1. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 Mallorca, Spain, 2009 March 31 – April 1 EPIC Calibration & Operations Meeting Update of EPIC pn noise suppression

2. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 “Noise events”: events which are not caused by photons, mainly evident at low Pulse Height Amplitudes (PHAs) “Noise events”: events which are not caused by photons, mainly evident at low Pulse Height Amplitudes (PHAs) 50.7 ks closed FF quadrant 0, rev 059 PHA [adu] number of events

3. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 raw_y 20-65 adu noise Previous attempts to suppress the noise events were based on their spatial/spectral characteristics (  epreject )

4. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 Previous attempts to suppress the noise events were based on their spatial/spectral characteristics (  epreject ) without noise suppression (epreject) Vela SNR, FF, rev 534, 38.8 ks with noise suppression (epreject)

5. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 However, the spatial/spectral characteristics of noise events turned out to be not sufficiently stable in time to achieve in all cases a satisfactory noise suppression with the concept of a temporally constant noise model. 2050 adu

6. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 However, the spatial/spectral characteristics of noise events turned out to be not sufficiently stable in time to achieve in all cases a satisfactory noise suppression with the concept of a temporally constant noise model. 2050 adu

7. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 An improved approach would be to scale the temporally constant noise model individually to each observation, by using information derived from the particular observation. This approach is under investigation, but it is fairly sophisticated, and it is not clear yet whether it will be reliable enough for general usage.

8. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 An improved approach would be to scale the temporally constant noise model individually to each observation, by using information derived from the particular observation. This approach is under investigation, but it is fairly sophisticated, and it is not clear yet whether it will be reliable enough for general usage.

9. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 An improved approach would be to scale the temporally constant noise model individually to each observation, by using information derived from the particular observation. This approach is under investigation, but it is fairly sophisticated, and it is not clear yet whether it will be reliable enough for general usage. In the process of investigating the temporal properties of noise events, it was found that individual frames are considerably noisier than the average. If these frames are rejected, the signal to noise ratio can be improved at low energies. This method is so straightforward that it can be easily implemented.

10. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 closed FF closed, rev 0462, 23 ks, CCD 1 Number of frames containing NEVT_FRM events within 20..30 adu NEVT_FRM > 7

11. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 closed FF closed, rev 0462, 23 ks, CCD 1 NEVT_FRM > 5 Number of frames containing NEVT_FRM events within 20..30 adu

12. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 closed FF closed, rev 0462, 23 ks, CCD 1 – 6 Number of frames containing NEVT_FRM events within 20..30 adu CCD 1 CCD 2 CCD 3 CCD 4 CCD 5 CCD 6

13. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 Number of frames containing NEVT_FRM events within 20..30 adu closed FF closed, rev 0462, 23 ks, CCD 7 - 12 CCD 7 CCD 8 CCD 9 CCD 10 CCD 11 CCD 12

14. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 closed EPIC-pn noise (LW), rev 0790, 61 ks closed, after offset corrections, all events 20 adu21 adu22 adu23 adu24 adu 25 adu26 adu27 adu28 adu29 adu 30 adu31-35 adu36-40 adu41-45 adu46-50 adu

15. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 rev 462 closed 23 ks closed FF no offset corrections all events 30-50 adu raw data At 30-50 adu, “noise” creates mainly undefined patterns:

16. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 rev 462 closed 23 ks closed FF no offset corrections non-singles processed data At 30-50 adu, “noise” creates mainly undefined patterns: 30-50 adu

17. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 rev 462 closed 23 ks closed FF no offset corrections singles processed data At 30-50 adu, “noise” creates mainly undefined patterns: 30-50 adu

18. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 singles, 20 – 30 adu, all frames LW thick, SNR 1E0102, rev 0803, 30 ks

19. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 total number of frames (reconstructed) number of frames with no event below 31 adu per CCD number of frames with 2 events below 31 adu per CCD SNR 1E 0102, rev 803, LW, thick, 30 ks number of frames with more than 9 events below 31 adu per CCD number of frames with 1 event below 31 adu per CCD

20. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 Number of frames containing NEVT_FRM events within 20..30 adu CCD 1 CCD 2 CCD 3 CCD 4 CCD 5 CCD 6 LW thick, SNR 1E0102, rev 0803, 30 ks, CCD 1 – 6

21. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 Number of frames containing NEVT_FRM events within 20..30 adu CCD 7 CCD 8 CCD 9 CCD 10 CCD 11 CCD 12 LW thick, SNR 1E0102, rev 0803, 30 ks, CCD 7 – 12

22. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 LW thick, SNR 1E0102, rev 0803, 30 ks imageimage maskimage mask applied

23. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 LW thick, SNR 1E0102, rev 0803, 30 ks

24. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 original imagecleaned imageremoved noise =+ LW thick, SNR 1E0102, rev 0803, 30 ks 20 – 30 adu, all events source practically invisible in removed events

25. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 LW thick, SNR 1E0102, rev 0803, 30 ks, CCD 4 before / after removal of noisy frames 20 – 30 adu all events same intensity cuts

26. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 singles, 0.3-3.0 keV mask for source regions to be avoided for noise determination source region mask In order to determine the noise properties, some areas have to be ignored: SNR 1E 0102, rev 803, LW, thick, 30 ks

27. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 final mask, excluding source regions and noisy pixelsnoisy pixel mask SNR 1E 0102, rev 803, LW, thick, 30 ks In order to determine the noise properties, some areas have to be ignored:

28. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 unfiltered data singles, 24 adu after noisy frame removal SNR 1E 0102, rev 803, LW, thick, 30 ks

29. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31

30. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 =+ singles, 20 – 30 adu, frames with more than 2 events below 31 adu per frame and CCD singles, 20 – 30 adu, frames with 1 or 2 events below 31 adu per frame and CCD singles, 20 – 30 adu, all frames LW thick, SNR 1E0102, rev 0803, 30 ks

31. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 unfiltered dataafter noisy frame removal singles, 120-130 eV LW thick, SNR 1E0102, rev 0803, 30 ks

32. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 epreject

33. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 At which stage should “noisy frames” be identified and removed ? raw data  recombined event list raw data: events not yet recombined  better discrimination of noisy frames  standard processing does not allow removal of frames before epevents  major changes of SAS may be required  time-consuming tasks (epevents..) need to be repeated in case of iterations  screening improves signal/noise ratio only at low energies and would cause unnecessary loss of exposure at higher energies recombined events list: quick and easy application: optional task at the end of the pipeline processing  number of events within PHA range not available anymore (patterns)

34. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 Solution: separate the determination of noisy frames from their removal !  only one change required for pipeline processing: keep the “rawevents.dat” files; they contain information about the raw events (no recombination yet performed) time tags: unique identification of frames possible, also in the final event list ! noise suppression is based on the removal of complete frames  no need for repeating the pattern recognition and energy correction, only exposure needs to be updated if frames are removed  one additional task (e.g. “epnoise”) would be sufficient: - filter a copy of the final event list according to criteria derived from the “rawevents.dat” files and other input: masks, adu range and cutoff criteria (e.g. discrepancy between observed distribution and poissonian fit) - update the exposure extensions  quick iterations possible  output from source detection could be used for creating masks

35. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 optional image mask upper ADU threshold “epnoise” raweventsxx.dat “Final” cleaned event file possible implementation:

36. EPIC Calibration Meeting, Mallorca Update of EPIC pn noise suppression K. Dennerl, 2009 March 31 Mallorca, Spain, 2009 March 31 – April 1 EPIC Calibration & Operations Meeting Update of EPIC pn noise suppression