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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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slide1

Low energy calibration with the Vela SNR

EPIC Calibration & Operations Meeting

Mallorca, Spain, 2009 March 31 – April 1

slide2

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

slide5

Comparison: trends at 0.57 keV and 1.49 keV

Vela SNR

0.57 keV

internal calibration source

1.49 keV

slide6

Comparison: trends at 0.57 keV and 1.49 keV

0.574 keV (Vela SNR)

1.486 keV (Al-K, scaled)

slide7

Internal calibration source onboard XMM-Newton / EPIC-pn

Al-K Mn-K

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

slide8

Superposition of all Vela SNR observations in FF mode

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

slide9

Spatial properties of the absolute energy scale

0.40 – 0.74 keV

photon map

(singles)

 adaptive binning into subareas of similar signal

slide10

Spatial properties of the absolute energy scale

vertical binning according to response matrices

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

 422 fields

slide11

Preparations for a joint fit

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

slide12

Spectral model used ( E = 0.43 – 0.74 keV )

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

slide15

result:

energy scale spatially homogeneous within ±10 eV

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

slide17

Checks for stability and reproducibility of the result

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

slide32

EPIC-Cal Meeting, MPE-Garching, Germany, 2006 May 4

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
slide33

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

slide34

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

slide35

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

slide36

Low energy calibration with the Vela SNR

EPIC Calibration & Operations Meeting

Mallorca, Spain, 2009 March 31 – April 1

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