Low energy calibration with the Vela SNR
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Low energy calibration with the Vela SNR. EPIC Calibration & Operations Meeting. Mallorca, Spain, 2009 March 31 – April 1. Vela SNR: extended source with bright OVII emission.  excellent calibration source. 2001- 2007: 12 long FF observations,

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Low energy calibration with the Vela SNR

EPIC Calibration & Operations Meeting

Mallorca, Spain, 2009 March 31 – April 1


Vela SNR: extended source with bright OVII emission

 excellent calibration source

2001- 2007: 12 long FF observations,

several with different pointing coordinates and roll angles

 fairly homogeneous illumination of the detector




Comparison: trends at 0.57 keV and 1.49 keV internal calibration source:

Vela SNR

0.57 keV

internal calibration source

1.49 keV


Comparison: trends at 0.57 keV and 1.49 keV internal calibration source:

0.574 keV (Vela SNR)

1.486 keV (Al-K, scaled)


Internal calibration source onboard XMM-Newton / EPIC-pn internal calibration source:

Al-K Mn-K

inhomogeneous irradiation at Mn-K, illumination of quadrant 3 very poor


Superposition of all Vela SNR observations in FF mode internal calibration source:

0.40 – 0.74 keV

photon map (singles)

exposure map

maximum: 172 singles/pixel

total exposure (after removing times of background flares): ~300 ks

exposure corrected map


Spatial properties of the absolute energy scale internal calibration source:

0.40 – 0.74 keV

photon map

(singles)

 adaptive binning into subareas of similar signal


Spatial properties of the absolute energy scale internal calibration source:

vertical binning according to response matrices

horizontal binning adaptively, criterion: ~5000 single events within 400 – 740 eV (above background)

 422 fields


Preparations for a joint fit internal calibration source:

removal of periods of enhanced background

correction for local energy shifts due to errors in the offset map (epreject)

correction for energy shifts between the individual observations

correction for out-of-time events


Spectral model used ( E = 0.43 – 0.74 keV ) internal calibration source:

all line energies and widths coupled to reference line (O VII r)

relative line fluxes of O VII triplet fixed

continuum approximated by powerlow

8 fit parameters


Spectral model used ( E = 0.43 – 0.74 keV ) internal calibration source:


result: internal calibration source:

energy scale spatially homogeneous within ±10 eV

however, also evidence for systematic shifts in a ring-like pattern


Checks for stability and reproducibility of the result internal calibration source:

removal of periods of enhanced background

correction for local energy shifts due to errors in the offset map (epreject)

correction for energy shifts between the individual observations

correction for out-of-time events different binning, different spectral models


EPIC-Cal Meeting, T internal calibration source:übingen, Germany, 2003 Feb 3-5

1.186 keV (Ge-L)

9.874 keV (Ge-K)


EPIC-Cal Meeting, T internal calibration source:übingen, Germany, 2003 Feb 3-5

1.186 keV (Ge-L)

9.874 keV (Ge-K)


Printed Circuit Board internal calibration source:


EPIC-Cal Meeting, T internal calibration source:übingen, Germany, 2003 Feb 3-5

1.186 keV (Ge-L)

9.874 keV (Ge-K)


EPIC-Cal Meeting, T internal calibration source:übingen, Germany, 2003 Feb 3-5




Comparison with Mn-K internal calibration source:


Comparison with Mn-K internal calibration source:


Mn-K internal calibration source:


EPIC-Cal Meeting, MPE-Garching, Germany, 2006 May 4 internal calibration source:

20 adu image, rev 546

Correcting spatial inhomogeneities of the absolute energy scale

  • offsets in the energy scale due to errors in the offset map

  • column gain variations after launch

  • CTI changes due to residual light through the ventilation hole


Correcting spatial inhomogeneities of the absolute energy scale

  • offsets in the energy scale due to errors in the offset map

  • column gain variations after launch

  • CTI changes due to residual light through the ventilation hole

EPIC-Cal Meeting, Mallorca, Spain, 2007 Nov 6-7


Correcting spatial inhomogeneities of the absolute energy scale

  • offsets in the energy scale due to errors in the offset map

  • column gain variations after launch

  • CTI changes due to residual light through the ventilation hole

EPIC-Cal Meeting, Mallorca, Spain, 2007 Nov 6-7


Correcting spatial inhomogeneities of the absolute energy scale

  • offsets in the energy scale due to errors in the offset map

  • column gain variations after launch

  • CTI changes due to residual light through the ventilation hole

EPIC-Cal Meeting, Mallorca, Spain, 2009 March 31 – April 1


Low energy calibration with the Vela SNR scale

EPIC Calibration & Operations Meeting

Mallorca, Spain, 2009 March 31 – April 1


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