XMM EPIC MOS Steve Sembay ([email protected]) Mallorca 01/04/09 A Phenomenological approach to the...

XMMEPICMOS

Steve Sembay ([email protected])Mallorca 01/04/09

A Phenomenological approach to the MOSdetector response.

Steve Sembay

Phenomenological Theory. A theory which expresses mathematically the results of observed phenomena without paying detailed attention to their fundamental significance.

i.e. If you don't understand it....describe it !

XMMEPICMOS


Motivation:

Develop a descriptive model of the RMF that is computationally quick to generate and provides a “reasonably” accuratedescription of the spatial and temporal variations observed in the MOS RMF (i.e. the patch)

A “quick” RMF makes deriving RMF parameters viaoptimisation procedures practical and allows one to providea description for changes to the RMF much more quickly than“manual tweaking”

Such a model could be used to inform a more physically realisticmodel.

XMMEPICMOS


tnmin optimisationprogram in IDL

IACHEC modelfor 1E0102

Automated RMF fitting

XMMEPICMOS


x (μm)1.0

0.0

f(x)

f(x) = α + (β E0)

E(x) = f(x) E0

I(e) = ∑I(x)exp(E(x),e,σ) dx

α = α(E0), β = β(E

0)

Current Empirical Surface Loss Model

XMMEPICMOS


Nov 1997 - FM1 = Flight Spare “Calibrate Orsay”

Apr 1998 – FM2 = MOS2 6 CCDs (1 faulty)Camera rebuild in June 1998

July 1998 – FM3 = MOS1 7 CCDs

Nov 1998 – FM1 = Flight Spare 7 CCDs

Orsay MOS Calibration Campaign

Data on 20 EPIC-MOS CCDsMOS1 - All 7 CCDs in orbit have Orsay ground cal dataMOS2 - Due to rebuild, 4 CCDs in orbit have Orsay ground cal data

XMMEPICMOS


FM1 MOS1 MOS2FM1 MOS1 MOS2FM1 MOS1 MOS2

Orsay Data

20 CCDs

Einput

= 350 eV

XMMEPICMOS


Orsay Data

20 CCDs

Einput

= 350 eV

Re-order bystrength of losspeak.

“Good”

“Bad”

What if the way the shape changes from “good” to bad” from CCD to CCD (at a given energy) is similar to the way the shape

of the loss peak in the patch changes with time on the central CCD (at that energy).

XMMEPICMOS


Position and Size of Loss Component have relatively simplefunctional forms versus energy

0.73

MOS1CCD1

XMMEPICMOS


Position of loss peak / position of main peak

Fraction ofcounts in losspeak

These two quantities are correlated!

XMMEPICMOS


The position of the loss peak relative to the main peak(The Epeak parameter) is constant with energy (at leastabove ~300 eV)

The strength of loss peak follows a simple exponentialrelation with energy.

The normalisation of this relation is correlated with Epeak.

In this simple descriptive model, a single parameter, Epeakdefines the position and strength of the loss peak as a functionof energy.

XMMEPICMOS


Descriptive Model: The VRMF Model Main Peak

Blue Wing:Gaussian

Red Wing:Voigt Function

= Gaussian convolved with a Lorentian.

Dampening factor= 0 (Gaussian)> 0 (Lorentz-like)

XMMEPICMOS


Descriptive Model: The VRMF Model Loss Peak

Blue Wing:Triangular

Red Wing:Gaussian

Time to generate 2400 x 2400 SAS p0 rmf ~ 60 seconds

Time to generate 2400 x 2400 VRMF p0 rmf ~ 2 seconds

XMMEPICMOS


0065 1082 1165

Comparing the Model to 1E0102 (MOS1)

XMMEPICMOS


IACHEC modelfor 1E0102

Automated RMF fitting

Epeak

σ = a + b*sqrt(E)

Global Norm

4 Free Parameters

XMMEPICMOS


χ2 (SAS) χ2 (VRMF) EpeakRev 0065 2.45 2.40 0.78Rev 1082 4.06 2.01 0.70Rev 1165 5.02 1.78 0.46

XMMEPICMOS


χ2 (SAS) χ2 (VRMF) EpeakRev 0065 2.45 2.40 0.78Rev 1082 4.06 2.01 0.70Rev 1165 5.02 1.78 0.46

c.f. Orsay Epeak = 0.73

XMMEPICMOS


Lines ~0.8-0.85 keV too strong ?

XMMEPICMOS


Conclusions:

1) It is possible to mathematically describe the energy dependentshape of the loss component of the RMF, as observed in our ground cal, with a model which has one dependent parameter = Epeak. (True > 300-350 eV)

2) Deriving Epeak assuming the IACHEC 1E0102 model givesvalues consistent with that measured at Orsay for off-axis andconsistent with our “picture” of the patch for on-axis.

3) What about low energies? Below ~300-350 eV

XMMEPICMOS


The Curious Case of Konrad's Comet

Obs:3.29 cts/s

Model:3.33 cts/s

χ2 = Bad!

XMMEPICMOS



Obs:3.25 cts/s

Model:3.37 cts/s

XMMEPICMOS



XMMEPICMOS


Orsay Data

20 CCDs

Einput

= 350 eV

Re-order bystrength of losspeak.

“Good”

“Bad”

XMM EPIC MOS Steve Sembay ([email protected]) Mallorca 01/04/09 A Phenomenological approach to the...

Documents

Transcript of XMM EPIC MOS Steve Sembay ([email protected]) Mallorca 01/04/09 A Phenomenological approach to the...