AChandraHETGS Observation of the Narrow‐Line Seyfert 1 Galaxy Arakelian 564

We present results from a 50 ks observation of the narrow-line Seyfert 1galaxy Ark 564 with the Chandra HETGS. The spectra above 2 keV are modeled by apower-law with a photon-index of 2.56+/-0.06. We confirm the presence of thesoft excess below about 1.5 keV. If we fit the excess with blackbody model, thebest-fit temperature is 0.124 keV. Ark 564 has been reported to show a peculiaremission line-like feature at 1 keV in various observations using lowerresolution detectors, and the Chandra grating spectroscopy rules out an originof blends of several narrow emission lines. We detect an edge-like feature at0.712 keV in the source rest frame. The preferred interpretation of thisfeature is combination of the O VII K-edge and a number of L-absorption linesfrom slightly ionized iron, which suggests a warm absorber with ionizationparameter xi~1 and N_H ~ 10^21 cm^-2. These properties are roughly consistentwith those of the UV absorber. We also detect narrow absorption lines of O VII,O VIII, Ne IX, Ne X, and Mg XI at the systemic velocity. From these lines, asecond warm absorber having log xi ~ 2 and N_H ~ 10^21 cm^-2 is required.Comment: 22 pages, including 5 figures and 2 tables. Accepted for publication in Ap