Gamma-ray Burst 160425A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 25 Apr 16 23:26:26 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     684098,   Seg_Num: 0
GRB_RA:          280.313d {+18h 41m 15s} (J2000),
                 280.647d {+18h 42m 35s} (current),
                 279.290d {+18h 37m 10s} (1950)
GRB_DEC:         -54.359d {-54d 21' 33"} (J2000),
                 -54.343d {-54d 20' 34"} (current),
                 -54.407d {-54d 24' 24"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1681 [cnts]    Image_Peak=178 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   123     E_range: 25-100 keV
BKG_INTEN:       23725 [cnts]
BKG_TIME:        84359.82 SOD {23:25:59.82} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17503 TJD;   116 DOY;   16/04/25
GRB_TIME:        84371.34 SOD {23:26:11.34} UT
GRB_PHI:         -126.98 [deg]
GRB_THETA:        24.65 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     32.95 [sigma]
IMAGE_SIGNIF:    11.80 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +2  +1  +0  +0 +41  +0 
SUN_POSTN:        33.86d {+02h 15m 25s}  +13.58d {+13d 34' 39"}
SUN_DIST:        114.46 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      256.84d {+17h 07m 21s}  -17.71d {-17d 42' 34"}
MOON_DIST:        40.96 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.34 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      277.00,-31.17 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate 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 = 12.15,15.67 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 25 Apr 16 23:29:40 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.288d {+18h 41m 09s} (J2000)
POINT_DEC:       -54.349d {-54d 20' 57"} (J2000)
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  84574.74 SOD {23:29:34.74} UT,   203.4 [sec] since BAT Trigger Time
COUNTS:          7    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    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:     Mon 25 Apr 16 23:32:35 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.287d {+18h 41m 09s} (J2000)
POINT_DEC:       -54.350d {-54d 20' 58"} (J2000)
POINT_ROLL:      101.326d
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  84579.50 SOD {23:29:39.50} UT,   208.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.004
N_STARS:         190
X_OFFSET:        619 [pixels]
Y_OFFSET:        519 [pixels]
X_MAX:           1578 [pixels]
Y_MAX:           1478 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00684098000msufc0208.fits
SUN_POSTN:        33.86d {+02h 15m 26s}  +13.58d {+13d 34' 44"}
SUN_DIST:        114.48 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      256.89d {+17h 07m 34s}  -17.71d {-17d 42' 50"}
MOON_DIST:        40.92 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.99,-31.16 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 25 Apr 16 23:33:04 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1083886,   Seg_Num: 189
GRB_RA:          280.313d {+18h 41m 15s} (J2000),
                 280.647d {+18h 42m 35s} (current),
                 279.290d {+18h 37m 10s} (1950)
GRB_DEC:         -54.359d {-54d 21' 33"} (J2000),
                 -54.343d {-54d 20' 34"} (current),
                 -54.407d {-54d 24' 24"} (1950)
GRB_DATE:        17503 TJD;   116 DOY;   16/04/25
GRB_TIME:        84371.34 SOD {23:26:11.34} UT
TRIGGER_INDEX:   123
GRB_PHI:         -126.98 [deg]
GRB_THETA:        24.65 [deg]
DELTA_TIME:      958.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    0.00 [sigma]
LC_URL:          sw00684098000msb.lc
SUN_POSTN:        33.86d {+02h 15m 27s}  +13.58d {+13d 34' 45"}
SUN_DIST:        114.46 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      256.90d {+17h 07m 35s}  -17.71d {-17d 42' 51"}
MOON_DIST:        40.93 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.34 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      277.00,-31.17 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        WARNING: No BAT_Position TDRSS message was received for this trigger_number!  
COMMENTS:           
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate 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 = 12.15,15.67 [deg].  
COMMENTS:        The 3rd packet (of 3) was missing in the lightcurve data stream.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 25 Apr 16 23:33:22 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.287d {+18h 41m 09s} (J2000)
POINT_DEC:       -54.350d {-54d 20' 58"} (J2000)
POINT_ROLL:      101.326d
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  84579.50 SOD {23:29:39.50} UT,   208.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.004
N_STARS:         190
X_OFFSET:        619 [pixels]
Y_OFFSET:        519 [pixels]
X_MAX:           1578 [pixels]
Y_MAX:           1478 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00684098000msufc0208.fits
SUN_POSTN:        33.86d {+02h 15m 27s}  +13.58d {+13d 34' 45"}
SUN_DIST:        114.48 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      256.90d {+17h 07m 35s}  -17.71d {-17d 42' 52"}
MOON_DIST:        40.91 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.99,-31.16 [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:     Mon 25 Apr 16 23:33:58 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.287d {+18h 41m 09s} (J2000)
POINT_DEC:       -54.350d {-54d 20' 58"} (J2000)
ROLL:            101.326d
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  84579.50 SOD {23:29:39.50} UT,   208.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     483319795
X_OFFSET:        938 [pixels]
Y_OFFSET:        838 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1098
Y_GRB_POS:       998
BINNING_INDEX:   1
IM_URL:          sw00684098000msuni0225.fits
SUN_POSTN:        33.86d {+02h 15m 27s}  +13.58d {+13d 34' 45"}
SUN_DIST:        114.48 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      256.90d {+17h 07m 37s}  -17.72d {-17d 42' 54"}
MOON_DIST:        40.91 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.99,-31.16 [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:     Mon 25 Apr 16 23:34:20 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.287d {+18h 41m 09s} (J2000)
POINT_DEC:       -54.350d {-54d 20' 58"} (J2000)
ROLL:            101.326d
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  84579.50 SOD {23:29:39.50} UT,   208.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     483319795
X_OFFSET:        938 [pixels]
Y_OFFSET:        838 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1098
Y_GRB_POS:       998
BINNING_INDEX:   1
IM_URL:          sw00684098000msuni0225.fits
SUN_POSTN:        33.86d {+02h 15m 27s}  +13.58d {+13d 34' 46"}
SUN_DIST:        114.48 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      256.91d {+17h 07m 38s}  -17.72d {-17d 42' 55"}
MOON_DIST:        40.91 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.99,-31.16 [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:     Mon 25 Apr 16 23:38:02 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     684098,   Seg_Num: 0
GRB_RA:          280.3213d {+18h 41m 17.11s} (J2000),
                 280.6549d {+18h 42m 37.17s} (current),
                 279.2978d {+18h 37m 11.47s} (1950)
GRB_DEC:         -54.3597d {-54d 21' 34.9"} (J2000),
                 -54.3432d {-54d 20' 35.3"} (current),
                 -54.4071d {-54d 24' 25.6"} (1950)
GRB_ERROR:       7.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  84881.00 SOD {23:34:41.00} UT,   509.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        33.86d {+02h 15m 27s}  +13.58d {+13d 34' 49"}
SUN_DIST:        114.46 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      256.94d {+17h 07m 45s}  -17.72d {-17d 43' 04"}
MOON_DIST:        40.92 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.34 [deg] galactic lon,lat of the burst
ECL_COORDS:      277.01,-31.17 [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 0.11% < P(seren) < 0.58%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 25 Apr 16 23:39:29 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     684098,   Seg_Num: 0
GRB_RA:          280.3273d {+18h 41m 18.55s} (J2000),
                 280.6609d {+18h 42m 38.61s} (current),
                 279.3038d {+18h 37m 12.91s} (1950)
GRB_DEC:         -54.3600d {-54d 21' 35.9"} (J2000),
                 -54.3435d {-54d 20' 36.4"} (current),
                 -54.4075d {-54d 24' 26.8"} (1950)
GRB_ERROR:       0.7 [arcsec radius, statistical only]
GRB_MAG:         19.90 +/- 0.17 [mag]
FILTER:          10, White
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  84577.00 SOD {23:29:37.00} UT,   205.7 [sec] since BAT Trigger Time
SUN_POSTN:        33.86d {+02h 15m 28s}  +13.58d {+13d 34' 50"}
SUN_DIST:        114.46 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      256.95d {+17h 07m 48s}  -17.72d {-17d 43' 08"}
MOON_DIST:        40.91 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.34 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      277.01,-31.17 [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:     Mon 25 Apr 16 23:44:19 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.282d {+18h 41m 08s} (J2000)
POINT_DEC:       -54.350d {-54d 21' 01"} (J2000)
POINT_ROLL:      101.332d
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  85230.85 SOD {23:40:30.85} UT,   859.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.082
N_STARS:         190
X_OFFSET:        379 [pixels]
Y_OFFSET:        279 [pixels]
X_MAX:           1818 [pixels]
Y_MAX:           1718 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00684098000msufc0859.fits
SUN_POSTN:        33.87d {+02h 15m 28s}  +13.58d {+13d 34' 54"}
SUN_DIST:        114.49 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:      256.99d {+17h 07m 59s}  -17.72d {-17d 43' 20"}
MOON_DIST:        40.87 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.98,-31.16 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 25 Apr 16 23:44:40 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.282d {+18h 41m 08s} (J2000)
POINT_DEC:       -54.350d {-54d 21' 01"} (J2000)
POINT_ROLL:      101.332d
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  85230.85 SOD {23:40:30.85} UT,   859.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.082
N_STARS:         190
X_OFFSET:        379 [pixels]
Y_OFFSET:        279 [pixels]
X_MAX:           1818 [pixels]
Y_MAX:           1718 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00684098000msufc0859.fits
SUN_POSTN:        33.87d {+02h 15m 28s}  +13.58d {+13d 34' 54"}
SUN_DIST:        114.49 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:      257.00d {+17h 07m 59s}  -17.72d {-17d 43' 21"}
MOON_DIST:        40.87 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.98,-31.16 [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:     Mon 25 Apr 16 23:44:57 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     684098,   Seg_Num: 0
GRB_RA:          280.3274d {+18h 41m 18.57s} (J2000),
                 280.6610d {+18h 42m 38.63s} (current),
                 279.3039d {+18h 37m 12.94s} (1950)
GRB_DEC:         -54.3603d {-54d 21' 37.0"} (J2000),
                 -54.3438d {-54d 20' 37.5"} (current),
                 -54.4078d {-54d 24' 27.9"} (1950)
GRB_ERROR:       2.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  84881.00 SOD {23:34:41.00} UT,   509.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        33.87d {+02h 15m 28s}  +13.58d {+13d 34' 54"}
SUN_DIST:        114.46 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      257.00d {+17h 08m 00s}  -17.72d {-17d 43' 22"}
MOON_DIST:        40.89 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.34 [deg] galactic lon,lat of the burst
ECL_COORDS:      277.01,-31.17 [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 0.11% < P(seren) < 0.58%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 25 Apr 16 23:45:48 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.282d {+18h 41m 08s} (J2000)
POINT_DEC:       -54.350d {-54d 21' 01"} (J2000)
ROLL:            101.332d
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  85230.85 SOD {23:40:30.85} UT,   859.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     483320447
X_OFFSET:        938 [pixels]
Y_OFFSET:        838 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1098
Y_GRB_POS:       998
BINNING_INDEX:   1
IM_URL:          sw00684098000msuni0876.fits
SUN_POSTN:        33.87d {+02h 15m 29s}  +13.58d {+13d 34' 55"}
SUN_DIST:        114.49 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:      257.01d {+17h 08m 02s}  -17.72d {-17d 43' 24"}
MOON_DIST:        40.87 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.98,-31.16 [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:     Mon 25 Apr 16 23:46:00 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     684098,   Seg_Num: 0
POINT_RA:        280.282d {+18h 41m 08s} (J2000)
POINT_DEC:       -54.350d {-54d 21' 01"} (J2000)
ROLL:            101.332d
IMG_START_DATE:  17503 TJD;   116 DOY;   16/04/25
IMG_START_TIME:  85230.85 SOD {23:40:30.85} UT,   859.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     483320447
X_OFFSET:        938 [pixels]
Y_OFFSET:        838 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1098
Y_GRB_POS:       998
BINNING_INDEX:   1
IM_URL:          sw00684098000msuni0876.fits
SUN_POSTN:        33.87d {+02h 15m 29s}  +13.58d {+13d 34' 55"}
SUN_DIST:        114.49 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:      257.01d {+17h 08m 02s}  -17.72d {-17d 43' 24"}
MOON_DIST:        40.87 [deg]
MOON_ILLUM:      88 [%]
GAL_COORDS:      341.31,-20.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.98,-31.16 [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 #19343
H. A. Krimm (CRESST/GSFC/USRA), A. D'Ai (INAF-IASFPA), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC), A. Maselli (INAF-IASFPA), D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 23:26:11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160425A (trigger=684098). Swift slewed to the burst after a short delay due to an observing constraint. The BAT on-board calculated location is RA, Dec 280.313, -54.359 which is
```
   RA(J2000) = 18h 41m 15s
   Dec(J2000) = -54d 21' 33"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 2 sec, followed by a 50 second-long peak at T+250s. There may also be a precursor peak of ~100 s duration at T-380s. The peak count rate was ~6000 counts/sec (15-350 keV), at ~0.2 sec after the trigger.
The XRT began observing the field at 23:29:34.7 UT, 203.4 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 280.3274, -54.3601 which is equivalent to:
```
   RA(J2000)  = 18h 41m 18.56s
   Dec(J2000) = -54d 21' 36.2"
```
with an uncertainty of 2.0 arcseconds (radius, 90% containment). This location is 30 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.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (7.74 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.5 (+2.72/-2.31) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 208 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	18:41:18.57 = 280.32738
  DEC(J2000) = -54:21:36.1  = -54.36004
```
with a 90%-confidence error radius of about 0.68 arc sec. This position is 2.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.91 with a 1-sigma error of about 0.17. No correction has been made for the expected extinction corresponding to E(B-V) of 0.06.
It is extremely unusual for a short GRB to have a long pulse a few minutes later with much more fluence. It is more common for a long GRB to have a short precursor pulse. Further characterization of this event will require the full downlinked data set.
Burst Advocate for this burst is H. A. Krimm (hans.krimm AT nasa.gov). 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 #19344
V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov Lomonosov Moscow State University, Sternberg Astronomical Institute
D.Buckley, S. Potter, A.Kniazev South African Astronomical Observatory
K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University
A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk
V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, Kourovka
Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA)
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was pointed to the GRB 160425A (trigger time 23:26:11.34) at 2016-04-25 23:28:59UT. On our first (30s, t_start=2016-04-25 23:28:59UT, m_lim=17.3, polarization) exposition there is marginally seen optical transient within SWIFT error-box up (H. A. Krimm et al., GCN #19343) at RA=280.32738,-54.36004
The observations will be continued.
GCN Circular #19347
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 1763 s of XRT Photon Counting mode data and 1 UVOT images for GRB 160425A, 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 = 280.32719, -54.36001 which is equivalent to:
```
RA (J2000): 18h 41m 18.53s
Dec (J2000): -54d 21' 36.0"
```
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 #19348
A. Melandri (INAF-OAB), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and H.A. Krimm report on behalf of the Swift-XRT team:
We have analysed 7.0 ks of XRT data for GRB 160425A (Krimm et al. GCN Circ. 19343), from 207 s to 18.4 ks after the BAT trigger. The data comprise 439 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 19347).
The late-time light curve (from T0+6.1 ks) can be modelled with a power-law decay with a decay index of alpha=0.78 (+/-0.23).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.18 (+/-0.04). The best-fitting absorption column is 5.26 (+0.23, -0.22) x 10^21 cm^-2, in excess of the Galactic value of 7.7 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.76 (+0.19, -0.18) and a best-fitting absorption column of 5.7 (+/-0.8) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 2.9 x 10^-11 (9.0 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     5.7 (+/-0.8) x 10^21 cm^-2
Galactic foreground: 7.7 x 10^20 cm^-2
Excess significance: 10.6 sigma
Photon index:	     2.76 (+0.19, -0.18)
```
If the light curve continues to decay with a power-law decay index of 0.78, the count rate at T+24 hours will be 0.019 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.5 x 10^-13 (1.7 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00684098.
This circular is an official product of the Swift-XRT team.
GCN Circular #19349
J. Bodensteiner (MPE Garching), S. Schmidl (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 160425A (Swift trigger 684098; Krimm et al. GCN Circ. 19343) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).
Observations started at 04:38 UT on April 26, 2016, 5.2 hrs after the GRB trigger. They were performed at an average seeing of 3.1" and at an average airmass of 1.2.
We detect an optical source at the position reported by Krimm et al. (GCN 19343) and Lipunov et al. (GCN 19344).
Based on total exposures of 24 minutes in g'r'i'z' and 20 minutes in JHK, at a midtime of 7.16 hrs after the burst, we measure the following preliminary magnitudes and upper limits (AB magnitude system):
```
g' = 22.2 +/- 0.3 mag,         
r' = 21.1 +/- 0.2 mag,
i' = 20.7 +/- 0.2 mag,
z' = 20.5 +/- 0.1 mag,
J  = 19.7 +/- 0.2 mag,         
H  = 19.4 +/- 0.3 mag, and
K  > 18.3 mag. 
```
The magnitudes and upper limits are calibrated against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.06 mag in the direction of the burst (Schlegel et al. 1998).
Relative to the UVOT and MASTER reports, the source has faded, though we do not detect significant fading in our data so far (strongly mitigated by the bad conditions). We therefore cannot distinguish between afterglow or host flux.
GCN Circular #19350
N. R. Tanvir (U. Leicester), D. Xu (NAO/CAS), T. Kruehler (MPE), D. Malesani, J. P. U. Fynbo (DARK/NBI), G. Pugliese (U. Amsterdam), A. J. Levan (U. Warwick), Z. Cano (U. Iceland) report on behalf of a larger collaboration:
We observed the optical counterpart of the unusual GRB 160425A (Krimm et al., GCN 19343) with the ESO Very Large Telescope UT 2 (Kueyen) equipped with the X-shooter spectrograph, covering the wavelength range 3500-20000 AA. Observations started on April 26.26 UT (approx 6.9 hr after the GRB) and consisted of 4 exposures of 1200 s each.
In our acquisition images, we detect an extended object consistent with the position of the UVOT counterpart, whose morphology exhibits two knots separated by ~1.2". That object is faintly visible in the digitized sky survey, and is likely the host galaxy of GRB 160425A.
The spectrum reveals two distinct systems at z=0.555, based on emission lines of Halpha, Hbeta, [O III], [O II] and [S III]. The velocity separation between them is ~180 km/s, and the spatial separation is consistent with the two knots seen in the imaging (corresponding to ~8 kpc at this distance), suggesting an interacting pair of galaxies.
We acknowledge expert support from the ESO observing staff, particularly Jose Velazquez and Juan Carlos Munoz, in obtaining these observations.
GCN Circular #19351
P.Balanutsa, V. Lipunov, E. Gorbovskoy, N.Tyurina, V.Kornilov, A.Kuznetsov Lomonosov Moscow State University, Sternberg Astronomical Institute
D.Buckley, S. Potter, A.Kniazev South African Astronomical Observatory
MASTER-SAAO telescope pointed to the unusual short GRB160425A (Krimm et al. GCN #19343 ) at 2016-04-25 23:28:59UT 168s after trigger time, 30s first expositions with orthogonal polarimeter filters . The delay is caused with the short rain, the roof was closed at the trigger time.
MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 280.32738,-54.36004 at the first 30s polarized image in 1 tube at 2016-04-25 23:28:59UT with unfiltered m_OT~18.2+-0.5 (w=0.2B+0.8R calibrated by USNO-B1) http://observ.pereplet.ru/images/MASTERGRB160425A.jpg . The second tube in orthogonal polarization filter doesn't see it with m_lim=17.7, possibly it depends on polarization of this source.
There is a faint optical source at the Palomar (POSS) both red and blue images. But this source doesn't present at USNO-B1 catalogue. There is blue source (in 0.411") in GSC2.3.2 with jmag=22.16. The most probable classification of it is the host galaxy of short GRB160425A.
SWIFT UVOT see optical afterglow 19.9m in white filter (150s expos., starting 208 seconds after the BAT trigger (23:26:11UT) (Krimm et al., GCN Circ. 19343) and GROND see afetrglow in g'r'i'z' started at 04:38 UT on April 26, 2016, 5.2 hrs after the GRB (Bodensteiner et al., GCN Circ. 19349).
The analyses will be continued.
GCN Circular #19354
B. E. Cobb (GWU), reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 160425A (GCN 19343, Krimm et al.) at two epochs. For each epoch, total summed exposure times amounted to 15 minutes in I and V and 12 minutes in J and K.
No source is detected at the position of the optical afterglow (e.g. GCN 19343, Krimm et al.; GCN 19344, Lipunov et al.; GCN 19349, Bodensteiner et al.) to the approximate limiting magnitudes listed below. The first epoch was obtained under particularly poor seeing conditions.
```
mid-exposure               mid-exposure time  
time                        post-burst limits
2016-04-26 04:53 UT  5.44083 hours      I > 19.5   J > 16.6   K > 15.7

2016-04-26 08:29 UT  9.04250 hours      I > 19.9   J > 17.9   K > 17.1
```
Magnitudes are calibrated using USNO-B1.0 stars in I, and 2MASS stars in J and K.
GCN Circular #19355
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), J. P. Norris (BSU), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160425A (trigger #684098) (Krimm, et al. GCN Circ. 19343). The BAT ground-calculated position is RA, Dec = 280.339, -54.343 deg which is
```
  RA(J2000)  =  18h 41m 21.5s
  Dec(J2000) = -54d 20' 34.6"
```
with an uncertainty of 3.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 71%.
The mask-weighted light curve shows several separate pulses. The first short pulse starts at ~ T-0.5 s, peaks at ~T+0.2 s, and ends at ~T+1.5 s. The second pulse occurs at ~T+60 s and is quite weak. Another strong pulse starts at ~T+250 s, peaks at ~T+270 s, and ends at ~ T+300 s. T90 (15-350 keV) is 304.58 +- 15.04 sec (estimated error including systematics). The potential precursor peak seen in the raw light curve at ~T-380 s (Krimm, et al., GCN Circ. 19343) is due to a noisy detector.
The time-averaged spectrum from T-0.53 to T+319.80 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.20 +- 0.18. The fluence in the 15-150 keV band is 2.1 +- 0.2 x 10^-6 erg/cm2. The total fluence is dominated by the pulse at ~T+270 s, which has a fluence of 1.1 +/- 0.1 x 10^-6 erg/cm2, while the fluence of the short pulse is 2.8 +/- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.27 sec in the 15-150 keV band is 2.8 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The spectrum of the initial short pulse is best-fitted by a simple power-law model with a power-law index of 1.71 +/- 0.14. This value is a typical number for a long GRB, but is also consistent with the majority of the short GRB population (Sakamoto et al. 2011).
Using a 32-ms binned light curve, the lag analysis of the initial short pulse is 57 (-27, +34) ms for the 100-350 keV to 25-50 keV, and 19 (-38, +32) ms for the 50-100 keV to 15-25 keV band. These numbers are consistent with those of a long GRB. However, we note that the low redshift (z=0.555, Tanvir et al, GCN Circ. 19350) indicates that this GRB might have a lower luminosity (the luminosity of the short pulse in the BAT observed energy band, 15-150 keV, is ~ 1.7 x 10^50 erg/s), and thus the this GRB might lie outside the usual lag-luminosity relation (Norris et al. 2000).
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/684098/BA/
GCN Circular #19356
A. Trotter, D. Reichart, J. Haislip, J. Moore, N. Frank, M. Maples, E. Johnson, R. Joyner, J. Martin, C. Salemi, J. A. Crain, K. Ivarsen, A. LaCluyze, and M. Nysewander report:
Skynet observed the Swift BAT/XRT localization of the unusual GRB 160425A (Krimm et al., GCN 19343, Swift trigger=684098) with with two 16" telescopes (P5, P6), and twp 24" telescopes (P1, P8) of the PROMPT array at CTIO, Chile. Starting at 2016-04-25 01:34 UT and continuing until 10:14 UT (t=2.1-10.8h post-trigger), Skynet took a total of 849 160s exposures in the I band (P1, P5), V band (P6) and B band (P8).
We detect a fading optical afterglow in I-band images at the UVOT position reported by Krimm et al. (GCN 19343), with I~17 at t=2.2h and I~20 at t=7.3h.
A preliminary light curve is at: http://www.skynet.unc.edu/grb/grb160425a.png
Preliminary magnitudes are in the Vega System, calibrated to 8 APASS DR9 stars in the field. Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.05 (Schlafly & Finkbeiner 2011).
No further Skynet observations are scheduled.

GCN Circular #19357
M. H. Siegel (PSU) and H. A. Krimm (CRESST/GSFC/USRA) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 160425A 208 s after the BAT trigger (Krimm et al., GCN Circ. 19343). A fading source consistent with the XRT position (Beardmore et al. GCN Circ. 19347) is detected in the initial UVOT exposures. This source is consistent with the optical transient reported by MASTER (Lipunov et al, GCN Circ. 19344) and GROND (Bodensteiner et al., GCN Circ. 19349). The source has plateaud over the last day, which may indicate detection of the host galaxy reported by MASTER (Balanutsa et al., GCN Circ. 19351).
The preliminary UVOT position is:

   RA  (J2000) =  18:41:18.58 = 280.32743 (deg.)
   Dec (J2000) = -54:21:36.3  = -54.36007 (deg.)

with an estimated uncertainty of 0.53 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 (fc)         208          358          147         19.57 +/- 0.10
white              859         1009          147         20.70 +/- 0.35
white             1164         2397          155        >20.19
white             6727         8221          254        >20.79
white            11858        12765          885         21.03 +/- 0.19
white            35282        41433         2162         21.48 +/- 0.23
white            46310        58620         3898         21.48 +/- 0.16
white           104099       111153         2061         21.80 +/- 0.30
v                  365         2447          233         19.22 +/- 0.31
b                  465         1852          156         20.16 +/- 0.32
u                  440         6517          410         20.07 +/- 0.26
w1                 415         7748          607         20.24 +/- 0.30
m2                 390         7542          430        >19.7
w2                 515        13672         1296        >20.8

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.06 in the direction of the burst (Schlegel et al. 1998).

GCN Circular #19358
Changsu Choi and Myungshin Im (CEOU/SNU)
We observed the field of GRB 160425A (Krimm et al. GCN Circ. 19343) using LSGT(Lee Sang Gak Telescope; Im et al. 2015, JKAS, 48, 207 ). Images were taken in R and I band starting on Apr. 26 15:14:22 UT(~15.24 hr after burst). We do not detect the optical afterglow candidate within the XRT enhanced error circle (Beardmore et al. GCN Circ. 19347) to the approximate limiting magnitudes listed below.
```
mid-time(UT)                    post-bust-hour    exposure(s)
filter(limiting mag)
-----------------------------------------------------------------------------------------------------------

2016-04-26 16:10:02        16.16722                2700                   R
> 19.55
2016-04-26 17:04:26        17.07396                2700
I   > 19.22
```
Magnitudes are calibrated using USNO-B1 stars in R1 and I.
GCN Circular #19454
B. E. Cobb (GWU), reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained additional optical/IR imaging of the error region of GRB 160425A (GCN 19343, Krimm et al.) at 7.3, 18.4 and 26.4 days post-burst. For each epoch, total summed exposure times amounted to 36 minutes in I and 30 minutes in J.
The possible host of GRB 160425A (GCN 19350, Tanvir et al., GCN 19351, Balanutsa et al.) is observed in these images. This object appears as two separate knots and, therefore, may be a merging pair of galaxies (GCN 19350, Tanvir et al.). The object, with a magnitude of I~20.1 (calibrated using USNO-B1.0 stars), exhibits no significant changes in brightness between 7 and 26 days post-burst, though changes in brightness of less than 0.05 magnitudes cannot be ruled out by the data. In this type of host, at a redshift of z=0.555 (GCN 19350, Tanvir et al.), a 1998bw-like supernova would be expected to increase the brightness of the host by approximately 0.1 magnitudes, and can therefore be excluded. If this unusual burst (GRB GCN 19343, Krimm et al.) is actually a long-duration GRB, than any associated supernova must be dimmer at peak than SN 1998bw.

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Jochen Greiner, last update: 24-May-2016 [Disclaimer]