Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Sagitta |
Right ascension | 19h 48m 32.19686s [2] |
Declination | +18° 12′ 03.69399″ [2] |
Apparent magnitude (V) | 10.51 |
Characteristics | |
Evolutionary stage | Wolf-Rayet |
Spectral type | WN4(h)-w [3] |
U−B color index | −0.89 [4] |
B−V color index | -0.02 [4] |
Astrometry | |
Radial velocity (Rv) | 100.00 [5] km/s |
Parallax (π) | 0.3129 ± 0.0417 mas [2] |
Distance | 2,900+540 −390 [6] pc |
Absolute magnitude (MV) | −3.27 [3] |
Details | |
Mass | 11 [3] M☉ |
Radius | 2.69 [3] R☉ |
Luminosity | 166,000 [3] L☉ |
Temperature | 70,800 [3] K |
Other designations | |
Database references | |
SIMBAD | data |
WR 128 is a Wolf–Rayet star located about 9,500 light years away in the constellation of Sagitta. A member of the WN class, WR 128's spectrum resembles that of a WN4 star, but hydrogen is clearly present in the star (hence the h in its spectrum), making it the only known hydrogen-rich WN4 star in the galaxy. However, similar H-rich very early WN stars can be found in the LMC and especially in the SMC, but the only other galactic examples of this are WR 3 and WR 152. [7]
Analysis of WR 128's spectrum with PoWR shows that it has a temperature of around 70,800 K and is losing mass at a very slow pace (in Wolf-Rayet terms), at 10-5.4 M☉/year, or in other words, 1 solar mass every 250,000 years. [3] All this mass is being carried by a very strong stellar wind with a terminal velocity of 2,050 kilometres per second. Taking its distance into account, WR 128 has a luminosity of 166,000 L☉, or 105.22 L☉, [3] making it one of the dimmest galactic WN stars. Using the Stefan-Boltzmann Law, we can calculate a radius of 2.69 R☉. A "transformed" radius at an optical depth of 2/3, more comparable to other types of stars, is at about 13 R☉. [3]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Sagitta |
Right ascension | 19h 48m 32.19686s [2] |
Declination | +18° 12′ 03.69399″ [2] |
Apparent magnitude (V) | 10.51 |
Characteristics | |
Evolutionary stage | Wolf-Rayet |
Spectral type | WN4(h)-w [3] |
U−B color index | −0.89 [4] |
B−V color index | -0.02 [4] |
Astrometry | |
Radial velocity (Rv) | 100.00 [5] km/s |
Parallax (π) | 0.3129 ± 0.0417 mas [2] |
Distance | 2,900+540 −390 [6] pc |
Absolute magnitude (MV) | −3.27 [3] |
Details | |
Mass | 11 [3] M☉ |
Radius | 2.69 [3] R☉ |
Luminosity | 166,000 [3] L☉ |
Temperature | 70,800 [3] K |
Other designations | |
Database references | |
SIMBAD | data |
WR 128 is a Wolf–Rayet star located about 9,500 light years away in the constellation of Sagitta. A member of the WN class, WR 128's spectrum resembles that of a WN4 star, but hydrogen is clearly present in the star (hence the h in its spectrum), making it the only known hydrogen-rich WN4 star in the galaxy. However, similar H-rich very early WN stars can be found in the LMC and especially in the SMC, but the only other galactic examples of this are WR 3 and WR 152. [7]
Analysis of WR 128's spectrum with PoWR shows that it has a temperature of around 70,800 K and is losing mass at a very slow pace (in Wolf-Rayet terms), at 10-5.4 M☉/year, or in other words, 1 solar mass every 250,000 years. [3] All this mass is being carried by a very strong stellar wind with a terminal velocity of 2,050 kilometres per second. Taking its distance into account, WR 128 has a luminosity of 166,000 L☉, or 105.22 L☉, [3] making it one of the dimmest galactic WN stars. Using the Stefan-Boltzmann Law, we can calculate a radius of 2.69 R☉. A "transformed" radius at an optical depth of 2/3, more comparable to other types of stars, is at about 13 R☉. [3]