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X-ray Polarimetry of Accreting White Dwarfs: A Case Study of EX Hydrae
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X-ray Polarimetry of Accreting White Dwarfs: A Case Study of EX Hydrae

Sean J Gunderson, Swati Ravi, Herman L Marshall, Dustin K Swarm, Richard Ignace, Yael Naze, David P Huenemoerder and Pragati Pradhan
ArXiv.org
Cornell University
08/05/2025
DOI: 10.48550/arxiv.2508.03412
url
https://doi.org/10.48550/arxiv.2508.03412View
Preprint (Author's original)This preprint has not been evaluated by subject experts through peer review. Preprints may undergo extensive changes and/or become peer-reviewed journal articles. Open Access

Abstract

We present the first first X-ray polarization measurements of a white dwarf, the intermediate polar EX Hya. We measured significant polarization only in the 2 -- 3 keV energy band with a polarization degree of 8 percent at a $3σ$ significance. No significant polarization was detected above 3 keV, which we attribute to the higher energy bands having lower signal-to-noise. We found that the scattering surface detected by the IXPE is nearly perpendicular to the optical scattering plane, showing that the X-ray scattering surface is the WD and close to the base of the accretion column. Finally, we show how the polarization can be used to estimate the height of the accretion shock above the white dwarf's surface.
Physics - High Energy Astrophysical Phenomena Physics - Solar and Stellar Astrophysics

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