CH Crucis

CH Crucis is a solitary[14] variable star in the southern constellation of Crux. It has the Gould designation 39 G. Crucis.[12] The object is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude that fluctuates around 4.91.[3] The star is located approximately 780 light years distant from the Sun based on parallax,[2] and is drifting further away with a radial velocity of about +12.5 km/s.[3] It is a member of the nearby Sco OB2 association.[15]

CH Crucis

A blue band light curve for CH Crucis, plotted from data published by Balona et al. (1992)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Crux
Right ascension 12h 41m 56.56824s[2]
Declination −59° 41′ 08.9564″[2]
Apparent magnitude (V) 4.91[3]
Characteristics
Spectral type B5III[4] or B6IV[5]
U−B color index −0.37[6]
B−V color index −0.044±0.03[3]
Variable type γ Cas?[7]
Astrometry
Radial velocity (Rv)+12.5±2.8[3] km/s
Proper motion (μ) RA: -23.987[2] mas/yr
Dec.: -4.110[2] mas/yr
Parallax (π)4.2068 ± 0.1651 mas[2]
Distance780 ± 30 ly
(238 ± 9 pc)
Absolute magnitude (MV)−2.41[3]
Details
Mass5.30±0.27[8] M☉
Radius11.20±0.22[9] R☉
Luminosity1,073[3] L☉
Surface gravity (log g)2.90±0.03[9] cgs
Temperature10,600±106[9] K
Rotational velocity (v sin i)240[10] km/s
Age120[11] Myr
Other designations
CH Cru, CPD−59° 4393, HD 110335, HIP 61966, HR 4823, SAO 240161, G 39 Crucis[12][13]
Database references
SIMBADdata

This is a conventional shell star, which is understood to be a Be star that is being viewed edge-on.[16] Houk (1975) found a stellar classification of B5III,[4] while Hiltner et al. assigned it to B6IV;[5] suggesting it is a B-type star that is evolving off the main sequence.[8] Samus et al. (2017) have tentatively classified it as a Gamma Cassiopeiae variable that ranges in brightness from magnitude 4.88 down to 5.7.[7]

CH Crucis has 5.3[8] times the mass of the Sun and 11.2[9] times the Sun's radius. It is radiating 1,073[3] times the luminosity of the Sun from its photosphere at an effective temperature of 10,600 K.[9] It is spinning rapidly with estimates of the projected rotational velocity ranging up to 240 or 250 km/s.[16][10] This is giving the star an oblate shape with an equatorial bulge that is an estimated 18% larger than the polar radius.[10]

References
  1. Balona, L. A.; Cuypers, J.; Marang, F. (February 1992). "Intensive photometry of southern Be variables. II. Summer objects". Astronomy & Astrophysics Supplement Series. 92: 533–563. Bibcode:1992A&AS...92..533B. Retrieved 18 December 2021.
  2. 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.
  3. 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.
  4. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1975mcts.book.....H.
  5. Hiltner, W. A.; Garrison, R. F.; Schild, R. E. (July 1969), "MK Spectral Types for Bright Southern OB Stars", Astrophysical Journal, 157: 313–326, Bibcode:1969ApJ...157..313H, doi:10.1086/150069.
  6. "39 Crucis, a blue subgiant star in Crux", Ashland Astronomy Studio, archived from the original on 2013-04-14, retrieved 2012-08-23
  7. Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  8. 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, S2CID 55586789.
  9. 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, S2CID 74872624.
  10. Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.
  11. "HIP 61966", Wolfram Alpha, retrieved 2012-08-23
  12. Gould, Benjamin Apthorp (1879), "Uranometria Argentina catalog of bright southern stars", Resultados del Observatorio Nacional Argentino, 1, Bibcode:1879RNAO....1.....G, retrieved 2012-05-08.
  13. "CH Cru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-08-15.
  14. 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, S2CID 14878976.
  15. Hoogerwerf, Ronnie (March 2000), "OB association members in the ACT and TRC catalogues", Monthly Notices of the Royal Astronomical Society, 313 (1): 43–65, Bibcode:2000MNRAS.313...43H, doi:10.1046/j.1365-8711.2000.03192.x.
  16. Rivinius, Th.; et al. (November 2006), "Bright Be-shell stars", Astronomy and Astrophysics, 459 (1): 137–145, Bibcode:2006A&A...459..137R, doi:10.1051/0004-6361:20053008.
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