Catalogue 4XMM-DR12s

The 4XMM-DR12s catalogue of serendipitous sources from overlapping XMM-Newton observations has been compiled from 1 620 groups of 9 355 overlapping XMM-Newton observations. They were taken between 2000 February 1 and 2021 December 4 and overlap by at least one arcminute in radius. The catalogue contains 386 043 unique sources, 298 626 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. 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. Besides a larger sample of observations compared to the previous data release, PSF photometry on poor-quality exposures has been introduced with this catalogue version. If these exposures overlap with higher-quality exposures, they are discarded from source detection in order not to contaminate the detection quality in the stack. Now, fluxes and flux-related parameters are derived for all sources at the position and extent with which they have been discovered in the detection run on the good exposures. The number of parameter measurements (total number of observations of all unique sources) has thus increased to almost 1.6 million. 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_v3.0_4xmmdr12s.fits.gz [1.2 GB] in FITS format and browsable via the web-based interfaces

• XSA at ESA’s XMM-Newton SOC
• XSA 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-DR12s is available in FITS format: xmmstack_v3.0_4xmmdr12s_obslist.fits.gz [1.8 MB]

Watchout: From two stacks, the deepest regions were excluded from the processing for technical reasons: the innermost part of M31 and the Galactic Centre.

	4XMM-DR12s	4XMM-DR11s	4XMM-DR10s	4XMM-DR9s	3XMM-DR7s
Number of stacks	1 620	1 475	1 396	1 329	434
Number of observations	9 355	8 292	7 803	6 604	1 789
First observation included	2000/02/01	2000/02/03	2000/02/03	2000/02/03	2000/02/20
Last observation included	2021/12/04	2020/12/17	2019/12/14	2018/11/13	2016/04/02
Approximate sky coverage	625 sq. deg.	560 sq. deg.	540 sq. deg.	485 sq. deg.	150 sq. deg.
Approximate multiply observed sky area	400 sq. deg.	350 sq. deg.	335 sq. deg.	300 sq. deg.	100 sq. deg.
Total number of sources	386 043	358 809	335 812	288 191	71 951
Sources with several contributing observations	298 626	275 440	256 213	218 283	57 665
Multiply observed sources with flag 0 or 1	252 445	233 542	216 699	191 497	55 450
Multiply observed and flagged manually	28 248	25 662	24 296	19 224	–
Multiply observed with a total detection likelihood of at least six	241 880	224 178	208 921	181 132	49 935
Multiply observed with a total detection likelihood of at least ten	205 394	189 556	176 680	153 487	42 077
Multiply observed point sources with VAR_PROB≤1% and flag 0 or 1	28 587	23 424	21 672	20 588	5 358
Multiply observed point sources with VAR_PROB≤10–5 and flag 0 or 1	10 447	8 326	7 728	7 478	1 839
Maximum number of observations per source	70	65	65	40	23
Maximum number of exposures per source	155	140	140	103	69
Total number of measurements	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	1.9 Ms	1.3 Ms