Gamma-ray Burst 150424A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:43:10 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     638946,   Seg_Num: 0
GRB_RA:          152.312d {+10h 09m 15s} (J2000),
                 152.488d {+10h 09m 57s} (current),
                 151.737d {+10h 06m 57s} (1950)
GRB_DEC:         -26.647d {-26d 38' 47"} (J2000),
                 -26.722d {-26d 43' 19"} (current),
                 -26.401d {-26d 24' 02"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2964 [cnts]    Image_Peak=333 [image_cnts]
TRIGGER_DUR:     0.064 [sec] 
TRIGGER_INDEX:   10427     E_range: 50-350 keV
BKG_INTEN:       16171 [cnts]
BKG_TIME:        27762.51 SOD {07:42:42.51} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17136 TJD;   114 DOY;   15/04/24
GRB_TIME:        27776.91 SOD {07:42:56.91} UT
GRB_PHI:         -175.16 [deg]
GRB_THETA:        34.06 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     250.96 [sigma]
IMAGE_SIGNIF:    15.22 [sigma]
MERIT_PARAMS:     +1  +0  +0  -4  +3  +4  +0  +0 +54  +0 
SUN_POSTN:        31.58d {+02h 06m 20s}  +12.79d {+12d 47' 29"}
SUN_DIST:        123.16 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.48d {+07h 01m 54s}  +17.40d {+17d 23' 47"}
MOON_DIST:        63.47 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.59, 23.57 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      165.64,-35.22 [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 = 202.28,-14.61 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:45:00 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     638946,   Seg_Num: 0
GRB_RA:          152.3087d {+10h 09m 14.08s} (J2000),
                 152.4850d {+10h 09m 56.40s} (current),
                 151.7333d {+10h 06m 55.99s} (1950)
GRB_DEC:         -26.6305d {-26d 37' 49.8"} (J2000),
                 -26.7060d {-26d 42' 21.7"} (current),
                 -26.3846d {-26d 23' 04.6"} (1950)
GRB_ERROR:       5.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       2.87e-09 [erg/cm2/sec]
GRB_SIGNIF:      10.09 [sigma]
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  27864.77 SOD {07:44:24.77} UT,   87.9 [sec] since BAT Trigger Time
TAM[0-3]:        327.68 237.21 261.56 243.72
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        31.58d {+02h 06m 20s}  +12.79d {+12d 47' 30"}
SUN_DIST:        123.15 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.49d {+07h 01m 58s}  +17.39d {+17d 23' 42"}
MOON_DIST:        63.44 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.58, 23.59 [deg] galactic lon,lat of the burst
ECL_COORDS:      165.63,-35.20 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.98 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:45:16 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     638946,   Seg_Num: 0
GRB_RA:          152.3087d {+10h 09m 14.0s} (J2000),
                 152.4850d {+10h 09m 56.4s} (current),
                 151.7333d {+10h 06m 55.9s} (1950)
GRB_DEC:         -26.6305d {-26d 37' 49.8"} (J2000),
                 -26.7060d {-26d 42' 21.7"} (current),
                 -26.3846d {-26d 23' 04.6"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       102 [cnts]
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  27864.77 SOD {07:44:24.77} UT,   87.9 [sec] since BAT Trigger Time
CENTROID_X:      321.13,  raw= 321  [pixels]
CENTROID_Y:      301.26,  raw= 301  [pixels]
ROLL:            268.24 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   8.16
GRB_POS_XRT_Z:   37.32
IMAGE_URL:       sw00638946000msxps_rw.img
SUN_POSTN:        31.58d {+02h 06m 20s}  +12.79d {+12d 47' 31"}
SUN_DIST:        123.15 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.50d {+07h 01m 59s}  +17.39d {+17d 23' 41"}
MOON_DIST:        63.44 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.58, 23.59 [deg] galactic lon,lat of the burst
ECL_COORDS:      165.63,-35.20 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:45:10 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     638946,   Seg_Num: 0
GRB_RA:          152.3087d {+10h 09m 14.0s} (J2000),
                 152.4850d {+10h 09m 56.4s} (current),
                 151.7333d {+10h 06m 55.9s} (1950)
GRB_DEC:         -26.6305d {-26d 37' 49.8"} (J2000),
                 -26.7060d {-26d 42' 21.7"} (current),
                 -26.3846d {-26d 23' 04.6"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       102 [cnts]
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  27864.77 SOD {07:44:24.77} UT,   87.9 [sec] since BAT Trigger Time
CENTROID_X:      321.13,  raw= 321  [pixels]
CENTROID_Y:      301.26,  raw= 301  [pixels]
ROLL:            268.24 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   8.16
GRB_POS_XRT_Z:   37.32
IMAGE_URL:       sw00638946000msxps_rw.img
SUN_POSTN:        31.58d {+02h 06m 20s}  +12.79d {+12d 47' 31"}
SUN_DIST:        123.15 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.50d {+07h 01m 59s}  +17.39d {+17d 23' 41"}
MOON_DIST:        63.44 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.58, 23.59 [deg] galactic lon,lat of the burst
ECL_COORDS:      165.63,-35.20 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:46:30 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     638946,   Seg_Num: 0
GRB_RA:          152.312d {+10h 09m 15s} (J2000),
                 152.488d {+10h 09m 57s} (current),
                 151.737d {+10h 06m 57s} (1950)
GRB_DEC:         -26.647d {-26d 38' 47"} (J2000),
                 -26.722d {-26d 43' 19"} (current),
                 -26.401d {-26d 24' 02"} (1950)
GRB_DATE:        17136 TJD;   114 DOY;   15/04/24
GRB_TIME:        27777.07 SOD {07:42:57.07} UT
TRIGGER_INDEX:   10427
GRB_PHI:         -175.16 [deg]
GRB_THETA:        34.06 [deg]
DELTA_TIME:      -15.00 [sec]
TRIGGER_DUR:     0.064 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     250.96 [sigma]
IMAGE_SIGNIF:    15.22 [sigma]
LC_URL:          sw00638946000msb.lc
SUN_POSTN:        31.58d {+02h 06m 20s}  +12.79d {+12d 47' 32"}
SUN_DIST:        123.16 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.51d {+07h 02m 02s}  +17.39d {+17d 23' 37"}
MOON_DIST:        63.44 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.59, 23.57 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      165.64,-35.22 [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 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 = 202.28,-14.61 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:47:27 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.297d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.629d {-26d 37' 42"} (J2000)
POINT_ROLL:      268.245d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  27875.94 SOD {07:44:35.94} UT,   99.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.863
N_STARS:         170
X_OFFSET:        404 [pixels]
Y_OFFSET:        568 [pixels]
X_MAX:           1363 [pixels]
Y_MAX:           1527 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00638946000msufc0099.fits
SUN_POSTN:        31.58d {+02h 06m 20s}  +12.79d {+12d 47' 32"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.52d {+07h 02m 04s}  +17.39d {+17d 23' 34"}
MOON_DIST:        63.41 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:47:58 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.297d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.629d {-26d 37' 42"} (J2000)
POINT_ROLL:      268.245d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  27875.94 SOD {07:44:35.94} UT,   99.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.863
N_STARS:         170
X_OFFSET:        404 [pixels]
Y_OFFSET:        568 [pixels]
X_MAX:           1363 [pixels]
Y_MAX:           1527 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00638946000msufc0099.fits
SUN_POSTN:        31.59d {+02h 06m 20s}  +12.79d {+12d 47' 33"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.52d {+07h 02m 05s}  +17.39d {+17d 23' 32"}
MOON_DIST:        63.41 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [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:     Fri 24 Apr 15 07:48:56 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.297d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.629d {-26d 37' 42"} (J2000)
ROLL:            268.245d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  27875.94 SOD {07:44:35.94} UT,   99.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     451554289
X_OFFSET:        724 [pixels]
Y_OFFSET:        888 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       884
Y_GRB_POS:       1048
BINNING_INDEX:   1
IM_URL:          sw00638946000msuni0113.fits
SUN_POSTN:        31.59d {+02h 06m 21s}  +12.79d {+12d 47' 34"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.53d {+07h 02m 07s}  +17.39d {+17d 23' 29"}
MOON_DIST:        63.40 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:49:06 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.297d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.629d {-26d 37' 42"} (J2000)
ROLL:            268.245d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  27875.94 SOD {07:44:35.94} UT,   99.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     451554289
X_OFFSET:        724 [pixels]
Y_OFFSET:        888 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       884
Y_GRB_POS:       1048
BINNING_INDEX:   1
IM_URL:          sw00638946000msuni0113.fits
SUN_POSTN:        31.59d {+02h 06m 21s}  +12.79d {+12d 47' 34"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.53d {+07h 02m 07s}  +17.39d {+17d 23' 29"}
MOON_DIST:        63.40 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:55:50 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.298d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.628d {-26d 37' 39"} (J2000)
POINT_ROLL:      268.247d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28088.01 SOD {07:48:08.01} UT,   311.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.603
N_STARS:         104
X_OFFSET:        404 [pixels]
Y_OFFSET:        568 [pixels]
X_MAX:           1363 [pixels]
Y_MAX:           1527 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00638946000msufc0311.fits
SUN_POSTN:        31.59d {+02h 06m 22s}  +12.79d {+12d 47' 39"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.59d {+07h 02m 22s}  +17.39d {+17d 23' 07"}
MOON_DIST:        63.36 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:56:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.298d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.628d {-26d 37' 39"} (J2000)
POINT_ROLL:      268.247d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28088.01 SOD {07:48:08.01} UT,   311.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.603
N_STARS:         104
X_OFFSET:        404 [pixels]
Y_OFFSET:        568 [pixels]
X_MAX:           1363 [pixels]
Y_MAX:           1527 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00638946000msufc0311.fits
SUN_POSTN:        31.59d {+02h 06m 22s}  +12.79d {+12d 47' 40"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.60d {+07h 02m 23s}  +17.39d {+17d 23' 07"}
MOON_DIST:        63.35 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [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:     Fri 24 Apr 15 07:56:46 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     638946,   Seg_Num: 0
GRB_RA:          152.3060d {+10h 09m 13.44s} (J2000),
                 152.4823d {+10h 09m 55.75s} (current),
                 151.7306d {+10h 06m 55.35s} (1950)
GRB_DEC:         -26.6310d {-26d 37' 51.6"} (J2000),
                 -26.7065d {-26d 42' 23.5"} (current),
                 -26.3851d {-26d 23' 06.5"} (1950)
GRB_ERROR:       2.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28079.00 SOD {07:47:59.00} UT,   302.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        31.59d {+02h 06m 22s}  +12.79d {+12d 47' 40"}
SUN_DIST:        123.15 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.60d {+07h 02m 24s}  +17.38d {+17d 23' 04"}
MOON_DIST:        63.36 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.58, 23.58 [deg] galactic lon,lat of the burst
ECL_COORDS:      165.62,-35.21 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:57:12 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.298d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.628d {-26d 37' 39"} (J2000)
ROLL:            268.247d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28088.01 SOD {07:48:08.01} UT,   311.1 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     451554501
X_OFFSET:        724 [pixels]
Y_OFFSET:        888 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       884
Y_GRB_POS:       1048
BINNING_INDEX:   1
IM_URL:          sw00638946000msuni0325.fits
SUN_POSTN:        31.59d {+02h 06m 22s}  +12.79d {+12d 47' 40"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.61d {+07h 02m 25s}  +17.38d {+17d 23' 03"}
MOON_DIST:        63.35 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 07:57:25 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.298d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.628d {-26d 37' 39"} (J2000)
ROLL:            268.247d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28088.01 SOD {07:48:08.01} UT,   311.1 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     451554501
X_OFFSET:        724 [pixels]
Y_OFFSET:        888 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       884
Y_GRB_POS:       1048
BINNING_INDEX:   1
IM_URL:          sw00638946000msuni0325.fits
SUN_POSTN:        31.59d {+02h 06m 22s}  +12.79d {+12d 47' 41"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.61d {+07h 02m 26s}  +17.38d {+17d 23' 02"}
MOON_DIST:        63.35 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #17743
A. P. Beardmore (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL) and T. N. Ukwatta (LANL) report on behalf of the Swift Team:
At 07:42:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150424A (trigger=638946). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 152.312, -26.647 which is
```
   RA(J2000) = 10h 09m 15s
   Dec(J2000) = -26d 38' 47"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single structure with a duration of about 0.5 sec. The peak count rate was ~55000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 07:44:24.7 UT, 87.9 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 152.3061, -26.6310 which is equivalent to:
```
   RA(J2000)  = 10h 09m 13.46s
   Dec(J2000) = -26d 37' 51.6"
```
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This location is 60 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 (6.03 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.8 (+3.00/-2.59) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 2.87e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 99 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.06.
Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 08:03:26 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.298d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.628d {-26d 37' 38"} (J2000)
POINT_ROLL:      268.247d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28643.31 SOD {07:57:23.31} UT,   866.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.828
N_STARS:         190
X_OFFSET:        164 [pixels]
Y_OFFSET:        328 [pixels]
X_MAX:           1603 [pixels]
Y_MAX:           1767 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00638946000msufc0866.fits
SUN_POSTN:        31.60d {+02h 06m 23s}  +12.80d {+12d 47' 46"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.66d {+07h 02m 39s}  +17.38d {+17d 22' 43"}
MOON_DIST:        63.30 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 24 Apr 15 08:03:45 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.298d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.628d {-26d 37' 38"} (J2000)
POINT_ROLL:      268.247d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28643.31 SOD {07:57:23.31} UT,   866.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.828
N_STARS:         190
X_OFFSET:        164 [pixels]
Y_OFFSET:        328 [pixels]
X_MAX:           1603 [pixels]
Y_MAX:           1767 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00638946000msufc0866.fits
SUN_POSTN:        31.60d {+02h 06m 23s}  +12.80d {+12d 47' 46"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.66d {+07h 02m 40s}  +17.38d {+17d 22' 42"}
MOON_DIST:        63.30 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [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:     Fri 24 Apr 15 08:04:43 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.298d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.628d {-26d 37' 38"} (J2000)
ROLL:            268.247d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28643.31 SOD {07:57:23.31} UT,   866.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     451555056
X_OFFSET:        723 [pixels]
Y_OFFSET:        887 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       883
Y_GRB_POS:       1047
BINNING_INDEX:   1
IM_URL:          sw00638946000msuni0880.fits
SUN_POSTN:        31.60d {+02h 06m 23s}  +12.80d {+12d 47' 47"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.67d {+07h 02m 42s}  +17.38d {+17d 22' 39"}
MOON_DIST:        63.29 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [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:     Fri 24 Apr 15 08:04:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     638946,   Seg_Num: 0
POINT_RA:        152.298d {+10h 09m 11s} (J2000)
POINT_DEC:       -26.628d {-26d 37' 38"} (J2000)
ROLL:            268.247d
IMG_START_DATE:  17136 TJD;   114 DOY;   15/04/24
IMG_START_TIME:  28643.31 SOD {07:57:23.31} UT,   866.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     451555056
X_OFFSET:        723 [pixels]
Y_OFFSET:        887 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       883
Y_GRB_POS:       1047
BINNING_INDEX:   1
IM_URL:          sw00638946000msuni0880.fits
SUN_POSTN:        31.60d {+02h 06m 23s}  +12.80d {+12d 47' 47"}
SUN_DIST:        123.14 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      105.68d {+07h 02m 42s}  +17.38d {+17d 22' 39"}
MOON_DIST:        63.29 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      263.57, 23.58 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      165.61,-35.21 [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 #17745
D. A. Perley (Caltech) and N. J. McConnell (IfA) report:
We observed the field of short-duration GRB 150424A (Beardmore et al., GCN 17743) with the Low Resolution Imaging Spectrometer (LRIS) on the Keck I 10m telescope. Three 120-second imaging exposures in g- and R-bands were acquired between 09:15 and 09:26 UT (approximately 1.6 hours after the GRB trigger), at low elevation through moderate cloud cover.
In both filters we detect a bright (R~20 mag) source, not visible in DSS, at the following location inside the XRT error circle:
```
  RA = 10:09:13.381
dec = -26:37:51.50
(+/- 0.5" or less)
```
We suggest this as the optical afterglow of GRB 150424A.
We also note the presence of a large galaxy (resolved in DSS) 5 arcsec to the southwest.
GCN Circular #17749
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 3164 s of XRT Photon Counting mode data and 6 UVOT images for GRB 150424A, 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 = 152.30569, -26.63092 which is equivalent to:
```
RA (J2000): 10h 09m 13.37s
Dec (J2000): -26d 37' 51.3"
```
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 #17751
F. E. Marshall (NASA/GSFC) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150424A 99 s after the BAT trigger (Beardmore et al., GCN Circ. 17743). A source consistent with the position of the suggested optical afterglow (Perley and McConnell, GCN Circ. 17745) is detected in the initial UVOT exposures. The source remains nearly constant in 6 exposures with the white filter starting 99 s after the trigger and ending 6786 s after the trigger. The magnitude is approximately that reported by Perley and McConnell. This may be a detection of the host galaxy.
The preliminary UVOT position is:
```
   RA  (J2000) =  10:09:13.38 = 152.30577 (deg.)
   Dec (J2000) =  26:37:51.1  = -26.63086 (deg.)
```
with an estimated uncertainty of 0.6 arcsec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limit 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               99         6786          609         20.38 +/- 0.07
v                  641         5881          432        >19.8
b                  567         6701          432         20.71 +/- 0.21
u                  311         5061          462         20.13 +/- 0.20
w1                 690         6291          413         20.00 +/- 0.24
m2                4452         6086          393         19.91 +/- 0.29
w2                 616         5677          216         20.03 +/- 0.31
```
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 #17752
S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report:
The short-duration, intense GRB 150424A (Swift/BAT detection: Beardmore et al., GCN Circ. 17743). triggered Konus-Wind at T0=27781.073 s UT (07:43:01.073).
The burst light curve shows a multipeak structure with a total duration of ~0.4 s. The emission is seen up to 4 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150424_T27781/
As observed by Konus-Wind, the burst had a fluence of 1.81(-0.11,+0.11)x10^-5 erg/cm2, and a 2-ms peak flux, measured from T0+0.212 s, of 1.85(-0.48,+0.48)x10^-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.37(-0.09,+0.10) and Ep = 919(-76,+82) keV (chi2 = 66/57 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.8 (chi2 = 66/56 dof)
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN Circular #17756
D. Malesani (DARK/NBI), D. Xu (NAOC/CAS), D. J. Watson (DARK/NBI), and P. Blay (IAC/NOT), report on behalf of a larger collaboration:
We observed the optical counterpart (Perley, GCN 17745; Marshall & Beardmore, GCN 17751) of the short GRB 150424A (Beardmore et al., GCN Circ. 17743), using the Nordic Optical Telescope equipped with the AlFOSC camera. The first 300-s R-band exposure was taken starting at 20:57 UT (13.2 hr after the GRB)
We clearly detect the counterpart with a magnitude R = 20.67 +- 0.06 (assuming R = 16.27 for the USNO star at RA = 10:09:11.09, Dec = -26:36:58.4).
This magnitude is just slightly fainter than the value reported by Perley (GCN 17745) 1.6 hr after the trigger, indicating a very slow decay - consistent with the UVOT report. The brightness of the afterglow is unprecedented for a short GRB this late after the GRB. Such a behaviour is unusual and we encourage further observations.
GCN Circular #17757
D. A. Kann (TLS Tautenburg), M. Tanga, and J. Greiner (both MPE Garching) report on behalf of the GROND team:
We observed the field of the extremely bright short GRB 150424A (Swift trigger 638946; Beardmore et al., GCN #17743) 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 23:09 UT on 2015-04-24, 15.4 hrs after the GRB trigger. They were performed at an average seeing of 1".2 and at an average airmass of 1.1.
We detect the optical afterglow (Perley & McConnell, GCN # 17745; Malesani et al., GCN # 17756).
Based on 7.7 min of total exposure time in g'r'i'z' and 8.0 min in JHK, centered 15.54 hrs after the GRB, we estimate the following preliminary magnitudes (all in AB system):
```
g' = 22.0 +/- 0.2 mag,
r' = 21.6 +/- 0.1 mag,
i' = 21.4 +/- 0.1 mag,
z' = 21.1 +/- 0.1 mag,
J  = 20.4 +/- 0.5 mag, and
H  > 19.9  mag.
```
Compared to the NOT detection about two hours earlier, the afterglow has faded by 0.7 magnitudes, indicating the transition to a very rapid decay.
Given magnitudes are calibrated against GROND zero points (g'r'i'z') as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.06 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular #17758
A. J. Castro-Tirado (IAA-CSIC, ISA-UMA), R. Sanchez-Ramirez (UPV/EHU, IAA-CSIC), G. Lombardi (IAC, ULL, GRANTECAN) and M. A. Rivero (GRANTECAN), on behalf of a larger collaboration, report:
Following the detection of the short-duration GRB 150424A by Swift/BAT (Beardmore et al. 2015, GCNC 17743) and Konus-Wind (Golenetskii et al. GCNC 17752), we have obtained an optical spectrum (2 x 900s) with the 10.4m GTC telescope (+OSIRIS) in La Palma (Spain), starting on Apr 24, 21:30 UT (i.e. 13.8 hr postburst), covering the 3700-10000 wavelength range. The slit included the position of the proposed optical afterglow (Perley and McConnell, GCNC 17745; Marshall and Beardmore, GCNC 17751; Malesani et al., GCNC 17756; Kann et al. GCNC 17757) as well as the extended galaxy 5 arcsec to the southwest (Perley and McConnell GCNC 17745).
At the position of the optical afterglow, we see no obvious absorption features with the continuum extending to 3700 A (implying an upper limit of z < 3 to the redshift of the GRB). At the position of the nearby galaxy, we detect [O II] and H-alpha in emission at a redshift z = 0.30. At this redshift, 5 arcsec corresponds to 22.5 kpc. A more detailed data reduction is ongoing.
We acknowledge D. Perley for providing the corresponding ID-chart.
GCN Circular #17759
J. P. Norris (BSU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), and N. Gehrels (GSFC) report:
We report spectral lag and extended emission measurements for the intense, short GRB 150424A (trigger=638946; GCN Circ. 17743, 17745 & 17756) based on Swift-BAT data.
Using a 4-ms binned light curve, the lag for the 25-50 keV to 100-350 keV bands is estimated as 0.6 (+0.6/-1.0) ms; and -2.4 (+1.3/-0.7) ms for the 15-25 keV to 50-100 keV bands.
A Bayesian Block analysis of the mask-tagged data reveals one significant block of duration ~ 106 seconds at a level of 0.006 counts/det/s, following the intense, initial pulse complex. This extended emission component is three orders of magnitude lower than the peak intensity of the burst, ~ 5.3 counts/pixel/s.
GCN Circular #17760
A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), P.A. Evans (U. Leicester), A. Amaral-Rogers (U. Leicester) and A.P. Beardmore report on behalf of the Swift-XRT team:
We have analysed 5.1 ks of XRT data for GRB 150424A (Beardmore et al. GCN Circ. 17743), from 77 s to 29.7 ks after the BAT trigger. The data comprise 206 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 17749).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.22 (+0.13, -0.29). At T+168 s the decay steepens to an alpha of 2.75 (+0.14, -0.19) before breaking again at T+676 s to a final decay with index alpha=0.64 (+0.08, -0.10).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.60 (+/-0.07). The best-fitting absorption column is 9.4 (+2.7, -2.5) x 10^20 cm^-2, in excess of the Galactic value of 6.0 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.00 (+0.19, -0.18) and a best-fitting absorption column of 1.1 (+0.6, -0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.1 (+0.6, -0.5) x 10^21 cm^-2
Galactic foreground: 6.0 x 10^20 cm^-2
Excess significance: 1.8 sigma
Photon index:	     2.00 (+0.19, -0.18)
```
If the light curve continues to decay with a power-law decay index of 0.64, the count rate at T+24 hours will be 0.022 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.4 x 10^-13 (9.2 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/00638946.
This circular is an official product of the Swift-XRT team.
GCN Circular #17761
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), 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 150424A (trigger #638946) (Beardmore, et al., GCN Circ. 17743). The BAT ground-calculated position is RA, Dec = 152.305, -26.646 deg which is
```
   RA(J2000)  =  10h 09m 13.2s
   Dec(J2000) = -26d 38' 45.7"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 69%.
BAT light curve shows a bright multi-peaked episode starting around T-0.05 sec, and ending around T+0.5 sec. Very weak extended emission can be seen up to about T+100 sec as mentioned in Norris, et al., GCN Circ. 17759. T90 (15-350 keV) is 91 +- 22 sec (estimated error including systematics).
The time-averaged spectrum from T-0.06 to T+106.32 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.23 +- 0.15. The fluence in the 15-150 keV band is 1.5 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T-0.06 sec in the 15-150 keV band is 12.0 +- 0.4 ph/cm2/sec. 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/638946/BA/
GCN Circular #17762
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 (ORAU/GSFC), 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 observed the field of the short-duration GRB 150424A (Beardmore, et al., GCN 17743) 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 2015/04 25.14 to 2015/04 25.28 UTC (19.54 to 23.05 hours after the BAT trigger), obtaining a total of 2.4 hours exposure in the r, i, and z bands.
The optical afterglow (Perley, GCN 17745; Marshall & Beardmore, GCN 17751; Malesani, et al., GCN 17756; Kann, et al., GCN 17757) is well-detected. In comparison with 2MASS and the USNO-B1 catalog, we obtain the following detections and upper limit (3-sigma):
```
  r     21.92 +/- 0.11
  i     21.65 +/- 0.09
  z     > 20.17
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. Compared to the earlier NOT and GROND observations, the source appears to be continuing its strong fade (Kann, et al. GCN 17757).
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro M=E1rtir.
GCN Circular #17804
W. Fong (Univ. of Arizona) reports:
"We observed the position of the short-duration GRB 150424A (Beardmore et al., GCN 17743) with the Karl G. Jansky Very Large Array (VLA) beginning on 2015 Apr 25.073 UT (18.02 hr post-burst) at a mean frequency of 9.8 GHz. In 1 hour of observations, we detect a faint radio source at the position:
```
RA(J2000) = 10:09:13.37
Dec(J2000) = -26:37:51.49
```
with an uncertainty of 0.5" in each coordinate. This position is coincident with the position of the X-ray afterglow (Goad et al., GCN 17749) as well as the position of the optical afterglow (Perley and McConnell., GCN 17745; Malesani et al., GCN 17756; Kann et al., GCN 17757; Butler et al., GCN 17762).
We measure a 9.8 GHz flux density of ~31 microJy. To assess the nature of this radio source, we obtained two additional sets of VLA observations starting at 4.67 and 7.88 days after the burst. The source is no longer detected in each of these observations, as well as a deep, combined image, to 3-sigma limits of 29 microJy and 20 microJy, respectively.
Due to the fading of the radio source, as well as the positional coincidence with the X-ray and optical afterglows, we consider this source to be the radio afterglow of GRB 150424A.
We thank the VLA staff for quickly executing these observations."
GCN Circular #18100
N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick), A. S. Fruchter (STScI), J. Hjorth, D. Watson (DARK), D. Perley (Caltech), J. Greiner (MPE), A. de Ugarte Postigo, C. Thoene (IAA-CSIC), R. A. Hounsell (Illinois), S. Rosswog (U. Stockholm) report:
We observed the optical/nIR counterpart of short-GRB 150424A (Perley et al. GCN 17745) with HST at three epochs, roughly 6.7, 9.3 and 13.9 days post-trigger. On each occasion we obtained imaging with the WFC3/UVIS F606W and the WFC3/IR F125W and F160W filters.
The optical transient is visible at all epochs, fading from J(AB)=25.3 to J(AB)=26.9 over the course of the observations. There is a suggestion of a colour change, from r-H(AB)~1.1 to r-H(AB)~2 between the first and last epoch, although the errors are large (and in particular suffer a rather uncertain background correction - see below).
Significantly, the OT is superimposed on a faint source that is extended over about 1 arcsec. We propose that this extended source is most likely the host galaxy of the burst, rather than the bright nearby spiral whose redshift (z=0.3) was reported by Castro-Tirado et al. (GCN 17758). Our current best estimates of the magnitude of this source are r(AB)=26.8, J(AB)=26.1 and H(AB)=25.7, although we note that much of the flux in the r-band is due to a single blue knot of emission, whereas the nIR is more diffuse. Given the luminosity, size and colour of the proposed host, it is likely to be at z>0.7, where the 4000A break would help explain the red r-J colour of most of this galaxy.
If the burst was at z=0.3 (e.g. if the faint extended source is a satellite of the spiral, or just a background galaxy aligned by chance), then we place limits on any kilonova/macronova emission of M_J(AB)>~-14.7 at 7 days post-burst in the rest frame. A more likely redshift of z~1, for example, would mean that our reddest filter only corresponds to the rest-frame I-band, here providing a limit of M_I(AB)>~-17.0 at 7 days in the rest-frame (i.e. ~1 mag fainter than typical for a collapsar-produced supernova at the same time).
Further analysis is in progress.
1511.03656 from 13 Nov 15
D.L. Kaplan et al.: A Deep Search for Prompt Radio Emission from the Short GRB 150424A With The Murchison Widefield Array
We present a search for prompt radio emission associated with the short-duration gamma-ray burst (GRB) 150424A using the Murchison Widefield Array (MWA) at frequencies from 80-133 MHz. Our observations span delays of 23 s-30 min after the GRB, corresponding to dispersion measures of 100-7700 pc/cm^3. We see no excess flux in images with timescales of 4 s, 2 min, or 30 min, and set a 3 sigma flux density limit of 3.0 Jy at 132 MHz on the shortest timescales: some of the most stringent limits to date on prompt radio emission from any type of GRB. We use these limits to constrain a number of proposed models for coherent emission from short-duration GRBs, although we show that our limits are not particularly constraining for fast radio bursts because of reduced sensitivity for this pointing. Finally, we discuss the prospects for using the MWA to search for prompt radio emission from gravitational wave transients and find that while the flux density and luminosity limits are likely to be very constraining, the latency of the gravitational wave alert may limit the robustness of any conclusions.

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Jochen Greiner, last update: 13-Nov-2015 [Disclaimer]