Catalogue 4XMM-DR13s

The 4XMM-DR13s catalogue of serendipitous sources from overlapping XMM-Newton observations has been compiled from 1 688 groups of 9 796 overlapping XMM-Newton observations. They were taken between 2000 February 1 and 2022 November 29 and overlap by at least one arcminute in radius. The catalogue contains 401 596 unique sources, 310 478 of them multiply observed, with positions and source parameters like fluxes in the XMM-Newton standard energy bands, hardness ratios, quality estimate, and information on inter-observation variability. The parameters are directly derived from the simultaneous fit, and, wherever applicable, additionally calculated for each contributing observation. For lower-quality exposures, not used in source detection to ensure the detection quality, the source parameters are derived from subsequent PSF photometry. The number of parameter measurements (total number of observations of all unique sources) has thus increased to almost 1.7 million. Total fluxes and rates are calculated from the measurements in all contributing images as error-weighted means (formerly: exposure-weighted).
The catalogue aims at exploring the multiply observed sky regions and exploit their survey potential, in particular to study the long-term behaviour of X-ray emitting sources. It thus makes use of the long(er) effective exposure time per sky area and offers the opportunity to investigate flux variability directly through the source detection process. The main catalogue properties are summarised in the table below, the data processing and the stacked source detection are described in the processing summary. More information on the compilation of the catalogues is provided in the online documentation.

The catalogue is available for download as a single file xmmstack_v3.1_4xmmdr13s.fits.gz [1.4 GB] in FITS format and browsable via the web-based interfaces

• XSA at ESA’s XMM-Newton SOC
• Browse at HEASARC NASA GSFC

Through the XSA, we provide access to the auxiliary charts per source: a broad-band X-ray image, a colour-coded three-band X-ray image, an optical finding chart, and a long-term X-ray light curve. Through xmmssc.aip.de, we provide access to the auxiliary data products per stack: broad-band and energy mosaic images, coverage maps including the number of observations and exposures, and exposure maps, all in FITS format.

The list of observations and stacks processed to create 4XMM-DR13s is available in FITS format: xmmstack_v3.1_4xmmdr13s_obslist.fits.gz [1.8 MB]

Watchouts For technical reasons, about 15 arcmin about the Galactic Center were excluded from the processing. In the deepest part of the M31 field, several good exposures were used for PSF photometry instead of source detection to reduce the detection runtime.
Due to the revised definition of combined rates and fluxes, related values including hardness ratios and variability measures should not be compared directly to previous catalogue editions.

	4XMM-DR13s	4XMM-DR12s	4XMM-DR11s	4XMM-DR10s	4XMM-DR9s	3XMM-DR7s
Number of stacks	1 688	1 620	1 475	1 396	1 329	434
Number of observations	9 688	9 355	8 292	7 803	6 604	1 789
First observation included	2000/02/01	2000/02/01	2000/02/03	2000/02/03	2000/02/03	2000/02/20
Last observation included	2022/11/29	2021/12/04	2020/12/17	2019/12/14	2018/11/13	2016/04/02
Approximate sky coverage	650 sq. deg.	625 sq. deg.	560 sq. deg.	540 sq. deg.	485 sq. deg.	150 sq. deg.
Approximate multiply observed sky area	420 sq. deg.	400 sq. deg.	350 sq. deg.	335 sq. deg.	300 sq. deg.	100 sq. deg.
Total number of sources	401 596	386 043	358 809	335 812	288 191	71 951
Sources with several contributing observations	310 478	298 626	275 440	256 213	218 283	57 665
Multiply observed sources with flag 0 or 1	262 842	252 445	233 542	216 699	191 497	55 450
Multiply observed and flagged manually	29 178	28 248	25 662	24 296	19 224	–
Multiply observed with a total detection likelihood of at least six	251 555	241 880	224 178	208 921	181 132	49 935
Multiply observed with a total detection likelihood of at least ten	213 812	205 394	189 556	176 680	153 487	42 077
Maximum number of observations per source	77	70	65	65	40	23
Maximum number of exposures per source	170	155	140	140	103	69
Total number of measurements	1 683 264	1 592 263	1 421 966	1 322 299	1 033 264	216 393
Maximum on-time per source	2.8 Ms	2.8 Ms	2.8 Ms	2.8 Ms	1.9 Ms	1.3 Ms