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Suppression of the low-energy noise: an improved approach. EPIC-pn detector noise. 50.7 ks closed FF (rev 059). Quadrant 0. adu. Suppression of the EPIC-pn detector noise. Original method (“method 1”), implemented in the SAS task epreject :

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slide2

EPIC-pn detector noise

50.7 ks closed FF (rev 059)

Quadrant 0

adu

Suppression of the low-energy noise

slide3

Suppression of the EPIC-pn detector noise

Original method (“method 1”), implemented in the SAS task epreject:

Use closed exposures to determine the noise properties (spatially and spectrally) and use them as input for the Monte-Carlo filtering

Suppression of the low-energy noise

slide4

closed FF rev 462 23.2 ks

3

0

50

0

application of the original method (implemented in the SAS task epreject)

Suppression of the low-energy noise

vela snr ff rev 534 38 8 ks
Vela SNR FF rev 534 38.8 ks

withoutepreject

Suppression of the low-energy noise

vela snr ff rev 534 38 8 ks1
Vela SNR FF rev 534 38.8 ks

with epreject

application of the original method (implemented in the SAS task epreject)

Suppression of the low-energy noise

slide7

EPIC-pn detector noise in LW mode

closed, 61 ks, rev 790

Suppression of the low-energy noise

slide8

20

50 adu

EPIC-pn detector noise (LW)

Original method (“method 1”):

Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures

Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source

100% suppression

Suppression of the low-energy noise

slide9

20

50 adu

EPIC-pn detector noise (LW)

Original method (“method 1”):

Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures

Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source

99% suppression

Suppression of the low-energy noise

slide10

20

50 adu

EPIC-pn detector noise (LW)

Original method (“method 1”):

Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures

Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source

90% suppression

Suppression of the low-energy noise

slide11

20

50 adu

EPIC-pn detector noise (LW)

Original method (“method 1”):

Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures

Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source

70% suppression

Suppression of the low-energy noise

slide12

20

50 adu

EPIC-pn detector noise (LW)

Original method (“method 1”):

Suppression of events below 50 adu according to a reference noise distribution deduced from long calclosed exposures

Shown in blue is the result of this method applied to a (long) calclosed exposure, to illustrate the effect on a very faint X-ray source

50% suppression

Suppression of the low-energy noise

slide13

20

50 adu

EPIC-pn detector noise (LW)

  • This method works well for bright sources, but may cause an apparent deficit of photons between ~150 and 250 eV for faint sources
  • Other problem: inhomogeneous residual noise at ~20 adu

Suppression of the low-energy noise

vela snr ff rev 740 29 4 ks

20 adu images after epreject

Vela SNR FF rev 740 29.4 ks

default noiseparameters adjusted

Suppression of the low-energy noise

slide15

Long closed LW exposures

Suppression of the low-energy noise

slide16

Suppression of the EPIC-pn detector noise

Alternative method (“method 2”):

Try to determine the noise properties (from closed exposures) at higher energies and extrapolate them down to 20 adu

Suppression of the low-energy noise

slide17

EPIC-pn detector noise (LW)

rev 790 (closed), all events

range used for fit: 40-100 adu

range shown: 20-400 adu

x log y log

Suppression of the low-energy noise

slide18

EPIC-pn detector noise (LW)

rev 790 (closed), all events

range used for fit: 40-100 adu

range shown: 20-400 adu

x log y log

Suppression of the low-energy noise

slide19

EPIC-pn detector noise (LW)

rev 790 (closed), all events

range used for fit: 40-100 adu

range shown: 20-400 adu

x log y log

for comparison: method 1

Suppression of the low-energy noise

slide20

EPIC-pn detector noise (LW)

method 2, noise properties derived from rev 790 (closed) applied to rev 790

Suppression of the low-energy noise

slide21

EPIC-pn detector noise (LW)

method 2, noise properties derived from rev 790 (closed) applied to rev 546

Suppression of the low-energy noise

slide22

EPIC-pn detector noise (LW)

method 2, noise properties derived from rev 790 (closed) applied to rev 553

Suppression of the low-energy noise

slide23

EPIC-pn detector noise (LW)

method 2, noise properties derived from rev 790 (closed) applied to rev 730

Suppression of the low-energy noise

slide24

EPIC-pn detector noise (LW)

method 2, noise properties derived from rev 790 (closed) applied to rev 974

Suppression of the low-energy noise

slide25

EPIC-pn detector noise (LW)

  • Method 2 would work well if there were no temporal changes of the low-energy noise

Whenever the noise properties of the sample and template are (slightly) different, the subtraction leads to residuals in the spectra and the images

Other problem: assumption of constant noise properties along CCD rows (required in order to get enough statistics) not valid for raw events:

Suppression of the low-energy noise

slide26

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

20 adu

Suppression of the low-energy noise

slide27

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

21 adu

Suppression of the low-energy noise

slide28

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

22 adu

Suppression of the low-energy noise

slide29

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

23 adu

Suppression of the low-energy noise

slide30

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

24 adu

Suppression of the low-energy noise

slide31

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

25 adu

Suppression of the low-energy noise

slide32

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

26 adu

Suppression of the low-energy noise

slide33

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

27 adu

Suppression of the low-energy noise

slide34

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

28 adu

Suppression of the low-energy noise

slide35

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

29 adu

Suppression of the low-energy noise

slide36

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

30 adu

Suppression of the low-energy noise

slide37

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

31-35 adu

Suppression of the low-energy noise

slide38

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

36-40 adu

Suppression of the low-energy noise

slide39

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

41-45 adu

Suppression of the low-energy noise

slide40

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

46-50 adu

Suppression of the low-energy noise

slide41

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

51-55 adu

Suppression of the low-energy noise

slide42

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

56-60 adu

Suppression of the low-energy noise

slide43

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

61-70 adu

Suppression of the low-energy noise

slide44

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

71-80 adu

Suppression of the low-energy noise

slide45

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

81-90 adu

Suppression of the low-energy noise

slide46

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

91-100 adu

Suppression of the low-energy noise

slide47

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

101-120 adu

Suppression of the low-energy noise

slide48

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

121-140 adu

Suppression of the low-energy noise

slide49

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

141-180 adu

Suppression of the low-energy noise

slide50

EPIC-pn detector noise (LW)

rev 790

61 ks closed

after offset corrections

all events

181-250 adu

Suppression of the low-energy noise

slide51

Suppression of the EPIC-pn detector noise

New approach (“method 3”):

Part A: Remove noisy frames, identified by the number of low (20-30) adu events per CCD

Suppression of the low-energy noise

slide52

SNR 1E 0102, rev 803, LW, thick, 30 ks

singles, 20 – 30 adu, frames with 1 event below 31 adu per frame and CCD

singles, 20 – 30 adu, frames with 2 events below 31 adu per frame and CCD

singles, 20 – 30 adu, frames with at least 3 events below 31 adu per frame and CCD

Suppression of the low-energy noise

slide53

SNR 1E 0102, rev 803, LW, thick, 30 ks

(reconstructed) number of frames with no event below 31 adu per CCD

number of frames with 1 event below 31 adu per CCD

number of frames with 2 events below 31 adu per CCD

total number of frames

number of frames with more than 9 events below 31 adu per CCD

Suppression of the low-energy noise

slide54

SNR 1E 0102, rev 803, LW, thick, 30 ks

=

+

singles, 20 – 30 adu, frames with 1 or 2 events below 31 adu per frame and CCD

singles, 20 – 30 adu, frames with more than 2 events below 31 adu per frame and CCD

singles, 20 – 30 adu, all frames

Suppression of the low-energy noise

slide55

SNR 1E 0102, rev 803, LW, thick, 30 ks

=

+

singles, 20 – 30 adu, frames with 1 event below 31 adu per frame and CCD

singles, 20 – 30 adu, frames with more than 1 event below 31 adu per frame and CCD

singles, 20 – 30 adu, all frames

Suppression of the low-energy noise

slide56

SNR 1E 0102, rev 803, LW, thick, 30 ks

removing frames with more than 1 event below 31 adu per CCD and frame:

number of frames removed

original number of frames

percentage of frames removed

Suppression of the low-energy noise

slide57

Suppression of the EPIC-pn detector noise

New approach (“method 3”):

Part B: Remove noise by rejecting invalid patterns and selecting only singles

Suppression of the low-energy noise

slide58

EPIC-pn detector noise (LW)

rev 790, 61 ks closed, no offset corrections, same intensity scale

30-50 adu

raw data: all events

processed data: all “entries”

Suppression of the low-energy noise

slide59

EPIC-pn detector noise (LW)

rev 790

61 ks closed

no offset corrections

non-singles

processed data

30-50 adu

Suppression of the low-energy noise

slide60

EPIC-pn detector noise (LW)

rev 790

61 ks closed

no offset corrections

singles

processed data

30-50 adu

Suppression of the low-energy noise

slide61

EPIC-pn detector noise (FF)

rev 462

23 ks closed

no offset corrections

all events

raw data

30-50 adu

Suppression of the low-energy noise

slide62

EPIC-pn detector noise (FF)

rev 462

23 ks closed

no offset corrections

all “entries”

processed data

30-50 adu

Suppression of the low-energy noise

slide63

EPIC-pn detector noise (FF)

rev 462

23 ks closed

no offset corrections

non-singles

processed data

30-50 adu

Suppression of the low-energy noise

slide64

EPIC-pn detector noise (FF)

rev 462

23 ks closed

no offset corrections

singles

processed data

30-50 adu

Suppression of the low-energy noise

slide65

Suppression of the EPIC-pn detector noise

New approach (“method 3”):

Part C: Try to determine the noise properties from the same exposure at higher energies and extrapolate them down to 20 adu

Suppression of the low-energy noise

slide66

SNR 1E 0102, rev 803, LW, thick, 30 ks

In order to determine the noise properties, some areas have to be ignored:

mask for source regions to be avoided for noise determination

singles, 0.3-3.0 keV

source region mask

Suppression of the low-energy noise

slide67

SNR 1E 0102, rev 803, LW, thick, 30 ks

In order to determine the noise properties, some areas have to be ignored:

noisy pixel mask

final mask, excluding source regions and noisy pixels

Suppression of the low-energy noise

slide68

Deriving the general properties of the detector noise from closed exposures

closed exposures 790 & 974, 73.6 ks

Suppression of the low-energy noise

slide69

Deriving the general properties of the detector noise from closed exposures

closed exposures 790 & 974, after removal of frames with more than 2 events/frame/ccd < 31 adu

Suppression of the low-energy noise

slide70

Deriving the general properties of the detector noise from closed exposures

common fit (for all CCDs) between 40 and 100 adu

Suppression of the low-energy noise

slide71

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions included

red: data set to be corrected, blue: closed exposure

Suppression of the low-energy noise

slide72

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

red: data set to be corrected, blue: closed exposure

Suppression of the low-energy noise

slide73

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

average 45-55 adu flux

Suppression of the low-energy noise

slide74

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

extrapolated flux at 20 adu

Suppression of the low-energy noise

slide75

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

extrapolated flux at 20 adu averaged between all CCDs

Suppression of the low-energy noise

slide76

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

spectrum after noise suppression

Suppression of the low-energy noise

slide77

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

spectrum after noise suppression, source regions excluded

Suppression of the low-energy noise

slide78

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

spectrum before/after noise suppression, source regions excluded

Suppression of the low-energy noise

slide79

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions included

original spectrum, source regions included

Suppression of the low-energy noise

slide80

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions included

original spectrum, source regions included, after noisy frame removal

Suppression of the low-energy noise

slide81

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions included

original spectrum, source regions included, after noisy frame removal and (spatially homogeneous) noise suppression

Suppression of the low-energy noise

slide82

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions included

original spectrum, including source regions, before/after noisy frame removal and (spatially homogeneous) noise suppression

Suppression of the low-energy noise

slide83

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 25 adu after noisy frame removal

Suppression of the low-energy noise

slide84

SNR 1E 0102, rev 803, LW, thick, 30 ks

every second single in CCD4 kept singles, 25 adu every 10th single in CCD4 kept

Suppression of the low-energy noise

slide85

SNR 1E 0102, rev 803, LW, thick, 30 ks

after noisy frame removal singles, 25 adu after spatially uniform noise suppression

Suppression of the low-energy noise

slide86

SNR 1E 0102, rev 803, LW, thick, 30 ks

after noisy frame removal singles, 25 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide87

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 20 adu after noisy frame removal

Suppression of the low-energy noise

slide88

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 20 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide89

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 21 adu after noisy frame removal

Suppression of the low-energy noise

slide90

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 21 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide91

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 22 adu after noisy frame removal

Suppression of the low-energy noise

slide92

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 22 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide93

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 23 adu after noisy frame removal

Suppression of the low-energy noise

slide94

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 23 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide95

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 24 adu after noisy frame removal

Suppression of the low-energy noise

slide96

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 24 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide97

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 25 adu after noisy frame removal

Suppression of the low-energy noise

slide98

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 25 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide99

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 26 adu after noisy frame removal

Suppression of the low-energy noise

slide100

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 26 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide101

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 27 adu after noisy frame removal

Suppression of the low-energy noise

slide102

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 27 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide103

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 28 adu after noisy frame removal

Suppression of the low-energy noise

slide104

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 28 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide105

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 29 adu after noisy frame removal

Suppression of the low-energy noise

slide106

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 29 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide107

SNR 1E 0102, rev 803, LW, thick, 30 ks

unfiltered data singles, 30 adu after noisy frame removal

Suppression of the low-energy noise

slide108

SNR 1E 0102, rev 803, LW, thick, 30 ks

after spatially uniform noise suppression singles, 30 adu after spatially variable noise suppression

Suppression of the low-energy noise

slide109

SNR 1E 0102, rev 803, LW, thick, 30 ks

singles, 100-130 eV

after noisy frame removal and spatially uniform noise suppression

after noisy frame removal and spatially variable noise suppression

original data

Suppression of the low-energy noise

slide110

SNR 1E 0102, rev 803, LW, thick, 30 ks

singles, 130-140 eV

after noisy frame removal and spatially uniform noise suppression

after noisy frame removal and spatially variable noise suppression

original data

Suppression of the low-energy noise

slide111

SNR 1E 0102, rev 803, LW, thick, 30 ks

singles, 140-150 eV

after noisy frame removal and spatially uniform noise suppression

after noisy frame removal and spatially variable noise suppression

original data

Suppression of the low-energy noise

slide112

SNR 1E 0102, rev 803, LW, thick, 30 ks

singles, 150-200 eV

after noisy frame removal and spatially uniform noise suppression

after noisy frame removal and spatially variable noise suppression

original data

Suppression of the low-energy noise

slide113

SNR 1E 0102, rev 803, LW, thick, 30 ks

singles, 200-300 eV

after noisy frame removal and spatially uniform noise suppression

after noisy frame removal and spatially variable noise suppression

original data

Suppression of the low-energy noise

slide114

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions included

original spectrum, including source regions, after noisy frame removal and (spatially variable) noise suppression

Suppression of the low-energy noise

slide115

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions included

original spectrum, including source regions, after noisy frame removal and (below 28 adu: spatially variable) noise suppression

Suppression of the low-energy noise

slide116

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

original spectrum, excluding source regions, after noisy frame removal and (below 28 adu: spatially variable) noise suppression

Suppression of the low-energy noise

slide117

SNR 1E 0102, rev 803, LW, thick, 30 ks, source regions excluded

original spectrum, excluding source regions, after noisy frame removal and (spatially variable) noise suppression

Suppression of the low-energy noise

slide118

SNR 1E 0102, rev 803, LW, thick, 30 ks

singles, 120-140 eV

unfiltered data

after noisy frame removal

after (spatially variable) noise suppression

Suppression of the low-energy noise

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