X-RAY-ABSORPTION IN THE STRONG FE-II NARROW-LINE SEYFERT-1 GALAXY MARKARIAN-507

We present results from spectral analysis of ASCA data on the strong F ell narrow-line Seyfert 1 galaxy Mrk 507. This galaxy was found to hav e an exceptionally flat ROSAT spectrum among the narrow-line Seyfert 1 galaxies (NLS1s) studied by Boiler, Brandt & Fink. The ASCA spectrum, however, shows a clear absorption feature in the energy band below 2 keV, which partly accounts for the flat spectrum observed with the ROS AT Position Sensitive Proportional Counter (PSPC). Such absorption is rarely observed in other NLS1s. The absorption is mainly the result of cold (neutral or slightly ionized) gas with a column density of (2-3) x 10(21) cm(-2) A reanalysis of the PSPC data shows that an extrapola tion of the best-fitting model for the ASCA spectrum underpredicts the X-ray emission observed with the PSPC below 0.4 keV if the absorber i s neutral (which indicates that the absorber is slightly ionized), cov ers only part of the central source, or there is extra soft thermal em ission from an extended region. There is also evidence that the X-ray absorption is complex; an additional edge feature marginally detected at 0.84 keV suggests the presence of an additional high-ionization abs orber, which imposes a strong O VIII edge on the spectrum. After corre ction for the absorption, the photon index of the intrinsic continuum, Gamma similar or equal to 1.8, obtained from the ASCA data is quite s imilar to that of ordinary Seyfert 1 galaxies. Mrk 507 still has one o f the flattest continuum slopes among the NLS1s, but is no longer exce ptional. The strong optical Fe II emission remains unusual in the ligh t of the correlation between Fe rr, strengths and steepness of soft X- ray slope.