V4381 Sagittarii

A light curve for V4381 Sagittarii, plotted from Hipparcos data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 08m 38.58558s[2]
Declination −21° 26′ 58.4136″[2]
Apparent magnitude (V) 6.538[3] (6.57p - 6.62p[4])
Characteristics
Evolutionary stage Supergiant[3]
Spectral type A2 Iab[3]
U−B color index +0.279[3]
B−V color index +0.856[3]
Variable type α Cyg[4]
Astrometry
Radial velocity (Rv)−16[5] km/s
Proper motion (μ) RA: −1.65[2] mas/yr
Dec.: −1.05[2] mas/yr
Parallax (π)2.25 ± 0.55 mas[2]
Distanceapprox. 1,400 ly
(approx. 400 pc)
Absolute magnitude (MV)−6.6[6]
Details
Mass7.00[7] M☉
Luminosity39,000[3] L☉
Surface gravity (log g)1.50[3] cgs
Temperature9,000[3] K
Rotational velocity (v sin i)18[3] km/s
Age43.3[7] Myr
Other designations
V4381 Sagittarii, HD 165784, HIP 88876, BD−21°4866, 2MASS J18083858-2126584
Database references
SIMBADdata

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.[8] It was first listed as VdB 113 and described as possibly associated with a loose open cluster.[9] 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.[10] 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.[11]

Distance estimations

The distance to V4381 remains poorly determined as of 2021. The 2018 research based on radio interferometry has measured 2.2±0.6 milliarcseconds parallax,[12] while Gaia Early Data Release 3, based on optical astrometry, have resulted in measured parallax 0.6273±0.0372.[13]

References

  1. ↑ "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
  2. 1 2 3 4 5 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  3. 1 2 3 4 5 6 7 8 9 Firnstein, M.; Przybilla, N. (2012). "Quantitative spectroscopy of Galactic BA-type supergiants. I. Atmospheric parameters". Astronomy & Astrophysics. 543: A80. arXiv:1207.0308. Bibcode:2012A&A...543A..80F. doi:10.1051/0004-6361/201219034. S2CID 54725386.
  4. 1 2 Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  5. ↑ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  6. ↑ Humphreys, R. M. (1978). "Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way". Astrophysical Journal. 38: 309. Bibcode:1978ApJS...38..309H. doi:10.1086/190559.
  7. 1 2 Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873.
  8. ↑ Magakian, T. Yu. (2003). "Merged catalogue of reflection nebulae". Astronomy and Astrophysics. 399: 141–145. Bibcode:2003A&A...399..141M. doi:10.1051/0004-6361:20021743.
  9. ↑ Van Den Bergh, S. (1966). "A study of reflection nebulae". Astronomical Journal. 71: 990. Bibcode:1966AJ.....71..990V. doi:10.1086/109995.
  10. ↑ Piskunov, A. E.; Schilbach, E.; Kharchenko, N. V.; Röser, S.; Scholz, R.-D. (2008). "Tidal radii and masses of open clusters". Astronomy and Astrophysics. 477 (1): 165–172. Bibcode:2008A&A...477..165P. doi:10.1051/0004-6361:20078525.
  11. ↑ Kharchenko, N. V.; Piskunov, A. E.; Schilbach, E.; Röser, S.; Scholz, R.-D. (2013). "Global survey of star clusters in the Milky Way. II. The catalogue of basic parameters". Astronomy & Astrophysics. 558: A53. arXiv:1308.5822. Bibcode:2013A&A...558A..53K. doi:10.1051/0004-6361/201322302. S2CID 118548517.
  12. ↑ Xu, Shuangjing; Zhang, Bo; Reid, Mark J.; Menten, Karl M.; Zheng, Xingwu; Wang, Guangli (2018), "The Parallax of the Red Hypergiant VX SGR with Accurate Tropospheric Delay Calibration", The Astrophysical Journal, 859 (1): 14, arXiv:1804.00894, Bibcode:2018ApJ...859...14X, doi:10.3847/1538-4357/aabba6, S2CID 55572194
  13. ↑ Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
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