V4381 Sagittarii
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 08m 38.58558s |
| Declination | −21° 26′ 58.4136″ |
| Apparent magnitude (V) | 6.538 (6.57p - 6.62p) |
| Characteristics | |
| Evolutionary stage | Supergiant |
| Spectral type | A2 Iab |
| U−B color index | +0.279 |
| B−V color index | +0.856 |
| Variable type | α Cyg |
| Astrometry | |
| Radial velocity (Rv) | −16 km/s |
| Proper motion (μ) | RA: −1.65 mas/yr Dec.: −1.05 mas/yr |
| Parallax (π) | 2.25±0.55 mas |
| Distance | approx. 1,400 ly (approx. 400 pc) |
| Absolute magnitude (MV) | −6.6 |
| Details | |
| Mass | 7.00 M☉ |
| Luminosity | 39,000 L☉ |
| Surface gravity (log g) | 1.50 cgs |
| Temperature | 9,000 K |
| Rotational velocity (v sin i) | 18 km/s |
| Age | 43.3 Myr |
| Other designations | |
| V4381 Sagittarii, HD 165784, HIP 88876, BD−21°4866, 2MASS J18083858-2126584 | |
| Database references | |
| SIMBAD | data |
V4381 Sagittarii is a variable star in the constellation Sagittarius. A white supergiant of spectral type A2/A3Iab, it is an Alpha Cygni variable that varies between apparent photographic magnitudes 6.57 and 6.62. Its visual apparent magnitude is about 6.54.
V4381 Sagittarii is associated with a small reflection and emission nebula, although it is not actually seen within the nebulosity. The nebula is catalogued as GN 18.05.6. It was first listed as VdB 113 and described as possibly associated with a loose open cluster. That name has since been used for the cluster itself, which is much more distant than the distance of V4381 Sagittarii derived from its Hipparcos parallax. The whole cluster is less than a quarter of a degree across, with dozens of members from 8th magnitude downwards. V4381 Sagittarii is listed as a probable member, while the nearby bright stars HD 165516 and WR 111 are considered unlikely to be members.