Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.40741

Likely Metal Scarring in the Magnetic White Dwarf LHS 2534

Ryan J. Souchet·Adam Moss·Jamie Tayar·Warren R. Brown·Mukremin Kilic·J. J. Hermes
View original source ↗Read source document ↗Export metadata ↓

Abstract

There are only three white dwarfs known to possess metal-enriched polar caps due to magnetically guided accretion. These rare systems offer a unique opportunity to study planetesimal accretion and how magnetic fields influence the spreading of material across the atmosphere. To better study these processes however, more targets are needed. Here we report our findings from an observing campaign on the magnetic white dwarf LHS 2534. Time-resolved spectra at the MMT show clear variability in the strength of the Na I and Cr I features. We find that the strengths of these features vary over a period of 19.46 and 19.36 hours respectively, closely matching the 20.22 hour period determined from K2 photometry. Our findings demonstrate the ability to detect and study these variable objects with spectroscopy, and time-series observations of similar targets in the future will provide more insight into how these atmospheres form.

Explore related subjects

astro-ph.SRastro-ph.EP

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Ryan J. Souchet, Adam Moss, Jamie Tayar, Warren R. Brown, Mukremin Kilic, J. J. Hermes. 2026-10-29. Likely Metal Scarring in the Magnetic White Dwarf LHS 2534. https://arxiv.org/abs/2610.40741

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Carbon-Reaction Constraints on Stellar Evolution: White-Dwarf Heating, Carbon-Burning Products, and Black-Hole Masses

The effects of ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion and ${}^{12}\mathrm{C}(α,γ){}^{16}\mathrm{O}$ capture on stellar heating, composition, and black-hole masses are examined. Rates from a published Bayesian analysis of carbon fusion are used in calculations with MESA. In an accreting carbon--oxygen white dwarf, the Bayesian rates move the point at which nuclear heating equals combined neutrino and surface photon losses to slightly larger stellar masses and higher central temperatures and densities. At an accretion rate of $10^{-7}\,M_\odot\,\mathrm{yr}^{-1}$, the Bayesian median gives a central temperature approximately $2.57\%$ higher and a central density $18.9\%$ higher than the calculation using the standard CF88 rate. A separate calculation follows carbon burning in an initially $20\,M_\odot$, $Z=0.0142$ star. Relative to the CF88 rate with MESA's standard division between proton and alpha channels, the Bayesian-median rate with the proton-to-alpha ratio of Yang et al. increases the neon-20 mass remaining at central carbon depletion by $10.8\%$ and decreases the sodium-23 mass by $28.7\%$. For helium capture on carbon, the nuclear constraint $S_{\rm tot}(300\,\mathrm{keV})=118\pm17\,\mathrm{keV\,b}$ is applied to the published $Z=10^{-5}$ stellar models of Farag et al. Linear interpolation gives a maximum black-hole mass below the pair-instability gap of approximately $61.5$--$77.4\,M_\odot$ within the assumptions of those models. New MESA calculations at $Z=0.00142$ give smaller bound masses before collapse. Differences in the stellar assumptions prevent attributing the difference between the two curves to metallicity alone.

astro-ph.SR↗
arXiv2026

A Detailed Polarimetric Imaging Study of Type II Solar Radio Burst with the MWA: Detection of Linear Polarization

Type II radio bursts, produced by magnetohydrodynamic shocks propagating through the solar corona and interplanetary medium, serve as powerful diagnostics of shock properties and ambient coronal magnetic fields. While circular polarization in type II bursts has been extensively studied, most investigations rely on dynamic spectra (DS), providing only spatially integrated measurements. DS obscures spatial variations of the polarization sign and magnitude, potentially causing cancellation effects and misrepresenting true polarization levels. We present a full-polarimetric imaging study of a metric type II burst observed with the Murchison Widefield Array at 78--133 MHz. Remarkably, we report the first detection of linear polarization in a metric type II burst, reaching a polarization fraction of $\sim12\%$ with significant spectro-temporal variability across observing bands. The spectro-temporal, spatial, and morphological properties found in this study establish linear polarization as a new diagnostic of large-scale coronal and interplanetary magnetic field structure through full-Stokes imaging of metric solar radio bursts -- challenging conventional paradigms predicting negligible linear polarization from coherent plasma emission processes.

astro-ph.SR↗
arXiv2026

MAGIC's interferometric diameters of $θ$ Ophiuchi and $β$ CMa and comparison with asteroseismic modelling

$β$ Cephei type stars are massive ($8-25$M$_{\odot}$) and known to have several pulsation modes with periods typically of a few hours. Despite a better understanding of their physics since 1992, the inner structure of these stars involves key stellar physics processes that are still uncertain. Asteroseismology offers insights into these variable stars by analysing pulsation modes, helping to probe their inner layers and understand their structure and mixing processes. We measure the angular diameter of two $β$ Cephei stars, $θ$ Oph and $β$ CMa, using the MAGIC Stellar Intensity Interferometer and compare them, together with the Gaia and Hipparcos parallaxes, to the predictions of the asteroseismic model. The latter are based on Levenberg-Marquardt local minimisation of stellar evolution model parameters to fit observed pulsation modes. In the case of $θ$ Oph, the observed angular diameters are compatible with the asteroseismic model. For $β$ CMa, the radius derived from the angular diameter and the Hipparcos parallax is in tension, at the $2.5σ$ level, with the asteroseismic prediction. We show that this tension mirrors a pre-existing conflict between independent spectroscopic determinations of the surface gravity of the star, that percent-level systematics of the stellar models are quantitatively insufficient to explain it, and that it most likely points to a bias of the Hipparcos parallax. In the frame of this paper, the statistical uncertainty on the interferometric results is similar to the systematic uncertainty on the parallaxes. With the already implemented addition in early 2024 of the first Large-Sized Telescope (CTAO-North LST-1) to the setup, the uncertainty in the angular diameter of these stars is expected to decrease by an order of magnitude, allowing to further constrain stellar evolution models and parallaxes.

astro-ph.SR↗