batgrbproduct Analysis for Trigger=313116

Analysis Summary

Notes:

======================================================================
                  BAT GRB EVENT DATA PROCESSING REPORT
    Process Script Ver: batgrbproduct v2.46
    Process Start Time (local time): Mon Jan 20 01:24:57 EST 2014
             Host Name: batevent1
   Current Working Dir: /local/data/batevent/batevent_reproc/trigger313116
======================================================================

  Trigger: 00313116      Segment: 000

  BAT Trigger Time: 234257224   [s; MET]
      Trigger Stop: 234257288   [s; MET]
               UTC: 2008-06-04T07:27:01.159600    [includes UTCF correction] 
       Where From?: TDRSS position message

  BAT 
    RA: 236.969995263586   Dec: 20.5553515503071  [deg; J2000]

     Catalogged Source?: NO
     Point Source?:      YES
     GRB Indicated?:     YES    [ by BAT flight software ]
     Image S/N Ratio:    11.68
     Image Trigger?:     YES
     Rate S/N Ratio:     0  [ if not an image trigger ]
     Image S/N Ratio:    11.68

  Flight Position:   [ source = BAT ]
    RA: 236.969995263586   Dec: 20.5553515503071  [deg; J2000]

  Ground Position:   [ source = BAT pre-slew burst ]
    RA: 236.957556880434   Dec: 20.5593469152126  [deg; J2000]  
        { 15h 47m 49.8s , +20d 33' 33.6" }
         +/- 1.99284906511066 [arcmin] (estimated 90% radius based on SNR)
         +/- 0.756041427085413 [arcmin] (formal 1-sigma fit error)
    SNR: 11.3578936597447
 
  Angular difference between Flight and Ground position is 0.738755 arcmin
 
  Partial Coding Fraction: 1.03125    [ including projection effects ]

  Duration
     T90: 77.608000010252 +/- 13.2472380709174
        Measured from: -24.33599999547
                   to: 53.272000014782     [s; relative to TRIGTIME]
     T50: 33.3560000061989 +/- 7.94457599923189
        Measured from: -3.42800000309944
                   to: 29.9280000030994     [s; relative to TRIGTIME]



  Fluence
     Peak Flux  (peak 1 second)
        Measured from: -3.03600001335144     
                   to: -2.03600001335144     [s; relative to TRIGTIME]
     Total Fluence        
        Measured from: -28.2639999985695     
                   to: 58.608000010252     [s; relative to TRIGTIME]
     
             Band 1     Band 2     Band 3     Band 4
              15-25      25-50     50-100    100-350     keV
 Total     0.449206   0.559082   0.322661   0.032594
           0.046664   0.045382   0.040086   0.034979 [error]
 Peak      0.013254   0.016385   0.014667   0.009566
           0.005082   0.004836   0.004291   0.003756 [error]

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

======================================================================
 
=== 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   Power-law 1.28e-07 2.12e-07 2.65e-07 6.57e-07 7.89e-07 1.26e-06   erg/cm2
              Error 1.91e-08 2.03e-08 3.83e-08 1.96e-07 9.01e-08 2.32e-07   erg/cm2
Peak flux Power-law 1.07e-01 1.22e-01 9.98e-02 1.36e-01 3.79e-01 4.66e-01   ph/cm2/s
              Error 5.79e-02 4.02e-02 3.46e-02 1.04e-01 1.11e-01 1.40e-01   ph/cm2/s
 
Fluence   Cutoff-PL 1.23e-07 2.25e-07 2.62e-07 2.81e-07 7.44e-07 8.90e-07   erg/cm2
              Error 2.11e-08 2.77e-08 4.30e-08 3.94e-07 1.10e-07 2.67e-07   erg/cm2
Peak flux Cutoff-PL 1.04e-01 1.24e-01 1.01e-01 1.14e-01 3.76e-01 4.43e-01   ph/cm2/s
              Error 6.62e-02 4.32e-02 3.86e-02 1.21e-01 1.15e-01 1.64e-01   ph/cm2/s
 
Fluence        Band -------- -------- -------- -------- -------- --------   erg/cm2
              Error -------- -------- -------- -------- -------- --------   erg/cm2
Peak flux      Band -------- -------- -------- -------- -------- --------   ph/cm2/s
              Error -------- -------- -------- -------- -------- --------   ph/cm2/s
 
=== Time-averaged spectral analysis ===
 
Model Ph_index Ph_90err Epeak  Epeak_90err Norm     Nomr_90err chi2   dof
PL    1.678    0.173    -      -           9.79e-04 1.05e-04   65.350 57
CPL   1.193    0.717      72.3  -25.0      1.84e-03 2.26e-03   63.920 56
 
 
=== 1-s peak spectral analysis ===
 
Model Ph_index Ph_90err Epeak  Epeak_90err Norm     Nomr_90err chi2   dof
PL    1.293    0.535    -      -           3.18e-03 9.10e-04   35.890 57
CPL   1.230    1.697     626.8    0.0      3.41e-03 2.95e-02   35.880 56
 
Model      : spectral model: simple power-law (PL) and cutoff power-law (CPL)
Ph_index   : photon index: E^-{Ph_index} (minus sign is not included in the 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 PL model and at 1 keV in CPL model
Nomr_90err : 90% error of the normalization
chi2       : Chi-Squared
dof        : degree of freedom
 
=== T90/T50 calculation in the 50-300 keV band (BATSE band) using 64 ms lc ===
 
T90 in the 50-300 keV band: 0.000000 sec.
T50 in the 50-300 keV band: 0.000000 sec.
 
=== Table of the duration information ==
 
        Value   tstart    tstop
T100   86.872  -28.264   58.608
T90    77.608  -24.336   53.272
T50    33.356   -3.428   29.928
Peak    1.000   -3.036   -2.036
  • Click here for the BAT GCN circular template

    Image

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

    #   RAcent    DECcent   POSerr    Theta     Phi              Peak Cts       SNR   Name
      236.9576    20.5593   0.0169    14.6358   -17.8866         1.2366684     11.358 TRIG_00313116                 
     
    Foreground time interval of the image:
    -28.264  58.608 (delta_t =  86.872 [sec])
    Background time interval of the image:
    -239.000 -28.264 (delta_t = 210.736 [sec])
    

    Lightcurves

    Notes:

    1 s binning

    From T0-310 s to T0+310 s
    From T100_start - 20 s to T100_end + 30 s
    Full time interval

    64 ms binning

    Full time interval
    From T100_start to T100_end
    From T0-5 sec to T0+5 sec

    16 ms binning

    From T100_start-5 s to T100_start+5 s

    8 ms binning

    From T100_start-3 s to T100_start+3 s

    2 ms binning

    From T100_start-1 s to T100_start+1 s

    SN=5 or 10 sec. binning (whichever binning is satisfied first)

    SN=5 or 10 sec. binning (T < 200 sec)

    Quad-rate summed light curves (from T0-300s to T0+1000s)

    Spectral Evolution

    Spectra

    Notes:

    Time averaged spectrum fit using the average DRM

    Power-law model
    Time interval is from  -28.264 sec. to   58.608 sec.
     
    Spectral model in power-law:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    Photon index: 1.67837     ( -0.170711   0.174371 )
    Norm@50keV  : 9.79447E-04    ( -0.000105239   0.000103788 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          65.35 using 59 PHA bins.
    # Reduced chi-squared =          1.147 for     57 degrees of freedom 
    # Null hypothesis probability =   2.092736e-01
     
    Photon flux (15-150 keV)    in 86.87 sec: 0.129114 ( -0.0124104  0.0124162 ) ph/cm2/s
    Energy fluence (15-150 keV)             : 7.8921e-07 ( -8.92555e-08  9.08556e-08 ) ergs/cm2
     
    
    Cutoff power-law model
    Time interval is from  -28.264 sec. to   58.608 sec.
    Spectral model in the cutoff power-law:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    Photon index: 1.19341     ( -0.834717   0.599365 )
    Epeak [keV] : 72.3010      ( -22.2543 -72.3238 )
    Norm@50keV  : 1.83543E-03    ( -0.000925941   0.00360125 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          63.92 using 59 PHA bins.
    # Reduced chi-squared =          1.141 for     56 degrees of freedom 
    # Null hypothesis probability =   2.182364e-01
     
    Photon flux (15-150 keV)    in 86.87 sec: 0.126301 ( -0.013065  0.013026 ) ph/cm2/s
    Energy fluence (15-150 keV)             : 7.44185e-07 ( -1.08819e-07  1.10688e-07 ) ergs/cm2
     
    
    Band function
    Time interval is from  -28.264 sec. to   58.608 sec.
     
    Spectral model in the Band function:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    alpha       : 4.90586   ( -5.6538   -4.90586 )
    beta        : -1.91184    ( -0.297723   0.227942 )
    Epeak [keV] : 26.6771      ( -3.95588 3.68342 )
    Norm@50keV   : 72.2442    ( -6.83173   235.914 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          59.46 using 59 PHA bins.
    # Reduced chi-squared =          1.081 for     55 degrees of freedom 
    # Null hypothesis probability =   3.164834e-01
     
    Photon flux (15-150 keV)    in 86.87 sec:  (    ) ph/cm2/s
    Energy fluence (15-150 keV)             : 0 ( 0  0 ) ergs/cm2
     
    
    Single BB
     
    Spectral model blackbody:
    ------------------------------------------------------------
    Parameters  : value    Lower 90%  Upper 90%
    kT [keV]    : 11.2743  (-1.27497  1.50331)
    R^2/D10^2   : 3.91881E-02  (-0.0145046   0.0220389)
    (R is the radius in km and D10 is the distance to the source in units of 10 kpc)
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          81.77 using 59 PHA bins.
    # Reduced chi-squared =          1.435 for     57 degrees of freedom 
    # Null hypothesis probability =   1.741063e-02
     
    Energy  Fluence     90% Error
    [keV]   [erg/cm2]   [erg/cm2]
    15- 25  9.082e-08   1.577e-08
    25- 50  2.650e-07   3.340e-08
    50-150  1.938e-07   4.708e-08
    15-150  5.496e-07   6.633e-08
    
    Thermal bremsstrahlung (OTTB)
     
     
    Spectral model: thermal bremsstrahlung
    ------------------------------------------------------------
    Parameters  : value         Lower 90%    Upper 90%
    kT [keV]    : 128.583       (-45.1773      -127.252)
    Norm        : 0.542377       (-0.0609734     0.0795364)
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          63.88 using 59 PHA bins.
    # Reduced chi-squared =          1.121 for     57 degrees of freedom 
    # Null hypothesis probability =   2.476834e-01
     
    Energy  Fluence     90% Error
    [keV]   [erg/cm2]   [erg/cm2]
    15- 25  1.223e-07   1.603e-08
    25- 50  2.214e-07   4.717e-08
    50-150  4.084e-07   2.090e-07
    15-150  7.521e-07   2.726e-07
    
    Double BB
     
     
    Spectral model: bbodyrad<1> + bbodyrad<2>
    ------------------------------------------------------------
    Parameters  : value         Lower 90%    Upper 90%
    kT1 [keV]   : 7.94494        (-1.72219      1.74305)
    R1^2/D10^2  : 0.111465        (-0.0521615      0.105401)
    kT2 [keV]   : 33.6922        (-13.625      95.625)
    R2^2/D10^2  : 5.23904E-04    (-0.000485131   0.00255851)
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          59.94 using 59 PHA bins.
    # Reduced chi-squared =          1.090 for     55 degrees of freedom 
    # Null hypothesis probability =   3.012577e-01
     
    Energy  Fluence     90% Error
    [keV]   [erg/cm2]   [erg/cm2]
    15- 25  1.175e-07   4.019e-08
    25- 50  2.386e-07   8.044e-08
    50-150  4.164e-07   2.160e-07
    15-150  7.724e-07   3.123e-07
    

    Peak spectrum fit

    Power-law model
    Time interval is from   -3.036 sec. to   -2.036 sec.
     
    Spectral model in power-law:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    Photon index: 1.29316     ( -0.54009   0.530692 )
    Norm@50keV  : 3.18315E-03    ( -0.00091106   0.000909732 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          35.89 using 59 PHA bins.
    # Reduced chi-squared =         0.6297 for     57 degrees of freedom 
    # Null hypothesis probability =   9.870544e-01
     
    Photon flux (15-150 keV)    in 1 sec: 0.379283 ( -0.110815  0.111602 ) ph/cm2/s
    Energy fluence (15-150 keV)             : 3.1508e-08 ( -9.98913e-09  1.02676e-08 ) ergs/cm2
     
    
    Cutoff power-law model
    Time interval is from   -3.036 sec. to   -2.036 sec.
    Spectral model in the cutoff power-law:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    Photon index: 1.22955     ( -2.50685   0.886866 )
    Epeak [keV] : 626.793      (   )
    Norm@50keV  : 3.41467E-03    ( -0.00116103   0.0578652 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          35.88 using 59 PHA bins.
    # Reduced chi-squared =         0.6407 for     56 degrees of freedom 
    # Null hypothesis probability =   9.833212e-01
     
    Photon flux (15-150 keV)    in 1 sec: 0.376469 ( -0.116797  0.113552 ) ph/cm2/s
    Energy fluence (15-150 keV)             : 3.11904e-08 ( -1.09487e-08  1.05302e-08 ) ergs/cm2
     
    
    Band function
    Time interval is from   -3.036 sec. to   -2.036 sec.
     
    Spectral model in the Band function:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    alpha       : -0.926297   ( 0.920341   0.920341 )
    beta        : -1.30113    ( 1.30193   0.547098 )
    Epeak [keV] : 73.4066      ( -70.5085 -70.5085 )
    Norm@50keV   : 5.96244E-03    ( -0.00389715   0 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          35.89 using 59 PHA bins.
    # Reduced chi-squared =         0.6525 for     55 degrees of freedom 
    # Null hypothesis probability =   9.785628e-01
     
    Photon flux (15-150 keV)    in 1 sec:  (    ) ph/cm2/s
    Energy fluence (15-150 keV)             : 0 ( 0  0 ) ergs/cm2
     
    
    Single BB
     
    Spectral model blackbody:
    ------------------------------------------------------------
    Parameters  : value    Lower 90%  Upper 90%
    kT [keV]    : 18.2161  (-6.09217  9.99425)
    R^2/D10^2   : 2.29180E-02  (-0.022885   0.0669983)
    (R is the radius in km and D10 is the distance to the source in units of 10 kpc)
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          38.44 using 59 PHA bins.
    # Reduced chi-squared =         0.6744 for     57 degrees of freedom 
    # Null hypothesis probability =   9.718942e-01
     
    Energy  Fluence     90% Error
    [keV]   [erg/cm2]   [erg/cm2]
    15- 25  1.517e-09   9.553e-10
    25- 50  7.077e-09   4.219e-09
    50-150  1.710e-08   1.149e-08
    15-150  2.569e-08   1.567e-08
    
    Thermal bremsstrahlung (OTTB)
     
     
    Spectral model: thermal bremsstrahlung
    ------------------------------------------------------------
    Parameters  : value         Lower 90%    Upper 90%
    kT [keV]    : 199.363       (-116.219      -199.363)
    Norm        : 1.56811       (-0.451712     0.451723)
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          36.60 using 59 PHA bins.
    # Reduced chi-squared =         0.6422 for     57 degrees of freedom 
    # Null hypothesis probability =   9.837193e-01
     
    Energy  Fluence     90% Error
    [keV]   [erg/cm2]   [erg/cm2]
    15- 25  3.905e-09   2.443e-09
    25- 50  7.511e-09   4.521e-09
    50-150  1.647e-08   1.011e-08
    15-150  2.789e-08   1.684e-08
    
    Double BB
     
     
    Spectral model: bbodyrad<1> + bbodyrad<2>
    ------------------------------------------------------------
    Parameters  : value         Lower 90%    Upper 90%
    kT1 [keV]   : 5.85439        (-5.85712      -5.85712)
    R1^2/D10^2  : 0.605746        (-0.604416      -0.604416)
    kT2 [keV]   : 25.6088        (-10.966      -25.6182)
    R2^2/D10^2  : 6.50601E-03    (-0.00649728   0.0391089)
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          35.87 using 59 PHA bins.
    # Reduced chi-squared =         0.6522 for     55 degrees of freedom 
    # Null hypothesis probability =   9.786550e-01
     
    Energy  Fluence     90% Error
    [keV]   [erg/cm2]   [erg/cm2]
    15- 25  3.392e-09   2.131e-09
    25- 50  6.715e-09   3.392e-09
    50-150  2.056e-08   1.199e-08
    15-150  3.067e-08   1.801e-08
    

    Pre-slew spectrum (Pre-slew PHA with pre-slew DRM)

    Power-law model
     
    Spectral model in power-law:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    Photon index: 1.67837     ( -0.170711   0.174371 )
    Norm@50keV  : 9.79447E-04    ( -0.000105239   0.000103788 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          65.35 using 59 PHA bins.
    # Reduced chi-squared =          1.147 for     57 degrees of freedom 
    # Null hypothesis probability =   2.092736e-01
     
    Photon flux (15-150 keV)    in 86.87 sec: 0.129114 ( -0.0124104  0.0124162 ) ph/cm2/s
    Energy fluence (15-150 keV)             : 7.8921e-07 ( -8.92555e-08  9.08556e-08 ) ergs/cm2
     
    
    Cutoff power-law model
    Spectral model in the cutoff power-law:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    Photon index: 1.19341     ( -0.834717   0.599365 )
    Epeak [keV] : 72.3010      ( -22.2543 -72.3238 )
    Norm@50keV  : 1.83543E-03    ( -0.000925941   0.00360125 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          63.92 using 59 PHA bins.
    # Reduced chi-squared =          1.141 for     56 degrees of freedom 
    # Null hypothesis probability =   2.182364e-01
     
    Photon flux (15-150 keV)    in 86.87 sec: 0.126301 ( -0.013065  0.013026 ) ph/cm2/s
    Energy fluence (15-150 keV)             : 7.44185e-07 ( -1.08819e-07  1.10688e-07 ) ergs/cm2
     
    
    Band function
     
    Spectral model in the Band function:
    ------------------------------------------------------------
    Parameters  : value       lower 90%   higher 90%
    alpha       : 4.90586   ( -5.6538   -4.90586 )
    beta        : -1.91184    ( -0.297723   0.227942 )
    Epeak [keV] : 26.6771      ( -3.95588 3.68342 )
    Norm@50keV   : 72.2442    ( -6.83173   235.914 )
    ------------------------------------------------------------
    #Fit statistic : Chi-Squared =          59.46 using 59 PHA bins.
    # Reduced chi-squared =          1.081 for     55 degrees of freedom 
    # Null hypothesis probability =   3.164834e-01
     
    Photon flux (15-150 keV)    in 86.87 sec:  (    ) ph/cm2/s
    Energy fluence (15-150 keV)             : 0 ( 0  0 ) ergs/cm2
     
    

    S(25-50 keV) vs. S(50-100 keV) plot

    S(25-50 keV)  = 2.12e-07
    S(50-100 keV) = 2.65e-07
    

    T90 vs. Hardness ratio plot

    T90                                   = 77.608000010252 sec.
    Hardness ratio (energy fluence ratio) = 1.25
    

    Color vs. Color plot

    Count Ratio  (25-50 keV) / (15-25 keV) = 1.2446
    Count Ratio (50-100 keV) / (15-25 keV) = 0.718292
    

    Mask shadow pattern

    IMX = 2.485255591582526E-01, IMY = 8.020716942434582E-02
    

    TIME vs. PHA plot around the trigger time

    TIME vs. DetID plot around the trigger time

    100 us light curve (15-350 keV)

    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:
    -239.000000 -28.264000
     
    # RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
    #  [deg]    [deg]    ['] [deg]  [deg]                   [']
    244.9937 -15.6426    0.5  32.1   81.1   9.1545  25.2    0.8	Sco X-1                       
    254.4744  35.3596    1.4  35.9  -21.2   1.8316   8.2    1.3	Her X-1                       
    268.3541  -1.3096    5.7  43.8   40.3   1.0191   2.0    8.6	SW J1753.5-0127               
    216.3023  -9.6719    2.2  22.3  143.2   0.9263   5.2 ------	UNKNOWN                       
    228.0567  31.2963    3.6  21.0  -57.8   0.6729   3.8 ------	UNKNOWN                       
    228.1987  31.6326    4.2  21.3  -57.5   0.6345   3.6 ------	UNKNOWN                       
    188.8443   8.2466    2.5  36.7 -152.9   0.9684   4.7 ------	UNKNOWN                       
    

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

    Time interval of the image:
    -28.264000 58.608000
     
    # RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
    #  [deg]    [deg]    ['] [deg]  [deg]                   [']
    245.1033 -15.5935    4.9  32.2   80.9   0.4821   2.3    7.7	Sco X-1                       
    254.5438  35.4844   45.2  36.1  -21.3  -0.0336  -0.3    9.5	Her X-1                       
    268.3891  -1.5911    5.0  43.9   40.7   0.7346   2.3    8.4	SW J1753.5-0127               
    261.4211 -12.7038    2.1  42.1   59.7   2.2821   5.5 ------	UNKNOWN                       
    258.2489 -13.9317    2.4  40.2   63.9   1.9674   4.8 ------	UNKNOWN                       
    236.9575  20.5593    1.0  14.6  -17.9   1.2366  11.4 ------	UNKNOWN                       
    

    Post-slew image of 15-350 keV band

    Time interval of the image:
    108.500600 963.105000
     
    # RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
    #  [deg]    [deg]    ['] [deg]  [deg]                   [']
    244.9843 -15.6331    0.5  37.0   97.8  35.2066  24.8    0.5	Sco X-1                       
    254.4533  35.3453    0.6  21.3  -27.0   9.3073  20.6    0.3	Her X-1                       
    268.3544  -1.3084   12.8  37.7   52.3   1.0735   0.9    8.7	SW J1753.5-0127               
    288.7891  10.9435    2.2  50.6   23.3  10.1022   5.3    0.6	GRS 1915+105                  
    299.5991  35.2002    0.5  56.3   -8.7  43.4614  21.2    0.4	Cyg X-1                       
    186.4376  17.4114    3.2  47.7 -154.1   3.8092   3.6 ------	UNKNOWN                       
    280.1053  61.6892    4.1  50.7  -44.6   7.7563   2.8 ------	UNKNOWN                       
    
    Plot creation:
    Sun May 31 07:19:37 EDT 2015