20 Vulpeculae

20 Vulpeculae is single[5] star located around 1,170[1] light years away in the northern constellation of Vulpecula.[8] It is visible to the naked eye as a dim, blue-white hued star with an apparent visual magnitude of 5.91.[2] The object is moving closer to the Earth with a heliocentric radial velocity of −22 km/s.[2]

20 Vulpeculae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Vulpecula
Right ascension  20h 12m 00.70176s[1]
Declination +26° 28′ 43.6989″[1]
Apparent magnitude (V) 5.91[2]
Characteristics
Evolutionary stage main sequence[3]
Spectral type B7 Ve[4][5]
B−V color index −0.107±0.003[2]
Astrometry
Radial velocity (Rv)−22.0±4.3[2] km/s
Proper motion (μ) RA: +4.096[1] mas/yr
Dec.: −9.524[1] mas/yr
Parallax (π)2.7904 ± 0.0726[1] mas
Distance1,170 ± 30 ly
(358 ± 9 pc)
Absolute magnitude (MV)−2.13[2]
Details
Mass4.02±0.14[3] M☉
Radius3.0[6] R☉
Luminosity460+88
−74[3] L☉
Surface gravity (log g)2.90[7] cgs
Temperature12,050+168
−165[3] K
Rotational velocity (v sin i)236[3] km/s
Other designations
20 Vul, BD+26°3828, HD 192044, HIP 99531, HR 7719, SAO 88339[8]
Database references
SIMBADdata

This is a Be star with a stellar classification of B7 Ve.[4] It is spinning rapidly with a projected rotational velocity of 236 km/s (compared to a critical velocity of 332 km/s)[3] and has an estimated polar inclination of 71.1°.[9] The star has four times the mass of the Sun and is radiating around 460 times the Sun's luminosity from its photosphere at an effective temperature of 12,050 km/s.[3]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  3. Zorec, J.; et al. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy and Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691.
  4. Antoniou, A.; et al. (2011), "Studying the UV mg II Resonance Lines in 20 Be Stars", Baltic Astronomy, 20: 572–575, Bibcode:2011BaltA..20..572A, doi:10.1515/astro-2017-0338.
  5. Eggleton, P. P.; Tokovinin, A. A. (2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  6. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  7. Chauville, J.; et al. (November 2001), "High and intermediate-resolution spectroscopy of Be stars 4481 lines" (PDF), Astronomy and Astrophysics, 378: 861–882, Bibcode:2001A&A...378..861C, doi:10.1051/0004-6361:20011202.
  8. "20 Vulpeculae". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-16.
  9. Frémat, Y.; Zorec, J.; Hubert, A.-M.; Floquet, M. (2005), "Effects of gravitational darkening on the determination of fundamental parameters in fast-rotating B-type stars", Astronomy and Astrophysics, 440: 305, arXiv:astro-ph/0503381, Bibcode:2005A&A...440..305F, doi:10.1051/0004-6361:20042229.
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