DETECTION OF THE IRON K-BETA EMISSION-LINE AND 2-COMPONENT X-RAY-EMISSION FROM EX HYA

We find that the hard X-ray spectrum from the intermediate polar EX Hya, observed with Ginga, can be interpreted by two emission components. One of these is optically thin thermal bremsstrahlung with temperature similar to 2 keV, which is separate from the well-known hard X-ray component, the spectrum of which is that of thermal bremsstrahlung with a temperature similar to 11 keV. We have also detected the iron K beta emission line from EX Hya. This is the first detection of the iron K beta emission line from a magnetized cataclysmic variable. Central energies of the K alpha and the K beta emission lines (6.8 and 8.0 keV, respectively) and their intensities indicate that they originate from optically thin thermal plasma in collisional ionization equilibrium. This is exceptional, since the central energies of the iron Ka emission lines from all the other intermediate polars observed with EXOSAT are similar to 6.4 keV, which indicate that the lines are of fluorescent origin. The properties of the iron K-emission lines of EX Hya also suggest that the observed continuum is composed of the two components noted above. The intensity of the soft component is modulated in phase with that of the hard component at the rotational period of the white dwarf, and its modulation amplitude is larger than that of the hard component. The fractional intensity deficit of the soft component during the well-known orbital eclipsing dip is, on the other hand, smaller than that of the hard component. The energy dependence of both the rotational intensity modulation and the intensity deficit during the orbital eclipsing dip are explained by the difference in modulation amplitudes of the soft and the hard components. The possible origin of the soft component is discussed.