batgrbproduct analysis for trigger=823014

batgrbproduct Analysis for Trigger=823014

Analysis Summary

Notes:

1) No attempt has been made to eliminate the non-significant decimal places.
2) This batgrbproduct analysis is done of the amount of data for this trigger downloaded to date.
3) This batgrbproduct analysis is using the flight position for the mask-weighting calculation.
4) This page will be updated for up to 15 downlinks after the trigger.

======================================================================
                  BAT GRB EVENT DATA PROCESSING REPORT
    Process Script Ver: batgrbproduct v2.46
    Process Start Time (local time): Sun Apr  8 07:04:36 EDT 2018
             Host Name: bat1
   Current Working Dir: /local/data/bat1/prebascript/trigger823014/GCN5_download_cron
======================================================================

  Trigger: 00823014      Segment: 000

  BAT Trigger Time: 544766739.008   [s; MET]
      Trigger Stop: 544766740.032   [s; MET]
               UTC: 2018-04-07T04:05:18.262140    [includes UTCF correction] 
       Where From?: TDRSS position message

  BAT 
    RA: 209.937846998469   Dec: 48.6535260416956  [deg; J2000]

     Catalogged Source?: NO
     Point Source?:      YES
     GRB Indicated?:     YES    [ by BAT flight software ]
     Image S/N Ratio:    6.69
     Image Trigger?:     NO
     Rate S/N Ratio:     16.1554944214035  [ if not an image trigger ]
     Image S/N Ratio:    6.69

  Flight Position:   [ source = BAT ]
    RA: 209.937846998469   Dec: 48.6535260416956  [deg; J2000]

  Ground Position:   [ source = BAT pre-slew burst ]
    RA: 210.197804202663   Dec: 48.72158027165  [deg; J2000]  
        { 14h 00m 47.5s , +48d 43' 17.7" }
         +/- 9.26221603500178 [arcmin] (estimated 90% radius based on SNR)
         +/- 7.00599069994528 [arcmin] (formal 1-sigma fit error)
    SNR: 1.26501910678331
 
  Angular difference between Flight and Ground position is 11.076934 arcmin
 
  Partial Coding Fraction: 0.9765625    [ including projection effects ]

  Duration
     T90: 52.4480000734329 +/- 33.857316606448
        Measured from: 0.104000091552734
                   to: 52.5520001649857     [s; relative to TRIGTIME]
     T50: 33.9680000543594 +/- 26.3017858326978
        Measured from: 5.94400012493134
                   to: 39.9120001792908     [s; relative to TRIGTIME]



  Fluence
     Peak Flux  (peak 1 second)
        Measured from: -0.00400006771087646     
                   to: 0.995999932289124     [s; relative to TRIGTIME]
     Total Fluence        
        Measured from: -0.296000003814697     
                   to: 54.3279999494553     [s; relative to TRIGTIME]
     
             Band 1     Band 2     Band 3     Band 4
              15-25      25-50     50-100    100-350     keV
 Total     0.049976  -0.053047  -0.061645   0.164600
           0.048943   0.053933   0.054829   0.062495 [error]
 Peak      0.012162   0.004856   0.016231   0.040284
           0.006007   0.006490   0.006387   0.007050 [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 0.00e+00 0.00e+00 0.00e+00 0.00e+001.51e-06 0.00e+009.90e-08 0.00e+001.69e-06   erg/cm2
              Error 1.52e-08 1.18e-08 3.43e-08 2.28e-06 1.20e-07 2.30e-06   erg/cm2
Peak flux Power-law 8.39e-04 6.80e-03 4.91e-02 1.97e+00 1.81e-01 2.03e+00   ph/cm2/s
              Error 1.26e-02 3.25e-02 7.22e-02 9.57e-01 1.71e-01 9.98e-01   ph/cm2/s
 
Fluence   Cutoff-PL 0.00e+00 0.00e+00 0.00e+00 0.00e+00 0.00e+00 0.00e+00   erg/cm2
              Error 2.38e-08 1.52e-08 3.62e-08 -------- 1.38e-07 4.38e-05   erg/cm2
Peak flux Cutoff-PL -------- -------- -------- -------- -------- --------   ph/cm2/s
              Error -------- -------- -------- -------- -------- --------   ph/cm2/s
 
Fluence        Band 0.00e+00 0.00e+00 0.00e+00 0.00e+00 0.00e+00 0.00e+00   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    1.500    0.000    -      -           0.00e+00 8.90e-05   52.930 57
CPL   1.000    0.000      50.0    0.0      0.00e+00 0.00e+00   52.930 56
 
The chi2 of BB fit is  which shows a significant improvement in the fit over a PL.
Check the BB fit.
 
=== 1-s peak spectral analysis ===
 
Model Ph_index Ph_90err Epeak  Epeak_90err Norm     Nomr_90err chi2   dof
PL   -1.851    1.154    -      -           4.50e-04 1.33e-03   74.970 57
CPL  -2.750    1.561    9999.9    0.0      1.82e-04 1.24e-03   74.580 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   54.624   -0.296   54.328
T90    52.448    0.104   52.552
T50    33.968    5.944   39.912
Peak    1.000   -0.004    0.996

Click here for the BAT GCN circular template

Estimated redshift from machine learning (Ukwatta et al. 2016) - may take a few minutes to calcaulte

Image

Pre-slew 15-350 keV image (Event data; bkg subtracted)

#   RAcent  DECcent POSerr  Theta    Phi     Peak Cts     SNR  Name
  210.1978 +48.7216 0.1527   17.7   22.9       0.0733     1.3  TRIG_00823014       
------------------------------------------
 
Foreground time interval of the image:
 -0.296  15.093 (delta_t =  15.389 [sec])
Background time interval of the image:
-60.008  -0.296 (delta_t =  59.712 [sec])

Lightcurves

Notes:

1) All plots contain as much data as has been downloaded to date.
2) The mask-weighted light curves are using the flight position.
3) Multiple plots of different time binning/intervals are shown to cover all scenarios of short/long GRBs, rate/image triggers, and real/false positives.
4) For all the mask-weighted lightcurves, the y-axis units are counts/sec/det where a det is 0.4 x 0.4 = 0.16 sq cm.
5) The verticle lines correspond to following: green dotted lines are T50 interval, black dotted lines are T90 interval, blue solid line(s) is a spacecraft slew start time, and orange solid line(s) is a spacecraft slew end time.
6) Time of each bin is in the middle of the bin.

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

Blue+Cyan dotted lines: Time interval of the scaled map
From 0.000000 to 1.024000

8 ms binning

From T100_start-3 s to T100_start+3 s

Blue+Cyan dotted lines: Time interval of the scaled map
From 0.000000 to 1.024000

2 ms binning

From T100_start-1 s to T100_start+1 s

Blue+Cyan dotted lines: Time interval of the scaled map
From 0.000000 to 1.024000

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

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

Spectra

Notes:

1) The fitting includes the systematic errors.
2) For long bursts, a spectral fit of 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.
4) For short bursts (T90<1sec), the specrtum is also fit with Blackbody, OTTB, and Double Blackbody.

Time averaged spectrum fit using the pre-slew DRM

Power-law model

Time interval is from   -0.296 sec. to   54.328 sec.
 
Spectral model in power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: 1.50000     ( -1.5   -1.5 )
Norm@50keV  : 0.0    ( 0   0.000178069 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          52.93 using 59 PHA bins.
# Reduced chi-squared =         0.9285 for     57 degrees of freedom 
# Null hypothesis probability =   6.286039e-01
 
Photon flux (15-150 keV)    in 54.62 sec: 0.0 ( 0  0.0257431 ) ph/cm2/s
Energy fluence (15-150 keV)             : 0 ( -9.64272e-08  1.42905e-07 ) ergs/cm2

Cutoff power-law model

Time interval is from   -0.296 sec. to   54.328 sec.
Spectral model in the cutoff power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: 1.00000     (     )
Epeak [keV] : 50.0000      (   )
Norm@50keV  : 0.0    (     )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          52.93 using 59 PHA bins.
# Reduced chi-squared =         0.9451 for     56 degrees of freedom 
# Null hypothesis probability =   5.919607e-01
 
Photon flux (15-150 keV)    in 54.62 sec: 0.0 8.51990E-03 7.73338E-03 7.24216E-03 7.13534E-04 6.02277E-04 4.85232E-04 1.88040E-04 (    ) ph/cm2/s
Energy fluence (15-150 keV)             : 0 ( 0  0 ) ergs/cm2

Band function

Time interval is from   -0.296 sec. to   54.328 sec.
 
Spectral model in the Band function:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
alpha       : -7.46846   ( 0.98395   0.98395 )
beta        : 1.52652    ( 2.5   2.5 )
Epeak [keV] : 5.17011      ( -80 -80 )
Norm@50keV   : 4.23597E-03    ( -0.00443318   0.0134857 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          51.48 using 59 PHA bins.
# Reduced chi-squared =         0.9360 for     55 degrees of freedom 
# Null hypothesis probability =   6.099130e-01
 
Photon flux (15-150 keV)    in 54.62 sec: 0.0 (    ) 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]    : 3.76123  (-3.7582  -3.7582)
R^2/D10^2   : 0.367048  (-0.369454   -0.369454)
(R is the radius in km and D10 is the distance to the source in units of 10 kpc)
------------------------------------------------------------
#Fit statistic : Chi-Squared =          51.94 using 59 PHA bins.
# Reduced chi-squared =         0.9113 for     57 degrees of freedom 
# Null hypothesis probability =   6.647415e-01
 
Energy  Fluence     90% Error
[keV]   [erg/cm2]   [erg/cm2]
15- 25  1.342e-08   9.545e-09
25- 50  4.051e-09   4.454e-09
50-150  3.356e-11   3.605e-11
15-150  1.751e-08   1.142e-08

Thermal bremsstrahlung (OTTB)

 
 
Spectral model: thermal bremsstrahlung
------------------------------------------------------------
Parameters  : value         Lower 90%    Upper 90%
kT [keV]    : 7.91088       (-7.91086      -7.91086)
Norm        : 0.476100       (-0.476073     -0.476073)
------------------------------------------------------------
#Fit statistic : Chi-Squared =          52.20 using 59 PHA bins.
# Reduced chi-squared =         0.9158 for     57 degrees of freedom 
# Null hypothesis probability =   6.554518e-01
 
Energy  Fluence     90% Error
[keV]   [erg/cm2]   [erg/cm2]
15- 25  1.098e-08   7.551e-09
25- 50  3.349e-09   3.736e-09
50-150  1.137e-10   1.600e-10
15-150  1.444e-08   1.094e-08

Double BB

 
 
Spectral model: bbodyrad<1> + bbodyrad<2>
------------------------------------------------------------
Parameters  : value         Lower 90%    Upper 90%
kT1 [keV]   : 3.75736        (-3.75729      -3.75729)
R1^2/D10^2  : 0.369327        (-0.36943      -0.36943)
kT2 [keV]   : 0.102243        (-0.102243      -0.102243)
R2^2/D10^2  : 3.38429E-03    (-0.00338506   -0.00338506)
------------------------------------------------------------
#Fit statistic : Chi-Squared =          51.94 using 59 PHA bins.
# Reduced chi-squared =         0.9444 for     55 degrees of freedom 
# Null hypothesis probability =   5.921700e-01
 
Energy  Fluence     90% Error
[keV]   [erg/cm2]   [erg/cm2]
15- 25  0.000e+00   0.000e+00
25- 50  0.000e+00   0.000e+00
50-150  0.000e+00   0.000e+00
15-150  0.000e+00   0.000e+00

Peak spectrum fit

Power-law model

Time interval is from   -0.004 sec. to    0.996 sec.
 
Spectral model in power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: -1.85105     ( -0.471431   1.8373 )
Norm@50keV  : 4.50047E-04    ( -0.000450055   0.00221447 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          74.97 using 59 PHA bins.
# Reduced chi-squared =          1.315 for     57 degrees of freedom 
# Null hypothesis probability =   5.548549e-02
 
Photon flux (15-150 keV)    in 1 sec: 0.180677 ( -0.129197  0.212963 ) ph/cm2/s
Energy fluence (15-150 keV)             : 3.21839e-08 ( -2.26757e-08  2.82956e-08 ) ergs/cm2

Cutoff power-law model

Time interval is from   -0.004 sec. to    0.996 sec.
Spectral model in the cutoff power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: -2.74975     ( -0.491749   2.62994 )
Epeak [keV] : 9999.94      ( -9999.94 -9999.94 )
Norm@50keV  : 1.82349E-04    ( -0.000182349   0.00230221 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          74.58 using 59 PHA bins.
# Reduced chi-squared =          1.332 for     56 degrees of freedom 
# Null hypothesis probability =   4.910830e-02
 
Photon flux (15-150 keV)    in 1 sec:  (    ) ph/cm2/s
Energy fluence (15-150 keV)             : 0 ( 0  0 ) ergs/cm2

Band function

Time interval is from   -0.004 sec. to    0.996 sec.
 
Spectral model in the Band function:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
alpha       : 6.60683E-02   ( -0.0673126   -0.0673126 )
beta        : 1.85094    ( -1.83871   0.471214 )
Epeak [keV] : 6.53400      ( -6.53553 -6.53553 )
Norm@50keV   : 2.12768E-03    ( -0.00212842   8289.45 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          74.97 using 59 PHA bins.
# Reduced chi-squared =          1.363 for     55 degrees of freedom 
# Null hypothesis probability =   3.798708e-02
 
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]    : 200.000  (-200  -200)
R^2/D10^2   : 1.70894E-04  (-6.24651e-05   -0.000171349)
(R is the radius in km and D10 is the distance to the source in units of 10 kpc)
------------------------------------------------------------
#Fit statistic : Chi-Squared =          76.36 using 59 PHA bins.
# Reduced chi-squared =          1.340 for     57 degrees of freedom 
# Null hypothesis probability =   4.439870e-02
 
Energy  Fluence     90% Error
[keV]   [erg/cm2]   [erg/cm2]
15- 25  3.020e-09   1.792e-09
25- 50  6.825e-10   5.410e-10
50-150  2.994e-12   3.379e-12
15-150  3.705e-09   2.139e-09

Thermal bremsstrahlung (OTTB)

 
 
Spectral model: thermal bremsstrahlung
------------------------------------------------------------
Parameters  : value         Lower 90%    Upper 90%
kT [keV]    : 199.353       (-199.36      -199.36)
Norm        : 1.14821       (-0.608529     0.610388)
------------------------------------------------------------
#Fit statistic : Chi-Squared =          87.10 using 59 PHA bins.
# Reduced chi-squared =          1.528 for     57 degrees of freedom 
# Null hypothesis probability =   6.286913e-03
 
Energy  Fluence     90% Error
[keV]   [erg/cm2]   [erg/cm2]
15- 25  2.859e-09   2.012e-09
25- 50  5.500e-09   3.878e-09
50-150  1.206e-08   8.620e-09
15-150  2.042e-08   1.447e-08

Double BB

------------------------------------------------------------
Parameters  : value         Lower 90%    Upper 90%
kT1 [keV]   : 2.98459        (-2.95712      -2.95712)
R1^2/D10^2  : 14.0145        (-14.0652      49.6842)
kT2 [keV]   : 199.042        (-142.72      -199.049)
R2^2/D10^2  : 1.69064E-04    (-6.29549e-05   0.000774818)
------------------------------------------------------------
#Fit statistic : Chi-Squared =          74.55 using 59 PHA bins.
#Fit statistic : Chi-Squared =          73.73 using 59 PHA bins.
# Reduced chi-squared =          1.356 for     55 degrees of freedom 
# Reduced chi-squared =          1.341 for     55 degrees of freedom 
# Null hypothesis probability =   4.073254e-02
# Null hypothesis probability =   4.669813e-02
 
Energy  Fluence     90% Error
[keV]   [erg/cm2]   [erg/cm2]
15- 25  2.707e-09   1.504e-09
25- 50  2.571e-09   1.729e-09
50-150  4.384e-08   4.597e-08
15-150  4.912e-08   4.565e-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: -1.55442     ( -1.13375   2.06373 )
Norm@50keV  : 9.48906E-05    ( -9.48029e-05   0.000306009 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          67.73 using 59 PHA bins.
# Reduced chi-squared =          1.188 for     57 degrees of freedom 
# Null hypothesis probability =   1.563536e-01
 
Photon flux (15-150 keV)    in 15.39 sec: 3.06873E-02 ( -0.0306661  0.031453 ) ph/cm2/s
Energy fluence (15-150 keV)             : 8.16914e-08 ( -8.16926e-08  7.35068e-08 ) ergs/cm2

Cutoff power-law model

Spectral model in the cutoff power-law:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
Photon index: -2.19350     ( -1.4586   3.29538 )
Epeak [keV] : 9999.97      ( -9999.97 -9999.97 )
Norm@50keV  : 5.91488E-05    ( -5.91488e-05   0.000300727 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          67.23 using 59 PHA bins.
# Reduced chi-squared =          1.201 for     56 degrees of freedom 
# Null hypothesis probability =   1.446172e-01
 
Photon flux (15-150 keV)    in 15.39 sec: 3.74684E-02 ( -0.0374684  0.0284423 ) ph/cm2/s
Energy fluence (15-150 keV)             : 4.20746e-17 ( 0  0 ) ergs/cm2

Band function

 
Spectral model in the Band function:
------------------------------------------------------------
Parameters  : value       lower 90%   higher 90%
alpha       : 4.38550   ( -0.436834   -0.436834 )
beta        : -9.37035    ( 0.758577   3.10523 )
Epeak [keV] : 488.881      ( -411.341 9382.13 )
Norm@50keV   : 4.35422E-05    ( -4.4332e-05   0.00093193 )
------------------------------------------------------------
#Fit statistic : Chi-Squared =          66.81 using 59 PHA bins.
# Reduced chi-squared =          1.215 for     55 degrees of freedom 
# Null hypothesis probability =   1.319690e-01
 
Photon flux (15-150 keV)    in 15.39 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)  = 0.00e+00
S(50-100 keV) = 0.00e+00

T90 vs. Hardness ratio plot

T90                                   = 52.4480000734329 sec.
Hardness ratio (energy fluence ratio) =

Color vs. Color plot

Count Ratio  (25-50 keV) / (15-25 keV) = -1.06145
Count Ratio (50-100 keV) / (15-25 keV) = -1.23349

Mask shadow pattern

IMX = 2.947731140545876E-01, IMY = -1.242349411577283E-01

TIME vs. PHA plot around the trigger time

Blue+Cyan dotted lines: Time interval of the scaled map
From 0.000000 to 1.024000

TIME vs. DetID plot around the trigger time

Blue+Cyan dotted lines: Time interval of the scaled map
From 0.000000 to 1.024000

100 us light curve (15-350 keV)

Blue+Cyan dotted lines: Time interval of the scaled map
From 0.000000 to 1.024000

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:
-60.008000 -0.296000
 
# RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
#  [deg]    [deg]    ['] [deg]  [deg]                   [']
254.5827  35.3761   13.0  51.5    4.6  -0.2678  -0.9    6.4	Her X-1                       
272.3857  50.2177    3.0  50.7  -20.7   1.0161   3.9 ------	UNKNOWN                       
 91.9578  59.8403    2.5  45.4 -121.4   2.4615   4.6 ------	UNKNOWN

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

Time interval of the image:
-0.296000 15.092600
 
# RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
#  [deg]    [deg]    ['] [deg]  [deg]                   [']
254.5104  35.1941  313.2  51.6    4.8  -0.0062  -0.0    9.3	Her X-1                       
154.6311  28.5618    2.1  33.4  152.9   0.4684   5.5 ------	UNKNOWN

Post-slew image of 15-350 keV band

Time interval of the image:
56.092590 86.452000
87.992000 183.122000
 
# RAcent  DECcent POSerr Theta    Phi  PeakCts   SNR AngSep     Name
#  [deg]    [deg]    ['] [deg]  [deg]                   [']
254.5842  35.4123    9.0  35.1  -11.3   1.8100   1.3    7.5	Her X-1                       
228.2605   4.8229    2.7  46.5   47.9  18.3916   4.3 ------	UNKNOWN                       
246.4342  13.8072    2.1  46.0   20.1  13.2310   5.5 ------	UNKNOWN                       
105.6715  72.8160    3.2  48.0 -129.1  20.5270   3.6 ------	UNKNOWN

Plot creation:
Sun Apr  8 07:09:14 EDT 2018