Investigation into the strong residuals seen
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Investigation into the strong residuals seen near the Oxygen edge in MOS spectra of bright continuum sources. Rate Dependent CTI effect ? Steve Sembay. Event 1. Readout direction. Event 2. Trap. Emission timescales for filled traps (Holland et al. 1993, NIMS, A326, 335).

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Investigation into the strong residuals seen

near the Oxygen edge in MOS spectra of

bright continuum sources.

Rate Dependent CTI effect ?

Steve Sembay


Event 1

Readout direction

Event 2

Trap


Emission timescales for filled traps

(Holland et al. 1993, NIMS, A326, 335)

σn electron capture cross section

Xn entropy factor

υth electron thermal velocity

Ncdensity of states in conduction band

E energy level of trap

T temperature


Emission timescales for filled traps

(Holland et al. 1993, NIMS, A326, 335)

c.f. row transfer time of MOS = 15 µs


Around O edge χ2 -> 3.90 – 2.13 with gain offset = 8.7±1.0 eV


Around Si and Au edge: χ2 -> 1.025 – 0.998 Offset ~ 12.5 eV


SW Obs.

MOS v RGS Line Energy: N line ~ 432 eV J. Carter (Mallorca 06)

Most MOS Large Window Mode




Is there a “possible” gain shift at O: CTI dependent on rate?

Method 1: Analyse spectra from different regions


Sample of bright AGN/BL Lacs: The “Usual Suspects” rate?

3C 273 0094

MKN 421 0165

MKN 421 0171

3C 273 0277

H1426+428 0278

PKS2155-304 0362

PKS2155-304 0450

ARK 120 0679

H1426+428 0852

PKS2155-304 1095

PKS2155-304 1266

3C 273 1299

MKN 421 1357


MOS1 rate?

Count Rate v Offset

In Boxes

Before/After Cooling


MOS2 rate?

Count Rate v Offset

In Boxes

Before/After Cooling


Is there a “possible” gain shift at O: CTI dependent on rate?

Method 2: Flag precursor events from event file


Flag Bad rate?

Flag Bad

Readout direction



|Summary: rate?

Observed offset is not affected by removal of

precursor events in CCD RAWY direction

This suggests offset is not caused by incorrect

application of CTI measurement due to trap

filling in CCD.


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