Detection of a variable ultrafast outflow in the narrow-line Seyfert 1 galaxy PG 1448+273

Abstract

Relativistically blueshifted absorption features of highly ionized ions, the so-called ultrafast outflows (UFOs), have been detected in the X-ray spectra of a number of accreting supermassive black holes. If these features truly originate from accretion disc winds accelerated to more than 10 per cent of the speed of light, their energy budget is very significant and they can contribute to or even drive galaxy-scale feedback from active galactic nuclei (AGNs). However, the UFO spectral features are often weak due to high ionization of the outflowing material, and the inference of the wind physical properties can be complicated by other spectral features in AGNs such as relativistic reflection. Here we study a highly accreting narrow-line Seyfert 1 galaxy PG 1448+273. We apply an automated, systematic routine for detecting outflows in accreting systems and achieve an unambiguous detection of a UFO in this AGN. The UFO absorption is observed in both soft and hard X-ray bands with the XMM-Newton observatory. The velocity of the outflow is (26 900 ± 600) km s<SUP>-1</SUP> (∼0.09c), with an ionization parameter of $\log (\XI / \textrm {erg~cm~s}^{-1})=4.03_{-0.08}^{+0.10}$ and a column density above 10<SUP>23</SUP> cm<SUP>-2</SUP>. At the same time, we detect weak warm absorption features in the spectrum of the object. Our systematic outflow search suggests the presence of further multiphase wind structure, but we cannot claim a significant detection considering the present data quality. The UFO is not detected in a second, shorter observation with XMM-Newton, indicating variability in time, observed also in other similar AGNs.