Confirming HD 23478 as a new magnetic B star hosting an Hα-bright centrifugal magnetosphere

J. Sikora, G. A. Wade, D. A. Bohlender, C. Neiner, M. E. Oksala, M. Shultz, D. H. Cohen, A. Ud-Doula, J. Grunhut, D. Monin, S. Owocki, V. Petit, T. Rivinus, R. H.D. Townsend

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Abstract

In this paper, we report 23 magnetic field measurements of the B3IV star HD23478: 12 obtained from high-resolution Stokes V spectra using the ESPaDOnS (Canada-France-Hawaii Telescope) and Narval (Télescope Bernard Lyot) spectropolarimeters, and 11 from mediumresolution Stokes V spectra obtained with the DimaPol spectropolarimeter (Dominion Astronomical Observatory). HD23478 was one of two rapidly rotating stars identified as potential 'centrifugal magnetosphere' hosts based on IR observations from the Apache Point Observatory Galactic Evolution Experiment survey. We derive basic physical properties of this star including its mass (M = 6.1+0.8-0.7M⊙), effective temperature (Teff = 20 ± 2 kK), radius (R = 2.7+1.6 -0.9 R⊙), and age (τage = 3+37 -1 Myr). We repeatedly detect weakly variable Zeeman signatures in metal, He, and H lines in all our observations corresponding to a longitudinal magnetic field of (Bz) ≈ -2.0 kG. The rotational period is inferred from Hipparcos photometry (Prot = 1.0498(4) d). Under the assumption of the Oblique RotatorModel, our observations yield a surface dipole magnetic field of strength Bd ≥ 9.5 kG that is approximately aligned with the stellar rotation axis. We confirm the presence of strong and broad Hα emission and gauge the volume of this star's centrifugal magnetosphere to be consistent with those of other Hα emitting centrifugal magnetosphere stars based on the large inferred Alfvén to Kepler radius ratio.

Original languageEnglish (US)
Pages (from-to)1928-1938
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Volume451
Issue number2
DOIs
StatePublished - May 1 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Sikora, J., Wade, G. A., Bohlender, D. A., Neiner, C., Oksala, M. E., Shultz, M., Cohen, D. H., Ud-Doula, A., Grunhut, J., Monin, D., Owocki, S., Petit, V., Rivinus, T., & Townsend, R. H. D. (2015). Confirming HD 23478 as a new magnetic B star hosting an Hα-bright centrifugal magnetosphere. Monthly Notices of the Royal Astronomical Society, 451(2), 1928-1938. https://doi.org/10.1093/mnras/stv1051