Highly Variable Active Galactic Nuclei in the SRG/eROSITA All-Sky Survey: I. Constructing Sample and Catalog of Sources Detected in Low State

TL;DR

This study identifies and catalogs highly variable active galactic nuclei (AGNs) using SRG/eROSITA X-ray data, highlighting sources with flux changes over an order of magnitude and providing detailed spectral and temporal analysis.

Contribution

The paper introduces a new catalog of highly variable AGNs detected in the SRG/eROSITA survey, including a method for identifying and analyzing low-state flux sources.

Findings

1325 sources vary by more than a factor of 10 in X-ray flux

635 objects classified as AGNs or candidates

49 sources with significant low-state flux detected

Abstract

We present the results of our search for highly variable active galactic nuclei (AGNs) the X-ray flux from which changed by more than an order of magnitude during the SRG/eROSITA all-sky survey. Using the eROSITA data obtained in the period from December 2019 to February 2022, we have found 1325 sources the X-ray flux from which in the 0.3-2.3 keV energy band changed by more than a factor of 10 at a confidence level of at least 99.73 %. Of them, 635 objects have been classified as AGNs or AGN candidates. We describe the procedure of searching for highly variable sources and the selection of extragalactic objects among them and describe the statistical properties of the produced catalog. We provide a catalog of 49 sources for which a statistically significant flux in their low state was detected. For the latter we provide their light curves and X-ray spectra and discuss in detail the most interesting of them.