Gamma-Cas X-Ray Emissions Explained by Hidden White Dwarf Companion

Sun, 03 May 2026 08:23:00 +0200

After more than five decades of scientific investigation, astronomers have identified the source of the unusually strong X-rays emitted by the bright star gamma-Cas. Observations from the X-Ray Imaging and Spectroscopy Mission (XRISM) confirmed that the emissions originate from a hidden white dwarf companion that is siphoning material from the larger gamma-Cas star. This accretion process heats the material to extreme temperatures, generating the intense X-rays observed. Gamma-Cas, a prominent star in the Cassiopeia constellation, has intrigued astronomers since the 19th century due to its bright hydrogen emission lines, which led to the classification of 'Be' stars. Previous theories suggested that the X-rays could result either from magnetic interactions between the star and its disc or from matter falling onto a companion. XRISM's high-precision spectrometer provided the decisive evidence that the white dwarf's orbital motion matches the hot plasma producing the X-rays, confirming t