Photometric signatures of corotating magnetospheres of hot stars governed by higher-order magnetic multipoles

Abstract

The light curves of magnetic, chemically peculiar stars typically show periodic variability due to surface spots that in most cases can be modeled by low-order harmonic expansion. However, high-precision satellite photometry reveals tiny complex features in the light curves of some of these stars that are difficult to explain as caused by a surface phenomenon under reasonable assumptions. These features might originate from light extinction in corotating magnetospheric clouds supported by a complex magnetic field dominated by higher-order multipoles. We aim to understand the photometric signatures of corotating magnetospheres that are governed by higher-order multipoles. We determined the location of magnetospheric clouds from the minima of the effective potential along the magnetic field lines for different orders of multipoles and their combination. From the derived magnetospheric density distribution, we calculated light curves accounting for absorption and subsequent emission of light. For axisymmetric multipoles, the rigidly rotating magnetosphere model is able to explain the observed tiny features in the light curves only when the higher-order multipoles dominate the magnetic field not only at the stellar surface, but even at the Kepler radius. However, even a relatively weak nonaxisymmetric component leads to warping of equilibrium surfaces. This introduces structures that can explain the tiny features observed in the light curves of chemically peculiar stars. The light emission contributes to the light variability only if a significant fraction of light is absorbed in the magnetosphere.

14 pages, accepted for publication in Astronomy & Astrophysics

References in corpus (20)

• The Transiting Exoplanet Survey Satellite
• The surprising magnetic topology of tauSco: fossil remnant or dynamo output?
• Weak magnetic fields in Ap/Bp stars: Evidence for a dipole field lower limit and a tentative interpretation of the magnetic dichotomy
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation
• The Magnetic Early B-type Stars III: A main sequence magnetic, rotational, and magnetospheric biography
• The Magnetic Early B-type Stars I: Magnetometry and Rotation
• 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
• An `Analytic Dynamical Magnetosphere' formalism for X-ray and optical emission from slowly rotating magnetic massive stars
• The Magnetic Early B-type Stars IV: Breakout or Leakage? H$\alpha$ emission as a diagnostic of plasma transport in centrifugal magnetospheres
• Stellar magnetosphere reconstruction from radio data. Multi-frequency VLA observations and 3D-simulations of CU Virginis
• Exploring the photometric signatures of magnetospheres around Helium-strong stars
• How the breakout-limited mass in B-star centrifugal magnetospheres controls their circumstellar H-alpha emission
• The surface magnetic field and chemical abundance distributions of the B2V helium-strong star HD184927
• Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712 II. Two-dimensional Magnetic Doppler Imaging in all four Stokes parameters
• Global properties of the light curves of magnetic, chemically peculiar stars as a testbed for the existence of dipole-like symmetry in surface structures
• The accelerating rotation of the magnetic He-weak star HD 142990
• Diffusion-plus-drift models for the mass leakage from centrifugal magnetospheres of magnetic hot-stars
• The complex magnetic field topology of the cool Ap star 49 Cam
• Putting atomic diffusion theory of magnetic ApBp stars to the test: evaluation of the predictions of time-dependent diffusion models

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• Periodic variable A-F spectral type stars in the northern TESS continuous viewing zone
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• Modeling the Photometric Variability of Alpha${}^2$ CVn with a Dynamical Magnetosphere
• MOBSTER -- VII. Using light curves to infer magnetic and rotational properties of stars with centrifugal magnetospheres