HD 54879

HD 54879
Location of HD 54879 (circled)
Observation data
Epoch J2000.0[1]      Equinox J2000.0[1]
Constellation Canis Major
Right ascension 07h 10m 08.14876s
Declination −11° 48′ 09.8389″
Apparent magnitude (V) 7.65[2]
Characteristics
Evolutionary stage O9.7V[3]
U−B color index −0.80[2]
B−V color index −0.05[2]
J−H color index −0.037[2]
J−K color index −0.079[2]
Astrometry
Radial velocity (Rv)34.46±0.27[4] km/s
Proper motion (μ) RA: −2.808[1] mas/yr
Dec.: 1.270[1] mas/yr
Parallax (π)0.799 ± 0.0347 mas[1]
Distance4,100 ± 200 ly
(1,250 ± 50 pc)
Details[5]
Mass14±7 M☉
Radius6.1±1.5 R☉
Luminosity28200+16500
−10400 L☉
Surface gravity (log g)4.0±0.1 cgs
Temperature30500±500 K
Rotation2562+63
−58 d[6]
Age5±1 Myr
Other designations
BD−11° 1822, Gaia DR2 3045391130111207808, HD 54879, HIP 34612, SAO 152491, PPM 218262, TIC 177860391, TYC 5402-632-1, GSC 05402-00632, 2MASS J07100815-1148097[2]
Database references
SIMBADdata

HD 54879 is a bluish-hued star in the southern constellation of Canis Major, close to the border with Monoceros. It is too faint to be seen by the naked eye, having an apparent magnitude of 7.65, but can be readily observed using a pair of binoculars.[7] The star is located some 4,100 light-years (1,300 pc) distant according to Gaia EDR3 parallax measurements, and is moving away from the Solar System at a heliocentric radial velocity of 34.46 km/s.

Stellar properties

This is an O-type main-sequence star with a stellar classification of O9.7V, indicating that it is near the border between the spectral types O and B. It radiates 28,200 times the luminosity of the Sun from its photosphere at an effective temperature of 30,500 K (30,200 °C; 54,400 °F), over five times hotter than the Sun. Its mass and radius are not well-constrained due to uncertainties in the star's distance, but simulations show that it likely formed with a mass of 16 ± 1 M☉ about 5 million years ago.[5]

Magnetic field

The star was found to have a strong magnetic field in 2014[8] with an average strength of 2,954 G and a dipole strength of 3,939 G,[6] thousands of times stronger than Earth's magnetic field (0.25–0.65 G[9]). Its strength slowly varies with a period of 7.41 years.[10] This is related to the extremely slow rotation of HD 54879[11] with a period of 7.02 years, the second longest recorded in an O-type star after HD 108.[6]

Since the magnetic fields trap stellar winds to an Alfvén radius of ≳12 times the stellar radius, HD 54879 experiences very little mass loss, estimated at 6.3×10−11 M☉/yr, compared to the ~1×10−9 M☉/yr if the star did not possess a magnetic field.[5] The entrapped gas forms a disk around the star in the equatorial plane of the magnetic field, which is probably the source of the Hα emissions seen in the star's spectra.[10]

Element distribution

In 2021, a spectroscopic study proposed the possibility that the stellar atmosphere was inhomogeneous in elemental makeup, with helium lines forming at much higher altitudes than the emission lines of oxygen and silicon.[3] This, however, was refuted in 2024, and a more uniform chemical composition is now favored.[6]

2019 controversy

In 2019, a research team announced that a sudden spike occurred in the strength of the magnetic field, the spectral type of the star shifted from O9.7V to B2V, and that the star displays radial velocity variations indicative of a long-period binary.[12] These findings were later retracted, the apparent changes attributed to an inadequate signal-to-noise ratio related to instabilities in the data reduction pipelines.[13] However, a follow-up study by another team was unable to confirm such instabilities and instead accredited the faulty results to human error.[14]

See also

References

  1. ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. ^ a b c d e f "HD 54879". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2 November 2024.
  3. ^ a b Järvinen, S P; Hubrig, S; Schöller, M; et al. (23 December 2021). "Detection of anomalous element distribution in the extremely slowly rotating magnetic O9.7 V star HD 54879". Monthly Notices of the Royal Astronomical Society. 510 (3). Oxford University Press (OUP): 4405–4419. arXiv:2112.14362. doi:10.1093/mnras/stab3720. ISSN 0035-8711.
  4. ^ Boyajian, T. S.; Gies, D. R.; Baines, E. K.; et al. (2007). "Radial Velocities of Six OB Stars". Publications of the Astronomical Society of the Pacific. 119 (857). IOP Publishing: 742–746. arXiv:0706.1221. Bibcode:2007PASP..119..742B. doi:10.1086/520707. ISSN 0004-6280.
  5. ^ a b c Shenar, T.; Oskinova, L. M.; Järvinen, S. P.; et al. (2017). "A combined HST and XMM-Newton campaign for the magnetic O9.7 V star HD 54879". Astronomy & Astrophysics. 606. EDP Sciences: A91. arXiv:1708.01261. doi:10.1051/0004-6361/201731291. ISSN 0004-6361.
  6. ^ a b c d Erba, C.; Folsom, C. P.; David-Uraz, A.; Wade, G. A.; Seadrow, S.; Bellotti, S.; Fossati, L.; Petit, V.; Shultz, M. E. (2024). "First Observation of the Complete Rotation Period of the Ultra-Slowly Rotating Magnetic O Star HD 54879". The Astrophysical Journal. 977 (1): 84. arXiv:2401.09722. Bibcode:2024ApJ...977...84E. doi:10.3847/1538-4357/ad865a.
  7. ^ Zarenski, Ed (2004). "Limiting Magnitude in Binoculars" (PDF). Cloudy Nights. Archived (PDF) from the original on 21 July 2011. Retrieved 6 May 2011.
  8. ^ Castro, N.; Fossati, L.; Hubrig, S.; et al. (10 July 2015). "B fields in OB stars (BOB). Detection of a strong magnetic field in the non-peculiar O9.7V star HD 54879". Astronomy & Astrophysics. EDP Sciences. arXiv:1507.03591. doi:10.1051/0004-6361/201425354. ISSN 0004-6361.
  9. ^ Finlay, C. C.; Maus, S.; Beggan, C. D.; et al. (December 2010). "International Geomagnetic Reference Field: the eleventh generation". Geophysical Journal International. 183 (3): 1216–1230. Bibcode:2010GeoJI.183.1216F. doi:10.1111/j.1365-246X.2010.04804.x. hdl:20.500.11850/27303.
  10. ^ a b Küker, Manfred; Järvinen, Silva; Hubrig, Swetlana; Ilyin, Ilya; Schöller, Markus (2024). "Characterizing the dynamical magnetosphere of the extremely slowly rotating magnetic O9.7 V star HD 54879 using rotational modulation of the H $α$ profile". Astronomische Nachrichten. 345 (4). arXiv:2402.11244. Bibcode:2024AN....34530169K. doi:10.1002/asna.20230169.
  11. ^ Hubrig, S; Järvinen, S P; Schöller, M; et al. (31 October 2019). "The very slow rotation of the magnetic O9.7 V star HD 54879". Monthly Notices of the Royal Astronomical Society. 491 (1). Oxford University Press (OUP): 281–288. arXiv:1910.13209. doi:10.1093/mnras/stz3046. ISSN 0035-8711.
  12. ^ Hubrig, S; Küker, M; Järvinen, S P; et al. (18 January 2019). "A short and sudden increase of the magnetic field strength and the accompanying spectral variability in the O9.7 V star HD 54879". Monthly Notices of the Royal Astronomical Society. 484 (4). Oxford University Press (OUP): 4495–4506. arXiv:1901.03975. doi:10.1093/mnras/stz198. ISSN 0035-8711.
  13. ^ Hubrig, S; Küker, M; Järvinen, S P; Kholtygin, A F; Schöller, M; Ryspaeva, E B; Sokoloff, D D (5 November 2019). "Erratum: A short and sudden increase of the magnetic field strength and the accompanying spectral variability in the O9.7 V star HD 54879". Monthly Notices of the Royal Astronomical Society. 490 (4). Oxford University Press (OUP): 5691. doi:10.1093/mnras/stz3095. ISSN 0035-8711.
  14. ^ Wade, G A; Bagnulo, S; Keszthelyi, Z; et al. (20 November 2019). "No evidence of a sudden change of spectral appearance or magnetic field strength of the O9.7V star HD 54879". Monthly Notices of the Royal Astronomical Society: Letters. 492 (1). Oxford University Press (OUP): L1 – L5. arXiv:1910.14495. doi:10.1093/mnrasl/slz174. ISSN 1745-3925.