High-resolution X-ray spectroscopy of the low and high states of the Seyfert 1 galaxy NGC 4051 with Chandra LETGS

TL;DR

This study uses Chandra X-ray spectroscopy to analyze the spectral changes in Seyfert 1 galaxy NGC 4051 during high and low flux states, revealing highly ionized outflows, relativistic lines, and variable absorption components.

Contribution

First detailed high-resolution X-ray spectral analysis of NGC 4051's flux states, identifying multiple ionized outflows and their variability.

Findings

Detection of a highly ionized outflow at -4670 km/s.

Observation of relativistic O VIII Ly alpha emission line.

Identification of four absorption components with varying ionization levels.

Abstract

Methods. We analyse two observations taken with the Low Energy Transmission Grating Spectrometer of Chandra. We investigated the spectral response to a sudden flux decrease by a factor of 5, which occurred during the second observation. Results. We detect a highly ionised absorption component with an outflow velocity of -4670 km/s, one of the highest outflow velocity components observed in a Seyfert 1 galaxy. The spectra contain a relativistic O VIII Ly alpha line, and four absorption components spanning a range in ionisation parameter xi between 0.07 and 3.19. An emission component producing radiative recombination continua of C VI and C V appears during the low state. The black body temperature decreases with the drop in flux observed in the second observation. Conclusions. For all absorber components we exclude that the ionisation parameter linearly responded to the decrease in flux by a factor of 5. The variability of the absorber suggest that at least three out of four detected components are located in the range 0.02-1 pc. ABRIDGED