DOI: 10.5281/zenodo.10876762
title: 4XMM-DR13

description: 4XMM-DR13 is the fourth generation catalogue of serendipitous X-ray sources from the European Space Agency's (ESA) XMM-Newton observatory, and has been created by the XMM-Newton Survey Science Centre (SSC) on behalf of ESA. It is an incremental version of the the 4XMM catalogue and contains 531 more observations and 44678 more detections than the preceding 4XMM-DR12 catalogue, which was made public in July 2022. In addition, we provide spectra and lightcurves for more than 16762 more detections than in 4XMM-DR12.

The catalogue contains source detections drawn from a total of 13243 XMM-Newton EPIC observations made between 2000 February 1 and 2022 December 31; all datasets included were publicly available by 2022 December 31 but not all public observations are included in this catalogue. For net exposure time  ≥  1ksec, the net area of the catalogue fields taking account of the substantial overlaps between observations is ~ 1328 deg2.

4XMM-DR13 contains 983948 X-ray detections above the processing likelihood threshold of 6. These X-ray detections relate to 656997 unique X-ray sources. A significant fraction of sources (129133, 20%) have more than one detection in the catalogue (up to 90 repeat observations in the most extreme case).

The catalogue distinguishes between extended emission and point-like detections. Parameters of detections of extended sources are only reliable up to the maximum extent measure of 80 arcseconds. There are 91763 detections of extended emission, of which 20971 are 'clean' (in the sense that they were not flagged).

Due to intrinsic features of the instrumentation as well as some shortcomings of the source detection process, some detections are considered to be spurious or their parameters are considered to be unreliable. It is recommended to use a detection flag and an observation flag as filters to obtain what can be considered a 'clean' sample. There are 854095 out of 983948 detections that are considered to be clean (i.e., summary flag < 3).

For 353538 detections, EPIC time series and 353821 detections, EPIC spectra were automatically extracted during processing, and a χ2-variability test was applied to the time series. 8029 detections in the catalogue are considered variable, within the timespan of the specific observation, at a probability of 10-5 or less based on the null-hypothesis that the source is constant. Of these, 6039 have a summary flag  < 3.

The median flux (in the total photon-energy band 0.2 - 12 keV) of the catalogue detections is ~ 2.2 × 10-14 erg/cm2/s; in the soft energy band (0.2 - 2 keV) the median flux is ~ 5.2 × 10-15, and in the hard band (2 - 12 keV) it is ~ 1.2 × 10-14. About 23% have fluxes below 1 × 10-14 erg/cm2/s. The flux values from the three EPIC cameras are, overall, in agreement to ~ 10% for most energy bands. The median positional accuracy of the catalogue point source detections is generally < 1.57 arcseconds (with a standard deviation of 1.43).

With 4XMM-DR13, we also release 4XMM-DR13s, a new version of the stacked catalogue built from 9796 4XMM-DR13 overlapping observations. 4XMM-DR13s contains 1688 stacks (or groups). Most of the stacks are composed of 2 observations and the largest has 372. The catalogue contains 401596 sources, of which 310478 have several contributing observations. Stacking observations allows yet fainter sources to be detected in sky regions observed more than once, increasing the number of detections and uncovering long-term variability on repeatedly observed objects. 4XMM-DR13s reaches a median depth of ~2.5E-15 and ~6.8E-15 erg/cm2/s in the soft (0.2-2 keV) and hard (2-12 keV) X-ray band, respectively.