The magnetic field and spectral variability of the He-weak star HR 2949

Abstract

We analyze a high resolution spectropolarimetric dataset collected for the He-weak B3p IV star HR 2949. The Zeeman effect is visible in the circularly polarized component of numerous spectral lines. The longitudinal magnetic field varies between approximately $-650$ and $+150$ G. The polar strength of the surface magnetic dipole is calculated to be 2.4${}_{-0.2}^{+0.3}$ kG. The star has strong overabundances of Fe-peak elements, along with extremely strong overabundances of rare-earth elements; however, He, Al, and S are underabundant. This implies that HR 2949 is a chemically peculiar star. Variability is seen in all photospheric lines, likely due to abundance patches as seen in many Ap/Bp stars. Longitudinal magnetic field variations measured from different spectral lines yield different results, likely a consequence of uneven sampling of the photospheric magnetic field by the abundance patches. Analysis of photometric and spectroscopic data for both HR 2949 and its companion star, HR 2948, suggests a revision of HR 2949's fundamental parameters: in particular, it is somewhat larger, hotter, and more luminous than previously believed. There is no evidence of optical or ultraviolet emission originating in HR 2949's magnetosphere, despite its moderately strong magnetic field and relatively rapid rotation; however, when calculated using theoretical and empirical boundaries on the initial rotational velocity, the spindown age is compatible with the stellar age. With the extensive phase coverage presented here, HR 2949 will make an excellent subject for Zeeman Doppler Imaging.

22 pages, 21 figures, published in MNRAS

References in corpus (9)

• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: III. Angular Momentum Loss and Rotational Spindown
• A new library of theoretical stellar spectra with scaled-solar and alpha-enhanced mixtures
• X-rays from Magnetically Confined Wind Shocks: Effect of Cooling-Regulated Shock Retreat
• The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution
• The surface magnetic field and chemical abundance distributions of the B2V helium-strong star HD184927
• Rotation and chemical abundances of Ap/Bp stars in the open cluster NGC 6475
• The Lorentz force in atmospheres of CP stars: $\theta$ Aurigae

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• MOBSTER -- IV. Detection of a new magnetic B-type star from follow-up spectropolarimetric observations of photometrically selected candidates
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