18 Andromedae

18 Andromedae, abbreviated 18 And, is a single[7] star in the northern constellation of Andromeda. 18 Andromedae is the Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 5.350.[2] The annual parallax shift of 7.9 mas[1] can be used to estimate a distance of 413 light years. It is moving further from the Earth with a heliocentric radial velocity of +10 km/s.[5]

18 Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension  23h 39m 08.33195s[1]
Declination +50° 28′ 18.2328″[1]
Apparent magnitude (V) 5.350[2]
Characteristics
Evolutionary stage main sequence[3]
Spectral type B9 Ve[4]
B−V color index −0.110[2]
Astrometry
Radial velocity (Rv)+9.9±2.2[5] km/s
Proper motion (μ) RA: −17.222[1] mas/yr
Dec.: −1.739[1] mas/yr
Parallax (π)7.8893 ± 0.1288[1] mas
Distance413 ± 7 ly
(127 ± 2 pc)
Details
Mass3.09±0.06[3] M☉
Luminosity146.6+14.1
−12.9[3] L☉
Surface gravity (log g)3.632±0.014[2] cgs
Temperature10,351±50[2] K
Rotational velocity (v sin i)183[3] km/s
Other designations
18 And, BD+49° 4180, FK5 3897, HD 222304, HIP 116709, HR 8967, SAO 35642[6]
Database references
SIMBADdata

This is a B-type main-sequence star with a stellar classification of B9 Ve,[4] where the 'e' notation indicates this is a Be star. The stellar spectrum of 18 And displays an emission line in the hydrogen Brackett series due to a dense gaseous circumstellar envelope.[4] The star is spinning rapidly with a projected rotational velocity of 183[3] km/s and has about three[3] times the mass of the Sun. It is radiating 147[3] times the Sun's luminosity from its photosphere at an effective temperature of 10,351 K.[2]

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.
  2. Soubiran, Caroline; et al. (2016), "The PASTEL catalogue: 2016 version", Astronomy & Astrophysics, 591: A118, arXiv:1605.07384, Bibcode:2016A&A...591A.118S, doi:10.1051/0004-6361/201628497.
  3. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691.
  4. Granada, A.; et al. (May 2010), "Simultaneous K- and L-band spectroscopy of Be stars: circumstellar envelope properties from hydrogen emission lines", The Astronomical Journal, 139 (5): 1983–1992, Bibcode:2010AJ....139.1983G, doi:10.1088/0004-6256/139/5/1983.
  5. Gontcharov, G. A. (November 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.
  6. "18 And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 20, 2018.
  7. Eggleton, P. P.; Tokovinin, A. A. (September 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.
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