HD 83953

HD 83953 (I Hydrae) is a single,[9] blue-white hued star in the equatorial constellation of Hydra. It is visible to the naked eye, having an apparent visual magnitude of 4.76.[2] Based upon an annual parallax shift of 6.6 mas,[1] the distance to this star is estimated as 500 light years. It is moving further from Earth with a heliocentric radial velocity of +16 km/s.[4]

This article is about I (upper case "i") Hydrae. It is not to be confused with l (lower case "L") Hydrae or ι (iota) Hydrae.
HD 83953
Observation data
Epoch J2000      Equinox J2000
Constellation Hydra
Right ascension 09h 41m 17.00785s[1]
Declination −23° 35′ 29.4325″[1]
Apparent magnitude (V) 4.76[2]
Characteristics
Spectral type B5 V[3]
B−V color index −0.117±0.015[2]
Astrometry
Radial velocity (Rv)+16.05±1.5[4] km/s
Proper motion (μ) RA: −29.969[1] mas/yr
Dec.: +1.914[1] mas/yr
Parallax (π)6.5733 ± 0.2851[1] mas
Distance500 ± 20 ly
(152 ± 7 pc)
Absolute magnitude (MV)−1.19[2]
Details
Mass4.57±0.08[5] M☉
Radius4.00±0.08[6] R☉
Luminosity708+60
−55[5] L☉
Surface gravity (log g)2.54±0.03[6] cgs
Temperature15,000±150[6] K
Rotational velocity (v sin i)315[5][7] km/s
Other designations
I Hya, BD−22° 2684, HD 83953, HIP 47522, HR 3858, SAO 177840[8]
Database references
SIMBADdata

This is a B-type main-sequence star with a stellar classification of B5 V.[3] It has been known to be a Be star since 1926, when an Hβ emission line was discovered in the stellar spectrum by Mount Wilson Observatory.[10] This energy is coming from a circumstellar envelope of heated gas that has been expelled from the central star and formed a thin orbiting disk.[11] HD 83953 is spinning rapidly with a projected rotational velocity of 315 km/s, giving the star an oblate shape with an equatorial bulge that is 18% larger than the polar radius.[7]

HD 83953 has 4.6[5] times the mass of the Sun and 4.0[6] times the Sun's radius. It is radiating 708[5] times the Sun's luminosity from its photosphere at an effective temperature of 15,000 K.[6]

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. 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. Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  4. Becker, Juliette C.; et al. (April 2015), "Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra", The Astrophysical Journal Supplement Series, 217 (2): 13, arXiv:1503.03874, Bibcode:2015ApJS..217...29B, doi:10.1088/0067-0049/217/2/29, 29.
  5. 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.
  6. Arcos, C.; et al. (March 2018), "Stellar parameters and H α line profile variability of Be stars in the BeSOS survey", Monthly Notices of the Royal Astronomical Society, 474 (4): 5287–5299, arXiv:1711.08675, Bibcode:2018MNRAS.474.5287A, doi:10.1093/mnras/stx3075.
  7. Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20: 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2.
  8. "HD 83953". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-25.
  9. 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  10. Merrill, Paul W.; Burwell, Cora G. (September 1933), "Catalogue and Bibliography of Stars of Classes B and A whose Spectra have Bright Hydrogen Lines", Astrophysical Journal, 78: 87, Bibcode:1933ApJ....78...87M, doi:10.1086/143490.
  11. Arcos, C.; et al. (June 2017), "Evidence for Different Disk Mass Distributions Between Early and Late-Type Be Stars in the BeSOS Survey", The Astrophysical Journal, 842 (1): 18, arXiv:1704.08133, Bibcode:2017ApJ...842...48A, doi:10.3847/1538-4357/aa6f5f, 48.
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