Transcript Search for GRBs Using ARGO Data in Shower Mode Guo Y.Q.

Search for GRBs
Using ARGO Data in Shower Mode
Guo Y.Q.
For ARGO-YBJ Collaboration
BeiJing 2008/09/26
Outline
1. Introduction
2. ARGO-YBJ experiment
3. Data Analysis
(1) Triggered Showers
(2) Low-Hit Showers
4. Results
5. Summary
1. Introduction
GRBs are intense bursts of photons with short
duration. They are one of the most intriguing
objects in the known universe.
cosmological origin
no cut-off
Time range:
ms ~ minutes
Energy range:
keV ~ MeV
GRB940217(EGRET)
~GeV Photons
2. ARGO-YBJ experiment
ARGO-YBJ
Full cover:
High altitude:
Large field of view:
6500m2
4300m
2.24 sr
Detectors
Cluster :
130(10×13) + 24 ring Cluster
RPC :
12/cluster
PAD
:
10/RPC
--the detector Unit(62cm×56cm).
3.1 Data Analysis
Triggered shower
TDC (ns)
Single-Front Event
Trigger condition:
≥ 20 fired pads ( i.e. nHits ≥ 20 )
Y (m)
TDC (ns)
X (m)
Double-front Event
Triggered Shower（nHits ≥ 20 ）
Low-Hit Shower（5 ≤ nHits ≤ 15)
Y (m)
X (m)
Events Threshold Energy and Trigger Rate
YBJ
Triggered Showers:
~hundreds of GeV
e+ e100TeV
10TeV
Low-Hit Showers:
~ tens of GeV
1TeV
100GeV
nHits=20
nHits= 5
10GeV
Can be used to search for GRB
N /s
Triggered Showers:
~3700 Hz
Low-Hit Showers :
~200 Hz
Trigger Rate
time
Sensitivity
Effective area for Triggered Gamma events
and Low-Hit events.
The sensitivity for Triggered gamma
events and Low-Hit gamma events.
MC: Index= -2.0 Zenith =100
From the Figs, we know at low energy, the Low-Hit event is better than
Triggered events.
3.2 GRBs Analysis Method
Search Method :
From satellite reported, we get to know the information about GRBs' trigger
time and direction. The events in the R+2o angle window are looked as the GRB
candidates to search for the largest significance event.
Candidate Events
R+20
Time
-300s ~ 300s
Position Precise:
Triggered Shower: R= 2.0o
Low-Hit Shower: R= 8.5o
3.2 Estimate Background for Triggered Showers
Non is the number of events that followed within the solid angle (on-source window)
and within the time duration (t).
t: 1s, 5s, 10s ..,100s
equi-zenith-angle method:
()
Estimate the background by the
off-source window, with same R
and same θ as on-source window.
(1) 10 off-source windows
are chosen to improve
statistic.
(2)Using ±1000s data to
estimate background
Zenith
Noff
Non
3.2 Estimate Background forLow-Hit Shower Analysis
Because of the Azimuth asymmetry
and the worse angle resolution(6.50),
equi-zenith-angle method can not be
used to estimate the background very
well.
we use the following method to do so:
Azimuth=0 is East (clockwise)
No
Nb
Time (s)
-1000
-210
0
210
1000
At the on-source window, using±210s ~1000s time range data to
estimate the background .
3.3 GRBs Sample in ARGO Field of View
Time range :
Cut condition:
2006.07 ~ 2008.03
( totaled 17 )
GRB060714A
GRB060805B
GRB061028A
GRB070201A
GRB070531A
GRB080325A
GRB060717A
GRB060807A
GRB061110A
GRB070219A
GRB070615A
GRB080328A
Dec: -8 ~70 degree
Zen: ≤ 50 degree
GRB060801A
GRB060927A
GRB061122A
GRB070306A
GRB080207A
From http://grb.sonoma.edu/
4.1 Triggered Event Analysis Results
Angle Radius
R = 2.00
Cut :
(1) inner events
(2) nHits<60
GRB061122
(3) chi2<10
Maximum Significance:
S-max = 4.80
GRB061122
Maximum Significance in ARGO data:
INTEGRAL data:
Mjd:54061.3311342691960
Mjd:54061.3320497685199
Ra:303.910 Dec:15.520
Ra:302.940 Dec:13.980
Zen:33.570 Azim:108.320
Zen:33.350 Azim:111.900
5s/bin
Light curve
det_T:
after 79s
det_θ:
1.80
Considering try number (n=3294), only 2.80 Significance Level.
4.2 Low-Hit Event Analysis Results
Angle Radius
R = 8.50
Cut:
(1) nHits<15
(2) chi2<10
Maximum Significance:
S-max = 4.58
GRB061028
GRB061028
Maximum Significance in ARGO data:
Swift data:
Mjd: 54036.059976861783
Mjd:54036.0585579861145
Ra:97.2080
Ra:110.1230
Dec:46.2700
Zen:42.4880 Azim:307.1340
Light curve
Dec:42.6630
Zen:32.5440 Azim:303.2090
det_T:
before 122.6s
det_θ:
9.880
But considering try number (n=536), only 3.03 Significance Level.
Result of ARGO Data Analysis
Date
Low-Hit Events Data
Triggered Events Data
S_max
4.13
20060714
4.67
20060717
4.37
20060801
4.53
20060805
3.93
20060807
3.73
20060927
3.39
20061028
4.05
20061110
20061122 4.81(2.80)
4.47
20070201
3.9
20070219
4.02
20070306
3.75
20070531
3.52
20070615
3.66
20080207
3.18
20080325
3.36
20080328
time(s)
95%U.L.(ph/cm^2/s)
S_max
time(s)
95%U.L.(ph/cm^2/s)
10
10
5
100
5
5
10
1
5
100
60
90
15
5
5
40
15
1.76E-003
2.10E-004
4.15E-004
2.84E-004
2.88E-004
1.16E-003
3.25E-003
1.39E-002
2.31E-003
9.85E-005
1.11E-003
8.84E-005
9.17E-004
5.15E-003
1.18E-003
1.50E-004
2.31E-003
3.78
><
4.24
4.3
4.4
3.57
4.58(3.03)
4.28
4.05
3.92
3.6
3.18
3.54
3.67
3.68
2.99
3.62
90
><
5
15
1
1
60
100
1
10
5
40
20
60
1
60
1
1.77E-003
><
1.01E-003
9.82E-004
2.13E-003
2.60E-003
8.50E-004
1.39E-003
3.84E-003
1.67E-003
3.04E-003
3.35E-004
3.96E-003
2.09E-003
2.78E-003
2.22E-003
1.76E-002
5. Summary
1. Base on M.C simulation we give the ARGO detector
sensitivity to search for GRB using Triggered and Low-Hit
events. At low energy, the sensitivity is better using Low-Hit
Events.
2. After ARGO data analysis, no GRBs' high energy emission
were observed and we give the integral flux uplimit for more
than 10 GRBs in ARGO view.
Significance
for signal(Non) obey the Poisson distributions:
P ( N on ) =
Nb
N on
N on !

defined:
e
 Nb
1
Pbk =  P (i ) + P ( Non)
2
i= Non+1
compare with Gauss distributions:

Pbk = 
s
2

1
t 
exp   dt
2
 2
Effective area and sensitivity
of single-front Gamma events for different Zenith
GRBs Sample in ARGO Field of Vision
Mjd
GRB060714
GRB060717
GRB060801
GRB060805
GRB060807
GRB060927
GRB061028
GRB061110
GRB061122
GRB070201
GRB070219
GRB070224
GRB070306
GRB070531
GRB070615
GRB080207
GRB080325
GRB080328
Zen
53930.6333
53933.3803
53948.5112
53952.6022
53954.6122
54005.5885
54036.0599
54049.4912
54061.3311
54132.6410
54150.0487
54155.8527
54165.6954
54251.0904
54266.0977
54503.8960
54550.1731
54553.3354
Azim T90
41.832
7.375
16.823
29.092
12.421
31.631
42.488
36.845
33.572
20.609
39.313
44.520
19.850
44.264
36.918
27.668
48.132
37.188
215.672
96.917
221.300
12.154
280.539
137.357
307.134
146.303
108.318
102.419
1.942
198.043
170.830
358.209
153.310
141.323
293.824
49.753
Z
Mission
20
2.710
5
--0.5 1.131
5
--15
--22.6 5.600
106
--30
0.758
20
--0.15
--15
--25
--210 1.497
20
--30
--340
--128.4 --110 ---
Flux(erg/cm2)
Swift
Swift
Swift
Konus-Wind
Swift
Swift
Swift
Swift
INTEGRAL
Konus-Wind
Swift
Swift
Swift
Swift
INTEGRAL
Swift
Swift
Swift/K-W
6.5e-08
8.1e-08
7.4e-08
7.3e-07
1.1e-06
9.7e-07
1.1e-06
3.2e-07
3.1e-07
5.5e-06
1.1e-06
6.1e-06
4.9e-06
9.4e-06
Azimuth distribution for different Zenith
(fluctuation: <6%)
10o—black, 20o—blue 30o—red, 40o—purple
Azimuth=0 is East (clockwise)
Azimuth distribution of
the low hit events for difference Zenith
10o—black, 20o—blue30o—red, 40o—purple
Azimuth=0 is East (clockwise)
the shape is similar to the triggered events. But the difference is large than
triggered events because the low energy.