A. Gupta, S. Mathur, Y. Krongold, F. Nicastro
We present Chandra high energy transmission grating spectra of the narrow-line Seyfert-1 galaxy Ark 564. The spectrum shows numerous absorption lines which are well modeled with low velocity outflow components usually observed in Seyfert galaxies (Gupta et al. 2013). There are, however, some residual absorption lines which are not accounted for by low-velocity outflows. Here we present identifications of the strongest lines as K{\alpha} transitions of OVII(two lines) and OVI at outflow velocities of ~0.1c. These lines are detected at 6.9{\sigma}, 6.2{\sigma}, and 4.7{\sigma} respectively and cannot be due to chance statistical fluctuations. Photoionization models with ultra-high velocity components improves the spectral fit significantly, providing further support for the presence of relativistic outflow in this source. Without knowing the location of the absorber, its mass and energy outflow rates cannot be well constrained; we find E$\dot{E}(outflow)/L_{bo}$ ranging from < 0.001% to 60% using different assumptions. This is the first time that absorption lines with ultra-high velocities are unambiguously detected in the soft X-ray band. The presence of outflows with relativistic velocities in AGNs with Seyfert-type luminosities is hard to understand and provides valuable constraints to models of AGN outflows.
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http://arxiv.org/abs/1301.6139
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