eROSITA DR1 variability catalogue

Within the 128,669 DR1 sources with light curves, our research pinpointed 808 light curves which show hints of variability according to the AMP test, and 298 according to the NEV test. However, after applying suitable thresholds, 90 (123) sources are significantly variable according to the AMP (NEV) tests. In addition, 1342 sources are considered variable according to the Bayesian test bexvar, the total number of unique sources is 1709, forming the catalogue of variable sources released with this paper.

We cross-matched with existing X-ray catalogues and identified 258, 318, 598, and 120 sources in 4XMM DR13, 2SXPS, 2RXS, and CSC2.1, respectively. Only 27 sources overlap across all catalogues, while 882 are new X-ray detections from eROSITA DR1. About 70 per cent are coronal stars, 5 per cent QSOs, and 1.6 per cent are normal galaxies.

We further subclassified 18 sources as LMXBs, 11 as HMXBs, and 14 as bright stars. In this paper, we analyse the variability of eRASS1 sources on a time scale of only a few days. To study the physics of variable sources, we need more deeply pointed observations with other X-ray missions or at least the final depth of the eRASS:8 observations.

The time scale of the eRASS1 observations is not representative of the time scales of the expected upcoming eRASS catalogues. A substantial 52 per cent of the eRASS1 variable sources were first discovered with eROSITA. The DR1 variability catalogue is excellent for follow-up observations with telescopes like XMM-Newton, Chandra, or Swift.