The eROSITA Final Equatorial-Depth Survey (eFEDS): The variability catalogue and multi-epoch comparison

Th. Boller, J. H. M. M. Schmitt, J. Buchner, M. Freyberg, A. Georgakakis, T. Liu, J. Robrade, A. Merloni, K. Nandra, A. Malyali, M. Krumpe, M. Salvato, T. Dwelly

Published 2021-06-28Version 1

The 140 square degree Final Equatorial-Depth Survey (eFEDS) field, observed with the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) aboard the Spectrum-Roentgen-Gamma (SRG) mission, provides a first look at the variable eROSITA sky. We analyze the intrinsic X-ray variability of the eFEDS sources, 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. respectively. We perform variability tests using the normalized excess variance and maximum amplitude variability methods as performed for the 2RXS catalogue and add results from the Bayesian excess variance and the Bayesian block methods. In total 65 sources have been identified 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 fits to stellar flare events reveal extreme flare properties. A few highly variable AGN have also been detected. About half of the variable eFEDS sources have been detected at X-rays with eROSITA for the first time. Comparison with 2RXS and XMM observations provide variability information on timescales of years to decades.