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HD 215441

From Wikipedia, the free encyclopedia
HD 215441
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Lacerta[1]
Right ascension 22h 44m 07.505s[2]
Declination +55° 35′ 21.211″[2]
Apparent magnitude (V) 8.73 to 8.90[3]
Characteristics
Spectral type B8p(Si)[3] or A0p[4]
B−V color index 0.031±0.015[1]
Variable type α2 CVn[3]
Astrometry
Radial velocity (Rv)−5.5±0.15[5] km/s
Proper motion (μ) RA: 4.523 mas/yr[2]
Dec.: −1.244 mas/yr[2]
Parallax (π)2.1702±0.0201 mas[2]
Distance1,500 ± 10 ly
(461 ± 4 pc)
Details
Mass3.9±0.1[6] M☉
Radius2.6[7] R☉
Luminosity204+47
−38[6] L☉
Temperature14,500±400[6] K
Rotation9.487792±0.000049 d[4]
Rotational velocity (v sin i)5[6] km/s
Other designations
Babcock's Star, GL Lac, BD+54°2846, HD 215441, HIP 112247, SAO 34741, PPM 41007[8]
Database references
SIMBADdata

HD 215441 is a peculiar variable star in the northern constellation of Lacerta. Alternatively, it is known as Babcock's Star and has the variable star designation GL Lac.[8][9] The apparent visual magnitude of this star varies from 8.73 to 8.90 over a period of 9.4871 days,[3] which is too faint to be viewed with the naked eye. Based on parallax measurements, it is located at a distance of approximately 1,500 light years.

Observations

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This was classified as a peculiar A-type star in the Henry Draper Catalogue. In 1960, American astronomer Horace W. Babcock decided to measure the magnetic field of HD 215441 using the Zeeman effect, and found an unusually strong field. The spectra demonstrated a mean field strength of 34,400±266 gauss.[10] Light curve measurements showed a regular luminosity variation with a period of 9.49 days and an amplitude of 0.140 in magnitude.[11] The magnetic field was found to vary periodically and in phase with the light variations.[5]

The spectrum of this peculiar star shows an anomalous abundance of silicon. Its absorption lines are very sharp, with a projected rotational velocity measured at under 6 km/s.[12] The strength of lines were found to vary by up to 120% over the course of a period.[13] Using an oblique rotator model, the variation of the magnetic field was found to fit an off center dipole tilted at an angle of around 35 degrees relative to the pole of rotation.[14][15] Abundance concentrations in the stellar atmosphere were found not to vary over an observation period of 16 years, and there is no significant activity or pulsations.[9] Zeeman–Doppler imaging of this star demonstrated that abundance anomalies are dependent on the orientation of the magnetic field lines.[16]

This is a magnetic silicon-rich[17] star with a stellar classification of B8p(Si)[3] or A0p.[4] It is classified as a α2 Canum Venaticorum variable,[3] which is a class of chemically peculiar stars of type CP2. The star has 3.9 times the mass of the Sun and radiates over 200 times the Sun's luminosity from its photosphere at an effective temperature of 14,500 K. It spins on its axis with a period of 9.5 days. It has one of the largest magnetic fields among Ap stars;[18] the dipole magnetic field has a strength of 62 kG and it is inclined at an angle of 37° relative to the rotation axis.[19] The star is a weak source of X-ray emission.[20]

References

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  1. 1 2 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. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023), "Gaia Data Release 3. Summary of the content and survey properties", Astronomy and Astrophysics, 674: A1, arXiv:2208.00211, Bibcode:2023A&A...674A...1G, doi:10.1051/0004-6361/202243940, S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 3 4 5 6 Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S.
  4. 1 2 3 Dukes, Robert J. Jr.; Adelman, Saul J. (April 2018), "Studies of FCAPT uvby Photometry with Period04: The mCP Stars HD 5797, HD 36792, HD 27309, HD 47913, HD 74521, HD 120198, HD 171263, and HD 215441", Publications of the Astronomical Society of the Pacific, 130 (986): 044202, Bibcode:2018PASP..130d4202D, doi:10.1088/1538-3873/aaa952.
  5. 1 2 Preston, George W. (June 1969), "The Magnetic Field of HD 215441", Astrophysical Journal, 156: 967, Bibcode:1969ApJ...156..967P, doi:10.1086/150028.
  6. 1 2 3 4 Shultz, M. E.; et al. (June 2022), "MOBSTER - VI. The crucial influence of rotation on the radio magnetospheres of hot stars", Monthly Notices of the Royal Astronomical Society, 513 (1): 1429–1448, arXiv:2201.05512, Bibcode:2022MNRAS.513.1429S, doi:10.1093/mnras/stac136.
  7. ↑ Biswas, Ayan; et al. (July 2026), "GMRT Survey of Radio Emission from Magnetic Massive Stars. I. Emission from Single Stars at Sub-GHz Frequencies", The Astrophysical Journal Supplement Series, 285 (1), id. 16, arXiv:2605.23768, Bibcode:2026ApJS..285...16B, doi:10.3847/1538-4365/ae7347.
  8. 1 2 "GL Lac", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2026-01-29.
  9. 1 2 Malanushenko, V. P.; et al. (June 1992), "Spectrum variations of HD 215441 (Babcock's star)", Astronomy and Astrophysics, 259: 567–573, Bibcode:1992A&A...259..567M.
  10. ↑ Babcock, Horace W. (November 1960), "The 34-KILOGAUSS Magnetic Field of HD 215441", The Astrophysical Journal, 132: 521, Bibcode:1960ApJ...132..521B, doi:10.1086/146960.
  11. ↑ Jarzębowski, T. (1960), "Light Curve of Magnetic Star HD 215441", Acta Astronomica, 10: 119, Bibcode:1960AcA....10..119J.
  12. ↑ Adelman, Saul J. (March 1974), "The Peculiar A Star HD 213441", Astrophysical Journal Supplement, 27: 203, Bibcode:1974ApJS...27..203A, doi:10.1086/190294.
  13. ↑ Krautter, A. H. (August 1977), "Line spectrum variations in the Ap star HD 215441", Astrophysical Journal, 216: 33–36, Bibcode:1977ApJ...216...33K, doi:10.1086/155439.
  14. ↑ Borra, E. F.; Landstreet, J. D. (May 1978), "The magnetic field geometry of HD 215441", Astrophysical Journal, 222: 226–233, Bibcode:1978ApJ...222..226B, doi:10.1086/156138.
  15. ↑ Landstreet, J. D.; et al. (September 1989), "The Magnetic Field and Abundance Distribution Geometry of the Peculiar B Star HD 215441", Astrophysical Journal, 344: 876, Bibcode:1989ApJ...344..876L, doi:10.1086/167855.
  16. ↑ Khokhlova, V. L.; et al. (July 1997), "Doppler-Zeeman mapping of the magnetic CP star HD 215441", Astronomy Letters, 23 (4): 465–482, Bibcode:1997AstL...23..465K.
  17. ↑ Monier, Richard (June 2023), "The FUSE Spectrum of HD 215441 (Babcock's Star)", Research Notes of the AAS, 7 (6), id. 111, Bibcode:2023RNAAS...7..111M, doi:10.3847/2515-5172/acd9cd.
  18. ↑ North, P.; Adelman, S. J. (May 1995), "Stroemgren and Geneva photometry of the magnetic CP stars 56 Tauri, HD 111133, HD 126515 and HD 215441", Astronomy and Astrophysics Supplement, 111: 41, Bibcode:1995A&AS..111...41N.
  19. ↑ Monier, Richard (May 2023), "The Behavior of Bp Si Stars in the far-UV-Paper VI: HD 215441", Research Notes of the AAS, 7 (5), id. 104, Bibcode:2023RNAAS...7..104M, doi:10.3847/2515-5172/acd76d.
  20. ↑ Czesla, S.; Schmitt, J. H. H. M. (April 2007), "Are magnetic hot stars intrinsic X-ray sources?", Astronomy and Astrophysics, 465 (2): 493–499, arXiv:astro-ph/0703524, Bibcode:2007A&A...465..493C, doi:10.1051/0004-6361:20065890.

Sources

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  • Adelman, S. J. (March 1983), "Spectrophotometry of peculiar B and A stars. XIV. 56 Arietis, 41 Tauri, 25 Sextantis, HD 170973, HD 205087, and HD 215441", Astronomy and Astrophysics, Supplement Series, 51: 511–531, Bibcode:1983A&AS...51..511A.
  • Goossens, M.; et al. (April 1982), "The magnetic field surface structure of HD 215441", Astrophysics and Space Science, 83 (1–2): 213–224, Bibcode:1982Ap&SS..83..213G, doi:10.1007/BF00648555.
  • Leckrone, D. S. (June 1974), "Ultraviolet photometry from the Orbiting Astronomical Observatory. XV. The strongly magnetic variable HD 215441", Astrophysical Journal, 190: 319–326, Bibcode:1974ApJ...190..319L, doi:10.1086/152879.
  • Kemp, James C.; Wolstencroft, Ramon D. (January 1973), "HD 215441 and 53 Camelopardalis: Intrinsic Polarization of Hβ and the Continuum", Astrophysical Journal, 179: L33, Bibcode:1973ApJ...179L..33K, doi:10.1086/181111.
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