# HD 125823

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Star in the constellation Centaurus

This article is about a Centauri; not to be confused with [α Centauri](/source/Alpha_Centauri), [A Centauri](/source/HD_100673), or [Centaurus A](/source/Centaurus_A).

HD 125823 Location of a Centauri (circled in red) Observation data Epoch J2000.0 Equinox J2000.0 Constellation Centaurus[1] Right ascension 14h 23m 02.24s[2] Declination −39° 30′ 42.5″[2] Apparent magnitude (V) +4.41[1] Characteristics Evolutionary stage main sequence[3][4] Spectral type B2V[5] U−B color index −0.75[6] B−V color index −0.19[6] Variable type SX Ari[7] Astrometry Radial velocity (Rv) +7.13±0.16[8] km/s Proper motion (μ) RA: −24.15±0.13[2] mas/yr Dec.: −21.90±0.13[2] mas/yr Parallax (π) 7.13±0.16 mas[2] Distance 460 ± 10 ly (140 ± 3 pc) Absolute magnitude (MV) −1.27[9] Details Mass 5.4501±0.0067[4] M☉ Radius 3.0071±0.0054[4] R☉ Luminosity 1,019±9[4] L☉ Surface gravity (log g) 4.20±0.12[9] cgs Temperature 18,863+57 −56[4] K Rotation 8.817744 days[9][10] Rotational velocity (v sin i) 16.0[11] km/s Age 23.61±0.13[4] Myr Other designations Bidelman's Helium Variable Star[12], a Centauri, V761 Centauri, CD−38 9329, HD 125823, HIP 70300, HR 5378, SAO 205497[13] Database references SIMBAD data

**HD 125823**, also known as **V761 Centauri** or **a Centauri**, is a [variable star](/source/Variable_star) in the [constellation](/source/Constellation) [Centaurus](/source/Centaurus). It is a blue-white star that is visible to the [naked eye](/source/Naked_eye) with a mean [apparent visual magnitude](/source/Apparent_visual_magnitude) of +4.41. The distance to this star is approximately 460 [light years](/source/Light_year) based on [parallax](/source/Stellar_parallax) measurements.[2] It is a member of the Upper Centaurus–Lupus subgroup of the [Scorpius–Centaurus association](/source/Scorpius%E2%80%93Centaurus_association).[14]

A [light curve](/source/Light_curve) V761 Centauri, plotted from *[Hipparcos](/source/Hipparcos)* data[15]

In 1965, [W. P. Bidelman](/source/William_P._Bidelman) discovered that the intensities of the star's neutral helium lines had varied on photographic plates taken over the period 1908 to 1911. This variation was confirmed by [A. D. Thackeray](/source/A._David_Thackeray) in 1966.[12] The star ranges from a [helium-strong](/source/Helium-strong) B2 class to a [helium-weak](/source/Helium-weak) B8 with a period of 8.82 days.[16] Radial velocity measurements during the 1970s showed differing velocity variations for helium and other elements.[17] The magnetic field strength peaks at a negative maximum in phase with the maximum helium line strength.[16] Weak emission has been detected in the singly-ionized lines of silicon, magnesium, and iron, but not in the neutral lines of hydrogen and helium.[16]

This is a magnetic peculiar [Bp star](/source/Bp_star) that shows periodic variation in the strength of its neutral helium lines. It is classified as an [SX Arietis type](/source/SX_Arietis_variable) [variable star](/source/Variable_star) and its brightness varies from magnitude +4.38 to +4.43 with a period of 8.82 days.[7] The star displays very different helium abundances between the two hemispheres, and, unusually, helium-3 has been detected in the weaker southern hemisphere. Latitudinal abundance concentrations have been found for iron, nitrogen, and oxygen.[10] The variation in helium concentration effects the density [scale height](/source/Scale_height) of the atmosphere, causing helium rich regions to have a lower luminosity in the visual band but emitting stronger levels of far ultraviolet.[18]

## References

1. ^ [***a***](#cite_ref-Anderson_Francis_2012_1-0) [***b***](#cite_ref-Anderson_Francis_2012_1-1) Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". *Astronomy Letters*. **38** (5): 331. [arXiv](/source/ArXiv_(identifier)):[1108.4971](https://arxiv.org/abs/1108.4971). [Bibcode](/source/Bibcode_(identifier)):[2012AstL...38..331A](https://ui.adsabs.harvard.edu/abs/2012AstL...38..331A). [doi](/source/Doi_(identifier)):[10.1134/S1063773712050015](https://doi.org/10.1134%2FS1063773712050015). [S2CID](/source/S2CID_(identifier)) [119257644](https://api.semanticscholar.org/CorpusID:119257644).

1. ^ [***a***](#cite_ref-van_Leeuwen2007_2-0) [***b***](#cite_ref-van_Leeuwen2007_2-1) [***c***](#cite_ref-van_Leeuwen2007_2-2) [***d***](#cite_ref-van_Leeuwen2007_2-3) [***e***](#cite_ref-van_Leeuwen2007_2-4) [***f***](#cite_ref-van_Leeuwen2007_2-5) van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". *Astronomy and Astrophysics*. **474** (2): 653–664. [arXiv](/source/ArXiv_(identifier)):[0708.1752](https://arxiv.org/abs/0708.1752). [Bibcode](/source/Bibcode_(identifier)):[2007A&A...474..653V](https://ui.adsabs.harvard.edu/abs/2007A&A...474..653V). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078357](https://doi.org/10.1051%2F0004-6361%3A20078357). [S2CID](/source/S2CID_(identifier)) [18759600](https://api.semanticscholar.org/CorpusID:18759600). [Vizier catalog entry](http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=70061)

1. **[^](#cite_ref-dr3_3-0)** Vallenari, A.; et al. (Gaia collaboration) (2023). ["*Gaia* Data Release 3. Summary of the content and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202243940). *Astronomy and Astrophysics*. **674**: A1. [arXiv](/source/ArXiv_(identifier)):[2208.00211](https://arxiv.org/abs/2208.00211). [Bibcode](/source/Bibcode_(identifier)):[2023A&A...674A...1G](https://ui.adsabs.harvard.edu/abs/2023A&A...674A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202243940](https://doi.org/10.1051%2F0004-6361%2F202243940). [S2CID](/source/S2CID_(identifier)) [244398875](https://api.semanticscholar.org/CorpusID:244398875). [Gaia DR3 record for this source](https://vizier.cds.unistra.fr/viz-bin/VizieR-4?-source=+I%2F355&-from=nav&-nav=cat%3AI%2F355%26tab%3A%7BI%2F355%2Fgaiadr3%7D%26key%3Asource%3D1355%2Fgaiadr3%26HTTPPRM%3A%26-out.add%3D.%26Source%3D%3D%3D6116497702589633152%26-go+%25%23Sesame%23%25%26) at [VizieR](/source/VizieR).

1. ^ [***a***](#cite_ref-Walczak2024_4-0) [***b***](#cite_ref-Walczak2024_4-1) [***c***](#cite_ref-Walczak2024_4-2) [***d***](#cite_ref-Walczak2024_4-3) [***e***](#cite_ref-Walczak2024_4-4) [***f***](#cite_ref-Walczak2024_4-5) Walczak, Przemysław; Kopacz, Agnieszka (2024-03-23). ["Asteroseismic modelling of the chemically peculiar B-type pulsator with an asymptotic period spacing – a Cen"](https://doi.org/10.1093%2Fmnras%2Fstae672). *Monthly Notices of the Royal Astronomical Society*. **529** (4): 4176–4191. [doi](/source/Doi_(identifier)):[10.1093/mnras/stae672](https://doi.org/10.1093%2Fmnras%2Fstae672). [ISSN](/source/ISSN_(identifier)) [0035-8711](https://search.worldcat.org/issn/0035-8711).

1. **[^](#cite_ref-houk1979_5-0)** Houk, Nancy (1979). *Michigan catalogue of two-dimensional spectral types for the HD stars*. Vol. 3. Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan. [Bibcode](/source/Bibcode_(identifier)):[1982mcts.book.....H](https://ui.adsabs.harvard.edu/abs/1982mcts.book.....H).

1. ^ [***a***](#cite_ref-cousins1971_6-0) [***b***](#cite_ref-cousins1971_6-1) Cousins, A. W. J. (1971). "Photometric standard stars". *Royal Observatory Annals*. **7**. [Bibcode](/source/Bibcode_(identifier)):[1971ROAn....7.....C](https://ui.adsabs.harvard.edu/abs/1971ROAn....7.....C).

1. ^ [***a***](#cite_ref-Samus_et_al_2017_7-0) [***b***](#cite_ref-Samus_et_al_2017_7-1) Samus, N. N.; et al. (2017). ["General Catalogue of Variable Stars"](http://www.sai.msu.su/gcvs/cgi-bin/search.cgi?search=V761+Cen). *Astronomy Reports*. GCVS 5.1. **61** (1): 80–88. [Bibcode](/source/Bibcode_(identifier)):[2017ARep...61...80S](https://ui.adsabs.harvard.edu/abs/2017ARep...61...80S). [doi](/source/Doi_(identifier)):[10.1134/S1063772917010085](https://doi.org/10.1134%2FS1063772917010085). [S2CID](/source/S2CID_(identifier)) [125853869](https://api.semanticscholar.org/CorpusID:125853869). Retrieved 2021-10-10.

1. **[^](#cite_ref-Soubiran2018_8-0)** Soubiran, C.; et al. (2018). "Gaia Data Release 2. The catalogue of radial velocity standard stars". *Astronomy and Astrophysics*. **616**: A7. [arXiv](/source/ArXiv_(identifier)):[1804.09370](https://arxiv.org/abs/1804.09370). [Bibcode](/source/Bibcode_(identifier)):[2018A&A...616A...7S](https://ui.adsabs.harvard.edu/abs/2018A&A...616A...7S). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201832795](https://doi.org/10.1051%2F0004-6361%2F201832795). [S2CID](/source/S2CID_(identifier)) [52952408](https://api.semanticscholar.org/CorpusID:52952408).

1. ^ [***a***](#cite_ref-aaa334_181_9-0) [***b***](#cite_ref-aaa334_181_9-1) [***c***](#cite_ref-aaa334_181_9-2) North, P. (June 1998). "Do SI stars undergo any rotational braking?". *Astronomy and Astrophysics*. **334**: 181–187. [arXiv](/source/ArXiv_(identifier)):[astro-ph/9802286](https://arxiv.org/abs/astro-ph/9802286). [Bibcode](/source/Bibcode_(identifier)):[1998A&A...334..181N](https://ui.adsabs.harvard.edu/abs/1998A&A...334..181N).

1. ^ [***a***](#cite_ref-Bohlender_et_al_2010_10-0) [***b***](#cite_ref-Bohlender_et_al_2010_10-1) Bohlender, D. A.; et al. (September 2010). "Doppler imaging of the helium-variable star a Centauri". *Astronomy and Astrophysics*. **520**: 9. [arXiv](/source/ArXiv_(identifier)):[1007.0977](https://arxiv.org/abs/1007.0977). [Bibcode](/source/Bibcode_(identifier)):[2010A&A...520A..44B](https://ui.adsabs.harvard.edu/abs/2010A&A...520A..44B). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201014157](https://doi.org/10.1051%2F0004-6361%2F201014157). [S2CID](/source/S2CID_(identifier)) [118374769](https://api.semanticscholar.org/CorpusID:118374769). A44.

1. **[^](#cite_ref-makarenko2021_11-0)** Makarenko, Ekaterina I.; Igoshev, Andrei P.; Kholtygin, A. F. (2021). ["Testing the fossil field hypothesis: Could strongly magnetized OB stars produce all known magnetars?"](https://doi.org/10.1093%2Fmnras%2Fstab1175). *Monthly Notices of the Royal Astronomical Society*. **504** (4): 5813. [arXiv](/source/ArXiv_(identifier)):[2104.10579](https://arxiv.org/abs/2104.10579). [Bibcode](/source/Bibcode_(identifier)):[2021MNRAS.504.5813M](https://ui.adsabs.harvard.edu/abs/2021MNRAS.504.5813M). [doi](/source/Doi_(identifier)):[10.1093/mnras/stab1175](https://doi.org/10.1093%2Fmnras%2Fstab1175).

1. ^ [***a***](#cite_ref-Jaschek_et_al_1968_12-0) [***b***](#cite_ref-Jaschek_et_al_1968_12-1) Jaschek, C.; et al. (August 1968). ["On the Spectrum of Bidelman's Helium Variable Star HD 125823"](https://doi.org/10.1086%2F180227). *Astrophysical Journal*. **153**: L87. [Bibcode](/source/Bibcode_(identifier)):[1968ApJ...153L..87J](https://ui.adsabs.harvard.edu/abs/1968ApJ...153L..87J). [doi](/source/Doi_(identifier)):[10.1086/180227](https://doi.org/10.1086%2F180227).

1. **[^](#cite_ref-SIMBAD_13-0)** ["HD 125823"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+125823). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2021-10-08.

1. **[^](#cite_ref-Bobylev_Bajkova_2007_14-0)** Bobylev, V. V.; Bajkova, A. T. (September 2007). "Kinematics of the Scorpius–Centaurus OB association". *Astronomy Letters*. **33** (9): 571–583. [arXiv](/source/ArXiv_(identifier)):[0708.0943](https://arxiv.org/abs/0708.0943). [Bibcode](/source/Bibcode_(identifier)):[2007AstL...33..571B](https://ui.adsabs.harvard.edu/abs/2007AstL...33..571B). [doi](/source/Doi_(identifier)):[10.1134/S1063773707090010](https://doi.org/10.1134%2FS1063773707090010). [S2CID](/source/S2CID_(identifier)) [15785349](https://api.semanticscholar.org/CorpusID:15785349).

1. **[^](#cite_ref-HipDataAccess_15-0)** ["Hipparcos Tools Interactive Data Access"](https://www.cosmos.esa.int/web/hipparcos/interactive-data-access). *Hipparcos*. ESA. Retrieved 8 December 2021.

1. ^ [***a***](#cite_ref-Hubrig_González_2007_16-0) [***b***](#cite_ref-Hubrig_González_2007_16-1) [***c***](#cite_ref-Hubrig_González_2007_16-2) Hubrig, S.; González, J. F. (May 2007). "Detection of variable Si II, Mn II, and Fe II emission lines in the magnetic Bp star a Centauri". *Astronomy and Astrophysics*. **466** (3): 1083–1087. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0703229](https://arxiv.org/abs/astro-ph/0703229). [Bibcode](/source/Bibcode_(identifier)):[2007A&A...466.1083H](https://ui.adsabs.harvard.edu/abs/2007A&A...466.1083H). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20066738](https://doi.org/10.1051%2F0004-6361%3A20066738). [S2CID](/source/S2CID_(identifier)) [15414222](https://api.semanticscholar.org/CorpusID:15414222).

1. **[^](#cite_ref-Underhill_et_al_1973_17-0)** Underhill, A. B.; et al. (May 1973). "The radial velocity variations of HD 125823 a Centauri". *Astronomy and Astrophysics*. **25**: 141. [Bibcode](/source/Bibcode_(identifier)):[1973A&A....25..141U](https://ui.adsabs.harvard.edu/abs/1973A&A....25..141U).

1. **[^](#cite_ref-Krtička_et_al_2020_18-0)** Krtička, J.; et al. (April 2020). ["Distorted surfaces of magnetic helium-peculiar stars: an application to a Cen"](https://doi.org/10.1093%2Fmnras%2Fstaa378). *Monthly Notices of the Royal Astronomical Society*. **493** (2): 2140–2148. [arXiv](/source/ArXiv_(identifier)):[2002.01385](https://arxiv.org/abs/2002.01385). [Bibcode](/source/Bibcode_(identifier)):[2020MNRAS.493.2140K](https://ui.adsabs.harvard.edu/abs/2020MNRAS.493.2140K). [doi](/source/Doi_(identifier)):[10.1093/mnras/staa378](https://doi.org/10.1093%2Fmnras%2Fstaa378).

v t e Constellation of Centaurus List of stars in Centaurus Centaurus in Chinese astronomy Stars Bayer α A (Rigil Kentaurus) B (Toliman) C (Proxima Centauri) β (Hadar) γ δ ε ζ (Leepwal) η θ (Menkent) ι (Kulou) κ λ μ ν (Heng) ξ1 ξ2 ο1 ο2 π ρ σ τ υ1 υ2 φ χ ψ x1 x2 C3 D E F G H J K M N Q Flamsteed 1 (i) 2 (g) 3 (k) 4 (h) Variable R T V Y RR SV SX BV DY UY V346 V553 V744 V752 V761 (a) V763 (C1) V766 V779 (Krzemiński's star) V803 V810 V816 (Przybylski's Star) V831 V842 V885 V886 V863 V1032 V1369 V1400 V1935 HR 4460 (A) 4466 (C2) 4499 4522 4523 4537 (j) 4546 (B) 4721 4748 (u) 4796 4817 (l) 4831 (w) 4874 (p) 4888 (e) 4889 (n) 4940 (f) 4979 4989 5006 (r) 5041 (m) 5089 (d) 5174 (z) 5222 (y) 5224 5241 5297 5358 (v) 5371 5471 (b) 5485 (c1) 5489 (c2) HD 97413 98176 100453 101581 101930 102117 (Uklun) 103197 107914 108236 109749 110113 113538 113766 114386 114729 115600 116434 (Matza) 117207 117618 (Dofida) 117939 120411 121228 121504 124448 (Popper's Star) 125072 125595 131399 Other 2MASS J1126−5003 2M1207 Gaia BH2 HD 131399 Ab PSR B1259−63 PSR J1311−3430 TOI-763 WASP-15 (Nyamien) WASP-41 WASP-42 WASP-167/KELT-13 Exoplanets 2M1207b b Centauri b HD 101930 b HD 102117 b (Leklsullun) HD 103197 b HD 109749 b HD 113538 b c HD 114386 b HD 114729 b HD 117207 b HD 117618 b (Noifasui) HD 121504 b HIP 65426 b (Najsakopajk) HIP 67522 b NGTS-13b Proxima Centauri b c d WASP-15b (Asye) Star clusters NGC 3766 4230 4507 5281 5286 5316 5460 5617 5662 Other IC 2944 ω Centauri Scorpius–Centaurus association Stock 16 Nebulae NGC 3918 5307 Other Boomerang Nebula Fleming 1 G292.0+1.8 G306.3-0.9 Gum 41 IC 2944 IRAS 13208−6020 RCW 79 RCW 86 Southern Crab Nebula SuWt 2 Galaxies NGC 3557 3568 3749 3783 4444 4603 4622 4650A 4683 4696 4706 4709 4729 4730 4743 4744 4909 4930 4945 4976 5011 A 5026 5064 5082 5090 5091 5102 5114 5121 5128 (Centaurus A) 5161 5206 5253 5266 5291 5398 5408 5419 5483 5516 Other ESO 269-57 ESO 325-4 ESO 383-76 ESO 444-46 Fourcade-Figueroa Object IC 3370 IC 4214 IC 4329A IRAS 13224−3809 J1144−4308 LEDA 677373 PKS 1144−379 PKS 1353−341 PKS 1424−418 Galaxy clusters Abell S740 Centaurus Cluster Shapley Supercluster Astronomical events GW190521 SN 185 SN 1895B (Z) SN 1972E SN 1986G J1407b SN 2019so Category

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