Experience with combined Fe 55 / Vela SNR calibration

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EPIC Calibration Meeting, MadridEPIC Calibration Meeting, Madrid Experience with combined FeExperience with combined Fe5555/Vela SNR calibration/Vela SNR calibration K. Dennerl, 2010 March K. Dennerl, 2010 March 2323

Experience with combined FeExperience with combined Fe5555 / Vela SNR calibration / Vela SNR calibration

Madrid, 2010 March 23-24Madrid, 2010 March 23-24

EPIC Calibration & Operations Meeting

NRCO 81

EPIC Calibration Meeting, MallorcaEPIC Calibration Meeting, Mallorca Experience with combined FeExperience with combined Fe5555/Tycho SNR /Tycho SNR calibrationcalibration

K. Dennerl, 2008 April 8K. Dennerl, 2008 April 8

Internal calibration source onboard XMM-Newton / EPIC-pn

Al-K Mn-K

30 ks in 2000

210 ks in 2008

390 ks in 2010

1.4 Ms in 2015

30 ks in 2000

210 ks in 2008

390 ks in 2010

1.4 Ms in 201510 ks

half-life of Fe55: 2.7 yr

activity in 2010:

7.7% of activity in 2000

Motivation: decay of the internal calibration source

81 0) offset map calculation

1) cal-closed

2) thin (Vela SNR)

3) cal-thin (Vela SNR)

Strategy:

1. start with regular Fe55 exposure

2. perform regular Vela observation

3. finish with Vela + Fe55 observation

Questions:

1. does Vela disturb the calibration exposure ?

2. does the internal calibration source disturb the Vela observation ?

same offset map used in all exposures,

all exposures performed in a contiguous mode, within one revolution

sequence: cal-closed thin cal-thin

NRCO 81

calclosed: 2009-10-24T22:35:25.790 2009-10-25T09:46:49.729thin: 2009-10-25T09:54:02.576 2009-10-25T21:14:05.294calthin: 2009-10-25T21:21:09.369 2009-10-26T08:53:37.906

red: 0.3 - 0.7 keV, 0 – 25 cts/pxgreen: 1.2 – 1.8 keV, 0 – 5 cts/pxblue: 5.0 – 7.0 keV, 0 – 4 cps/px

Spectra and images, derived from singles

cal-closed thin cal-thin

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

Method: compare line position in 30 subfields* for every quadrant

*with sufficient photon statistics

errors determined

from the spread of

the line energies

cal-closed, quadrant 0 cal-thin (Vela SNR), quadrant 0

1179.1 ± 2.31178.5 ± 3.1 + 0.6 adu

1178.5 ± 1.9

1179.6 ± 1.7 + 1.1 adu

1178.3 ± 1.6

1178.8 ± 1.4 + 0.5 adu

1177.9 ± 3.2

1178.0 ± 2.2 + 0.1 adu

quadrant 0: +0.6 adu

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..

1178.5 ± 3.1 1179.2 ± 2.3 + 0.7 adu

1179.7 ± 1.7 + 1.2 adu1178.5 ± 1.8

1178.9 ± 1.3 + 0.5 adu1178.4 ± 1.6

1178.4 ± 3.1 + 0.1 adu1178.3 ± 2.3

singles

photons in cal-thin:

shift ?

same analysis with first singles..

photons in cal-thin:

shift ?

same analysis with first singles.. energy shift not

caused by (visible)

precursors

first singles

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..

cal-closed, all singles cal-thin, all singles

1σ errors determined from Δχ2 = +1

cal-closed, first singles cal-thin, first singles

the energy shift happens between the observations

an energy shift happens also at Al-K

cal-closed, all singles

spectrum over the full detector and the whole time interval

cal-thin, all singles

E = (5.8945 +/ - 0.0005) keV E = (5.8995 +/ - 0.0005) keV

from total exposures:from total exposures:

+ (5.0 ± 0.7) eV

cal-closed, all singles

E = (1.4920 +/- 0.0004) keV E = (1.4965 +/- 0.0007) keV+ (4.5 ± 0.8) eV

Does the presence of the internal Fe55 source affect the calibration measurements with the Vela SNR ?

comparison thin cal-thin

thin, all singles

E = ( 0.5862 +/- 0.0004) keV E = (0.5865 +/- 0.0004) keV

+ (0.3 ± 0.6) eV

no energy shift happens at OVII between thin and cal-thin

thin, all singles cal-thin, all singles

Does the presence of the internal Fe55 source affect the calibration measurements with the Vela SNR ?OVII

E = (0.5862 +/- 0.0004) keV E = (0.5865 +/- 0.0004) keV

E = (1.4920 +/- 0.0004) keV E = (1.4965 +/- 0.0007) keVE = (1.493 +/- 0.002) keV

E = (5.8945 +/ - 0.0005) keV E = (5.8995 +/ - 0.0005) keV

Summary: line energies (all singles, whole detector)

+ (0.3 ± 0.6) eV

+ (4.5 ± 0.8) eV

+ (5.0 ± 0.7) eV

Summary of NRCO 81

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.

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.

Experience with combined FeExperience with combined Fe5555 / Vela SNR calibration / Vela SNR calibration

Madrid, 2010 March 23-24Madrid, 2010 March 23-24

EPIC Calibration & Operations Meeting

NRCO 81

Experience with combined Fe 55 / Vela SNR calibration

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