Gamma-ray Burst 130420A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:29:47 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     553977,   Seg_Num: 0
GRB_RA:          196.100d {+13h 04m 24s} (J2000),
                 196.235d {+13h 04m 56s} (current),
                 195.589d {+13h 02m 21s} (1950)
GRB_DEC:         +59.424d {+59d 25' 25"} (J2000),
                 +59.352d {+59d 21' 09"} (current),
                 +59.691d {+59d 41' 29"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=2323 [image_cnts]
TRIGGER_DUR:     64.000 [sec] 
TRIGGER_INDEX:   20000     E_range: 15-50 keV
BKG_INTEN:       0 [cnts]
BKG_TIME:        0.00 SOD {00:00:00.00} UT
BKG_DUR:         0 [sec]
GRB_DATE:        16402 TJD;   110 DOY;   13/04/20
GRB_TIME:        26909.53 SOD {07:28:29.53} UT
GRB_PHI:         -19.09 [deg]
GRB_THETA:        28.56 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    12.77 [sigma]
MERIT_PARAMS:     +1  +0  +0  +6  +1  +2  +0  +0 +31  +0 
SUN_POSTN:        28.28d {+01h 53m 07s}  +11.61d {+11d 36' 23"}
SUN_DIST:        108.38 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.27d {+09h 25m 05s}   +9.64d {+09d 38' 38"}
MOON_DIST:        64.37 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.85, 57.63 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 157.58,-12.01 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:30:47 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      43
TRIGGER_NUM:     388135822
GRB_RA:          188.017d {+12h 32m 04s} (J2000),
                 188.172d {+12h 32m 41s} (current),
                 187.430d {+12h 29m 43s} (1950)
GRB_DEC:         +55.183d {+55d 10' 60"} (J2000),
                 +55.110d {+55d 06' 36"} (current),
                 +55.459d {+55d 27' 33"} (1950)
GRB_ERROR:       15.90 [deg radius, statistical plus systematic]
GRB_INTEN:       147 [cnts/sec]
DATA_SIGNIF:     6.30 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        16402 TJD;   110 DOY;   13/04/20
GRB_TIME:        27019.92 SOD {07:30:19.92} UT
GRB_PHI:          94.00 [deg]
GRB_THETA:       140.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      1.49
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,1, 0,0,0, 0,0,0, 0,1,0, 0,0,
SUN_POSTN:        28.28d {+01h 53m 07s}  +11.61d {+11d 36' 24"}
SUN_DIST:        111.17 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      141.28d {+09h 25m 07s}   +9.64d {+09d 38' 28"}
MOON_DIST:        58.48 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      128.77, 61.72 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      155.85, 51.71 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 14.88,25.13 [deg].

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:31:02 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      55
TRIGGER_NUM:     388135822
GRB_RA:          202.350d {+13h 29m 24s} (J2000),
                 202.481d {+13h 29m 55s} (current),
                 201.858d {+13h 27m 26s} (1950)
GRB_DEC:         +54.650d {+54d 38' 60"} (J2000),
                 +54.582d {+54d 34' 54"} (current),
                 +54.908d {+54d 54' 29"} (1950)
GRB_ERROR:       5.09 [deg radius, statistical only]
DATA_SIGNIF:     9.40 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        16402 TJD;   110 DOY;   13/04/20
GRB_TIME:        27019.92 SOD {07:30:19.92} UT
GRB_PHI:         100.00 [deg]
GRB_THETA:       133.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4143 (Gnd S/W Version number)
SUN_POSTN:        28.28d {+01h 53m 07s}  +11.61d {+11d 36' 24"}
SUN_DIST:        113.63 [deg]   Sun_angle= -11.6 [hr] (East of Sun)
MOON_POSTN:      141.28d {+09h 25m 08s}   +9.64d {+09d 38' 26"}
MOON_DIST:        65.69 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      111.35, 61.62 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      167.10, 56.70 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:32:25 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     553977,   Seg_Num: 0
GRB_RA:          196.100d {+13h 04m 24s} (J2000),
                 196.235d {+13h 04m 56s} (current),
                 195.589d {+13h 02m 21s} (1950)
GRB_DEC:         +59.424d {+59d 25' 25"} (J2000),
                 +59.352d {+59d 21' 09"} (current),
                 +59.691d {+59d 41' 29"} (1950)
GRB_DATE:        16402 TJD;   110 DOY;   13/04/20
GRB_TIME:        26909.53 SOD {07:28:29.53} UT
TRIGGER_INDEX:   20000
GRB_PHI:         -19.09 [deg]
GRB_THETA:        28.56 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     64.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    12.77 [sigma]
LC_URL:          sw00553977000msb.lc
SUN_POSTN:        28.28d {+01h 53m 08s}  +11.61d {+11d 36' 25"}
SUN_DIST:        108.38 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.29d {+09h 25m 10s}   +9.64d {+09d 38' 12"}
MOON_DIST:        64.36 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.85, 57.63 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is an image trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 157.58,-12.01 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:40:52 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.097d {+13h 04m 23s} (J2000)
POINT_DEC:       +59.419d {+59d 25' 09"} (J2000)
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27644.86 SOD {07:40:44.86} UT,   735.3 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:43:39 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.097d {+13h 04m 23s} (J2000)
POINT_DEC:       +59.419d {+59d 25' 10"} (J2000)
POINT_ROLL:      347.438d
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27648.09 SOD {07:40:48.09} UT,   738.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.436
N_STARS:         31
X_OFFSET:        524 [pixels]
Y_OFFSET:        572 [pixels]
X_MAX:           1483 [pixels]
Y_MAX:           1531 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00553977000msufc0738.fits
SUN_POSTN:        28.29d {+01h 53m 09s}  +11.61d {+11d 36' 35"}
SUN_DIST:        108.38 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.39d {+09h 25m 33s}   +9.61d {+09d 36' 25"}
MOON_DIST:        64.34 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.86, 57.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:44:00 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.097d {+13h 04m 23s} (J2000)
POINT_DEC:       +59.419d {+59d 25' 10"} (J2000)
POINT_ROLL:      347.438d
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27648.09 SOD {07:40:48.09} UT,   738.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.436
N_STARS:         31
X_OFFSET:        524 [pixels]
Y_OFFSET:        572 [pixels]
X_MAX:           1483 [pixels]
Y_MAX:           1531 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00553977000msufc0738.fits
SUN_POSTN:        28.29d {+01h 53m 09s}  +11.61d {+11d 36' 35"}
SUN_DIST:        108.38 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.39d {+09h 25m 34s}   +9.61d {+09d 36' 22"}
MOON_DIST:        64.34 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.86, 57.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:45:23 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     553977,   Seg_Num: 0
GRB_RA:          196.1081d {+13h 04m 25.94s} (J2000),
                 196.2436d {+13h 04m 58.47s} (current),
                 195.5970d {+13h 02m 23.27s} (1950)
GRB_DEC:         +59.4229d {+59d 25' 22.4"} (J2000),
                 +59.3518d {+59d 21' 06.4"} (current),
                 +59.6907d {+59d 41' 26.5"} (1950)
GRB_ERROR:       3.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27652.00 SOD {07:40:52.00} UT,   742.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 36"}
SUN_DIST:        108.37 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.40d {+09h 25m 37s}   +9.60d {+09d 36' 08"}
MOON_DIST:        64.35 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.85, 57.63 [deg] galactic lon,lat of the burst
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:45:44 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.097d {+13h 04m 23s} (J2000)
POINT_DEC:       +59.419d {+59d 25' 10"} (J2000)
ROLL:            347.438d
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27648.09 SOD {07:40:48.09} UT,   738.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     388136458
X_OFFSET:        843 [pixels]
Y_OFFSET:        891 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1003
Y_GRB_POS:       1051
BINNING_INDEX:   1
IM_URL:          sw00553977000msuni0749.fits
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 37"}
SUN_DIST:        108.37 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.41d {+09h 25m 37s}   +9.60d {+09d 36' 05"}
MOON_DIST:        64.34 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.86, 57.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:46:00 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.097d {+13h 04m 23s} (J2000)
POINT_DEC:       +59.419d {+59d 25' 10"} (J2000)
ROLL:            347.438d
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27648.09 SOD {07:40:48.09} UT,   738.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     388136458
X_OFFSET:        843 [pixels]
Y_OFFSET:        891 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1003
Y_GRB_POS:       1051
BINNING_INDEX:   1
IM_URL:          sw00553977000msuni0749.fits
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 37"}
SUN_DIST:        108.37 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.41d {+09h 25m 38s}   +9.60d {+09d 36' 02"}
MOON_DIST:        64.34 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.86, 57.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:47:47 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.092d {+13h 04m 22s} (J2000)
POINT_DEC:       +59.418d {+59d 25' 05"} (J2000)
POINT_ROLL:      347.433d
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27801.97 SOD {07:43:21.97} UT,   892.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.411
N_STARS:         98
X_OFFSET:        284 [pixels]
Y_OFFSET:        332 [pixels]
X_MAX:           1723 [pixels]
Y_MAX:           1771 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00553977000msufc0892.fits
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 38"}
SUN_DIST:        108.38 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.42d {+09h 25m 41s}   +9.60d {+09d 35' 45"}
MOON_DIST:        64.33 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.86, 57.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      156.45, 57.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:48:05 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.092d {+13h 04m 22s} (J2000)
POINT_DEC:       +59.418d {+59d 25' 05"} (J2000)
POINT_ROLL:      347.433d
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27801.97 SOD {07:43:21.97} UT,   892.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.411
N_STARS:         98
X_OFFSET:        284 [pixels]
Y_OFFSET:        332 [pixels]
X_MAX:           1723 [pixels]
Y_MAX:           1771 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00553977000msufc0892.fits
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 39"}
SUN_DIST:        108.38 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.43d {+09h 25m 42s}   +9.60d {+09d 35' 42"}
MOON_DIST:        64.33 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.86, 57.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      156.45, 57.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:48:49 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     553977,   Seg_Num: 0
GRB_RA:          196.1065d {+13h 04m 25.56s} (J2000),
                 196.2420d {+13h 04m 58.09s} (current),
                 195.5954d {+13h 02m 22.89s} (1950)
GRB_DEC:         +59.4241d {+59d 25' 26.7"} (J2000),
                 +59.3530d {+59d 21' 10.7"} (current),
                 +59.6919d {+59d 41' 30.9"} (1950)
GRB_ERROR:       0.8 [arcsec radius, statistical only]
GRB_MAG:         17.21 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27647.00 SOD {07:40:47.00} UT,   737.5 [sec] since BAT Trigger Time
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 39"}
SUN_DIST:        108.37 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.43d {+09h 25m 44s}   +9.59d {+09d 35' 35"}
MOON_DIST:        64.34 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.85, 57.63 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:49:25 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.092d {+13h 04m 22s} (J2000)
POINT_DEC:       +59.418d {+59d 25' 05"} (J2000)
ROLL:            347.433d
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27801.97 SOD {07:43:21.97} UT,   892.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     388136612
X_OFFSET:        843 [pixels]
Y_OFFSET:        891 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1003
Y_GRB_POS:       1051
BINNING_INDEX:   1
IM_URL:          sw00553977000msuni0903.fits
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 40"}
SUN_DIST:        108.37 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.44d {+09h 25m 45s}   +9.59d {+09d 35' 30"}
MOON_DIST:        64.33 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.86, 57.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      156.45, 57.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #14405
C. Guidorzi (U. Ferrara), A. Melandri (INAF-OAB), D. Kopac, A. Gomboc (U. Ljubljana), on behalf of a large collaboration report:
The 2-m Faulkes Telescope North automatically began observing GRB 130420A at 4.35 minutes from the Swift/BAT trigger time. The automatic LT-TRAP procedure identified a bright uncatalogued object at the following position:
```
RA=   13:04:25.57
Dec= +59:25:26.7
```
(J2000.0). Its magnitude is estimated to be 15.9 in the R band.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:49:14 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     553977,   Seg_Num: 0
POINT_RA:        196.092d {+13h 04m 22s} (J2000)
POINT_DEC:       +59.418d {+59d 25' 05"} (J2000)
ROLL:            347.433d
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27801.97 SOD {07:43:21.97} UT,   892.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     388136612
X_OFFSET:        843 [pixels]
Y_OFFSET:        891 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1003
Y_GRB_POS:       1051
BINNING_INDEX:   1
IM_URL:          sw00553977000msuni0903.fits
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 40"}
SUN_DIST:        108.37 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.44d {+09h 25m 44s}   +9.59d {+09d 35' 31"}
MOON_DIST:        64.33 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.86, 57.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      156.45, 57.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 20 Apr 13 07:49:06 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     553977,   Seg_Num: 0
GRB_RA:          196.1060d {+13h 04m 25.43s} (J2000),
                 196.2416d {+13h 04m 57.97s} (current),
                 195.5949d {+13h 02m 22.76s} (1950)
GRB_DEC:         +59.4241d {+59d 25' 26.7"} (J2000),
                 +59.3530d {+59d 21' 10.7"} (current),
                 +59.6919d {+59d 41' 30.9"} (1950)
GRB_ERROR:       2.6 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16402 TJD;   110 DOY;   13/04/20
IMG_START_TIME:  27652.00 SOD {07:40:52.00} UT,   742.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        28.29d {+01h 53m 10s}  +11.61d {+11d 36' 40"}
SUN_DIST:        108.37 [deg]   Sun_angle= -11.2 [hr] (East of Sun)
MOON_POSTN:      141.43d {+09h 25m 44s}   +9.59d {+09d 35' 33"}
MOON_DIST:        64.34 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:      119.85, 57.63 [deg] galactic lon,lat of the burst
ECL_COORDS:      156.45, 57.78 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN Circular #14406
M. J. Page (UCL-MSSL), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), S. R. Oates (UCL-MSSL) and D. M. Palmer (LANL) report on behalf of the Swift Team:
At 07:28:29 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 130420A (trigger=553977). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 196.100, +59.424 which is
```
   RA(J2000) = 13h 04m 24s
   Dec(J2000) = +59d 25' 25"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a very gradual beginning and a large peak at T+100 seconds. The total duration was about 200 sec. Because of the gradual beginning, the trigger was an image rather than a rate trigger. The peak count rate was ~3985 counts/sec (15-350 keV), at ~110 sec after the trigger.
The XRT began observing the field at 07:40:44.8 UT, 735.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 196.1061, 59.4241 which is equivalent to:
```
   RA(J2000)  = 13h 04m 25.46s
   Dec(J2000) = +59d 25' 26.8"
```
with an uncertainty of 2.6 arcseconds (radius, 90% containment). This location is 11 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.26 x 10^20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 738 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	13:04:25.57 = 196.10654
  DEC(J2000) = +59:25:26.9  =  59.42415
```
with a 90%-confidence error radius of about 0.75 arc sec. This position is 5.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.22 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01.
Burst Advocate for this burst is M. J. Page (m.page AT ucl.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular #14407
T. Guver (Sabanci U), report on behalf of the ROTSE collaboration: ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 130420A (Swift trigger 553977). The first image was at 07:29:51.5 UT, 82.0 s after the burst (7.5 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a 15.5 magnitude, fading source with coordinates:
```
     13:04:25.5      +59:25:27.2    (J2000), with positional uncertainty of 1" or better

start UT mag mlim(of image)
----------------------------------
07:34:12.7 15.5 16.5
```
This source is not visible in DSS (second epoch), 2MASS or the MPChecker database.
A jpeg image is available at http://www.rotse.net/images/gsq553977_3b03_img.jpg Note that the object marked 91 is the candidate in question.
Continuing observations are in progress.
GCN Circular #14408
A. N. Morgan (UC Berkeley) reports:
We observed the field of GRB 130420A (Page et al., GCN 14406) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at 2013-Apr-20 07h37m23s UT, 8.9 minutes after the Swift Trigger. In mosaics (effective exposure time of ~10 minutes) taken simultaneously in the J, H, and Ks filters, we detect the optical afterglow (Guidorzi et al., GCN 14405; Page et al., GCN 14406; Guver et al., GCN 14407).
The preliminary photometry yields:
```
post burst
t_mid (hr) exp.(m)  filt  mag   m_err
0.28       9.75     J     15.59  0.05
0.28       9.75     H     14.99  0.07
0.28       9.75     Ks    14.13  0.12
```
Observations are ongoing. All magnitudes are given in the Vega system, calibrated to 2MASS. No correction for Galactic extinction has been made to the above reported values.
GCN Circular #14409
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels= (GSFC),=20 and Harvey Moseley (GSFC) report:
We observed the field of GRB 130420A (Page, et al., GCN 14406) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional = on Sierra San Pedro M=E1rtir from 2013/04 20.41 to 2013/04 20.45 UTC (2.48 to 3.38 hours after the BAT trigger), obtaining a total of 0.36 hours exposure in the r' and i' bands and 0.14 hours exposure in the Z, Y, J, and H bands.
For a source within the Swift-XRT error circle, in comparison with SDSS D= R8 and 2MASS, we find:
```
r'	19.81 +/- 0.02
i'	19.41 +/- 0.02
Z	19.37 +/- 0.06
Y	18.99 +/- 0.07
J	19.16 +/- 0.07
H	18.87 +/- 0.11
```
These magnitudes are in the AB system and not corrected for Galactic extinction in the direction of the GRB. Uncertainties are 1-sigma.
Comparison to the earlier photometry of Morgan et al. (GCN 14408) shows t= hat this source has faded by about 2.5 magnitudes in J and H.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr= o=20 M=E1rtir.
Dr. Alan M. Watson Instituto de Astronom=EDa Universidad Nacional Aut=F3noma de M=E9xico
GCN Circular #14410
Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill Observatory, Varkaus, Finland) report:
We have detected GRB 130420A optical afterglow at iTelescope Observatory T21 (Mayhill, New Mexico) 0.43-m/6.8 astrograph and FLI ProLine PL6303E CCD. Two unfiltered images with 600 sec exposure time were made.
The afterglow was detected at following position RA 13:04:25.51 and DEC +59:25:27.2.
The following magnitudes were obtained from the observations using NOMAD1 1494-0215473 (R=16.220) as the comparison:
```
Tmid(sec)+T0  Filter         Exp. time   Mag           Mag err.  Limit
7258                unfiltered   600            19.49CR   0.20        20.60
7885                unfiltered   600            19.61CR   0.24        20.48
```
GCN Circular #14413
D. Xu (DARK/NBI), C. Cao, S.M. Hu (SDU) report:
We observed the field of GRB 130420A (Page et al., GCN 14406) using the 1m telescope located in Weihai, Shandong Province, China. Observations started at 11:41:32 UT, 2013-04-20 (i.e., 4.218 hr after the BAT trigger) and 12x180s I-band frames were obtained.
The optical afterglow (Page et al., GCN 14406) is clearly detected in our stacked image to be of I=19.4 mag, calibrated with nearby USNO B1 stars. It has decayed by about 0.5 mag, compared to the measurement in Watson et al. (GCN 14409).
We thank Dayong Ren for carrying out these observations.
GCN Circular #14415
L.P. Xin, M. Zhai, J. Y. Wei, Y. L. Qiu, J. Wang, J. S. Deng, C. Wu, X.H. Han report on behalf of EAFON team:
We began to observe the field of GRB 130420A (Page et al., GCN 14406 ) using 80cm TNT telescope located at Xinglong observatory, China at 12:16:56 UT on 2013-04-20. We obtained 12x300s R-band images in a poor seeing and cloudy weather, with a median time of 5.3 hr after the BAT trigger.
The afterglow reported (Page et a., GCN 14406 ) is not detected in the stacked image, down to a 3 sigma limit of R~18.0 mag, calibrated with USNO B2 stars.
This message may be cited.
GCN Circular #14416
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 2151 s of XRT Photon Counting mode data and 2 UVOT images for GRB 130420A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 196.10626, +59.42406 which is equivalent to:
```
RA (J2000): 13h 04m 25.50s
Dec (J2000): +59d 25' 26.6"
```
with an uncertainty of 1.7 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #14418
X.-H. Zhao (YNAO and PSU), J. Mao (RIKEN and YNAO), J.-M. Bai (YNAO) report on behalf of a larger collaboration:
We observed the field of GRB 130420A (Page et al., GCN 14406) with 2.4m Gao-Mei-Gu (GMG) telescope. Observations started at 13:36:00 UT on 2013-04-20 (i.e., 6.13 hrs after the burst, ~2 hrs later than the observation of Xu et al., GCN 14413) and 3x600s R-band and 1x600s I-band images were obtained. The optical counterpart of this burst was detected in both bands. The mag are R~19.4 and I~20.2 calibrated with USNO B1 stars.
We thank the GMG staff, especially Yu-Xin Xin, Gui-Hua He and Jian-Duo He for performing these observations.
GCN Circular #14419
GRB 130420A, Swift-BAT refined analysis
A. Y. Lien (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), M. J. Page (UCL-MSSL), D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+303 sec from the recent telemetry downlink, we report further analysis of BAT GRB 130420A (trigger #553977) (Page et al., GCN 14406). The BAT ground-calculated position is RA, Dec = 196.118, 59.421 deg which is
```
    RA(J2000)  =  13h 04m 28.3s
    Dec(J2000) = +59d 25' 16.8"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 86%.
The mask-weighted light curve shows a precursor beginning gradually at about T-20 seconds and increasing irregularly to about T+100 seconds. The main emission had a FRED shape peaking at about T+110 seconds that was detectable until about T+200 seconds. T90 (15-350 keV) is 123.5 +- 13.1 sec (estimated error including systematics).
The time-averaged spectrum from T-19.7 to T+189.9 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.52 +- 0.25, and Epeak of 33.2 +- 6.8 keV (chi squared 42.40 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 7.1 +- 0.3 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+110.67 sec in the 15-150 keV band is 3.4 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.18 +- 0.05 (chi squared 66.06 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/553977/BA/
GCN Circular #14422
A. Maselli (INAF-IASFPA), V. Mangano (INAF-IASFPA), M.C. Stroh (PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB) and M.J. Page report on behalf of the Swift-XRT team:
We have analysed 7.9 ks of XRT data for GRB 130420A (Page et al. GCN Circ. 14406), from 742 s to 19.7 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 14416).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.81 (+/-0.05).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.29 (+0.14, -0.13). The best-fitting absorption column is 7.1 (+2.5, -2.4) x 10^20 cm^-2, in excess of the Galactic value of 1.3 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.1 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     7.1 (+2.5, -2.4) x 10^20 cm^-2
Galactic foreground: 1.3 x 10^20 cm^-2
Excess significance: 4.1 sigma
Photon index:	     2.29 (+0.14, -0.13)
```
If the light curve continues to decay with a power-law decay index of 0.81, the count rate at T+24 hours will be 0.021 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.5 x 10^-13 (8.5 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00553977.
This circular is an official product of the Swift-XRT team.
GCN Circular #14424
S. R. Oates, M. De Pasquale, and M. J. Page (UCL-MSSL) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 130420A 739 s after the BAT trigger (Page et al., GCN Circ. 14406). A source consistent with the XRT position (Goad et al. GCN Circ. 14416) is detected in the initial UVOT exposures. The GRB is detected in all filters and is therefore consistent with being at a redshift of ~<1.6.
The preliminary UVOT position is:
```
  RA  (J2000) =  13:04:25.55 = 196.10647 (deg.)
  Dec (J2000) = +59:25:27.1  =  59.42420 (deg.)
```
with an estimated uncertainty of 0.50 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              739          888          147         17.14 +/- 0.03
v                 1072         1092           20         17.66 +/- 0.31
b                 1171         1191           19         18.13 +/- 0.21
u                 1146         1166           20         17.19 +/- 0.17
w1                1122         1141           19         17.51 +/- 0.29
m2                1097         1465           58         18.30 +/- 0.31
w2                1049         1240           39         18.50 +/- 0.33
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #14427
A. Trotter, N. Frank, A. LaCluyze, D. Reichart, K. McLin, L. Cominsky, T. Berger, J. A. Crain, H. T. Cromartie, R. Egger, A. Foster, J. Haislip, K. Ivarsen, M. Maples, J. Moore, M. Nysewander, and E. Speckhard report:
Skynet observed the Swift/BAT localization of GRB 130420A (Page et al., GCN 14406, Swift trigger 553977) with the 14" GLAST Optical Robotic Telescope (GORT) at the Hume observatory in California, beginning ~100s after the trigger in RcIc, and continuing until the source set at t=4.9h. We detect the afterglow reported by Guidorzi et al. (GCN 14405) at RA 13:04:06.6, Dec +59:25:25.2 (J2000), within the error circle reported by the Swift XRT (GCN 14406). Photometry was calibrated to six SDSS stars in the field. The afterglow exhibits a rising light curve in both Rc and Ic bands at early times, peaking at t=330s (peak Rc~16, Ic~15.5), after which it fades with an approximate temporal index alpha~-1. There is some evidence for flattening of the Ic-band light curve at t>1h, at which time Ic~18.7.
Follow-up observations at GORT have been scheduled.
A preliminary light curve of the first night's data can be found at: http://skynet.unc.edu/grb/grb130420a.png
GCN Circular #14428
L. Elenin (KIAM), A. Volnova ( IKI), V. Savanevych (KNURE), A. Bryukhovetskiy (NSFCTC), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 130420A (Page et al., GCN 14406) with 0.45-m telescope of ISON-NM observatory on Apr. 20, between (UT) 07:30:54 - 10:51:49. The observation started automatically 144 s after burst trigger. We took several unfiltered images of 30, 60 and 300 s exposures. The optical counterpart of GRB 130418A (Guidorzi et al., GCN 14405; Page et al., GCN 14406; Guver et al., GCN 14407) is clearly visible in single images.
Coordinates of the counterpart are (J2000) RA = 13:04:25.56 Dec = +59:25:26.8 with uncertainties of 0.2" coincide with the coordinates reported early (Guidorzi et al., GCN 14405, Guver et al., GCN 14407).
A photometry of single and later combined image is based on the SDSS stars with assumed R-magnitude
```
J130421.49+592547.6 R = 16.13
J130416.49+592509.2 R = 16.95
J130443.88+592659.3 R = 14.54
```
Preliminary light curve can be found at http://grb.rssi.ru/GRB130420A/GRB130420A_lightcurve_ISON-NM.png The light curve is clearly exhibit a fast rise and peaked with 16.1 mag at ~0.0207days after burst trigger following steep power law decay and later at 0.05 days swallowing to the typical afterglow power law.
GCN Circular #14429
Shaolin Xiong (UAH) and Arne Rau (MPE) report on behalf of the Fermi GBM Team:
"At 07:30:19.92 UT on 20 April 2013, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 130420A (trigger 388135822 / 130420313), which was also detected by the Swift (Page et al. 2013, GCN 14406). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 134 degrees.
The GBM light curve consists of precursors and a bright peak with a duration (T90) of about 102 s (50-300 keV). The time-averaged spectrum from T0-10 s to T0+27 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is 1.00 +/- 0.13 and the cutoff energy, parameterized as Epeak, is 56 +/- 3 keV.
The event fluence (10-1000 keV) in this time interval is (1.4 +/- 0.05)E-5 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.0 s in the 10-1000 keV band is 5.2 +/- 0.4 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #14431
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), Willia= m H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UC= B) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC= ), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UC= SC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1le= z (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels (GSFC), and Harv= ey Moseley (GSFC) report:
We again observed the field of GRB 130420A (Page et al., GCN 14406) with = the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on= the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Naci= onal on Sierra San Pedro M=E1rtir from 2013/04 21.30 to 2013/04 21.47UTC = (23.66 to 27.79 hours after the BAT trigger), obtaining a total of 1.44 h= ours exposure in the r' and i' bands and 0.59 hours exposure in the Z, Y,= J, and H bands.
The afterglow is well-detected. In comparison with SDSS DR8 and 2MASS, w= e obtain:
```
 r'   22.11 +/- 0.08
 i'   21.90 +/- 0.09
 Z   21.52 +/- 0.18
 Y   21.40 +/- 0.31
 J   21.24 +/- 0.26
 H   20.38 +/- 0.23
```
These magnitudes are in the AB system, quoted with 1-sigma uncertainty, a= nd not corrected for Galactic extinction in the direction of the GRB. In= comparison with our observations on the previous night (Watson et al., G= CN 14409), the afterglow has faded by more than about 2 magnitudes in all= bands.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr= o M=E1rtir.
GCN Circular #14436
J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis, of Los Alamos National Laboratory report:
The RAPTOR network of robotic optical telescopes made follow-up observations of Swift trigger 553977 (Page, et al., GCN 14406). Our RAPTOR-S and RAPTOR-T robotic telescopes located in Los Alamos, NM, began imaging at 07:29:52.95 UTC, 83.4 s after the Swift BAT trigger and continued during the entire period the BAT was detecting the dominant gamma-ray pulse (Lien, et al., GCN 14419). We detect optical emission during the gamma-ray emitting interval at the location of the counterpart reported by the Faulkes team (Guidorzi, et al., GCN 14405). In subsequent images we see a rapid rise in brightness at the same location, peaking at about T+300s. These observations were made simultaneously using SDSS g', r', i', z' and clear filters. Our unfiltered observations are consistent with the lightcurve published by the ISON team (Elenin, et al., GCN 14428).
GCN Circular #14437
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), N. Tanvir (U. Leicester), R. Sanchez-Ramirez (IAA-CSIC), C.C. Thoene (IAA-CSIC), J. Gorosabel (UPV/EHU, IAA-CSIC), and J. P. U. Fynbo (DARK/NBI) report:
We obtained spectroscopy of the afterglow of GRB 130420A (Page et al. GCN 14406) with the 10.4m GTC telescope on the 22nd April 2013, starting at 03:42 UT (1.84 days after the burst). The observation consisted of 4x900 s using the R500B grating, with a resolution of R~500 in the range 3600 - 8700 A.
The spectrum shows an emission line that we identify as [OII] from the host and several absorption features that correspond to MgII, MgI, FeII and AlIII at a common redshift of 1.297, which we identify as the redshift of the GRB.
We also note the presence of an unrelated nearby galaxy (at an angular separation of 2.5") which shows emission lines of [OII], H-beta and [OIII] at a redshift of 0.584.
We acknowledge the excellent support of the GTC staff.
GCN Circular #14439
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels= (GSFC), and Harvey Moseley (GSFC) report:
We again observed the field of GRB 130420A (Page et al., GCN Circular 14406) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional on Sierra San Pedro M=E1rtir from 2013/04 22.35 to 2013/04 22.47 UTC (48.84 to 51.69 hours after the BAT trigger), obtaining a total of 0.71 hours exposure in the r' and i' bands and 0.29 hours exposure in the Z, Y, J, and H bands.
The afterglow is again detected in several bands. In comparison with SDSS DR8 and 2MASS, we obtain:
```
r' 22.63 +/- 0.17
i' 22.46 +/- 0.17
Z  21.62 +/- 0.25
Y > 21.32
J > 21.39
H > 20.91
```
These magnitudes are in the AB system, quoted with 1-sigma uncertainty, and not corrected for Galactic extinction in the direction of the GRB.=20 The upper limits are at the 3-sigma level.
In comparison with our earlier observations (Watson et al., GCN Circular 14409; Butler et al., GCN Circular 14431), we see that the afterglow faded by about 2 magnitudes from about 3 to about 25 hours after the Swift trigger, but then by only about another 0.5 magnitudes from about 25 to about 50 hours after the Swift trigger.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr= o M=E1rtir.
GCN Circular #14440
F. V. Ferrante (SMU), G. Dhungana (SMU), T. Guver (Sabanci U), W. Zheng (UC Berkeley), H. Flewelling (IfA/Hawaii), F. Yuan (Australian National University), and R. Kehoe (SMU) report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 130420A (Swift trigger 553977; Guidorzi et al., GCN 14405; Page et al., GCN 14406; Guver et al., GCN 14407). The first image was at 07:29:51.5 UT, 82.0 s after the burst (7.5 s after the GCN notice time). We continued to monitor the source reported in GCN 14405, 14406, and 14407. The unfiltered images are calibrated relative to USNO A2.0. We took 220 20-sec exposures and observed a maximum magnitude of 15.5.
Further analysis of ROTSE-IIIb data using RPHOT indicates that the afterglow of GRB 130420A displays a single power-law decay with index alpha = - 0.70 up to ~1500 s after the burst. After the power law fall-off, the afterglow continued to be detected in subsequent images for ~6 ks. The minimum observed magnitude was 17.5.
GCN Circular #14441
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels= (GSFC), and Harvey Moseley (GSFC) report:
We again observed the field of GRB 130420A (Page et al., GCN Circular 14406) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional on Sierra San Pedro M=E1rtir from 2013/04 24.26 to 2013/04 24.46 UTC (94.73 to 99.64 hours after the BAT trigger), obtaining a total of 2.84 hours exposure in the r' and i' bands and 1.19 hours exposure in the Z, Y, J, and H bands.
For a source within the Swift-XRT error circle, in comparison with SDSS DR8 and 2MASS, we obtain the following upper limits (3-sigma) in the AB magnitude system:
```
r'	> 23.15
i'	> 23.02
Z	> 21.75
Y	> 21.44
J	> 21.72
H	> 21.16
```
These magnitudes are not corrected for Galactic extinction in the direction of the GRB.
In comparison with our earlier observations (Watson et al., GCN Circular 14409; Butler et al., GCN Circular 14431; Watson et al., GCN Circular 14439), the source has faded by about at least a magnitude in r' and i' between about 50 and about 97 hours.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedr= o M=E1rtir.
GCN Circular #14445
A. Trotter, N. Frank, A. LaCluyze, D. Reichart, K. McLin, L. Cominsky, T. Berger, H. T. Cromartie, R. Egger, A. Foster, J. Haislip, K. Ivarsen, M. Maples, J. Moore, M. Nysewander, E. Speckhard, and J. A. Crain report:
Skynet continued observing the field of GRB 130420A (Page et al., GCN 14406, Swift trigger #553977) with the 14" GLAST Optical Robotic Telescope (GORT) at the Hume Observatory in California. It took 214 80-s exposures in Ic at times t=20.48-23.30h and t=26.25-28.56h after burst trigger, and 96 80-s exposures in Rc at t=23.33-26.15h. We performed photometry on the stacked exposures in each band, calibrated to six SDSS stars in the field. We detect the afterglow in both Ic and Rc bands at t~24h:
```
band   exp length   mean time since trig   mag(Vega)
Ic     4.76h        24.37h                 21.04 (+0.43,-0.31)
Rc     2.47h        24.77h                 21.00 (+0.25,-0.21)
```
As we note in Trotter et al. (GCN 14427), and as Elenin et al. (GCN 14428) confirm, the afterglow exhibits a rising light curve at early times, peaking at t=330s (peak Rc~16, Ic~15.5). After the peak, the light curve fades with a power law index alpha~-0.9.
A preliminary light curve of the first and second nights' data is at: http://skynet.unc.edu/grb/grb130420a_2.png

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Jochen Greiner, last update: 26-Apr-2013 [Disclaimer]