GRB060908: Summary Image Light curves Spectra Distribution Others

Analysis Summary

Notes:

• 1) No attempt has been made to eliminate the non-significant decimal places.
• 2) This batgrbproduct analysis is done using the HEASARC data.
• 3) This batgrbproduct analysis is using the flight position for the mask-weighting calculation.

======================================================================
                  BAT GRB EVENT DATA PROCESSING REPORT
    Process Script Ver: batgrbproduct v2.46
    Process Start Time: Wed Jan 22 13:44:52 EST 2014
             Host Name: batevent1
   Current Working Dir: /local/data/batevent/batevent_reproc/trigger228581
======================================================================

  Trigger: 00228581      Segment: 000

  BAT Trigger Time: 179398643.776   [s; MET]
      Trigger Stop: 179398644.8   [s; MET]
               UTC: 2006-09-08T08:57:22.344940    [includes UTCF correction] 
       Where From?: TDRSS position message

  BAT 
    RA: 31.8346478600979   Dec: 0.370562530869732  [deg; J2000]

     Catalogged Source?: NO
     Point Source?:      YES
     GRB Indicated?:     YES    [ by BAT flight software ]
     Image S/N Ratio:    8.73
     Image Trigger?:     NO
     Rate S/N Ratio:     16.5227116418583  [ if not an image trigger ]
     Image S/N Ratio:    8.73

  Analysis Position:   [ source = BAT ]
    RA: 31.8346478600979   Dec: 0.370562530869732  [deg; J2000]

  Refined Position:   [ source = BAT pre-slew burst ]
    RA: 31.8254284889535   Dec: 0.332127749613838  [deg; J2000]  
        { 02h 07m 18.1s , +00d 19' 55.7" }
         +/- 1.12462930891569 [arcmin] (estimated 90% radius based on SNR)
         +/- 0.324412987317729 [arcmin] (formal 1-sigma fit error)
    SNR: 25.7186289144099
 
  Angular difference between the analysis and refined position is 2.371500 arcmin
 
  Partial Coding Fraction: 0.4609375    [ including projection effects ]

  Duration
     T90: 19.2960000038147 +/- 1.30215974506912
        Measured from: -8.05599999427795
                   to: 11.2400000095367     [s; relative to TRIGTIME]
     T50: 7.41600000858307 +/- 0.639362196036938
        Measured from: -4.81999999284744
                   to: 2.59600001573563     [s; relative to TRIGTIME]



  Fluence
     Peak Flux  (peak 1 second)
        Measured from: 0.540000021457672     
                   to: 1.54000002145767     [s; relative to TRIGTIME]
     Total Fluence        
        Measured from: -12.9799999892712     
                   to: 15.5119999945164     [s; relative to TRIGTIME]
     
             Band 1     Band 2     Band 3     Band 4
              15-25      25-50     50-100    100-350     keV
 Total     0.931341   1.574684   1.417656   0.382264
           0.041339   0.045124   0.041821   0.034491 [error]
 Peak      0.072703   0.134049   0.147337   0.042294
           0.008527   0.010216   0.009715   0.007370 [error]

     [ fluence units of on-axis counts / fully illuminated detector ] 

======================================================================
 
 
====== Table of the duration information =============================
 
        Value   tstart    tstop
T100   28.492  -12.980   15.512
T90    19.296   -8.056   11.240
T50     7.416   -4.820    2.596
Peak    1.000    0.540    1.540
 
 
====== Spectral Analysis Summary =====================================
 
Model      : spectral model: simple power-law (PL) and cutoff power-law (CPL)
Ph_index   : photon index: E^{Ph_index}
Ph_90err   : 90% error of the photon index
Epeak      : Epeak in keV
Epeak_90err: 90% error of Epeak
Norm       : normalization at 50 keV in both the PL model and CPL model
Nomr_90err : 90% error of the normalization
chi2       : Chi-Squared
dof        : degree of freedo
 
=== Time-averaged spectral analysis ===
(Best model with acceptable fit: CPL)
 
Model Ph_index Ph_90err_low Ph_90err_hi  Epeak  Epeak_90err_low  Epeak_90err_hi  Norm       Nomr_90err_low    Norm_90err_hi    chi2    dof
PL      -1.324    -0.059      0.059       -           -               -         1.03e-02     -3.39e-04          3.39e-04      54.350   57
CPL     -0.928    -0.243      0.258      147.687     -37.497       138.491      1.57e-02     -3.51e-03          4.82e-03      46.350   56
 
 
=== 1-s peak spectral analysis ===
(Best model with acceptable fit: CPL)
 
Model Ph_index Ph_90err_low Ph_90err_hi  Epeak  Epeak_90err_low  Epeak_90err_hi  Norm       Nomr_90err_low    Norm_90err_hi    chi2    dof
PL      -1.069     -0.125     0.126       -           -               -         2.65e-02     -2.01e-03          2.01e-03      59.870   57
CPL     -0.274     -0.555     0.638      123.016     -31.616       144.627      6.06e-02     -2.61e-02          5.41e-02      53.620   56
 
 
=== Fluence/Peak Flux Summary ===
 
              Model    Band1     Band2     Band3     Band4     Band5     Total
                       15-25     25-50    50-100    100-350    15-150    15-350    keV
Fluence         PL   3.17e-07  6.49e-07  1.04e-06  3.69e-06  2.88e-06  5.70e-06   erg/cm2
      90%_error_low -2.03e-08 -2.48e-08 -4.12e-08 -3.21e-07 -1.03e-07 -3.47e-07   erg/cm2
      90%_error_hi   2.07e-08  2.47e-08  4.11e-08  3.42e-07  1.03e-07  3.64e-07   erg/cm2
Peak flux       PL   7.23e-01  9.41e-01  8.97e-01  1.52e+00  3.06e+00  4.08e+00   ph/cm2/s
      90%_error_low -1.03e-01 -8.61e-02 -7.50e-02 -2.50e-01 -2.37e-01 -3.31e-01   ph/cm2/s
      90%_error_hi   1.09e-01  8.53e-02  7.45e-02  2.78e-01  2.38e-01  3.37e-01   ph/cm2/s
 
Fluence        CPL   2.90e-07  6.68e-07  1.07e-06  2.19e-06  2.81e-06  4.22e-06   erg/cm2
      90%_error_low -2.55e-08 -2.76e-08 -4.71e-08 -5.59e-07 -1.13e-07 -5.62e-07   erg/cm2
      90%_error_hi   2.60e-08  2.79e-08  4.75e-08  7.97e-07  1.12e-07  7.92e-07   erg/cm2
Peak flux      CPL   5.92e-01  9.86e-01  9.84e-01  7.58e-01  2.98e+00  3.32e+00   ph/cm2/s
      90%_error_low -1.30e-01 -9.70e-02 -9.61e-02 -2.71e-01 -2.45e-01 -3.73e-01   ph/cm2/s
      90%_error_hi   1.37e-01  9.84e-02  9.78e-02  4.55e-01  2.45e-01  4.96e-01   ph/cm2/s
 
======================================================================

Image

Pre-slew 15.0-350.0 keV image (Event data)

#   RAcent    DECcent   POSerr    Theta     Phi              Peak Cts       SNR   Name
   31.8254     0.3321   0.0075    26.4050    89.2068         4.1098168     25.719 TRIG_00228581                 
 
Foreground time interval of the image:
-12.980  11.125 (delta_t =  24.105 [sec])
Background time interval of the image:
-19.475 -12.980 (delta_t =   6.495 [sec])

Light Curves

Note: The mask-weighted lightcurves have units of either count/det or counts/sec/det, where a det is 0.4 x 0.4 = 0.16 sq cm.

Full-time range; 1 s binning

Other quick-look light curves:

• 64 ms binning (zoomed)
• 16 ms binning (zoomed)
• 8 ms binning (zoomed)
• 2 ms binning (zoomed)
• SN=5 or 10 s binning (full-time range)
• Raw light curve

Spectra

Notes:

• 1) The fitting includes the systematic errors.
• 2) When the burst includes telescope slew time periods, the fitting uses an average response file made from multiple 5-s response files through out the slew time plus single time preiod for the non-slew times, and weighted by the total counts in the corresponding time period using addrmf. An average response file is needed becuase a spectral fit using the pre-slew DRM will introduce some errors in both a spectral shape and a normalization if the PHA file contains a lot of the slew/post-slew time interval.
• 3) For fits to more complicated models (e.g. a power-law over a cutoff power-law), the BAT team has decided to require a chi-square improvement of more than 6 for each extra dof.

Time averaged spectrum fit using the average DRM

Power-law model

Time interval is from  -12.980 sec. to   15.512 sec.
 
Spectral model in power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: -1.32426     ( -0.0593623   0.0594856 )
Norm@50keV  : 1.02825E-02    ( -0.000338894   0.000338894 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          54.35 using 59 PHA bins.
# Reduced chi-squared =         0.9534 for     57 degrees of freedom 
# Null hypothesis probability =   5.752514e-01
 
Photon flux (15-150 keV)    in 28.49 sec: 1.23240 ( -0.04304  0.04311 ) ph/cm2/s
Energy fluence (15-150 keV)             : 2.87849e-06 ( -1.02788e-07  1.02996e-07 ) ergs/cm2
 

Cutoff power-law model

Time interval is from  -12.980 sec. to   15.512 sec.
Spectral model in the cutoff power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: -0.927525     ( -0.243389   0.257859 )
Epeak [keV] : 147.687      ( -37.4967 138.491 )
Norm@50keV  : 1.57030E-02    ( -0.00350909   0.00482301 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          46.35 using 59 PHA bins.
# Reduced chi-squared =         0.8278 for     56 degrees of freedom 
# Null hypothesis probability =   8.174606e-01
 
Photon flux (15-150 keV)    in 28.49 sec: 1.20472 ( -0.04599  0.04605 ) ph/cm2/s
Energy fluence (15-150 keV)             : 2.80661e-06 ( -1.12831e-07  1.12443e-07 ) ergs/cm2
 

1-s peak spectrum fit

Power-law model

Time interval is from    0.540 sec. to    1.540 sec.
 
Spectral model in power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: -1.06905     ( -0.124686   0.12622 )
Norm@50keV  : 2.64976E-02    ( -0.00200854   0.00200716 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          59.87 using 59 PHA bins.
# Reduced chi-squared =          1.050 for     57 degrees of freedom 
# Null hypothesis probability =   3.718275e-01
 
Photon flux (15-150 keV)    in 1 sec: 3.06499 ( -0.23734  0.23762 ) ph/cm2/s
Energy fluence (15-150 keV)             : 2.79866e-07 ( -2.30571e-08  2.3174e-08 ) ergs/cm2
 

Cutoff power-law model

Time interval is from    0.540 sec. to    1.540 sec.
Spectral model in the cutoff power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: -0.274293     ( -0.555017   0.637936 )
Epeak [keV] : 123.016      ( -31.616 144.627 )
Norm@50keV  : 6.06299E-02    ( -0.0261365   0.0540655 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          53.62 using 59 PHA bins.
# Reduced chi-squared =         0.9575 for     56 degrees of freedom 
# Null hypothesis probability =   5.653944e-01
 
Photon flux (15-150 keV)    in 1 sec: 2.98284 ( -0.24546  0.24483 ) ph/cm2/s
Energy fluence (15-150 keV)             : 2.70608e-07 ( -2.46789e-08  2.45537e-08 ) ergs/cm2
 

Time-resolved spectra

Distribution

T90 vs. Hardness ratio plot

T90                                   = 19.296 sec.
Hardness ratio (energy fluence ratio) = 1.60712534292

S(15-50 keV) vs. S(50-150 keV) plot

S(15-50 keV)  = 9.576475e-07
S(50-150 keV) = 1.8489935e-06

The dash-dotted line and the dashed line traces the fluences calculated from the Band function with Epeak = 15 and 150 keV, respectively. Both lines assume a canonical values of alpha = -1 and beta = -2.5.

Mask shadow pattern

IMX = 6.873748454635550E-03, IMY = -4.964660977543811E-01

Spacecraft aspect plot

Bright source in the pre-burst/pre-slew/post-slew images

Pre-burst image of 15-350 keV band

Time interval of the image:
-19.475410 -12.980000
 
# RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
#  [deg]    [deg]    ['] [deg]  [deg]                   [']
 83.6714  21.9983    1.5  33.6 -137.1   0.2521   7.9    2.3	Crab                          
 23.2029 -37.7097    2.5  49.0   33.9   0.4589   4.5 ------	UNKNOWN                       
 82.8716 -16.6496    2.3  29.0  -58.4   0.1514   4.9 ------	UNKNOWN                       

Pre-slew background subtracted image of 15-350 keV band

Time interval of the image:
-12.980000 11.124560
 
# RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
#  [deg]    [deg]    ['] [deg]  [deg]                   [']
 83.7769  21.9267    7.6  33.7 -136.9  -0.2157  -1.5    9.6	Crab                          
 31.8254   0.3321    0.4  26.4   89.2   4.1099  25.8 ------	UNKNOWN                       
 78.6572  -5.8143    2.0  21.0  -78.6   0.6698   5.7 ------	UNKNOWN                       
 78.6779 -57.5572    2.4  59.1  -15.7   3.0158   4.9 ------	UNKNOWN                       

Post-slew image of 15-350 keV band

Time interval of the image:
60.724590 962.244000
 
# RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
#  [deg]    [deg]    ['] [deg]  [deg]                   [']
 63.1816 -27.4164    3.8  40.9  -36.4   2.0217   3.0 ------	UNKNOWN                       
 69.6160  -2.9302    4.2  37.9  -76.4   3.2684   2.7 ------	UNKNOWN                       
 76.3790 -29.6774    4.1  52.0  -42.3   7.0313   2.9 ------	UNKNOWN                       
 72.8538   1.4095    3.5  41.0  -83.3   6.8253   3.3 ------	UNKNOWN