HY Velorum

HY Velorum is a binary star[6] system in the southern constellation of Vela. It is a dim star but visible to the naked eye with an apparent visual magnitude of 4.83.[4] The distance to this system, as estimated from its annual parallax shift of 7.1 mas,[1] is 460 light years. HY Vel most likely forms a gravitationally bound pair with the magnitude 5.45 binary system KT Vel (HD 74535);[11] both are members of the IC 2391 open cluster.[12] As of 1998, HY Vel and KT Vel had an angular separation of 76.1″ along a position angle of 311°.[13]

HY Velorum
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 08h 42m 25.38667s[1]
Declination −53° 06′ 50.3324″[1]
Apparent magnitude (V) 4.81 - 4.86[2]
Characteristics
Spectral type B3 IV[3]
B−V color index −0.173±0.007[4]
Variable type SPB[2]
Astrometry
Radial velocity (Rv)+15.6±0.2[4] km/s
Proper motion (μ) RA: −24.83[5] mas/yr
Dec.: +23.21[5] mas/yr
Parallax (π)7.1141 ± 0.2302[1] mas
Distance460 ± 10 ly
(141 ± 5 pc)
Absolute magnitude (MV)−1.25[4]
Orbit[6]
Period (P)8.378±0.001 d
Eccentricity (e)0.24±0.04
Periastron epoch (T)2450741.3 ± 0.2 HJD
Argument of periastron (ω)
(secondary)		93±9°
Semi-amplitude (K1)
(primary)		8.0±0.3 km/s
Details
HY Vel Aa
Mass5.4[7] M☉
Luminosity830+927
−743[7] L☉
Surface gravity (log g)4.07[8] cgs
Temperature16,865+235
−231[7] K
Metallicity [Fe/H]0.03±0.02[8] dex
Rotational velocity (v sin i)45[7] km/s
Age179[9] Myr
Other designations
HY Vel, CPD−52° 1607, HD 74560, HIP 42726, HR 3467, SAO 236205, WDS J08424-5307A[10]
Database references
SIMBADdata

This is a single-lined spectroscopic binary system with an orbital period of 8.4 days and an eccentricity of 0.24. The visible component has an a sin i value of 0.006 AU, where a is the semimajor axis and i is the (unknown) orbital inclination to the line of sight.

The primary is a slowly pulsating B-type star having at least three pulsational modes, with the dominant mode showing a frequency of 0.64472 cycles per day,[6] corresponding to the catalogued period of 1.55106 days.[2] It has a stellar classification of B3 IV, matching a B-type subgiant star.[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. 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.
  3. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. 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, S2CID 119257644.
  5. van Leeuwen, F. (November 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.
  6. De Cat, P.; Aerts, C.; De Ridder, J.; Kolenberg, K.; Meeus, G.; Decin, L. (2000), "A study of bright southern slowly pulsating B stars. I. Determination of the orbital parameters and of the main frequency of the spectroscopic binaries", Astronomy and Astrophysics, 355: 1015–1030, Bibcode:2000A&A...355.1015D.
  7. Szewczuk, W.; Daszyńska-Daszkiewicz, J. (June 2015), "Identification of pulsational modes in rotating slowly pulsating B-type stars", Monthly Notices of the Royal Astronomical Society, 450 (2): 1585–1603, arXiv:1504.04490, Bibcode:2015MNRAS.450.1585S, doi:10.1093/mnras/stv715, S2CID 119194953.
  8. Niemczura, E. (June 2003), "Metallicities of the SPB stars from the IUE ultraviolet spectra", Astronomy and Astrophysics, 404 (2): 689–700, Bibcode:2003A&A...404..689N, doi:10.1051/0004-6361:20030546.
  9. Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035, S2CID 119108982.
  10. "HD 74560". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 16 August 2018.
  11. 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, S2CID 14878976.
  12. Dodd, R. J. (April 2007), "Unified Absolute Spectrophotometry for Star Clusters", in Sterken, C. (ed.), The Future of Photometric, Spectrophotometric and Polarimetric Standardization. Proceedings of a conference held 8-11 May, 2006 in Blankenberge, Belgium, ASP Conference Series, 364, San Francisco: Astronomical Society of the Pacific, p. 237, Bibcode:2007ASPC..364..237D.
  13. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
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