,100[3] K |
Other designations | |
Database references | |
SIMBAD | data |
Like most extremely massive stars, HD 151932 is losing mass via its stellar wind. The total rate of mass loss is 5×10−5 M☉/yr.[10] The multiplicity (i.e., whether the star is a single star or a binary star system) of HD 151932 has not been studied very much.[11] A periodic shift in the spectrum with a period of 3.3 days (implying it is a spectroscopic binary) has been noticed, but it may be spurious; the star appears to be a single star but may be orbiting face-on and/or with a lower-mass companion.[8]
The spectrum of HD 151932 is unusual: part of the He I absorption lines are known to be shifted towards the violet side of the electromagnetic spectrum – this has been interpreted as an expanding stellar shell.[8] Related to this is the fact that the Si IV line varies irregularly in radial velocity, the nature of which is largely unknown.[12] X-rays have been detected from this star, along with several other Wolf-Rayet stars such as WR 24 and WR 136.[10]
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