1. Jonathan Gimeno Boal, UCM MODEL PSF EFFECTS OF PILE-UP Jonathan Gimeno Boal, UCM Tutor: Martin Stuhlinger

2. Jonathan Gimeno Boal, UCM Index: Selection of the observations. Determination of the counts per second. Selection of point sources. Determination of pile-up. Aim of the project. Next steps.

3. Jonathan Gimeno Boal, UCM Aim of the project: - Pile-up: Arrival of two or more photons within the readout time of the detectors. - For very bright sources there is a considerable amount of pile-up. - The centre of the PSF (Point Spread Function) gets distorted: Loss of counts at the centre of the PSF. Clean PSF.

4. Jonathan Gimeno Boal, UCM Aim of the project: Finally a 3D model of the PSF will be created :

5. Jonathan Gimeno Boal, UCM What is pile-up? Pattern pile-up: Two or more photons arriving next to each other in the same readout time. Photon pile-up: One single photon causes multiple pixel activation SAS task Epatplot output. Consequences: Less counts at the PSF centre. Shifts the spectrum towards higher energies.

6. Jonathan Gimeno Boal, UCM Selection of observations: ● Distinguish point sources : Observation Modes Filters

7. Jonathan Gimeno Boal, UCM Selection of point sources: In order to automatically determine if an observation is of an extended source or a point source the counts per second of two annuli around the source were calculated and then the ratio of these two count-rates. Point source: ratio = counts outer counts inner Extended source: >X% =[5%, 15%]

8. Jonathan Gimeno Boal, UCM Determination of counts per second: Once the number of events registered by the detectors and the exposure time is known, the count rate is determined.

9. Jonathan Gimeno Boal, UCM Source coordinates determination: Annuli extraction needsPSF centre, position of the source in the detector. First Attempt: Header sky coordinates Detector coordinates SAS task esky2det

10. Jonathan Gimeno Boal, UCM Chosen Solution: Find the centre of mass using IDL software Work on the Generated Image

11. Jonathan Gimeno Boal, UCM Similar ratio as in the extended source case: Avoid the identification of extended sources as strong pile-up observations Strong pile-up case Chosen Solution: Extended source singles doubles ratio: inner annulus outer annulus

12. Jonathan Gimeno Boal, UCM Ratio between the single events and double events in energy band of 1keV to 1.8keV. (TBD) singles doubles ~=2 Determination of pile-up: Pile-up singles doubles Clean PSF:

13. Jonathan Gimeno Boal, UCM Investigating in using vertical and horizontal bipixels: (S. Molendi & S. Sembay, 2003 “Assessing the EPIC spectral calibration in the hard band with a 3C 273 observation”) Determination of pile-up: Clean PSF: Probability true horizontal bipix. < True vertical bipix. Pile-up: Probability horizontal bipix. from 2 piled up photons = Vertical bipix. from 2 piled up photons To assess pile-up calculate: vertical bipix. pattern 0 On the source and inside an annulus, then calculate the ratio of both results. Repeat with horizontal bipix. and compare with vertical Equal ratios: pile-up free. Different ratios: Pile-up case.

14. Jonathan Gimeno Boal, UCM Sum up observations with clean PSF: Superposition. Normalize. Next steps: Summing up observations in different pile-ups and comparison with clean PSF: MOS camera examples.

15. Jonathan Gimeno Boal, UCM Questions ?