IXPE measures accretion column on white dwarf EX Hydrae

NASA’s Imaging X-ray Polarization Explorer (IXPE) has been used for the first time to study a white dwarf star, focusing on the intermediate polar EX Hydrae in the constellation Hydra about 200 light-years from Earth. IXPE spent nearly one week in 2024 observing the system. The nearly week-long observation produced results published in the Astrophysical Journal.

The study was led by astrophysics research scientists at the Massachusetts Institute of Technology, with co-authors at the University of Iowa, East Tennessee State University, the University of Liége and Embry-Riddle Aeronautical University. Using IXPE’s X-ray polarization capability, the team measured the height of the accreting column on the white dwarf to be "almost 2,000 miles high," and reported that the X-rays observed likely scattered off the white dwarf’s surface.

In intermediate polar systems like EX Hydrae, the star’s magnetic field does not fully channel infalling gas to the poles; material forms an accretion disk while also being pulled toward the magnetic poles, reaching tens of millions of degrees Fahrenheit and producing high-energy X-rays.

Information from IXPE’s polarization data of EX Hydrae will help scientists understand other highly energetic binary systems.

Key Topics

Science, Ex Hydrae, Hydra, Ixpe, White Dwarf, Accretion Column