Detection of a variable ultra-fast outflow in the Narrow Line Seyfert 1 galaxy PG 1448+273

TL;DR

This study reports the first unambiguous detection of a relativistically blueshifted ultra-fast outflow in the Narrow Line Seyfert 1 galaxy PG 1448+273, revealing a highly ionized wind with variable properties that impacts our understanding of AGN feedback.

Contribution

The paper introduces an automated systematic routine for detecting ultra-fast outflows in AGN, successfully identifying a variable UFO in PG 1448+273 with detailed physical parameters.

Findings

Detected a UFO with velocity ~0.09c in PG 1448+273

Observed variability of the UFO between observations

Indicated presence of multi-phase wind structure

Abstract

Relativistically blueshifted absorption features of highly ionised ions, the so-called ultra-fast 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 (AGN). However, the UFO spectral features are often weak due to high ionisation of the outflowing material, and the inference of the wind physical properties can be complicated by other spectral features in AGN 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 (26900 +- 600) km/s (~0.09c), with an ionisation parameter of log ({\xi} / erg cm s^-1)=4.03_{-0.08}^{+0.10} and a column density above 10^23 cm^-2. 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 multi-phase 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 AGN.