NGC 6822-WR 12
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Sagittarius |
Right ascension | 19h 45m 13.5s[1] |
Declination | −14° 45′ 12.9″[1] |
Apparent magnitude (V) | 18.96[2] |
Characteristics | |
Evolutionary stage | Wolf-Rayet |
Spectral type | WN4[3] |
U−B color index | -0.54[1] |
B−V color index | -0.17[1] |
Absolute magnitude (MV) | −5.41[3] |
Details | |
Mass | 36[3] M☉ |
Radius | 3.77[3] R☉ |
Luminosity | 1,288,000[3] L☉ |
Temperature | 100,000[3] K |
Other designations | |
LGGS J194513.50-144512.9 | |
Database references | |
SIMBAD | data |
NGC 6822-WR 12 is a WN-type
Discovery
In 1983, a Wolf-Rayet (WR) star was identified in the
NGC 6822-WR 12 was the 12th candidate of 12 candidate WR stars found in NGC 6822 during a survey of NGC 6822 and IC 1613.[7] In a follow-up study, only 4 of the WR candidates in NGC 6822 were confirmed as WR stars,[8] and they are still the only WR stars known in NGC 6822.[6]
Properties
High-resolution
Composition
As is typical of WN stars, NGC 6822-WR 12 has almost no hydrogen, it having been either fused to helium or lost through strong stellar winds. However, due to the very low metallicity of NGC 6822, similar to that of the Small Magellanic Cloud, it has a lower nitrogen abundance than that of galactic WN stars, containing just 0.3% nitrogen. The emission lines of ionised nitrogen in the spectrum are correspondingly weak. The rest of the star is helium and its spectrum is dominated by emission lines of ionised helium.[3]