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Suppression of the low-energy noise: an improved approach

Suppression of the low-energy noise: an improved approach

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Suppression of the low-energy noise: an improved approach

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  1. Suppression of the low-energy noise: an improved approach Suppression of the low-energy noise

  2. EPIC-pn detector noise 50.7 ks closed FF (rev 059) Quadrant 0 adu Suppression of the low-energy noise

  3. Suppression of the EPIC-pn detector noise Original method (“method 1”), implemented in the SAS task epreject: Use closed exposures to determine the noise properties (spatially and spectrally) and use them as input for the Monte-Carlo filtering Suppression of the low-energy noise

  4. closed FF rev 462 23.2 ks 3 0 50 0 application of the original method (implemented in the SAS task epreject) Suppression of the low-energy noise

  5. Vela SNR FF rev 534 38.8 ks withoutepreject Suppression of the low-energy noise

  6. Vela SNR FF rev 534 38.8 ks with epreject application of the original method (implemented in the SAS task epreject) Suppression of the low-energy noise

  7. EPIC-pn detector noise in LW mode closed, 61 ks, rev 790 Suppression of the low-energy noise

  8. 20 50 adu EPIC-pn detector noise (LW) Original method (“method 1”): Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source 100% suppression Suppression of the low-energy noise

  9. 20 50 adu EPIC-pn detector noise (LW) Original method (“method 1”): Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source 99% suppression Suppression of the low-energy noise

  10. 20 50 adu EPIC-pn detector noise (LW) Original method (“method 1”): Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source 90% suppression Suppression of the low-energy noise

  11. 20 50 adu EPIC-pn detector noise (LW) Original method (“method 1”): Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source 70% suppression Suppression of the low-energy noise

  12. 20 50 adu EPIC-pn detector noise (LW) Original method (“method 1”): Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source 50% suppression Suppression of the low-energy noise

  13. 20 50 adu EPIC-pn detector noise (LW) • This method works well for bright sources, but may cause an apparent deficit of photons between ~150 and 250 eV for faint sources • Other problem: inhomogeneous residual noise at ~20 adu Suppression of the low-energy noise

  14. 20 adu images after epreject Vela SNR FF rev 740 29.4 ks default noiseparameters adjusted Suppression of the low-energy noise

  15. Long closed LW exposures Suppression of the low-energy noise

  16. Suppression of the EPIC-pn detector noise Alternative method (“method 2”): Try to determine the noise properties (from closed exposures) at higher energies and extrapolate them down to 20 adu Suppression of the low-energy noise

  17. EPIC-pn detector noise (LW) rev 790 (closed), all events range used for fit: 40-100 adu range shown: 20-400 adu x log y log Suppression of the low-energy noise

  18. EPIC-pn detector noise (LW) rev 790 (closed), all events range used for fit: 40-100 adu range shown: 20-400 adu x log y log Suppression of the low-energy noise

  19. EPIC-pn detector noise (LW) rev 790 (closed), all events range used for fit: 40-100 adu range shown: 20-400 adu x log y log for comparison: method 1 Suppression of the low-energy noise

  20. EPIC-pn detector noise (LW) method 2, noise properties derived from rev 790 (closed) applied to rev 790 Suppression of the low-energy noise

  21. EPIC-pn detector noise (LW) method 2, noise properties derived from rev 790 (closed) applied to rev 546 Suppression of the low-energy noise

  22. EPIC-pn detector noise (LW) method 2, noise properties derived from rev 790 (closed) applied to rev 553 Suppression of the low-energy noise

  23. EPIC-pn detector noise (LW) method 2, noise properties derived from rev 790 (closed) applied to rev 730 Suppression of the low-energy noise

  24. EPIC-pn detector noise (LW) method 2, noise properties derived from rev 790 (closed) applied to rev 974 Suppression of the low-energy noise

  25. EPIC-pn detector noise (LW) • Method 2 would work well if there were no temporal changes of the low-energy noise Whenever the noise properties of the sample and template are (slightly) different, the subtraction leads to residuals in the spectra and the images Other problem: assumption of constant noise properties along CCD rows (required in order to get enough statistics) not valid for raw events: Suppression of the low-energy noise

  26. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 20 adu Suppression of the low-energy noise

  27. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 21 adu Suppression of the low-energy noise

  28. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 22 adu Suppression of the low-energy noise

  29. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 23 adu Suppression of the low-energy noise

  30. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 24 adu Suppression of the low-energy noise

  31. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 25 adu Suppression of the low-energy noise

  32. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 26 adu Suppression of the low-energy noise

  33. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 27 adu Suppression of the low-energy noise

  34. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 28 adu Suppression of the low-energy noise

  35. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 29 adu Suppression of the low-energy noise

  36. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 30 adu Suppression of the low-energy noise

  37. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 31-35 adu Suppression of the low-energy noise

  38. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 36-40 adu Suppression of the low-energy noise

  39. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 41-45 adu Suppression of the low-energy noise

  40. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 46-50 adu Suppression of the low-energy noise

  41. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 51-55 adu Suppression of the low-energy noise

  42. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 56-60 adu Suppression of the low-energy noise

  43. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 61-70 adu Suppression of the low-energy noise

  44. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 71-80 adu Suppression of the low-energy noise

  45. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 81-90 adu Suppression of the low-energy noise

  46. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 91-100 adu Suppression of the low-energy noise

  47. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 101-120 adu Suppression of the low-energy noise

  48. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 121-140 adu Suppression of the low-energy noise

  49. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 141-180 adu Suppression of the low-energy noise

  50. EPIC-pn detector noise (LW) rev 790 61 ks closed after offset corrections all events 181-250 adu Suppression of the low-energy noise