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Search for GRBs Using ARGO Data in Shower Mode

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.

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Search for GRBs Using ARGO Data in Shower Mode

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  1. Search for GRBs Using ARGO Data in Shower Mode Guo Y.Q. For ARGO-YBJ Collaboration BeiJing 2008/09/26

  2. Outline 1. Introduction 2. ARGO-YBJ experiment 3. Data Analysis (1) Triggered Showers (2) Low-Hit Showers 4. Results 5. Summary

  3. 1. Introduction GRBs are intense bursts of photonswith short duration. They are one of the most intriguing objects in the known universe. cosmological origin Time range: ms ~ minutes Energy range: keV ~ MeV no cut-off GRB940217(EGRET) ~GeV Photons

  4. 2. ARGO-YBJ experiment ARGO-YBJ Detectors Full cover: 6500m2 High altitude: 4300m Large field of view: 2.24 sr Cluster : 130(10×13) + 24 ring Cluster RPC : 12/cluster PAD : 10/RPC --the detector Unit(62cm×56cm).

  5. TDC (ns) Y (m) X (m) TDC (ns) Y (m) X (m) 3.1 Data Analysis Single-Front Event Triggered shower Trigger condition: ≥ 20 fired pads( i.e. nHits ≥ 20 ) Double-front Event Triggered Shower（nHits ≥ 20 ） Low-Hit Shower（5 ≤ nHits ≤15)

  6. YBJ e+ e- 100TeV 10TeV 1TeV 100GeV nHits=20 10GeV nHits= 5 Events Threshold Energy and Trigger Rate N/s Triggered Showers: ~hundreds of GeV Low-Hit Showers: ~tens of GeV Canbe used to search for GRB Trigger Rate Triggered Showers:~3700 Hz time Low-Hit Showers :~200 Hz

  7. Sensitivity Effective area for Triggered Gamma events and Low-Hit events. The sensitivity for Triggered gamma events and Low-Hit gamma events. MC:Index=-2.0Zenith=100 Very Preliminary From the Figs, we know at low energy, the Low-Hit event is better than Triggered events.

  8. 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

  9. 3.2 Estimate Background for Triggered Showers Zenith Nonis 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: () Noff Estimate the background by the off-sourcewindow, with same Rand same θ as on-sourcewindow. Non (1)10 off-source windows are chosen to improve statistic. (2)Using ±1000s data to estimate background

  10. No Nb Time (s) -1000 -210 0 210 1000 3.2 Estimate BackgroundforLow-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) At the on-source window, using±210s ~1000s time range data to estimate the background .

  11. 3.3GRBs SampleinARGOField of View Timerange: 2006.07~2008.03 ( totaled 17 ) Cut condition: Dec: -8 ~70 degree Zen: ≤ 50 degree GRB060714 A GRB060717 A GRB060801A GRB060805 B GRB060807A GRB060927 A GRB061028A GRB061110A GRB061122A GRB070201 A GRB070219A GRB070306 A GRB070531A GRB070615A GRB080207A GRB080325 A GRB080328A From http://grb.sonoma.edu/

  12. 4.1 Triggered Event Analysis Results Angle Radius R = 2.00 Cut : (1) inner events (2) nHits<60 (3) chi2<10 GRB061122 Maximum Significance: S-max = 4.80

  13. 5s/bin Light curve Maximum Significance in ARGO data: Mjd:54061.3320497685199 Ra:302.940 Dec:13.980 Zen:33.350 Azim:111.900 INTEGRAL data: Mjd:54061.3311342691960 Ra:303.910 Dec:15.520 Zen:33.570 Azim:108.320 GRB061122 det_T: after 79s det_θ: 1.80 Considering try number (n=3294), only 2.80 Significance Level.

  14. 4.2 Low-Hit Event Analysis Results Angle Radius R = 8.50 Cut: (1) nHits<15 (2) chi2<10 GRB061028 Maximum Significance: S-max = 4.58

  15. Maximum Significance inARGO data: Mjd:54036.0585579861145 Ra:110.1230 Dec:42.6630 Zen:32.5440 Azim:303.2090 Swift data: Mjd: 54036.059976861783 Ra:97.2080 Dec:46.2700 Zen:42.4880 Azim:307.1340 GRB061028 det_T: before 122.6s det_θ: 9.880 Light curve But considering try number (n=536), only 3.03 Significance Level.

  16. Result of ARGO Data Analysis

  17. 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.

  18. Significance for signal(Non) obey the Poisson distributions: defined: compare with Gauss distributions:

  19. Effective area and sensitivity of single-front Gamma events for different Zenith

  20. GRBs SampleinARGOField of Vision Mjd Zen Azim T90 Z Mission Flux(erg/cm2) GRB060714 53930.6333 41.832 215.672 20 2.710 Swift GRB060717 53933.3803 7.375 96.917 5 --- Swift 6.5e-08 GRB060801 53948.5112 16.823 221.300 0.5 1.131 Swift 8.1e-08 GRB060805 53952.6022 29.092 12.154 5 --- Konus-Wind 7.4e-08 GRB060807 53954.6122 12.421 280.539 15 --- Swift 7.3e-07 GRB060927 54005.5885 31.631 137.357 22.6 5.600 Swift 1.1e-06 GRB061028 54036.0599 42.488 307.134 106 --- Swift 9.7e-07 GRB061110 54049.4912 36.845 146.303 30 0.758 Swift 1.1e-06 GRB061122 54061.3311 33.572 108.318 20 --- INTEGRAL GRB070201 54132.6410 20.609 102.419 0.15 --- Konus-Wind GRB070219 54150.0487 39.313 1.942 15 --- Swift 3.2e-07 GRB070224 54155.8527 44.520 198.043 25 --- Swift 3.1e-07 GRB070306 54165.6954 19.850 170.830 210 1.497 Swift 5.5e-06 GRB070531 54251.0904 44.264 358.209 20 --- Swift 1.1e-06 GRB070615 54266.0977 36.918 153.310 30 --- INTEGRAL GRB080207 54503.8960 27.668 141.323 340 --- Swift 6.1e-06 GRB080325 54550.1731 48.132 293.824 128.4 --- Swift 4.9e-06 GRB080328 54553.3354 37.188 49.753 110 --- Swift/K-W 9.4e-06

  21. Azimuth distribution for different Zenith (fluctuation: <6%) 10o—black, 20o—blue 30o—red, 40o—purple Azimuth=0 is East (clockwise)

  22. 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.

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