The XMM deep survey in the CDF-S VIII. X-ray properties of the two brightest sources

TL;DR

This study analyzes the X-ray properties and variability of the two brightest AGN sources in the CDFS using deep XMM-Newton data over a decade, revealing moderate flux variability, absorption features, and broad Fe K emission lines.

Contribution

It provides high-quality spectral analysis and variability tracking of two bright AGN, highlighting their accretion disk origins and spectral features with long-term XMM-Newton observations.

Findings

Both sources show 10-20% flux variability.

Fe K emission lines are detected with EW~0.2 keV.

Lines exhibit marginal variability, indicating disk origin.

Abstract

We present results from the deep XMM-Newton observations of the two brightest X-ray sources in the Chandra Deep Field South (CDFS), PID 203 (z=0.544) and PID 319 (z=0.742). The long exposure of 2.5 Ms over a 10 year period (net 4 yr with a 6 yr gap) makes it possible to obtain high quality X-ray spectra of these two Type I AGN with X-ray luminosity of 10^44 erg/s, typical luminosity for low-redshift PG quasars, track their X-ray variability both in flux and spectral shape. Both sources showed X-ray flux variability of ~10-20 per cent in rms which is similar in the soft (0.5-2 keV) and hard (2-7 keV) bands. PID 203, which has evidence for optical extinction, shows modest amount of absorption (nH~1e21cm^-2) in the X-ray spectrum. Fe K emission is strongly detected in both objects with EW~0.2 keV. The lines in both objects are moderately broad and exhibit marginal evidence for variability in shape and flux, indicating that the bulk of the line emission come from their accretion disks rather than distant tori.