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We present results from a 50 ks observation of the narrow-line Seyfert 1 galaxy Ark 564 with the Chandra HETGS. The spectra above 2 keV are modeled by a power-law with a photon-index of 2.56+/-0.06. We confirm the presence of the soft excess below about 1.5 keV. If we fit the excess with blackbody model, the best-fit temperature is 0.124 keV. Ark 564 has been reported to show a peculiar emission line-like feature at 1 keV in various observations using lower resolution detectors, and the Chandra grating spectroscopy rules out an origin of blends of several narrow emission lines. We detect an edge-like feature at 0.712 keV in the source rest frame. The preferred interpretation of this feature is combination of the O VII K-edge and a number of L-absorption lines from slightly ionized iron, which suggests a warm absorber with ionization parameter xi~1 and N_H ~ 10^21 cm^-2. These properties are roughly consistent with 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, a second warm absorber having log xi ~ 2 and N_H ~ 10^21 cm^-2 is required.
We present the results of a long-term (1999--2010) spectral optical monitoring campaign of the active galactic nucleus (AGN) Ark 564, which shows a strong Fe II line emission in the optical. This AGN is a narrow line Seyfert 1 (NLS1) galaxies, a grou
We analyse eight XMM-Newton observations of the bright Narrow-Line Seyfert 1 galaxy Arakelian 564 (Ark 564). These observations, separated by ~6 days, allow us to look for correlations between the simultaneous UV emission (from the Optical Monitor) w
We present simultaneous ASCA and RXTE observations of Ark 564, the brightest known ``narrow-line Seyfert 1 in the 2-10 keV band. The measured X-ray spectrum is dominated by a steep (Gamma~2.7) power-law continuum extending to at least 20 keV, with im
We present a power spectral analysis of a 100 ksec XMM-Newton observation of the narrow line Seyfert 1 galaxy Ark~564. When combined with earlier RXTE and ASCA observations, these data produce a power spectrum covering seven decades of frequency whic
Beginning in 1999 January, the bright, strongly variable Narrow-Line Seyfert 1 (NLS1) galaxy Akn 564 has been observed by RXTE once every ~4.3 days. It was also monitored every ~3.2 hr throughout 2000 July. These evenly-sampled observations have allo