BG Canis Minoris

Light curves for BG Canis Minoris, adapted from McHardy et al. (1984)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Minor
Right ascension 07h 31m 29.008s[2]
Declination 09° 56′ 23.03″[2]
Apparent magnitude (V) 14.5[3] (14.7 to 15.2)[4]
Characteristics
Variable type Intermediate polar[1]
Astrometry
Proper motion (μ) RA: −13.616 mas/yr[2]
Dec.: 3.347 mas/yr[2]
Parallax (π)1.1199 ± 0.0334 mas[2]
Distance2,910 ± 90 ly
(890 ± 30 pc)
Orbit[5]
Period (P)0.1349 d
Semi-major axis (a)1.09–1.33 R☉
Eccentricity (e)0.0
Periastron epoch (T)2,445,731.8184±12.0 HJD
Semi-amplitude (K1)
(primary)		75.00 km/s
Details
White dwarf
Mass0.78+0.08
−0.07[6] M☉
Donor star
Mass0.38[5] M☉
Other designations
3A 0729+103, BG CMi, 2MASS J07312900+0956231[7]
Database references
SIMBADdata

BG Canis Minoris is a binary star system in the equatorial constellation of Canis Minor, abbreviated BG CMi. With an apparent visual magnitude that fluctuates around 14.5,[3] it is much too faint to be visible to the naked eye. Parallax measurements provide a distance estimate of approximately 2,910 light years from the Sun.[2]

In 1981, I. M. McHardy and associates included the X-ray source '3A 0729+103' in their Ariel 5 satellite 3A catalogue.[8] The team used a localized search of those coordinates with the Einstein Observatory to isolate an X-ray source that matched the location of a blue-hued star with a visual magnitude of 14.5. The light curve for this star proved quite similar to other intermediate polars that had been identified as X-ray sources. The overall brightness variation of 3A 0729+103 matched a binary system with an orbital period of 194.1 minutes. It displays a more rapid variation with a period of 913 seconds, which was interpreted as related to a spin period.[1]

The standard model for this category of variable star consists of a magnetized white dwarf in a close orbit with a cool main sequence secondary star. The Roche lobe of the secondary is overflowing, and this stream of matter is falling onto an accretion disk in orbit around the primary. X-ray observations with the EXOSAT observatory in 1984–1985 demonstrated there are two regions of emission. One of these is believed to be at the magnetic poles of the white dwarf component, while the second is located where the accretion stream is striking the white dwarf's magnetosphere. The emission at the pole is partially eclipsed by the rotation of the white dwarf.[9]

In 1987, cyclotron radiation was discovered based on the circular polarization of its near infrared output, the first conclusive identification of this behavior for an intermediate polar. This emission confirmed the model of a magnetic white dwarf that is accreting mass.[10] Measurements suggested a magnetic field strength of 2 to 6 MG.[11] Changes in the rotation period over time indicate that the white dwarf is slowly being spun up due to torque from accreted matter.[3] It has an estimated 78%[6] of the mass of the Sun, while the donor companion has about 38%.[5]

References

  1. ^ a b c McHardy, I. M.; et al. (October 1984), "Identification of 3A 0729+103 with an intermediate polar-type cataclysmic variable", Monthly Notices of the Royal Astronomical Society, 210 (3): 663–672, Bibcode:1984MNRAS.210..663M, doi:10.1093/mnras/210.3.663.
  2. ^ a b c d e 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.
  3. ^ a b c Augusteijn, T.; et al. (July 1991), "Spin-up of the white dwarf in the intermediate polar BG Canis Majoris/3A0729+103", Astronomy and Astrophysics, 247: 64, Bibcode:1991A&A...247...64A.
  4. ^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  5. ^ a b c Penning, W. R. (February 1985), "Time-resolved spectroscopy of long-period DQ Herculis stars", Astrophysical Journal, 289: 300–309, Bibcode:1985ApJ...289..300P, doi:10.1086/162889.
  6. ^ a b Shaw, A. W.; et al. (November 2020), "Measuring the masses of magnetic white dwarfs: a NuSTAR legacy survey", Monthly Notices of the Royal Astronomical Society, 498 (3): 3457–3469, arXiv:2008.09684, Bibcode:2020MNRAS.498.3457S, doi:10.1093/mnras/staa2592.
  7. ^ "BG CMi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-08-12.
  8. ^ McHardy, I. M.; Lawrence, A.; Pye, J. P.; Pounds, K. A. (December 1981), "The Ariel V (3A) catalogue of X-ray sources. II", Monthly Notices of the Royal Astronomical Society, 197: 893–919, Bibcode:1981MNRAS.197..893M, doi:10.1093/mnras/197.4.893.
  9. ^ McHardy, I. M.; et al. (March 1987), "Detailed EXOSAT and optical observations of the intermediate polar 3A0729+103 : discovery of two medium energy X-ray emission regions", Monthly Notices of the Royal Astronomical Society, 225 (2): 355–368, Bibcode:1987MNRAS.225..355M, doi:10.1093/mnras/225.2.355.
  10. ^ West, Steven C.; et al. (November 1987), "The Discovery of Near-Infrared Polarized Cyclotron Emission in the Intermediate Polar BG Canis Minoris", The Astrophysical Journal, 322: L35–L39, Bibcode:1987ApJ...322L..35W, doi:10.1086/185032.
  11. ^ Chanmugam, G.; et al. (February 1990), "The Magnetic Field of the Intermediate Polar BG Canis Minoris", Astrophysical Journal Letters, 350: L13, Bibcode:1990ApJ...350L..13C, doi:10.1086/185656.

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