HD 105382

HD 105382 (also known as V863 Centauri) is a star in the constellation Centaurus. Its apparent magnitude is 4.47. From parallax measurements, it is located 130 parsecs (440 light years) from the sun.

HD 105382
Observation data
Epoch J2000      Equinox J2000
Constellation Centaurus
Right ascension  12h 08m 05.22401s[1]
Declination −50° 39′ 40.5728″[1]
Apparent magnitude (V) 4.47[2]
Characteristics
Spectral type B6III[3]
U−B color index −0.67[2]
B−V color index −0.15[2]
Variable type rotating variable[4]
Astrometry
Radial velocity (Rv)16.5[2] km/s
Proper motion (μ) RA: −35.16[1] mas/yr
Dec.: −6.47[1] mas/yr
Parallax (π)7.44 ± 0.61[1] mas
Distance440 ± 40 ly
(130 ± 10 pc)
Absolute magnitude (MV)−1.2±0.3[3]
Absolute bolometric
magnitude (Mbol)		−2.9 ± 0.4[3]
Details
Mass5.7 ± 0.4[4] M☉
Radius3.0 ± 0.6[4] R☉
Luminosity1000+590
−370[3] L☉
Surface gravity (log g)4.18 ± 0.15[4] cgs
Temperature17400 ± 400[4] K
Rotation1.295 ± 0.001[4] days
Rotational velocity (v sin i)90[3] km/s
Other designations
CD−49° 6813, HD 105382, HIP 59173, HR 4618, SAO 239687[2]
Database references
SIMBADdata

HD 105382 is a variable star whose apparent magnitude varies with an amplitude of 0.012 over a period of 1.295 days. It has been previously classified as a Be star, which would explain the variability as stellar pulsations, but this classification was probably due to accidental observation of the nearby Be star δ Centauri.[5] A 2004 study showed that the 1.295 day period is actually the rotation period of the star, and that the variability is caused by non-homogeneous distribution of elements in the stellar surface. In particular, HD 105382 is a helium-weak chemically peculiar star with a helium abundance varying between 0.5% and 15% of the solar abundance, and a silicon abundance varying between 0.00044% and 0.0069% the solar value. Regions with more helium appear to coincide with the regions with less silicon, and vice versa.[4] This peculiar abundance pattern is probably related to HD 105382's magnetic field,[4] which has a polar strength of 2.3 kG.[3]

From astrometric measurements by the Hipparcos spacecraft, HD 105382 is identified as a probable astrometric binary.[6] It is only 267" away from δ Centauri, and both stars appear to be at the same distance from Earth and have the same motion through space, so they may be related. In total, this may be a five star system.[7] It is a member of the Lower Centaurus-Crux (LCC) subgroup of the Scorpius–Centaurus Association.[8]

References
  1. van Leeuwen, F. (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.
  2. "HD 105382". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 25 October 2017.
  3. Petit, V.; et al. (February 2013), "A magnetic confinement versus rotation classification of massive-star magnetospheres", Monthly Notices of the Royal Astronomical Society, 429 (1): 398–422, arXiv:1211.0282, Bibcode:2013MNRAS.429..398P, doi:10.1093/mnras/sts344.
  4. Briquet, M.; et al. (January 2004). "He and Si surface inhomogeneities of four Bp variable stars". Astronomy and Astrophysics. 413: 273–283. Bibcode:2004A&A...413..273B. doi:10.1051/0004-6361:20031450.
  5. Briquet, M.; Aerts, C.; De Cat, P. (January 2001). "Optical variability of the B-type star HD 105382: Pulsation or rotation?". Astronomy and Astrophysics. 366: 121–128. Bibcode:2001A&A...366..121B. doi:10.1051/0004-6361:20000193.
  6. Makarov, V. V.; Kaplan, G. H. (May 2005), "Statistical Constraints for Astrometric Binaries with Nonlinear Motion", The Astronomical Journal, 129 (5): 2420–2427, Bibcode:2005AJ....129.2420M, doi:10.1086/429590.
  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.
  8. de Geus, E. J.; de Zeeuw, P. T.; Lub, J. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1–2): 44–61, Bibcode:1989A&A...216...44D
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