XRISM identifies gamma Cas X-ray origin, solving a 50-year-old stellar mystery‎

Visible to the naked eye in the constellation Cassiopeia, the star γ Cas has puzzled astrophysicists for half a century. It emits X-rays of an intensity and temperature incompatible with what one would expect from an ordinary massive star. Observations, carried out using the Resolve instrument aboard the Japanese XRISM telescope, now allow us to attribute this emission to the white dwarf orbiting γ Cas. This also confirms the existence of a family of binary systems long predicted to exist but never identified.