XMM-Newton SAS Home Page
XMM-Newton Science Analysis System

emtaglenoise (emtaglenoise-1.3) [xmmsas_20230412_1735-21.0.0]


The task emtaglenoise writes a new attribute called LENOISnn, for each of the MOS CCDs nn = 02–07, to an EPIC MOS calibrated event list generated by emchain or emproc, or from the Pipeline Processing Products; the value of this attribute is 1 if the corresponding CCD is in an anomalous state, and 0 otherwise. The current version of this task does not consider the central CCD (nn = 01) at all; see Section 9 for details.

An `anomalous state' (Kuntz and Snowden, 2008 [1]), aka the `MOS2CCD5 effect' (Stuhlinger, 2008 [2]), or `electron noise in CCD 5 bands 1 and 2' (SSC data screening team), manifests itself as elevated event rates between 0 and 1 keV, forming a plateau in the event spectrum. This effect appears most frequently, but not exclusively, in MOS 2 CCD 5. It has been present in short phases since the beginning of the mission, but became continuous since Revolution 874. No switch-on/off has been detected within an observation; the event times are consistent with Poisson statistics, and the spatial distribution is fairly (but not entirely) homogeneous both within and outside the field of view. Events rarely repeat at the same pixels in the same observation. Patterns 0, 2 and 4 occur more frequently than in ordinary events.

Both Kuntz and Snowden and Stuhlinger have proposed ways to identify the presence of this effect given an EPIC MOS observation. As of January 2009, the true cause of the effect is as yet unknown, and there has not been an effective method for its correction. We implement Kuntz and Snowden's method of identification with this SAS task.

The optional parameter filterbadccds, if set, allows the user to filter all events in all CCDs tagged as noisy out of the input DataSet. The optional parameter filteredset specifies the output filename.

XMM-Newton SOC -- 2023-04-16