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Experience with combined Fe 55 / Vela SNR calibration

Experience with combined Fe 55 / Vela SNR calibration. NRCO 81. EPIC Calibration & Operations Meeting. Madrid, 2010 March 23-24. Internal calibration source onboard XMM-Newton / EPIC-pn. Al-K Mn-K. 30 ks.

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Experience with combined Fe 55 / Vela SNR calibration

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  1. Experience with combined Fe55 / Vela SNR calibration NRCO 81 EPIC Calibration & Operations Meeting Madrid, 2010 March 23-24

  2. Internal calibration source onboard XMM-Newton / EPIC-pn Al-K Mn-K

  3. 30 ks Motivation: decay of the internal calibration source • half-life of Fe55: 2.7 yr • activity in 2010: 7.7% of activity in 2000 • 30 ks in 2000 •  210 ks in 2008 • 390 ks in 2010 • 1.4 Ms in 2015 10 ks

  4. NRCO 81

  5. 0) offset map calculation 1) cal-closed 2) thin (Vela SNR) 3) cal-thin (Vela SNR) NRCO 81

  6. NRCO 81

  7. Questions: • does Vela disturb the calibration exposure ? • does the internal calibration source disturb the Vela observation ? • Strategy: • start with regular Fe55 exposure • perform regular Vela observation • finish with Vela + Fe55 observation NRCO 81 same offset map used in all exposures, all exposures performed in a contiguous mode, within one revolution sequence: cal-closed  thin  cal-thin

  8. Spectra and images, derived from singles cal-closed thin cal-thin red: 0.3 - 0.7 keV, 0 – 25 cts/px green: 1.2 – 1.8 keV, 0 – 5 cts/px blue: 5.0 – 7.0 keV, 0 – 4 cps/px calclosed: 2009-10-24T22:35:25.790 2009-10-25T09:46:49.729 thin: 2009-10-25T09:54:02.576 2009-10-25T21:14:05.294 calthin: 2009-10-25T21:21:09.369 2009-10-26T08:53:37.906

  9. Does the presence of the Vela SNR (and the different filter wheel position) affect the calibration measurements with the internal Fe55 source ?  comparison cal-closed cal-thin

  10. Method: compare line position in 30 subfields* for every quadrant *with sufficient photon statistics errors determined from the spread of the line energies

  11. cal-closed, quadrant 0 cal-thin (Vela SNR), quadrant 0 all singles + 0.6 adu 1178.5 ± 3.1 1179.1 ± 2.3

  12. cal-closed, quadrant 1 cal-thin (Vela SNR), quadrant 1 all singles + 1.1 adu 1178.5 ± 1.9 1179.6 ± 1.7

  13. cal-closed, quadrant 2 cal-thin (Vela SNR), quadrant 2 all singles + 0.5 adu 1178.3 ± 1.6 1178.8 ± 1.4

  14. cal-closed, quadrant 3 cal-thin (Vela SNR), quadrant 3 all singles + 0.1 adu 1177.9 ± 3.2 1178.0 ± 2.2

  15. Does the presence of the Vela SNR (and the different filter wheel position) affect the calibration measurements with the internal Fe55 source ?  comparison cal-closed cal-thin  yes, systematic shift of Mn-Kα to higher energies: quadrant 0: +0.6 adu quadrant 1: +1.1 adu quadrant 2: +0.5 adu quadrant 3: +0.1 adu

  16. Does the presence of the Vela SNR (and the different filter wheel position) affect the calibration measurements with the internal Fe55 source ?  comparison cal-closed cal-thin  yes, systematic shift of Mn-Kα to higher energies: quadrant 0: +0.6 adu quadrant 1: +1.1 adu quadrant 2: +0.5 adu quadrant 3: +0.1 adu Main difference: presence of additional photons in cal-thin  could an inappropriate correction of precursor induced CTI changes cause the shift ?  same analysis with first singles..

  17. cal-closed, quadrant 0 cal-thin (Vela SNR), quadrant 0 all first singles + 0.7 adu 1178.5 ± 3.1 1179.2 ± 2.3

  18. cal-closed, quadrant 1 cal-thin (Vela SNR), quadrant 1 all first singles + 1.2 adu 1178.5 ± 1.8 1179.7 ± 1.7

  19. cal-closed, quadrant 2 cal-thin (Vela SNR), quadrant 2 all first singles + 0.5 adu 1178.4 ± 1.6 1178.9 ± 1.3

  20. cal-closed, quadrant 3 cal-thin (Vela SNR), quadrant 3 all first singles + 0.1 adu 1178.3 ± 2.3 1178.4 ± 3.1

  21. Does the presence of the Vela SNR (and the different filter wheel position) affect the calibration measurements with the internal Fe55 source ? singles first singles quadrant 0: +0.6 adu quadrant 1: +1.1 adu quadrant 2: +0.5 adu quadrant 3: +0.1 adu quadrant 0: +0.7 adu quadrant 1: +1.2 adu quadrant 2: +0.5 adu quadrant 3: +0.1 adu  comparison cal-closed cal-thin  yes, systematic shift of Mn-Kα to higher energies: Main difference: presence of additional photons in cal-thin: could an inappropriate correction of precursor induced CTI changes cause the shift ?  same analysis with first singles..  energy shift not caused by (visible) precursors

  22. Does the presence of the Vela SNR (and the different filter wheel position) affect the calibration measurements with the internal Fe55 source ?  The systematic energy shift of Mn-Kα when the Vela SNR is in the FOV is not due to imperfect modeling of (visible) precursors. Could this be a temporal effect due to, e.g., temperature changes ?  Splitting the exposures into pieces of the same length (~600s) and monitoring the line energy (from the whole detector) with XSPEC..

  23. Does the presence of the Vela SNR (and the different filter wheel position) affect the calibration measurements with the internal Fe55 source ? Mn-K  Splitting the exposures into pieces of the same length (~600s) and monitoring the line energy (from the whole detector) with XSPEC.. 1σ errors determined from Δχ2 = +1 cal-closed, all singles cal-thin, all singles

  24. Does the presence of the Vela SNR (and the different filter wheel position) affect the calibration measurements with the internal Fe55 source ? Mn-K  Splitting the exposures into pieces of the same length (~600s) and monitoring the line energy (from the whole detector) with XSPEC.. 1σ errors determined from Δχ2 = +1 cal-closed, first singles cal-thin, first singles

  25. cal-closed, first singles cal-thin, first singles cal-thin, all singles  the energy shift happens between the observations cal-closed, all singles

  26. Does the presence of the Vela SNR (and the different filter wheel position) affect the calibration measurements with the internal Fe55 source ?  an energy shift happens also at Al-K Al-K  Splitting the exposures into pieces of the same length (~600s) and monitoring the line energy (from the whole detector) with XSPEC.. 1σ errors determined from Δχ2 = +1 cal-closed, all singles cal-thin, all singles

  27. from total exposures: cal-closed, all singles cal-thin, all singles E = (5.8945 +/ - 0.0005) keV E = (5.8995 +/ - 0.0005) keV + (5.0 ± 0.7) eV spectrum over the full detector and the whole time interval spectrum over the full detector and the whole time interval

  28. from total exposures: cal-closed, all singles cal-thin, all singles + (4.5 ± 0.8) eV E = (1.4920 +/- 0.0004) keV E = (1.4965 +/- 0.0007) keV spectrum over the full detector and the whole time interval spectrum over the full detector and the whole time interval

  29. Does the presence of the internal Fe55 source affect the calibration measurements with the Vela SNR ?  comparison thin cal-thin

  30. from total exposures: thin, all singles cal-thin, all singles E = (0.5865 +/- 0.0004) keV E = ( 0.5862 +/- 0.0004) keV + (0.3 ± 0.6) eV spectrum over the full detector and the whole time interval spectrum over the full detector and the whole time interval

  31. Does the presence of the internal Fe55 source affect the calibration measurements with the Vela SNR ?  no energy shift happens at OVII between thin and cal-thin OVII  Splitting the exposures into pieces of the same length (~600s) and monitoring the line energy (from the whole detector) with XSPEC.. 1σ errors determined from Δχ2 = +1 thin, all singles cal-thin, all singles

  32. Summary: line energies (all singles, whole detector) cal-closed thin cal-thin E = (0.5862 +/- 0.0004) keV E = (0.5865 +/- 0.0004) keV + (0.3 ± 0.6) eV + (4.5 ± 0.8) eV E = (1.4920 +/- 0.0004) keV E = (1.493 +/- 0.002) keV E = (1.4965 +/- 0.0007) keV + (5.0 ± 0.7) eV E = (5.8945 +/ - 0.0005) keV E = (5.8995 +/ - 0.0005) keV

  33. Changing from cal-closed to cal-thin, with the Vela SNR in the FOV, increases the energies of Al-K and Mn-K by ~ 5 eV. No change in the line energy is observed at the OVII emission from the Vela SNR, if the detector is additionally irradiated with the internal calibration source. Summary of NRCO 81 cal-closed thin cal-thin

  34. Conclusions from NRCO 81 The change observed between cal-closed and cal-thin is not caused by deficiencies in the code for the precursor correction. It is, however, possible that photons/particles penetrating the thin filter release additional charge in the CCDs which is below the low energy threshold and thus not transmitted, but still capable of reducing the charge transfer losses by trap saturation. Independent of its origin, the fact that an energy shift is observed between the cal-closed and cal-thin observation indicates that cal-thin conditions may be more appropriate for exposures with the internal calibration source. Cal-thin (and probably also cal-medium and cal-thick) observations of suitable targets offer promising opportunities for future calibration exposures. The Vela SNR is definitively suited for such a purpose.

  35. Experience with combined Fe55 / Vela SNR calibration NRCO 81 EPIC Calibration & Operations Meeting Madrid, 2010 March 23-24

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