The eROSITA Final Equatorial-Depth Survey (eFEDS)

Variability catalogue and multi-epoch comparison^★

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
e-mail: bol@mpe.mpg.de
² Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
³ National Observatory of Athens, I. Metaxa & V. Pavlou, P. Penteli, 15236 Athens, Greece
⁴ Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

Received: 21 April 2021
Accepted: 21 June 2021

Abstract

The 140-square-degrees Final Equatorial-Depth Survey (eFEDS) field, observed with the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Spectrum-Roentgen-Gamma mission, provides a first look at the variable eROSITA sky. We analysed the intrinsic X-ray variability of the eFEDS sources and provide X-ray light curves and tables with variability test results in the 0.2–2.3 keV (soft) and 2.3–5.0 keV (hard) bands. We performed variability tests using the traditional normalised excess variance and maximum amplitude variability methods (as performed for the 2RXS catalogue), and we present results from the Bayesian excess variance and Bayesian block methods. We identified 65 sources as being significantly variable in the soft band. In the hard band, only one source is found to vary significantly. For the most variable sources, the light curves are well fit by an empirical stellar flare model and reveal extreme flare properties. A few highly variable active galactic nuclei have also been detected. About half of the variable eFEDS sources are detected in the X-rays for the first time with eROSITA. Comparison with 2RXS and XMM-Newton observations provides variability information on timescales of years to decades.