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

Level (eV) te (-90°C) (-100°C) (-120°C) 0.17 0.44 Emission timescales for filled traps (Holland et al. 1993, NIMS, A326, 335) Level (eV) te (-90°C) (-100°C) (-120°C) 0.17 0.07 µs 0.19 µs 1.1 µs 0.44 3.8 s 22.9 s 1.4 x 103 s 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

MOS v RGS Line Energy: N line ~ 432 eV J. Carter (Mallorca 06) Most MOS Large Window Mode SW Obs.

Closed Cal Al line in small window mode

Closed Cal Al line in small 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” 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 Count Rate v Offset In Boxes Before/After Cooling

MOS2 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 Readout direction Flag Bad

Flagged events

|Summary: 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.