Discovery of Relativistic Outflow in the Seyfert Galaxy Ark 564. (arXiv:1301.6139v1 [astro-ph.HE])

Discovery of Relativistic Outflow in the Seyfert Galaxy Ark 564. (arXiv:1301.6139v1 [astro-ph.HE]):
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.