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20 Abr 2004 Udine bootcamp 1

First Analysis Results of the Crab Nebula and Mrk421

M. López MoyaU.C.M.

1. Analysis chain

2. Mrk421• Camera rotation study• Light Curve

3. Crab Nebula


Analysis chain (1)

• Calibration and Pedestal substraction– Used the standard calibration classes– P,C runs selected by hand: needed a method to

look autmotically for the closer P,C runs to a given D run.

– Pedestal runs seem to work fine, but many problems using calibration runs: many pixels look after calibration.


• Image cleaning– Lvl1 = 3.0, Lvl2 = 2.5 (one ring)– We started to investigate the dependence of

cleaning cuts, but no conclusive results yet: just that 5:3 seems to work better for the Crab.

– Forseen insland analysis and moun rings rejection, specially to analysis at low energies.

Analysis chain (2)


• Signal Extraction– We use: MExtractSignal2

• Hillas Paramter cuts– for the time being, only use SIZE, LENGTH,

WIDTH & DIST.– we used static cuts: no dependence with zenith

angle took into accout

Analysis chain (3)


• Getting the telescope pointing postion– Poiting position stored only in CC reports at a

fixed frecuency– For having it in an event by event base, we

extrapolated it using the arrival time of the event.

Analysis chain (4)


Analysis of Mkn 421


• Data Set 15 Feb.2004

Mrk 421 (1)

Type Runs # Events Duration [m]

ON

P

C

D

17457

17458

17206-17456 1.019.354 104

OFF D 17459-17543 401.362 50


Mrk 421 (2)

• Hillas cuts:

SIZE > 2000

0.1 < LENGTH < 0.3

0.05 < WIDTH < 0.12

0.6 < DIST < 1.4


Mrk 421 (3)

• Correcting the mispointing: The False Source Plot– We consider as source position, the position at the

maximum in the 2D alpha plot

• Fitting the Alpha Plot– Signal region < 10– Backg. region: between 30 - 90– Fit the Backg. region to a 2nd order polinomial. From it

extrapolate the bg. in the signal region– The significance is calculated according to LiMa


ON data

OFF data


• Alpha plot at Src position


• Alpha plot for SIZE > 3000


• We get nearly 20 , but a relative broad alpha plot.

• The significance is high enough to split this day into subsamples. This allows:– Study camera rotation: is really the rotation

uniform?– Get the ligth curve for that day

Mrk 421 (4)


• We divide the whole night (1:45 h) into 10

subsamples

• Now, we don´t apply the camera rotation algorithm.

Mrk 421 : Camera rotation (1)


Mrk 421: Camera rotation (2)



• For each of the subsamples, we get the source position and it corresponding alpha plot.

• From each alpha plot, we get the number of excess events, that we plot vs. Time, obtaining the light curve for that night.

Mrk 421: Light curve (1)






• BUT, this light curve depends strongly on:– the binning criterium (binning in RunNumber,

RunTime,...)– the hillas cuts

• Also we check the time stamp



Mrk 421: Checking timestamp (1)


Mrk 421: Checking timestamp (2)


Analysis of the Crab Nebula


• Data Set 15 Feb.2004

Crab Nebula (1)

Runs Duration [m]

ON 16745-16767

16830-16980

17036-17123

84

OFF 16770-16877

16894-17030

17126-17190

33


• Alpa plot


• So far, only analyzed the night: 15 Feb 2004.

• For Mrk 421 seems easy to get a nice signal, without using a detailed calibration or cut optimization. We get around 20 .

• According the light curve, although we see some variation, it is difficult for the time being to relay on it.

• Mrk 421 also quite useful to understand telescope behaviour.

• For the Crab the situation is more complex. Seems that different cuts should be used. We get only about 6 .

Conclusions