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

Sean Gunderson; Swati Ravi; Herman L. Marshall; Dustin K. Swarm; Richard Ignace; Yaël Nazé; David P. Huenemoerder; Pragati Pradhan

doi:10.48550/arXiv.2508.03412

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

Sean Gunderson
, Swati Ravi
, Herman L. Marshall
, Dustin K. Swarm
, Richard Ignace
, Yaël Nazé
, David P. Huenemoerder
, Pragati Pradhan

Department of Physics and Astronomy

Kavli Institute for Astrophysics and Space Research
University of Iowa
University of Liège
Fund for Scientific Research-FNRS
Massachusetts Institute of Technology
Massachusetts Institute of Technology
Embry-Riddle Aeronautical University, Prescott

Research output: Contribution to journal › Article

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.

Original language	American English
Number of pages	8
Journal	arXiv: Astrophysics
DOIs	https://doi.org/10.48550/arXiv.2508.03412
State	Published - Sep 30 2025

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10.48550/arXiv.2508.03412

Cite this

@article{c4f71241c46f405dafa12d43137dbad8,

title = "X-ray Polarimetry of Accreting White Dwarfs: A Case Study of EX Hydrae",

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 {\textendash} 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{\textquoteright}s surface. ",

author = "Sean Gunderson and Swati Ravi and Marshall, \{Herman L.\} and Swarm, \{Dustin K.\} and Richard Ignace and Ya{\"e}l Naz{\'e} and Huenemoerder, \{David P.\} and Pragati Pradhan",

year = "2025",

month = sep,

day = "30",

doi = "10.48550/arXiv.2508.03412",

language = "American English",

journal = "arXiv: Astrophysics",

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TY - JOUR

T1 - X-ray Polarimetry of Accreting White Dwarfs

T2 - A Case Study of EX Hydrae

AU - Gunderson, Sean

AU - Ravi, Swati

AU - Marshall, Herman L.

AU - Swarm, Dustin K.

AU - Ignace, Richard

AU - Nazé, Yaël

AU - Huenemoerder, David P.

AU - Pradhan, Pragati

PY - 2025/9/30

Y1 - 2025/9/30

N2 - 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.

AB - 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.

U2 - 10.48550/arXiv.2508.03412

DO - 10.48550/arXiv.2508.03412

M3 - Article

JO - arXiv: Astrophysics

JF - arXiv: Astrophysics

ER -