V4381 Sagittarii is a

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

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 A nebula ('cloud' or 'fog' in Latin; pl. nebulae, nebulæ or nebulas) is a distinct luminescent part of interstellar medium, which can consist of ionized, neutral or molecular hydrogen and also cosmic dust. Nebulae are often star-forming regio ...

, 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 An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

. 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 WR 111 (HD 165763) is a Wolf-Rayet (WR) star in the constellation Sagittarius. It is magnitude 7.8 and lies about 5,150 light-years away. It is one of the brightest and most closely studied WR stars. History In 1880, Edward Pickerin ...

are considered unlikely to be members.

Distance estimations

The distance to V4381 remains poorly determined as of 2021. The 2018 research based on radio interferometry has measured 2.2 milliarcseconds parallax, while Gaia Early Data Release 3, based on optical astrometry, have resulted in measured parallax 0.6273.

References

External links

Image of VdB 113
V4381 Sgr is the upper of the two bright white stars.
WEBDA page for vdBergh 113
V4381 Sgr is the brightest star

{{DEFAULTSORT:V4381 Sagittarii Sagittarius (constellation) Alpha Cygni variables A-type supergiants Sagittarii, V4381 165784 088876 BD-21 4866 J18083858-2126584 Sagittarii, 34