The XMMSSC table contains the Fourth XMM-Newton Serendipitous Source Catalog, Thirteenth Data Release, or 4XMM-DR13. 4XMM-DR13 is the fourth-generation catalog 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 catalog and contains 531 more observations and 44,678 more detections than the preceding 4XMM-DR12 catalog, which was made public in July 2022. In addition, the team provides spectra and lightcurves for more than 16,762 more detections than in 4XMM-DR12. The catalog contains source detections drawn from a total of 13,243 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 catalog. For net exposure time >= 1ksec, the net area of the catalog fields taking account of the substantial overlaps between observations is ~1,328 deg<sup>2</sup>. 4XMM-DR13 contains 983,948 X-ray detections above the processing likelihood threshold of 6. These X-ray detections relate to 656,997 unique X-ray sources. A significant fraction of sources (129,133, 20%) have more than one detection in the catalog (up to 90 repeat observations in the most extreme case). The catalog 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 91,763 detections of extended emission, of which 20,971 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 854,095 out of 983,948 detections that are considered to be clean (i.e., summary flag < 3). For 353,538 detections, EPIC time series and 353,821 detections, EPIC spectra were automatically extracted during processing, and a chi<sup>2</sup>-variability test was applied to the time series. 8,029 detections in the catalog are considered variable, within the timespan of the specific observation, at a probability of 10<sup>-5</sup> or less based on the null-hypothesis that the source is constant. Of these, 6,039 have a summary flag <3. The median flux (in the total photon-energy band 0.2 - 12 keV) of the catalog detections is ~ 2.2 x 10<sup>-14</sup> erg/cm<sup>2</sup>/s; in the soft energy band (0.2 - 2 keV) the median flux is ~ 5.2 x 10<sup>-15</sup>, and in the hard band (2 - 12 keV) it is ~1.2 x 10<sup>-14</sup>. About 23% have fluxes below 1 x 10<sup>-14</sup> erg/cm<sup>2</sup>/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 catalog point source detections is generally < 1.57 arcseconds (with a standard deviation of 1.43 arcseconds). With 4XMM-DR13, the team also released 4XMM-DR13s, available from HEASARC as <a href="/W3Browse/xmm-newton/xmmstack.html">XMMSTACK</a>, a new version of the stacked catalog built from 9,796 4XMM-DR13 overlapping observations. 4XMM-DR13s contains 1,688 stacks (or groups). Most of the stacks are composed of 2 observations and the largest has 372. The catalog contains 401,596 sources, of which 310,478 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 depth of ~2.5 x 10<sup>-15</sup> and ~6.8 x 10<sup>-15</sup> erg/cm<sup>2</sup>/s in the soft (0.2-2keV) and hard (2-12 keV) X-ray band, respectively. The energy bands used in the 4XMM-DR13 processing were the same as for the 3XMM catalog. The following are the basic energy bands: <pre> 1 = 0.2 - 0.5 keV 2 = 0.5 - 1.0 keV 3 = 1.0 - 2.0 keV 4 = 2.0 - 4.5 keV 5 = 4.5 - 12.0 keV </pre> while these are the broad energy bands: <pre> 6 = 0.2 - 2.0 keV soft band, no images made 7 = 2.0 - 12.0 keV hard band, no images made 8 = 0.2 - 12.0 keV total band 9 = 0.5 - 4.5 keV XID band </pre> This database table was last updated by the HEASARC in June 2023. It contains the 4XMM-DR13 catalog, released by ESA on 2023-06-12 and obtained from the XMM-Newton Survey Science Center Consortium (<a href="http://xmmssc.irap.omp.eu/Catalogue/4XMM-DR13/4XMM_DR13.html">http://xmmssc.irap.omp.eu/Catalogue/4XMM-DR13/4XMM_DR13.html</a>;). It is also available as a gzipped FITS file at <a href="https://heasarc.gsfc.nasa.gov/FTP/xmm/data/catalogues/4XMM_DR13cat_v1.0.fits.gz">https://heasarc.gsfc.nasa.gov/FTP/xmm/data/catalogues/4XMM_DR13cat_v1.0.fits.gz</a>;. <p> The previous versions of the Serendipitous Source Catalog, 3XMM-DR5, 3XMM-DR6, 3XMM-DR7, 3XMM-DR8, 4XMM-DR9, 4XMM-DR10, 4XMM-DR11, and 4XMM-DR12 are also available in the same directory for comparison purposes as the files 3XMM_DR5cat_v1.0.fits.gz, 3XMM_DR6cat_v1.0.fits.gz, 3XMM_DR7cat_v1.0.fits.gz, 3XMM_DR8_cat_v1.0.fits.gz, 4XMM_DR9_cat_v1.0.fits.gz, 4XMM_DR10cat_v1.0.fits.gz, 4XMM_DR11cat_v1.0.fits.gz, and 4XMM_DR12cat_v1.0.fits.gz, respectively. This is a service provided by NASA HEASARC .
