HD 110432

HD 110432 is a Be star in the south-east of Crux, behind the center of the southern hemisphere's dark Coalsack Nebula. It has a stellar classification of B1IVe, which means it is a subgiant star of class B that displays emission lines in its spectrum. This is a variable star of the Gamma Cassiopeiae type, indicating it is a shell star with a circumstellar disk of gas about the equator, and has the variable star designation BZ Crucis. It is not known to be a member of a binary system, although it is probably a member of the open cluster NGC 4609. This star is moderately luminous in the X-ray band, with a variable energy emission of 1032–33 erg s−1 in the range 0.2−12 keV. The X-ray emission may be caused by magnetic activity, or possibly by accretion onto a white dwarf companion.[3]

HD 110432
Location of BZ Crucis (circled). The other star shown overlapping/underlying the dark nebula is HD 109000 (HR 4771) which is a red/brown star about half the distance to the nebula, having parallax of 12.8 ± 0.05 thus about 250 light years away[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Crux
Right ascension  12h 42m 50.2656s[1]
Declination −63° 03′ 31.048″[1]
Apparent magnitude (V) 5.24 - 5.45[2]
Characteristics
Spectral type B1IVe[3]
U−B color index −0.82[4]
B−V color index +0.27[4]
Variable type γ Cas[2]
Astrometry
Radial velocity (Rv)+35[5] km/s
Proper motion (μ) RA: −12.512[1] mas/yr
Dec.: −3.984[1] mas/yr
Parallax (π)2.3834 ± 0.1228[1] mas
Distance1,370 ± 70 ly
(420 ± 20 pc)
Absolute magnitude (MV)−2.56[6]
Details
Mass9.6[3] M☉
Radius6.5±1.2[7] R☉
Luminosity1,153[1] L☉
Surface gravity (log g)3.5–3.9[3] cgs
Temperature22,510–25,000[3] K
Rotational velocity (v sin i)300–400[3] km/s
Other designations
BZ Cru, HR 4830, CD-62 671, HD 110432, GCTP, SAO 252002, FK5 3015, HIP 62027.[8]
Database references
SIMBADdata
BZ Crucis is the bright star between the open clusters NGC 4609 and Hogg 15

Distance

The distance of 388 pc published in the 2007 new Hipparcos reduction is over twice the distance of the Coalsack Nebula.[9] The distance from Gaia Data Release 2 is even further at 420 pc.[1]

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: B/gcvs. Bibcode:2009yCat....102025S.
  3. Lopes de Oliveira, R.; et al. (November 2007). "On the X-ray and optical properties of the Be star HD 110432: a very hard-thermal X-ray emitter". Astronomy and Astrophysics. 474 (3): 983–996. arXiv:astro-ph/0701767. Bibcode:2007A&A...474..983L. doi:10.1051/0004-6361:20077295.
  4. Cousins, A. W. J. (1973). "UBV photometry of some southern stars". Monthly Notes of the Astronomical Society of Southern Africa. 32: 11. Bibcode:1973MNSSA..32...11C.
  5. Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E.
  6. 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.
  7. Stee, Ph; Meilland, A.; Bendjoya, Ph.; Millour, F.; Smith, M.; Spang, A.; Duvert, G.; Hofmann, K. -H.; Massi, F. (2013). "Evidence of an asymmetrical Keplerian disk in the Brγ and He I emission lines around the be star HD 110432". Astronomy and Astrophysics. 550: A65. arXiv:1301.2877. Bibcode:2013A&A...550A..65S. doi:10.1051/0004-6361/201220302.
  8. "HR 4830 -- Be Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-12-09.
  9. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
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