Catalogue 4XMM-DR9s

4XMM-DR9s logo

The 4XMM-DR9s catalogue of serendipitous sources from overlapping XMM-Newton observations has been compiled from 1 329 groups, comprising 6 604 overlapping good-quality XMM-Newton observations. They were selected from the public observations taken between 2000 February 3 and 2018 November 13 which overlap by at least one arcminute in radius and are not affected by very high background emission. It contains 288 191 unique sources, 218 283 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. Updates compared to the previous version include a significantly larger sample of observations, event-based astrometric corrections before running source detection, revised background parameters, and manually set flags marking obviously spurious detections.

The catalogue is available for download as a single file

in FITS format and browsable via the web-based interfaces

The XSA provides access to the auxiliary data products 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.

Catalogue overview

4XMM-DR9s   3XMM-DR7s
Number of stacks 1 329 434
Number of observations 6 604 1 789
First observation included 2000/02/03 2000/02/20
Last observation included 2018/11/13 2016/04/02
Approximate sky coverage 485 sq. deg. 150 sq. deg.
Approximate multiply observed sky area 300 sq. deg. 100 sq. deg.
Total number of sources 288 191 71 951
Sources with several contributing observations 218 283 57 665
Multiply observed sources with flag 0 or 1 191 497 55 450
Multiply observed and flagged manually 19 224
Multiply observed with a total detection likelihood of at least six 181 132 49 935
Multiply observed with a total detection likelihood of at least ten 153 487 42 077
Multiply observed extended sources with flag 0 or 1 9 457 2 648
Multiply observed point sources with VAR_PROB ≤ 1% and flag 0 or 1 20 588 5 358
Multiply observed point sources with VAR_PROB ≤ 10–5 and flag 0 or 1 7 478 1 839