J/A+A/704/L13 Internal magnetic field in HD 192575 (Vandersnickt+, 2025)
Asteroseismic detection of an internal magnetic field in the B0.5V pulsator
HD 192575.
Vandersnickt J., Vanlaer V., Vanrespaille M., Aerts C.
<Astron. Astrophys. 704, L13 (2025)>
=2025A&A...704L..13V 2025A&A...704L..13V (SIMBAD/NED BibCode)
ADC_Keywords: Stars, OB ; Stars, variable ; Magnetic fields ; Models ;
Photometry
Keywords: asteroseismology - stars: evolution - stars: interiors -
stars: magnetic field - stars: oscillations - stars: rotation
Abstract:
Internal magnetic fields are an elusive component of stellar
structure. However, they can play an important role in stellar
structure and evolution models through efficient angular momentum
transport and through their impact on internal mixing.
We strive to explain the nine components of one frequency multiplet
identified as a low-order quadrupole gravity mode detected in the
light curve of the β Cep pulsator HD 192575 assembled by the
Transiting Exoplanet Survey Satellite (TESS).
We updated the frequencies of the quadrupole mode under investigation
using a standard pre-whitening method applied to the 1951.46 d TESS
light curve. This showed that an internal magnetic field is required
to simultaneously explain all nine components. We implemented
theoretical pulsation computations applicable to the low-order modes
of a β Cep pulsator including the Coriolis force as well as a
magnetic field that is misaligned with respect to the rotation axis.
We applied the theoretical description to perform asteroseismic
modelling of the amplitudes and frequencies in the multiplet of the
quadrupole g-mode of this evolved β Cep star.
Pulsation predictions based on the measured internal rotation
frequency of the star cannot explain the observed nine-component
frequency splittings of the quadrupole low-order gravity mode. By
contrast, we show that the combined effect of the Coriolis force
caused by the near-core rotation with a period of ∼5.3d and the
Lorentz force due to an internal inclined magnetic field with a
maximum strength of ∼24kG does provide a proper explanation of the
nine multiplet frequencies and their relative amplitudes.
Given HD 192575's stellar mass of about 12M☉, this work
presents the detection and magneto-gravito-asteroseismic modelling of
a stable internal magnetic field buried inside an evolved rotating
supernova progenitor.
Description:
In the photometry Transiting Exoplanet Survey Satellite (TESS)
photometry of the beta Cep pulsator HD 192575, the signatures of
nonradial oscillation modes with both rotationally and magnetically
induced frequency splitting have been detected. This discovery was
enabled by the detection of very fine magnetic splitting in a
rotationally split multiplet, which could only be detected thanks to
the extensive TESS light curve and an appropriate Fourier analysis.
From these split components, the star's rotational and magnetic
properties can be constrained.
Photometric signals from TESS's stitched light curve from cycles 2, 4,
5, and 6, analysed with an adapted version of the STAR SHADOW code of
IJspeert et al. (2024, see https://github.com/LucIJspeert/star_shadow).
We include all frequencies detected at a signal-to-noise ratio greater
than 2.
Objects:
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RA (2000) DE Designation(s)
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20 10 56.91 +68 16 19.9 HD 192575 = TIC 402894425
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
signals.dat 100 215 The photometric signals detected in the
TESS light curve
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Byte-by-byte Description of file: signals.dat
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Bytes Format Units Label Explanations
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1- 12 F12.9 d-1 Freq Frequency
14- 23 E10.5 d-1 e_Freq Uncertainty on frequency
25- 44 F20.15 umag Ampl Photometric amplitude
46- 60 F15.13 umag e_Ampl Uncertainty on photometric amplitude
62- 73 F12.9 rad Phase Phase
75- 85 F11.9 rad e_Phase Uncertainty on phase
87-100 F14.9 --- SNR Signal-to-noise ratio
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Acknowledgements:
Mathijs Vanrespaille, mathijs.vanrespaille(at)kuleuven.be
(End) Patricia Vannier [CDS] 27-Nov-2025