Speaker
Description
Based on a detailed spectral analysis using Suzaku, we investigate an ionization structure of a accretion column plasma of EX Hya, a magnetic cataclysmic variable (mCV).Due to high density and high cooling rate, the plasma has been assumed to be in a collisional ionization equilibrium (CIE) state so far.Trying a fitting of the X-ray spectrum with a CIE model, we found large residuals at 9-10 keV, which is consistent with a radiative recombination continuum generated by free-bound transition of electron capture by fully ionized Fe (Fe XXVI RRC).The Fe XXVI RRC indicates the plasma has larger fraction of Fe XXVII ions than that of CIE, suggesting recombining plasma (RP).A possible scenario is photoionization; X-rays from high-temperature plasma ionize low-temperature plasma.We construct a RP model based on the photo-ionization scenario to fit the X-ray spectrum. Then, the 9-10 keV residuals are improved significantly.This is the first discovery of the RP from mCVs.
