A comprehensive reanalysis of HD 99458. Not a magnetic Ap star but an oscillating Algol with ongoing mass transfer
Abstract
Context. Since 2019, HD 99458 has been known as a unique example of a δ Sct variable with chemical peculiarities of Ap type in an eclipsing binary. Aims. We aim to review the peculiar status of the star with new observational materials. Methods. The current study is the result of meticulous analysis of space-based photometry from Kepler K2 and TESS, multi-site spectroscopic and spectropolarimetric observations, as well as speckle-interferometric data. Asteroseismic modelling of stellar pulsation is an essential part of the research. Results. We find HD 99458 to be an eclipsing Algol-type system with active mass transfer from the cool companion filling its Roche lobe to the pulsating primary. We identified signatures of a disc and accretion with varying rates in spectra and light curves. The system's orbital period increases with the rate Ṗorb of 5.045 s yr−1, indicating potential multiplicity. We failed to detect traces of the primary's magnetic field or excessive abundances, both of which are necessary to classify HD 99458 as an Ap star. We have constrained the fundamental parameters of the pulsating primary and analysed its pulsation using asteroseismology. In space-based photometry, we identified pulsation modes with angular degree ℓ≤3. Two-dimensional Fourier analysis of spectroscopic time series reveals pulsations in the form of standing waves with the azimuthal orders |m|=5±1. Combined analysis of photometry and spectroscopy confirms the status of HD 99458 as a triaxial gravitationally distorted pulsator. Conclusions. Our comprehensive study affirms the new classification for HD 99458.
Related
- Ongoing and Post-Mass-Transfer Binaries: A Living Catalog and Unified Review of Binary Mass Transfer Products
- A Comprehensive Study of the Magnetic White Dwarfs in DESI DR1
- Evidence for the emergence of stellar magnetic fields during rapid mass transfer
- Wave optical imaging of an oscillating electric dipole orbiting a black hole
- Oscillating dynamo models with a time-nonlocal α effect
BibTeX
@misc{semenko2026comprehensive,
title = {{A comprehensive reanalysis of HD 99458. Not a magnetic Ap star but an oscillating Algol with ongoing mass transfer}},
author = {E. Semenko and Z. Mikulášek and D. Mkrtichian and P. Walczak and M. Gabdeev and J. Janík and O. Kochukhov and J. Kolář and E. Paunzen and M. E. Shultz and M. Skarka and V. N. Aitov and A. S. Beskakotov and R. Brahm and V. V. Dyachenko and L. Eyer and P. Kabáth and O. Kvaratskhelia and T. Kvernadze and J. Lipták and A. V. Moiseeva and V. Schaffenroth and L. Vanzi and J. Žák},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.32406},
eprint = {2610.32406},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.32406},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A comprehensive reanalysis of HD 99458. Not a magnetic Ap star but an oscillating Algol with ongoing mass transfer
AU - E. Semenko
AU - Z. Mikulášek
AU - D. Mkrtichian
AU - P. Walczak
AU - M. Gabdeev
AU - J. Janík
AU - O. Kochukhov
AU - J. Kolář
AU - E. Paunzen
AU - M. E. Shultz
AU - M. Skarka
AU - V. N. Aitov
AU - A. S. Beskakotov
AU - R. Brahm
AU - V. V. Dyachenko
AU - L. Eyer
AU - P. Kabáth
AU - O. Kvaratskhelia
AU - T. Kvernadze
AU - J. Lipták
AU - A. V. Moiseeva
AU - V. Schaffenroth
AU - L. Vanzi
AU - J. Žák
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2610.32406
UR - https://arxiv.org/abs/2610.32406
AB - Context. Since 2019, HD 99458 has been known as a unique example of a δ Sct variable with chemical peculiarities of Ap type in an eclipsing binary. Aims. We aim to review the peculiar status of the star with new observational materials. Methods. The current study is the result of meticulous analysis of space-based photometry from Kepler K2 and TESS, multi-site spectroscopic and spectropolarimetric observations, as well as speckle-interferometric data. Asteroseismic modelling of stellar pulsation is an essential part of the research. Results. We find HD 99458 to be an eclipsing Algol-type system with active mass transfer from the cool companion filling its Roche lobe to the pulsating primary. We identified signatures of a disc and accretion with varying rates in spectra and light curves. The system's orbital period increases with the rate Ṗ_orb of 5.045 s yr^−1, indicating potential multiplicity. We failed to detect traces of the primary's magnetic field or excessive abundances, both of which are necessary to classify HD 99458 as an Ap star. We have constrained the fundamental parameters of the pulsating primary and analysed its pulsation using asteroseismology. In space-based photometry, we identified pulsation modes with angular degree ℓ≤3. Two-dimensional Fourier analysis of spectroscopic time series reveals pulsations in the form of standing waves with the azimuthal orders |m|=5±1. Combined analysis of photometry and spectroscopy confirms the status of HD 99458 as a triaxial gravitationally distorted pulsator. Conclusions. Our comprehensive study affirms the new classification for HD 99458.
ER -