V4381 Sagittarii

{{short description|Star in the constellation Sagittarius}}

{{Starbox begin

| name = V4381 Sagittarii

}}

{{Starbox image

| image = 250px

| caption = A light curve for V4381 Sagittarii, plotted from Hipparcos data

}}

{{Starbox observe

| epoch = J2000

| constell = Sagittarius

| ra = {{RA|18|08|38.58558}}{{cite journal|bibcode=2007A&A...474..653V|title=Validation of the new Hipparcos reduction|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|last1=Van Leeuwen|first1=F.|year=2007|doi=10.1051/0004-6361:20078357|arxiv = 0708.1752 |s2cid=18759600}}

| dec = {{DEC|-21|26|58.4136}}

| appmag_v = 6.538{{cite journal|bibcode=2012A&A...543A..80F|arxiv=1207.0308|title=Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters|journal=Astronomy & Astrophysics|volume=543|pages=A80|last1=Firnstein|first1=M.|last2=Przybilla|first2=N.|year=2012|doi=10.1051/0004-6361/201219034|s2cid=54725386}} {{nowrap|(6.57p - 6.62p)}}

}}

{{Starbox character

| type=Supergiant

| class=A2 Iab

| b-v=+0.856

| u-b=+0.279

| variable=α Cyg{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}

}}

{{Starbox astrometry

| prop_mo_ra=−1.65

| prop_mo_dec=−1.05

| parallax= 2.25

| p_error=0.55

| parallax_footnote=

| dist_ly =

| dist_pc =

| absmag_v=−6.6{{cite journal|bibcode=1978ApJS...38..309H|title=Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way|journal=Astrophysical Journal|volume=38|pages=309|last1=Humphreys|first1=R. M.|year=1978|doi=10.1086/190559}}

| absmag_bol=

| radial_v=−16{{cite journal|bibcode=2006AstL...32..759G|title=Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system|journal=Astronomy Letters|volume=32|issue=11|pages=759–771|last1=Gontcharov|first1=G. A.|year=2006|doi=10.1134/S1063773706110065|arxiv = 1606.08053 |s2cid=119231169}}

}}

{{Starbox detail

| source =

| mass = 7.00

| radius =

| gravity = 1.50

| luminosity = 39,000

| luminosity_visual =

| temperature = 9,000

| rotational_velocity = 18

| age_myr = 43.3{{cite journal|bibcode= 2011MNRAS.410..190T|title= A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun|journal= Monthly Notices of the Royal Astronomical Society|volume= 410|pages= 190–200|last1= Tetzlaff|first1= N.|last2= Neuhäuser|first2= R.|last3= Hohle|first3= M. M.|year= 2011|issue= 1|doi= 10.1111/j.1365-2966.2010.17434.x|doi-access= free|arxiv = 1007.4883 |s2cid= 118629873}}

}}

{{Starbox catalog

| names = V4381 Sagittarii, HD 165784, HIP 88876, BD−21°4866, 2MASS J18083858-2126584

}}

{{Starbox reference

| Simbad = V4381+Sgr

}}

{{Starbox end}}

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.{{cite journal|bibcode=2003A&A...399..141M|title=Merged catalogue of reflection nebulae|journal=Astronomy and Astrophysics|volume=399|pages=141–145|last1=Magakian|first1=T. Yu.|year=2003|doi=10.1051/0004-6361:20021743|doi-access=free}} It was first listed as VdB 113 and described as possibly associated with a loose open cluster.{{cite journal|bibcode=1966AJ.....71..990V|title=A study of reflection nebulae|journal=Astronomical Journal|volume=71|pages=990|last1=Van Den Bergh|first1=S.|year=1966|doi=10.1086/109995}} 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.{{cite journal|bibcode=2008A&A...477..165P|title=Tidal radii and masses of open clusters|journal=Astronomy and Astrophysics|volume=477|pages=165–172|last1=Piskunov|first1=A. E.|last2=Schilbach|first2=E.|last3=Kharchenko|first3=N. V.|last4=Röser|first4=S.|last5=Scholz|first5=R.-D.|year=2008|issue=1|doi=10.1051/0004-6361:20078525|doi-access=free}} 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.{{cite journal|bibcode=2013A&A...558A..53K|title=Global survey of star clusters in the Milky Way. II. The catalogue of basic parameters|journal=Astronomy & Astrophysics|volume=558|pages=A53|last1=Kharchenko|first1=N. V.|last2=Piskunov|first2=A. E.|last3=Schilbach|first3=E.|last4=Röser|first4=S.|last5=Scholz|first5=R.-D.|year=2013|doi=10.1051/0004-6361/201322302|arxiv = 1308.5822 |s2cid=118548517}}