Gamma-ray Burst 100418A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:10:18 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     419797,   Seg_Num: 0
GRB_RA:          256.376d {+17h 05m 30s} (J2000),
                 256.497d {+17h 05m 59s} (current),
                 255.790d {+17h 03m 10s} (1950)
GRB_DEC:         +11.464d {+11d 27' 50"} (J2000),
                 +11.451d {+11d 27' 02"} (current),
                 +11.531d {+11d 31' 51"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       5137 [cnts]    Image_Peak=177 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   138     E_range: 15-50 keV
BKG_INTEN:       36422 [cnts]
BKG_TIME:        76194.28 SOD {21:09:54.28} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15304 TJD;   108 DOY;   10/04/18
GRB_TIME:        76208.04 SOD {21:10:08.04} UT
GRB_PHI:         133.96 [deg]
GRB_THETA:        29.69 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.66 [sigma]
IMAGE_SIGNIF:    7.06 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  -3  +0  +0 +58  +0 
SUN_POSTN:        26.69d {+01h 46m 46s}  +11.02d {+11d 01' 09"}
SUN_DIST:        125.66 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.91d {+05h 23m 39s}  +25.20d {+25d 12' 02"}
MOON_DIST:       143.10 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.47, 28.66 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      253.80, 34.14 [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 = 83.89,-4.44 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:11:46 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     419797,   Seg_Num: 0
GRB_RA:          256.3623d {+17h 05m 26.95s} (J2000),
                 256.4829d {+17h 05m 55.90s} (current),
                 255.7767d {+17h 03m 06.41s} (1950)
GRB_DEC:         +11.4616d {+11d 27' 41.7"} (J2000),
                 +11.4481d {+11d 26' 53.3"} (current),
                 +11.5286d {+11d 31' 43.0"} (1950)
GRB_ERROR:       5.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.27e-09 [erg/cm2/sec]
GRB_SIGNIF:      7.81 [sigma]
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76287.13 SOD {21:11:27.13} UT,   79.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.69 237.24 261.50 243.62
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        26.69d {+01h 46m 46s}  +11.02d {+11d 01' 11"}
SUN_DIST:        125.67 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.93d {+05h 23m 42s}  +25.20d {+25d 12' 01"}
MOON_DIST:       143.10 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.46, 28.67 [deg] galactic lon,lat of the burst
ECL_COORDS:      253.79, 34.14 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.81 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:12:03 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     419797,   Seg_Num: 0
GRB_RA:          256.3623d {+17h 05m 26.9s} (J2000),
                 256.4829d {+17h 05m 55.9s} (current),
                 255.7767d {+17h 03m 06.4s} (1950)
GRB_DEC:         +11.4616d {+11d 27' 41.7"} (J2000),
                 +11.4481d {+11d 26' 53.3"} (current),
                 +11.5286d {+11d 31' 43.0"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       61 [cnts]
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76287.13 SOD {21:11:27.13} UT,   79.1 [sec] since BAT Trigger Time
CENTROID_X:      382.84,  raw= 383  [pixels]
CENTROID_Y:      313.79,  raw= 314  [pixels]
ROLL:            67.26 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   37.24
GRB_POS_XRT_Z:   189.87
IMAGE_URL:       sw00419797000msxps_rw.img
SUN_POSTN:        26.69d {+01h 46m 46s}  +11.02d {+11d 01' 11"}
SUN_DIST:        125.67 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.93d {+05h 23m 43s}  +25.20d {+25d 12' 00"}
MOON_DIST:       143.10 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.46, 28.67 [deg] galactic lon,lat of the burst
ECL_COORDS:      253.79, 34.14 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:11:56 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     419797,   Seg_Num: 0
GRB_RA:          256.3623d {+17h 05m 26.9s} (J2000),
                 256.4829d {+17h 05m 55.9s} (current),
                 255.7767d {+17h 03m 06.4s} (1950)
GRB_DEC:         +11.4616d {+11d 27' 41.7"} (J2000),
                 +11.4481d {+11d 26' 53.3"} (current),
                 +11.5286d {+11d 31' 43.0"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       61 [cnts]
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76287.13 SOD {21:11:27.13} UT,   79.1 [sec] since BAT Trigger Time
CENTROID_X:      382.84,  raw= 383  [pixels]
CENTROID_Y:      313.79,  raw= 314  [pixels]
ROLL:            67.26 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   37.24
GRB_POS_XRT_Z:   189.87
IMAGE_URL:       sw00419797000msxps_rw.img
SUN_POSTN:        26.69d {+01h 46m 46s}  +11.02d {+11d 01' 11"}
SUN_DIST:        125.67 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.93d {+05h 23m 43s}  +25.20d {+25d 12' 00"}
MOON_DIST:       143.10 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.46, 28.67 [deg] galactic lon,lat of the burst
ECL_COORDS:      253.79, 34.14 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:13:56 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     419797,   Seg_Num: 0
GRB_RA:          256.376d {+17h 05m 30s} (J2000),
                 256.497d {+17h 05m 59s} (current),
                 255.790d {+17h 03m 10s} (1950)
GRB_DEC:         +11.464d {+11d 27' 50"} (J2000),
                 +11.451d {+11d 27' 02"} (current),
                 +11.531d {+11d 31' 51"} (1950)
GRB_DATE:        15304 TJD;   108 DOY;   10/04/18
GRB_TIME:        76208.04 SOD {21:10:08.04} UT
TRIGGER_INDEX:   138
GRB_PHI:         133.96 [deg]
GRB_THETA:        29.69 [deg]
DELTA_TIME:      64.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.66 [sigma]
IMAGE_SIGNIF:    7.06 [sigma]
LC_URL:          sw00419797000msb.lc
SUN_POSTN:        26.69d {+01h 46m 47s}  +11.02d {+11d 01' 13"}
SUN_DIST:        125.66 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.95d {+05h 23m 48s}  +25.20d {+25d 11' 59"}
MOON_DIST:       143.09 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.47, 28.66 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      253.80, 34.14 [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 = 83.89,-4.44 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:14:31 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.416d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.473d {+11d 28' 22"} (J2000)
POINT_ROLL:      67.261d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76295.62 SOD {21:11:35.62} UT,   87.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.056
N_STARS:         119
X_OFFSET:        184 [pixels]
Y_OFFSET:        640 [pixels]
X_MAX:           1143 [pixels]
Y_MAX:           1599 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00419797000msufc0087.fits
SUN_POSTN:        26.69d {+01h 46m 47s}  +11.02d {+11d 01' 13"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.96d {+05h 23m 49s}  +25.20d {+25d 11' 59"}
MOON_DIST:       143.09 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:15:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.416d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.473d {+11d 28' 22"} (J2000)
POINT_ROLL:      67.261d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76295.62 SOD {21:11:35.62} UT,   87.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.056
N_STARS:         119
X_OFFSET:        184 [pixels]
Y_OFFSET:        640 [pixels]
X_MAX:           1143 [pixels]
Y_MAX:           1599 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00419797000msufc0087.fits
SUN_POSTN:        26.69d {+01h 46m 47s}  +11.02d {+11d 01' 14"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.96d {+05h 23m 51s}  +25.20d {+25d 11' 58"}
MOON_DIST:       143.09 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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:     Sun 18 Apr 10 21:14:31 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.416d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.473d {+11d 28' 22"} (J2000)
POINT_ROLL:      67.261d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76295.62 SOD {21:11:35.62} UT,   87.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.056
N_STARS:         119
X_OFFSET:        184 [pixels]
Y_OFFSET:        640 [pixels]
X_MAX:           1143 [pixels]
Y_MAX:           1599 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00419797000msufc0087.fits
SUN_POSTN:        26.69d {+01h 46m 47s}  +11.02d {+11d 01' 13"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.96d {+05h 23m 49s}  +25.20d {+25d 11' 59"}
MOON_DIST:       143.09 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:15:56 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.416d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.473d {+11d 28' 22"} (J2000)
ROLL:            67.261d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76295.62 SOD {21:11:35.62} UT,   87.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     293317901
X_OFFSET:        417 [pixels]
Y_OFFSET:        981 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       577
Y_GRB_POS:       1141
BINNING_INDEX:   1
IM_URL:          sw00419797000msuni0093.fits
SUN_POSTN:        26.70d {+01h 46m 47s}  +11.02d {+11d 01' 14"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.97d {+05h 23m 53s}  +25.20d {+25d 11' 58"}
MOON_DIST:       143.09 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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:     Sun 18 Apr 10 21:16:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.416d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.473d {+11d 28' 22"} (J2000)
ROLL:            67.261d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76295.62 SOD {21:11:35.62} UT,   87.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     293317901
X_OFFSET:        417 [pixels]
Y_OFFSET:        981 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       577
Y_GRB_POS:       1141
BINNING_INDEX:   1
IM_URL:          sw00419797000msuni0093.fits
SUN_POSTN:        26.70d {+01h 46m 47s}  +11.02d {+11d 01' 15"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       80.98d {+05h 23m 54s}  +25.20d {+25d 11' 57"}
MOON_DIST:       143.09 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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:     Sun 18 Apr 10 21:23:18 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
POINT_ROLL:      67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76507.49 SOD {21:15:07.49} UT,   299.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.528
N_STARS:         67
X_OFFSET:        97 [pixels]
Y_OFFSET:        661 [pixels]
X_MAX:           1056 [pixels]
Y_MAX:           1620 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00419797000msufc0299.fits
SUN_POSTN:        26.70d {+01h 46m 48s}  +11.02d {+11d 01' 21"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.05d {+05h 24m 11s}  +25.20d {+25d 11' 52"}
MOON_DIST:       143.08 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:23:18 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
POINT_ROLL:      67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76507.49 SOD {21:15:07.49} UT,   299.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.528
N_STARS:         67
X_OFFSET:        97 [pixels]
Y_OFFSET:        661 [pixels]
X_MAX:           1056 [pixels]
Y_MAX:           1620 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00419797000msufc0299.fits
SUN_POSTN:        26.70d {+01h 46m 48s}  +11.02d {+11d 01' 21"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.05d {+05h 24m 11s}  +25.20d {+25d 11' 52"}
MOON_DIST:       143.08 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:23:46 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
POINT_ROLL:      67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76507.49 SOD {21:15:07.49} UT,   299.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.528
N_STARS:         67
X_OFFSET:        97 [pixels]
Y_OFFSET:        661 [pixels]
X_MAX:           1056 [pixels]
Y_MAX:           1620 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00419797000msufc0299.fits
SUN_POSTN:        26.70d {+01h 46m 48s}  +11.02d {+11d 01' 21"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.05d {+05h 24m 12s}  +25.20d {+25d 11' 52"}
MOON_DIST:       143.08 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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:     Sun 18 Apr 10 21:24:32 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
ROLL:            67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76507.49 SOD {21:15:07.49} UT,   299.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     293318113
X_OFFSET:        417 [pixels]
Y_OFFSET:        981 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       577
Y_GRB_POS:       1141
BINNING_INDEX:   1
IM_URL:          sw00419797000msuni0305.fits
SUN_POSTN:        26.70d {+01h 46m 48s}  +11.02d {+11d 01' 22"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.06d {+05h 24m 14s}  +25.20d {+25d 11' 52"}
MOON_DIST:       143.08 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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:     Sun 18 Apr 10 21:24:39 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     419797,   Seg_Num: 0
GRB_RA:          256.3634d {+17h 05m 27.21s} (J2000),
                 256.4840d {+17h 05m 56.16s} (current),
                 255.7778d {+17h 03m 06.67s} (1950)
GRB_DEC:         +11.4618d {+11d 27' 42.4"} (J2000),
                 +11.4483d {+11d 26' 54.0"} (current),
                 +11.5288d {+11d 31' 43.7"} (1950)
GRB_ERROR:       3.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76393.00 SOD {21:13:13.00} UT,   185.0 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        26.70d {+01h 46m 48s}  +11.02d {+11d 01' 22"}
SUN_DIST:        125.68 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.06d {+05h 24m 15s}  +25.20d {+25d 11' 51"}
MOON_DIST:       143.08 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.46, 28.67 [deg] galactic lon,lat of the burst
ECL_COORDS:      253.79, 34.14 [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:     Sun 18 Apr 10 21:24:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
ROLL:            67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76507.49 SOD {21:15:07.49} UT,   299.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     293318113
X_OFFSET:        417 [pixels]
Y_OFFSET:        981 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       577
Y_GRB_POS:       1141
BINNING_INDEX:   1
IM_URL:          sw00419797000msuni0305.fits
SUN_POSTN:        26.70d {+01h 46m 48s}  +11.02d {+11d 01' 22"}
SUN_DIST:        125.62 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.06d {+05h 24m 15s}  +25.20d {+25d 11' 51"}
MOON_DIST:       143.08 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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 #10612
F. E. Marshall (NASA/GSFC), A. P. Beardmore (U Leicester), J. M. Gelbord (PSU), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), O. M. Littlejohns (U Leicester), C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester), C. Pagani (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), A. Rowlinson (U Leicester), M. C. Stroh (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team:
At 21:10:08 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100418A (trigger=419797). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 256.376, +11.464 which is
```
   RA(J2000) = 17h 05m 30s
   Dec(J2000) = +11d 27' 50"
```
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 4 sec. The peak count rate was ~700 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 21:11:27.1 UT, 79.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 256.3635, 11.4619 which is equivalent to:
```
   RA(J2000)  = 17h 05m 27.24s
   Dec(J2000) = +11d 27' 42.7"
```
with an uncertainty of 3.1 arcseconds (radius, 90% containment). This location is 44 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 consistent with the Galactic value of 4.78e+20 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 1.27e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 87 seconds after the BAT trigger. A possible afterglow candidate has been found in the initial data products at the location of the XRT afterglow. The preliminary UVOT position is
```
    RA(J2000.0) =  17:05:26.96  =  256.36233 (deg)   
   Dec(J2000.0) = +11:27:41.9   =  +11.46164 (deg)
```
with an estimated uncertainty of 1.0 arcsec (radius, 90% confidence, statistical + systematic). The estimated white magnitude is 20.7 +/- 0.3. No correction has been made for the expected extinction corresponding to E(B-V) of 0.07.
Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:30:23 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
POINT_ROLL:      67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  77085.61 SOD {21:24:45.61} UT,   877.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.289
N_STARS:         190
X_OFFSET:        0 [pixels]
Y_OFFSET:        421 [pixels]
X_MAX:           1439 [pixels]
Y_MAX:           1860 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00419797000msufc0877.fits
SUN_POSTN:        26.70d {+01h 46m 49s}  +11.02d {+11d 01' 27"}
SUN_DIST:        125.63 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.12d {+05h 24m 29s}  +25.20d {+25d 11' 47"}
MOON_DIST:       143.07 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:30:58 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
POINT_ROLL:      67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  77085.61 SOD {21:24:45.61} UT,   877.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.289
N_STARS:         190
X_OFFSET:        0 [pixels]
Y_OFFSET:        421 [pixels]
X_MAX:           1439 [pixels]
Y_MAX:           1860 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00419797000msufc0877.fits
SUN_POSTN:        26.71d {+01h 46m 49s}  +11.02d {+11d 01' 27"}
SUN_DIST:        125.63 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.13d {+05h 24m 30s}  +25.20d {+25d 11' 47"}
MOON_DIST:       143.07 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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:     Sun 18 Apr 10 21:31:44 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
ROLL:            67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  77085.61 SOD {21:24:45.61} UT,   877.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     293318691
X_OFFSET:        559 [pixels]
Y_OFFSET:        980 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       719
Y_GRB_POS:       1140
BINNING_INDEX:   1
IM_URL:          sw00419797000msuni0883.fits
SUN_POSTN:        26.71d {+01h 46m 49s}  +11.02d {+11d 01' 28"}
SUN_DIST:        125.63 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.13d {+05h 24m 32s}  +25.20d {+25d 11' 46"}
MOON_DIST:       143.07 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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:     Sun 18 Apr 10 21:30:23 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
POINT_ROLL:      67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  77085.61 SOD {21:24:45.61} UT,   877.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.289
N_STARS:         190
X_OFFSET:        0 [pixels]
Y_OFFSET:        421 [pixels]
X_MAX:           1439 [pixels]
Y_MAX:           1860 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00419797000msufc0877.fits
SUN_POSTN:        26.70d {+01h 46m 49s}  +11.02d {+11d 01' 27"}
SUN_DIST:        125.63 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.12d {+05h 24m 29s}  +25.20d {+25d 11' 47"}
MOON_DIST:       143.07 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Apr 10 21:32:02 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     419797,   Seg_Num: 0
POINT_RA:        256.417d {+17h 05m 40s} (J2000)
POINT_DEC:       +11.471d {+11d 28' 15"} (J2000)
ROLL:            67.263d
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  77085.61 SOD {21:24:45.61} UT,   877.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     293318691
X_OFFSET:        559 [pixels]
Y_OFFSET:        980 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       719
Y_GRB_POS:       1140
BINNING_INDEX:   1
IM_URL:          sw00419797000msuni0883.fits
SUN_POSTN:        26.71d {+01h 46m 49s}  +11.02d {+11d 01' 28"}
SUN_DIST:        125.63 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.14d {+05h 24m 33s}  +25.20d {+25d 11' 46"}
MOON_DIST:       143.07 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.50, 28.62 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      253.85, 34.15 [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:     Sun 18 Apr 10 21:34:36 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     419797,   Seg_Num: 0
GRB_RA:          256.3623d {+17h 05m 26.95s} (J2000),
                 256.4829d {+17h 05m 55.90s} (current),
                 255.7767d {+17h 03m 06.41s} (1950)
GRB_DEC:         +11.4616d {+11d 27' 41.7"} (J2000),
                 +11.4481d {+11d 26' 53.3"} (current),
                 +11.5286d {+11d 31' 43.0"} (1950)
GRB_ERROR:       10.0 [arcsec radius, statistical only]
GRB_MAG:         19.10 +/- 3.00 [mag]
FILTER:          10, White
IMG_START_DATE:  15304 TJD;   108 DOY;   10/04/18
IMG_START_TIME:  76299.00 SOD {21:11:39.00} UT,   91.0 [sec] since BAT Trigger Time
SUN_POSTN:        26.71d {+01h 46m 50s}  +11.03d {+11d 01' 31"}
SUN_DIST:        125.68 [deg]   Sun_angle= 8.7 [hr] (West of Sun)
MOON_POSTN:       81.16d {+05h 24m 40s}  +25.20d {+25d 11' 44"}
MOON_DIST:       143.07 [deg]
MOON_ILLUM:      20 [%]
GAL_COORDS:       31.46, 28.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      253.79, 34.14 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The UVOT position is 0.4 arcsec from the XRT position.

GCN Circular #10613
S. B. Pandey (U Mich), W. Zheng (U Mich), Limin Xiao (Louisiana State) and T. Guver (U Arizona), report on behalf of the ROTSE collaboration:
ROTSE-IIId, located at the Turkish National Observatory at Bakirlitepe, Turkey, responded to GRB 100418A (Swift trigger 419797), producing images beginning 4.6 s after the GCN notice time. An automated response took the first image at 21:10:30.5 UT, 16.7 s after the burst, and during the gamma-ray emission, under fair conditions. We took 10 5-sec, 10 20-sec and 10 60-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going.
Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle or the XRT error circle, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 15.1-16.2; we set the following specific limits.
```
start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
21:10:30.6   21:10:35.6         5     15.4           16.7       N
21:10:30.6   21:12:37.9       127     16.8           16.7       Y
```
Further observations are ongoing.
GCN Circular #10614
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1381 s of XRT Photon Counting mode data and 2 UVOT images for GRB 100418A, 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 = 256.36327, +11.46114 which is equivalent to:
```
RA (J2000): 17h 05m 27.18s
Dec (J2000): +11d 27' 40.1"
```
with an uncertainty of 1.9 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 #10615
T. N. Ukwatta (GWU) 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/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) (i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from recent telemetry downlinks, we report further analysis of BAT GRB 100418A (trigger #419797) (Marshall, et al., GCN Circ. 10612). The BAT ground-calculated position is RA, Dec = 256.358, 11.457 deg, which is
```
   RA(J2000)  =  17h 05m 25.8s 
   Dec(J2000) = +11d 27' 26.8" 
```
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 49%.
The mask-weighted light curve shows two overlapping peaks starting at ~T-10 sec, peaking at ~T+2 sec, and ending at ~T+40 sec. T90 (15-350 keV) is 7.0 +- 1.0 sec (estimated error including systematics).
The time-averaged spectrum from T-1.1 to T+7.8 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.16 +- 0.25. The fluence in the 15-150 keV band is 3.4 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.47 sec in the 15-150 keV band is 1.0 +- 0.2 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/419797/BA/
GCN Circular #10616
GROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started follow-up observations of GRB 100418A (Marshall et al. 2010, GCN 10612) on Apr 19, at 4:50 UT (about 7.5 hrs after the burst).
Within the enhanced XRT 1.9 arcsec error circle reported by Osborne et al. (GCN 10614) we find a fading point source at coordinates RA, DEC (J2000) =
```
17:05:27.09,
11:27:42.3
```
with an uncertainty of 0.5" in each coordinate and estimate the following preliminary magnitudes (in the AB system):
```
g' = 19.2 +- 0.1 
r' = 18.8 +- 0.1
i' = 18.4 +- 0.1
z' = 18.1 +- 0.1
J  = 17.7 +- 0.1
```
Given magnitudes are calibrated against SDSS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.07 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular #10617
R. Filgas (MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE Garching), report on behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started follow-up observations of GRB 100418A (Marshall et al. 2010, GCN 10612) on Apr 19, at 4:50 UT (about 7.5 hrs after the burst).
Within the enhanced XRT 1.9 arcsec error circle reported by Osborne et al. (GCN 10614) we find a fading point source at coordinates RA, DEC (J2000) =
```
17:05:27.09,
11:27:42.3
```
with an uncertainty of 0.5" in each coordinate and estimate the following preliminary magnitudes (in the AB system):
```
g' = 19.2 +- 0.1
r' = 18.8 +- 0.1
i' = 18.4 +- 0.1
z' = 18.1 +- 0.1
J  = 17.7 +- 0.1
```
Given magnitudes are calibrated against SDSS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.07 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular #10619
Adria C. Updike, Dieter H. Hartmann (Clemson University), and Brian Murphy (Butler University) report:
We observed the field of GRB 100418A (Marshall et al., GCN 10612) using the 0.9m SARA telescope located at KPNO beginning 10 hours and 18 min after the trigger. We detect the afterglow (Filgas et al., GCN 10617) in our first 10 min exposure at high airmass (2.1) at a magnitude of R = 18.3 upon comparison to the USNO B1.0 catalog. Observations are continuing.
GCN Circular #10620
L.A. Antonelli, J.R. Maund, E. Palazzi, P. Goldoni, S.D. Vergani, H. Flores, A. de Ugarte-Postigo, S. Covino, J. Fynbo, J. Hjorth, D. Malesani, J. Sollerman, C.C. Thoene, on behalf of the X-shooter GRB collaboration report:
We observed the field of GRB 100418A (Marshall et al. 2010, GCN 10612) with VLT/X-Shooter at Cerro Paranal (Chile). The observation started on Apr 19, at 5:32 UT (about 8.37 hrs after the burst) under very good observing conditions (seeing about 0.7"). The object reported by Filgas and Greiner (GCN 10617) is clearly seen in our image at flux level of R = 18.1+/- 0.1 mag calibrated against USNO B.1 catalog.
Spectra were acquired and in a preliminary analysis they show an abundance of UV absorption lines (Fe II, Mg II, Mg I, Mn II, Ca H,K) as well as [O II] emission at z = 0.6235 (wavelength calibration was obtained with archive calibration data).
We acknowledge the Paranal staff for the support.
GCN Circular #10621
Daniele Malesani (DARK/NBI) reports:
At the position of the optical afterglow of GRB 100418A (Marshall et al., GCN 10612; Filgas et al., GCN 10617), a faint, compact object is well visible in the SDSS frames and catalogs ( Abazajian et al. 2009, ApJS, 182, 543), in the g, r, and i bands.
The (AB) model magnitudes as reported in the SDSS catalog are:
```
u: not detected
g = 22.89 +- 0.17
r = 22.41 +- 0.16
i = 21.94 +- 0.17
z: not detected
```
See e.g. http://cas.sdss.org/astrodr7/en/tools/explore/obj.asp?id=758879770841908118
The host detection is consistent with the relatively low redshift and the report of nebular emission lines superimposed on the bright afterglow continuum (Antonelli et al., GCN 10620). A SN as bright as SN1998bw would peak at r ~ 24 at the position of GRB 100418A.
GCN Circular #10622
C. Pagani (U. Leicester), A. P. Beardmore (U. Leicester)=C2=A0 and F. E. Marshall (NASA/GSFC) report on behalf of the Swift-XRT team:
We have analysed 3.7 ks of XRT data for GRB 100418A (Marshall et al. GCN Circ. 10612), from 70 s to 7.3 ks after the BAT trigger. The data comprise 97 s in Windowed Timing (WT) mode (the first 7 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 Osborne et al. (GCN. Circ 10614).
The light curve can be modelled with an initial power-law decay with an index of alpha=3D4.23 (+0.17, -0.16), followed by a break at T+474 s to an alpha of 0.21 (+0.22, -0.24).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 4.29 (+0.33, -0.30). The best-fitting absorption column is 2.1 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 4.8 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 2.0 x 10^-11 (1.3 x 10^-10) erg cm^-2 count^-1.
If the light curve continues to decay with a power-law decay index of 0.21, the count rate at T+24 hours will be 0.012 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x 10^-13 (1.6 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/00419797.
This circular is an official product of the Swift-XRT team.
GCN Circular #10624
A. Cucchiara and D. B. Fox (PSU) report on behalf of a larger collaboration:
"Starting on 2010 April 19.41 UT we used the GMOS spectrograph on the Gemini North 8-m telescope to observe the field of the Swift GRB 100418A (Marshall et al. GCN 10612).
A sequence of 2x1200s spectra were obtained covering the spectral range of 4000-8000A.
A series of metal absorption features were identified (MgII2796, 2803,FeI3720, Ca H&K, CaI4227) and H-beta in emission at the common redshift of z= 0.624, confirming the previously reported result of Antonelli et al. GCN 10620.
We thank the Gemini staff for performing this observation, in particular A. Fritz."
GCN Circular #10625
M. H. Siegel (PSU) and F. Marshall (NASA/GSFC) report on behalf of the Swift/UVOT team.
The Swift/UVOT began settled observations of the field of GRB 100418A 87s after the BAT trigger (Marshall et al., GCN Circ. 10612). Data summed from the first and second orbits reveals the source reported by Marshall et al. The source shows no fading between the first and second orbits within the photometric uncertainties. The photometry is consistent with a constant source with a white magnitude of 20.48+-0.13. This likely represents the GRB host galaxy reported by Malesani (GCN Circ. 10621) and not the afterglow reported by Filgas et al. (GCN Circ. 10617), Updike et al. (GCN Circ. 10619) and Antonelli et al. (GCN Circ. 10620). The UVOT position of the source is:
```
     RA(J2000.0) =  17:05:26.96  =  256.36278 (deg)
    Dec(J2000.0) = +11:27:41.9   =  +11.46167 (deg)
```
with a 90% confidence interval of 0."67.
The 3-sigma upper limits for the finding chart (fc) and summed exposures from the first and second orbits are reported below:
```
FILTER     T_start(s)  T_stop    Exposure     Mag/3UL
========================================================
white fc      87        237        147        20.62+-0.29
white         89       1548        390        20.58+-0.20
white       6143       6343        196        20.32+-0.20
v            628       6754        491        >19.90
b            554       6138        294        20.61+-.44
u            299       7348        697        20.47+-0.41
uvw1         678       7164        491        20.47+-0.42
uvm2         653       6959        491        20.09+-0.32
uvw2         604       6548        308        20.73+-0.54
=======================================================
```
The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.07 (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #10626
R. Pearson, J. Ward Moody, and C. Pace report for Brigham Young University's (BYUs) ROVOR team:
Beginning 9.12 hours after the initial Swift detection of GRB 100418A (GCN 10612), the 16-inch ROVOR telescope observed its optical afterglow. Twenty-eight 2 minute R band exposures were recorded at high airmass (2.48) and subsequently averaged together; a combined frame of 56 minutes was produced. An optical afterglow was located at the position specified by Filgas, Klose, and Greiner (GCN 10617).
We report a middle observing time of 06:55:21.474 (9.75 hrs post-burst) and a R band magnitude of 18.2+/-0.2mag. It was calibrated using GSC 00984-01465 located at 17:05:55.02+11:27:55.46 (J2000). Additional follow-up observations are scheduled with ROVOR as well as BYU's 36-inch telescope on West Mountain Observatory, supported by the NSF grant AST-0618209.
GCN Circular #10627
C. R. Klein, A. N. Morgan, D. A. Perley, and J. S. Bloom (UC Berkeley) report:
We observed the location of the optical afterglow of GRB 100418A (Marshall et al., GCN 10612) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at 2010-04-19 07:51:27 UT, ~10.69 hours after the Swift Trigger, under non-ideal sky conditions, and continued until clouds obscured the sky. In mosaics (effective exposure time of 0.92 hours) taken simultaneously in the J, H, and Ks filters, we detect the afterglow (Filgas et al., GCN 10617; Updike et al., GCN 10619; Antonelli et al., GCN 10620; Pearson et al., GCN 10626).
The preliminary photometry yields:
```
post burst
t_mid (hr) exp.(hr) filt  mag   m_err
11.13      0.92     J     16.8  0.1
11.13      0.92     H     15.9  0.1
11.13      0.92     Ks    15.3  0.1
```
We note that our J band point is consistent with little to no fading since the GROND detection ~3.6 hours prior (using J_AB = J_2mass + 0.90). This is consistent with the shallow decay implied by the R band magnitudes in this time period reported thus far (Filgas et al., GCN 10617; Updike et al., GCN 10619; Antonelli et al., GCN 10620; Pearson et al., GCN 10626), and with the the non-fading behavior seen in the UVOT data (Siegel et al., GCN 10625). Further, the XRT light curve is roughly flat between ~1000s and ~1 day (see http://astro.berkeley.edu/~nat/Swift/00419797/xrt/swx00419797.html), indicating a long optical/X-ray plateau phase. Continued observations are encouraged.
Intermittent clouds led to highly variable transmission and sky brightnesses during the PAIRITEL observations. 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 #10630
S. Martin (ESO), G. Petitpas (SMA), A. de Ugarte Postigo (INAF-OAB), M. Gurwell (SMA), A.J. Castro-Tirado, J. Gorosabel (IAA-CSIC), D. Garcia-Apaadoo, C. de Breuck, A. Lundgren (ESO) report:
"We have observed the field of GRB 100418A (Marshall et al., GCNC 10612) from SMA in the 345 GHz band starting on April 19th 13:00 UT. In a preliminary analysis of the data we detect a single source coincident with the position of the afterglow with a flux density of 20+/-2.4 mJy.
Further observations of this very peculiar source are encouraged."
GCN Circular #10631
Daniele Malesani and Eliana Palazzi report:
We obtained an R-band image of the afterglow of GRB 100418A (Marshall et al., GCN 10612; Filgas et al., GCN 10617) with the X-shooter acquisition camera 34.63 hr after the GRB. The afterglow has decayed by 1.11+-0.03 mag since our previous observation taken 8.37 hr after the GRB (Antonelli et al., GCN 10620).
We encourage further observations at all wavelengths of this interesting event. We acknowledge support from the ESO staff at Paranal, in particular Alvaro Alvarez, Claudia Cid, and Fernando Selman.
GCN Circular #10633
K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, V.Lenok, O.Gres, O. Irkutsk State University
V.Yurkov, Yu.Sergienko, D.Varda, A.Garusina Blagoveschensk Educational State University, Blagoveschensk
E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zimnukhov, M. Kornilov Sternberg Astronomical Institute, Moscow State University
A. Tlatov, A.V. Parkhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
V.Krushinski, I.Zalozhnih, T.Kopytova, A.Popov Ural State University, Kourovka
MASTER robotic telescope (MASTER-Net: http://observ.pereplet.ru, testing telescope) located at Tunka Valley (Baykal, Siberia) was responted to the GRB 100418A (Swift Bat alert, Marshall et al, GCN CIRC 10612) 21 sec after Notice time (~ 8 sec delay in internet socket) and 31 s after the GRB time ( Sun Alt -8 degrees) .
There is now OT on the first 10-s exposition time unfiltered images inside Swift XRT error box (Pagani et al., GCN CIRC 10622) brighter 14.5.
The message may be cited.
mailto: lipunov@sai.msu.ru
GCN Circular #10634
V. Rumyantsev, D. Shakhovkoy (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 100418A (Marshall et al. GCN 10612) with AZT-11 telescope of CrAO between (UT) Apr. 19 01:26 -- 01:54 under poor seeing of about 4 arcsec. The optical afterglow (Marshall et al. GCN 10612, Filgas et al. GCN 10617) is clearly detected in enhanced XRT error circle (Osborne et al. GCN 10614). The coordinates of the afterglow are (J2000) RA= 17:05:27.08 Dec= +11:27:42.3
The photometry of the afterglow in a stacked image based on USNO-B1.0 star 1014-0271368 (RA(J2000) = 17:05:26.42 Dec(J2000)= +11:27:32.9) assuming R=17.32 is following:
```
T0+      Filter,   Exposure, mag.
(mid, d)              (s)

0.1883     R       9x180    18.54 +/-0.03
```
A finding char can be found at http://grb.rssi.ru/GRB100418A/GRB100418a_100418_R_azt11.gif
GCN Circular #10635
I. Bikmaev (KSU/AST), I. Khamitov (TUG), S. Melnikov, N. Sakhibullin (KSU/AST), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
report:
The optical afterglow of GRB 100418A (Marshall et al., GCN 10612, Filgas et al., GCN 10617) was observed with Russian-Turkish 1.5-m telescope (RTT150,Bakirlitepe, TUBITAK National Observatory, Turkey) in April 18/19 and April 19/20, 2010, in partially cloudy conditions. We obtained a serie of 300 sec images in Rc-band in April 18/19, and serie of 600 sec images in April 19/20.
We found that during April 18 set OT shows strong brightness variations of Rc ~ 18-20 mag within hour time scale. In the Table below we give our Rc estimates relative to the nearby USNO-B1.0 star 1014-0271368 (R2Mag=17.32).
```
April 18
UT (T-T0),h   Rc    err
=================================
21:43 0.5   20.29 +/-0.10
22:38 1.5  >20.50 3-sigma image limit
23:25 2.25  18.64 +/-0.04
23:51 2.6   18.30 +/-0.04
23:58 2.9   18.33 +/-0.02
=================================

April 20
UT (T-T0),h   Rc    err
=================================
00:40 27.5  18.88 +/-0.03
```
RTT-150 data shows that brightness of OT sharply increased from 20 to 18 mag at (T-T0) ~ 2 hours. The OT was observed at maximum brigtness atapproximately 2.6 hours after the burst and then its flux started to decline, which is consistent with other measurements made later on (Rumyantsev et al., GCN 10634, Filgas et al GCN 10617).
The brightening of the OT is shown in the following RTT150 images: http://hea.iki.rssi.ru/grb/100418a/indexeng.html
GCN Circular #10637
Adria C. Updike, Dieter H. Hartmann (Clemson University), and Chris De Pree (Agnes Scott College) report:
We re-observed the field of GRB 100418A (Marshall et al., GCN 10612) using the 0.9m SARA telescope located at KPNO beginning 1.44 days after the trigger. Observations consisted of 40 minutes in the R band. We detect the afterglow (Filgas et al., GCN 10617) at R = 19.3 +/- 0.1, fading 1.0 mag from our previous detection (upon comparison to USNO B1.0 catalog field stars). Further observations are planned.
GCN Circular #10643
I. Bikmaev (KSU/AST), I. Khamitov (TUG), S. Melnikov, N. Sakhibullin (KSU/AST), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
report:
The optical afterglow of GRB 100418A (Marshall et al., GCN 10612, Filgas et al., GCN 10617) was observed with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey) in April 20/21, 2010, at moderate seeing conditions.
We obtained a serie of 600 sec and 300 sec images in Rc-band.
The Table gives our Rc value estimation relative nearby USNO-B1.0 star 1014-0271368 (R2Mag=17.32).
April 21, 2010
```
  UT    (T-T0), h    Rc       err
=================================
00:48  51.6     20.05   +/-0.03
```
GCN Circular #10644
R. Filgas (MPE Garching), D. A. Kann, S. Klose (all Tautenburg), M. Nardini, and J. Greiner (all MPE Garching), report on behalf of the GROND team:
GROND on La Silla (Greiner et al. 2008, PASP 120, 405) continues observing the afterglow of GRB 100418A. GROND data, with the first epoch at 28 ks after the burst and the last data point at 133 ks after the burst, in combination with data from Updike et al. (GCN 10619), Antonelli et al. (GCN 10620), Malesani (GCN 10621), Pearson et al. (GCN 10626), Malesani et al. (GCN 10631), Rumyantsev et al. (GCN 10634), Bikmaev et al. (GCN 10635), Updike et al. (GCN 10637), and Bikmaev et al. (GCN 10643), show that the R-band afterglow light curve had a break at t = 1.11 +/- 0.01 days and is now decaying with a slope of 2.41 +/- 0.08.
While the steep decay of the afterglow is in favor of a SN search, the bright host (Malesani, GCN 10621) might make a detection difficult. Assuming a SN 1998bw template, a Galactic visual extinction along the line of sight of 0.2 mag, no GRB host extinction but 0.2 mag host extinction for SN 1998bw, we predict the following SN peak times and magnitudes:
```
      band         dt/days         mag
      V            21.5           24.5
      R            22.5           23.7
      I            24.0           22.9
      J            29.5           22.8
```
This message can be cited.
GCN Circular #10645
M. H. Siegel (PSU), F. E. Marshall (NASA/GSFC), S. T. Holland (NASA/GSFC), M. M. Chester (PSU), M. de Pasquale (MSS-UCL) and S. R. Oates (MSSL-UCL) report on behalf of the Swift/UVOT team.
Ongoing Swift/UVOT observations of the field of GRB 100418A (Marshall et al., GCN Circ. 10612) have continued to monitor the behavior of the optical transient. UVOT photometry taken about 50 ks after the burst shows an increase in brightness of about a magnitude compared to the initial detection, confirming the late increase in brightness reported by Bikamev et al. (GCN Circ. 10635). The OT has since decayed from this peak with a decay rate of -1.0+-0.1 in the UVOT white filter. This decay is slightly shallower than the decay observed by Malesani et al. (GCN Circ. 10631, 10643), Updike et al. (GCN Circ. 10637) and Filgas et al. (GCN Circ 10644). Such a late peak in brightness is very unusual and Swift will continue to monitor the GRB.
Photometry from the summed exposures is reported below:
```
FILTER     T_start(s)  T_stop    Exposure        Mag
=========================================================
white fc      88        237        147        20.62+-0.29
white         88       1548        390        20.58+-0.20
white       6143       6343        196        20.32+-0.20
white      50996      52990       1959        19.38+-0.03
white      86204      92193       2308        19.77+-0.04
white     149282     156466       3812        20.54+-0.06
=========================================================
```
The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.07 (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #10646
S. Covino (INAF/Brera), D. Fugazza (INAF/Brera), L.A. Antonelli (INAF/Roma), D. Malesani (DARK/NBI), on behalf of the REM team report:
The robotic 60-cm REM telescope located at La Silla (Chile) observed automatically the field of GRB 100418A (GCN 10612, Marshall et al.) from April 19 3:25 UT to 4:34 UT (about 6.2 to 7.4 hr from the burst) in the optical and in the near-infrared.
Nothing is visible at the position of the optical counterpart reported by GROND (GCN 10617, Filgas et al.) except for a single H-band frame with mean time 4:14 UT (about 6.9 hr after the burst) and 5 min exposure. During this observation the afterglow is clearly detected at H=14.3 +- 0.2. The 3sigma upper limits in other H-band frames obtained always with 5 min exposure is H>15.2.
This rapid variability resembles the one observed by Bikmaev et al. (GCN 10635) with the RTT150 which, however, observed the field several hours before. Given this very unusual behavior, we encourage inspection of other datasets taken at comparable epochs.
GCN Circular #10647
A.J. van der Horst (NASA/MSFC/ORAU), A.P. Kamble, R.A.M.J. Wijers, E. Rol (U of Amsterdam), C. Kouveliotou (NASA/MSFC) and K. Wiersema (U of Leicester) report on behalf of a large collaboration:
"We observed the position of the GRB 100418A afterglow with the Westerbork Synthesis Radio Telescope at 4.8 GHz at April 20 20.74 UT to April 21 8.71 UT, i.e. 1.98 - 2.48 days after the burst (GCN 10612). We detect a radio source with a flux density of 369 +/- 29 microJy at the position of the optical counterpart (GCN 10616).
We would like to thank the WSRT staff for rapidly scheduling and obtaining these observations."
GCN Circular #10648
A. N. Morgan, D. A. Perley, C. R. Klein, and J. S. Bloom (UC Berkeley) report:
We continued to observe the location of the optical afterglow of GRB 100418A (Marshall et al., GCN 10612) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona for a second epoch beginning at 2010-04-20 07:59 UT, ~34.8 hours after the Swift trigger. In mosaics (effective exposure time of 1.27 hours) taken simultaneously in the J, H, and Ks filters, we observe that the afterglow has faded approximately 1 magnitude since our first epoch (Klein et al., GCN 10627). Unfortunately, poor weather conditions prevented further observations on 2010-04-21 and 2010-04-22.
The preliminary photometry yields:
```
post burst
t_mid (hr) exp.(hr) filt  mag   m_err
35.81      1.27     J     18.0  0.1
35.81      1.27     H     17.2  0.1
35.81      1.27     Ks    16.3  0.1
```
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 #10650
Poonam Chandra (RMC) and Dale A. Frail (NRAO) report on behalf of a larger collaboration:
We used the Expanded Very Large Array (EVLA) to observe the Swift GRB 100418A (Marshall et al., GCN 10612) on 2010 Apr 21 UT.
We detect the GRB afterglow with a flux density of 458 +/- 20 uJy at the GROND optical afterglow position (Filgas et al, GCN 10617).
The EVLA is undergoing active commissioning and as such these results should be considered preliminary. Further observations are planned.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities Inc.
GCN Circular #10661
S. T. Holland (CRESST/USRA/GSFC), F. E. Marshall (NASA/GSFC), M. Page (MSSL-UCL), M. de Pasquale (MSSL-UCL), and M. H. Siegel (PSU) report on behalf of the Swift/UVOT team:
Swift/UVOT white photometry of GRB 100418A reveals a light curve with a rise and decay that are broadly similar to the white light curve of GRB 060218/SN2006aj. The UVOT spectral energy distribution at 6400 s is consistent with a power law with a spectral index of beta = 0.2 (f = nu^-beta), which is similar to the UVOT spectral energy distribution for GRB 060218/SN2006aj at 9300 s. In addition, the X-ray light curve of GRB 100418A is broadly similar to the X-ray light curves of GRB 100316D and GRB 060218, both of which had supernova components. Therefore, we suggest that the brightening of the afterglow of GRB 100418A seen at approximately 10,000 s (Bikamev et al. 2010, GCNC 10635; Siegel et al. 2010, GCNC 10645) may be the shock breakout from a supernova associated with this burst. If this is the case, and the supernova is similar to SN1998bw, then the supernova has not yet reached maximum light. Ground based observations to determine if a supernova is present are encouraged.
GCN Circular #10664
J. W. Moody, D. Laney, R. Pearson, and C. Pace report for the BYU ROVOR team:
Beginning 35 hours after the initial detection of GRB 100418A we obtained BVR optical data using the BYU WMO 0.9m telescope. Preliminary magnitudes were found by referencing against USNO-B1.0 star 1014-0271368 (RA(J2000) = 17:05:26.42, Dec(J2000) = +11:27:32.9). Assuming B=18.66, V=18.00 and R=17.32 we obtain the following values:
```
post burst
t_mid(hr)   exp.(min)  filter  mag.  error
37.18        25
35.91
35.25
```
Poor weather prevented observations on 2010-04-21 and 2010-04-22
GCN Circular #10665
J. W. Moody, D. Laney, R. Pearson, and C. Pace report for the BYU ROVOR team:
Beginning approximately 35 hours after the initial detection of GRB 100418A we obtained BVR optical data using the BYU WMO 0.9m telescope. Preliminary magnitudes were found by referencing against USNO-B1.0 star 1014-0271368 (RA(J2000) = 17:05:26.42, Dec(J2000) = +11:27:32.9). Assuming its values are B=18.66, R=17.32 (from catalog) and V=18.0 (our estimate) we obtain the following values:
```
post burst
t_mid(hr)   exp.(min)  filter  mag.  error
37.18        25            B      19.9  0.15
35.91        25            V      19.3  0.1
35.25        20            R      18.5  0.1
```
Poor weather has prevented subsequent observations.
GCN Circular #10694
M. Andreev, =A0A. Sergeev (Terskol Branch of =A0Institute of Astronomy), A. Volnova (SAI MSU), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 100418A (Marshall et al. GCN 10612) with the Z-600 telescope of Mt.Terskol observatory in R-filter between (UT) Apr. 20 19:47 - 23:00 under good weather conditions with mean seeing of about 1.6 arcsec. The optical afterglow (Marshall et al. GCN 10612, Filgas et al. GCN 10617) is clearly detected in enhanced XRT error circle (Osborne et al. GCN 10614). The photometry of the afterglow in a stacked image based on USNO-B1.0 star 1014-0271368 (RA(J2000) =3D 17:05:26.42 Dec(J2000)=3D +11:27:32.9) assuming R=17.32 is following:
```
T0+ � � � Filter, � Exposure, � �mag. � � � � � �L
(mid, d) � � � � � �(s)

2.0175 � R � � � � 50x180 � � � 19.85 +/- 0.18 � 20.8
```
GCN Circular #10700
I. Bikmaev (KSU/AST), I. Khamitov (TUG), S. Melnikov, N. Sakhibullin (KSU/AST), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
report:
The optical afterglow of GRB 100418A (Marshall et al., GCN 10612, Filgas et al., GCN 10617) was observed with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey) in April 23/24 and April 27/28, 2010, in partially cloudy conditions. We obtained one useful 900 sec image in Rc-band in April 24 and nine 900 sec images in April 28. In spite of bright Moon in April 27/28 observations OT is clearly detected in combined image.
In the Table below we give our Rc estimates of the OT brightness relative to the nearby USNO-B1.0 star 1014-0271368 (R2Mag=17.32).
```
Date     UT  (T-T0),h    Rc      err
Apr.24 00:20 123.1       20.6  +/-0.10
Apr.28 00:50 220.0       21.25 +/-0.05
```
Preliminary Rc-light curve can be found at: http://hea.iki.rssi.ru/grb/100418a/indexeng.html
OT is still brighter compared with its host galaxy (Malesani, GCN10621) and further spectroscopic and photometric observations of this event are very important to check possible SN contribution in the OT flux.
GCN Circular #10720
F.E. Marshall (NASA/GSFC) and S.T. Holland (CRESST/USRA/GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT has monitored the optical flux from GRB 100418A since shortly after the BAT trigger (Marshall et al., GCN Circ. 10612). The highest flux was seen at about T+50 ks, followed by a power-law decay with an index of -1.0 +/- 0.1 in the UVOT white filter (Siegel et al., GCN Circ. 10645). The power-law decay continued until about T+700 ks, after which time the flux has remained approximately constant at about 22.3 mag in the white filter through the latest observation at about T+1.2 Ms. This late plateau may be due to flux from the host galaxy (Malesani, GCN Circ. 10621). We note that the white magnitude is 0.6 mag brighter than the SDSS g magnitude, but this may be due to the very different filter responses. Other possibilities for the plateau include a very bright SN (Malesani, GCN Circ. 10621; Filgas et al., GCN Circ. 10644) or optical flaring, which was seen earlier in the light curve (Bikmaev, GCN Circ. 10635; Covino et al., GCN Circ. 10646).
Swift continues to monitor GRB 100418A and observations with other telescopes are encouraged.
The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.07 (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #10726
I. Bikmaev (KSU/AST), I. Khamitov (TUG), N. Sakhibullin (KSU/AST), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
report:
The optical afterglow of GRB 100418A (Marshall et al., GCN 10612, Filgas et al., GCN 10617) was observed with Russian-Turkish 1.5-m telescope (RTT150,Bakirlitepe, TUBITAK National Observatory, Turkey) every night during May 1/2 - 6/7, 2010.
We obtained 4 - 12 exposures by 900 sec each in Rc filter. Estimates of Rc magnitudes were made relative to the nearby USNO-B1.0 star 1014-0271368 (R2Mag=17.32).
Additionally we made 4 x 900 sec exposures in g',r',i' SDSS filters in May 5/6, 2010. OT is still existed in all filters as compared with SDSS host images.
We found that OT brightness has decreased from Rc = 21.25 in April 28 (Bikmaev et al., GCN 10700, T+0.792 Ms) to Rc = 21.60 +/- 0.05 in May 5, 2010 (T+1.48 Ms) following a power-law decay with an index of -0.8 +/- 0.1, without plateau reported by Marshall et al. (GCN10720).
In May 7, UT(mean) = 0h50m, we estimated Rc = 21.7+/-0.07 mag. It means that OT is began to fade faster after T+1.48 Ms.
GCN Circular #10727
D. A. Perley, S. B. Cenko, A. A. Miller, D. Poznanski, A. V. Filippenko,=20 J. S. Bloom (UC Berkeley), and P. Nugent (LBNL) report:
We imaged the field of GRB 100418A (Marshall et al., GCN 10612) with the=20 Low Resolution Imaging Spectrometer on the Keck I 10-m telescope during=20 morning twilight on 2010-05-06 UT. Two exposures of 380 seconds each=20 were acquired in the g and R bands simultaneously. The midpoint of the=20 observation was 14:54 UT, 17.739 days after the GRB.
At the position of the afterglow and calibrating to 9 nearby unsaturated=20 SDSS stars, we measure magnitudes of:
```
g = 22.67 =B1 0.07
R = 21.85 =B1 0.05
```
The g-band magnitude is marginally consistent with the SDSS magnitude=20 (Malesani et al., GCN 10621) of g =3D 22.89 =B1 0.17, and suggests that t= he=20 UVOT flattening (Marshall et al., GCN 10720) is primarily due to the=20 host galaxy, not an associated supernova. Our reported R-band magnitude=20 is significantly brighter than the host, but this excess is consistent=20 with an afterglow origin (Bikmaev et al., GCN 10726). Additional=20 follow-up observations will be necessary to comment on the presence (or=20 absence) of a supernova counterpart.
GCN Circular #10783
V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 100418A (Marshall et al. GCN 10612) with Shajn telescope of CrAO between (UT) May, 14 21:07 -- 22:48 under photometric weather conditions and mean seeing of about 2 arcsec. The preliminary photometry of the afterglow+host in a stacked image based on USNO-B1.0 star 1014-0271368 (RA(J2000) = 17:05:26.42 Dec(J2000)= +11:27:32.9) assuming R=17.32 is following:
```
T0+      Filter,   Exposure,  mag.
(mid, d)              (s)

26.0332     R       90x60    21.86 +/-0.06
```
The photometry is compatible with R-magnitude reported by Perley et al, GCN 10727 (R=21.85+/-0.05 at 17.739 days) and still brighter than assumed R-magnitude of the normal type of host galaxy (SDSS based ugriz-> R conversion) which cannot be explained solely by afterglow contribution fading steeper than power law with decay index of .~0.8.
GCN Circular #10794
T. Hattori and K. Aoki (Subaru Telescope) report on behalf of the Subaru GRB team:
We observed the field of GRB 100418A (Marshall et al. GCN 10612) with FOCAS on Subaru Telescope under an excellent condition (seeing 0.3"-0.4"), starting at 12:13 UT on May 14 2010, 25.63 days after the trigger. Single exposure of 120 seconds in each V, Rc, and Ic bands was acquired. We detected and resolved the host galaxy (Malesani GCN 10621), but could not find any point source in the galaxy. The host galaxy magnitudes (Vega system) are V=22.62 +-0.06, Rc=21.90 +-0.03 and Ic=21.34 +-0.05. Rc-band magnitude is consistent with the values reported in GCN 10727 (R=21.85 +-0.05 at 17.7 days after) and GCN 10783 (R=21.86 +-0.06 at 26.0 days after). No time variation of R-band magnitude was thus detected during 17.7 days and 26.0 days.
We also performed optical spectroscopy for the host galaxy starting 12:35 UT May 14. We used two settings of the spectrograph with 0.8" width slit. One was covering the wavelengths between 3900 A and 8300 A, and the other between 5800 A and 1 micron. The integration time of the each setting was 1 hour (1200 seconds x 3). We found strong emission-lines such as [O II], Hgamma, Hbeta, [O III] at z=0.624 which are same as reported in GCN 10620 and GCN 10624. The continuum of the galaxy is very similar to that of the nearby blue compact dwarf galaxy NGC 1140. We could not identify any supernova feature like broad emission-lines and bumps.
GCN Circular #10821
A. Volnova (SAI MSU), M. Ibrahimov, R. Karimov (MAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 100418A (Marshall et al. GCN 10612) with AZT-22 telescope of Maidanak observatory on (UT) Apr. 22 (22:34 -- 23:35) and May 7 (22:49 -- 23:27). The optical afterglow (Marshall et al. GCN 10612, Filgas et al. GCN 10617) is detected in single images on Apr. 22 and in a stacked image on May 7. The photometry of the afterglow based on USNO-B1.0 star 1014-0271368 (RA(J2000) = 17:05:26.42 Dec(J2000)= +11:27:32.9) assuming R=17.32 is following:
```
T0+      Filter,   Exposure, seeing, mag.
(mid, d)              (s)
 4.0793     R       11x300    0.7 20.56 +/- 0.02
19.0821    R         6x300    1.3 22.05 +/- 0.25
```
GCN Circular #10832
Aquib Moin (Curtin Institute of Radio Astronomy / International Centre for Radio Astronomy Research / CSIRO Astronomy and Space Science)
Steven Tingay (Curtin Institute of Radio Astronomy / International Centre for Radio Astronomy Research)
Chris Phillips (CSIRO Astronomy and Space Science)
Gregory Taylor (University of New Mexico)
Mark Wieringa (CSIRO Astronomy and Space Science)
Ralph Martin (Perth Observatory) report:
We observed the field of Swift GRB100418a (GCN 10612, GCN 10614, GCN 10616) at 5.5 GHz and 9.0 GHz with the Australia Telescope Compact Array (ATCA) between 12:30:00 UT and 19:30:00 UT on May 26, 2010.
We clearly detected the radio afterglow at the optical afterglow position of the GRB 100418a (GCN 10616) at both frequencies with flux densities 0.91 +/- 0.04 mJy and 1.46 +/- 0.07 mJy respectively.
Further observations are planned.
The Australia Telescope Compact Array (/ Parkes telescope / Mopra telescope / Long Baseline Array) is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.
See the GRB 100418a field images:
http://cira.ivec.org/dokuwiki/doku.php/grb/grb100418a
GCN Circular #10883
V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 100418A (Marshall et al. GCN 10612) with Shajn telescope of CrAO between (UT) June, 11 20:07 -- 21:50 under photometric weather conditions and mean seeing of about 2 arcsec. The preliminary photometry of the afterglow+host in a stacked image based on USNO-B1.0 star 1014-0271368 (RA(J2000) = 17:05:26.42 Dec(J2000)= +11:27:32.9) assuming R=17.32 is following:
```
T0+      Filter,   Exposure,  mag.
(mid, d)              (s)

53.9919     R       88x60    22.05 +/-0.07
```
The brightness of the host is less but compatible with early reported magnitudes on May 14 (R = 21.86 +/-0.06; GCN 10783) and (Rc = 21.90 +/-0.03; GCN 10794)
1204.0575 from 4 Apr 12
Lan-Wei Jia et al.: Physical origin of multi-wavelength emission of GRB 100418A and implications for its progenitor
GRB 100418A is a long burst at z=0.624 without detection of any associated supernova (SN). Its lightcurves in both the prompt and afterglow phases are similar to GRB 060614, a nearby long GRB without an associated SN. We analyze the observational data of this event and discuss the possible origins of its multi-wavelength emission. We show that its joint lightcurve at 1 keV derived from Swift BAT and XRT observations is composed of two distinguished components. The first component, whose spectrum is extremely soft (\Gamma = 4.32), ends with a steep decay segment, indicating the internal origin of this component. The second component is a slowly-rising, broad bump which peaks at ~10^5 seconds post the BAT trigger. Assuming that the late bump is due to onset of the afterglow, we derive the initial Lorentz factor (Gamma_0) of the GRB fireball and find that it significantly deviates from the relation between the Gamma_0 and Eiso of typical GRBs. We also check whether it follows the same anti-correlation between X-ray luminosity and the break time observed in the shallow decay phase of many typical GRBs, which is usually regarded as a signal of late energy injection from the GRB central engine. However, we find that it does not obey this correlation. We propose that the late bump could be contributed by a two-component jet. We fit the second component with an off-axis jet model for a constant medium density and find the late bump can be represented by the model. The derived jet half-opening angle is 0.30 rad and the viewing angle is 0.315 rad. The medium density is 0.05 cm^-3, possibly suggesting that it may be from a merger of compact stars. The similarity between GRBs 060614 and 100418A may indicate that the two GRBs are from the same population and the late bump observed in the two GRBs may be a signal of a two-component jet powered by the GRB central engine.
1204.0583 from 4 Apr 12
Yuu Niino et al.: GRB 100418A: a Long GRB without a Bright Supernova in a High-Metallicity Host Galaxy
We present results of a search for a supernova (SN) component associated with GRB 100418A at the redshift of 0.624. The field of GRB 100418A was observed with FOCAS on Subaru 8.2m telescope under a photometric condition (seeing 0.3"-0.4") on 2010 May 14 (UT). The date corresponds to 25.6 days after the burst trigger (15.8 days in the restframe). We did imaging observations in V, Rc, and Ic bands, and two hours of spectrophotometric observations. We got the resolved host galaxy image which elongated 1.6" (= 11 kpc) from north to south. No point source was detected on the host galaxy. The time variation of Rc-band magnitude shows that the afterglow of GRB 100418A has faded to Rc \sim > 24 without SN like rebrightening, when we compare our measurement to the reports in GCN circulars. We could not identify any SN feature such as broad emission-lines or bumps in our spectrum. Assuming the SN is fainter than the 3{\sigma} noise spectrum of our observation, we estimate the upper limit on the SN absolute magnitude MIc,obs > -17.2 in observer frame Ic-band. This magnitude is comparable to the faintest type Ic SNe. We also estimate host galaxy properties from the spectrum. The host galaxy of GRB 100418A is relatively massive (log M_{star}/M_{sun} = 9.54) compared to typical long GRB host galaxies, and has 12+log(O/H) = 8.75.
1407.8180 from 1 Aug 14
E R Stanway et al.: Radio Observations of GRB Host Galaxies
We present 5.5 and 9.0 GHz observations of a sample of seventeen GRB host galaxies at z = 0.5-1.4, using the radio continuum to explore their star formation properties in the context of the small but growing sample of galaxies with similar observations. Four sources are detected, one of those (GRB 100418A) likely due to lingering afterglow emission. We suggest that the previously-reported radio afterglow of GRB 100621A may instead be due to host galaxy flux. We see no strong evidence for redshift evolution in the typical star formation rate of GRB hosts, but note that the fraction of `dark' bursts with detections is higher than would be expected given constraints on the more typical long GRB population. We also determine the average radio-derived star formation rates of core collapse supernovae at comparable redshift, and show that these are still well below the limits obtained for GRB hosts, and show evidence for a rise in typical star formation rate with redshift in supernova hosts.
1507.03772 from 15 Jul 15
Ritsuko Imatani et al.: Soft X-ray Observation of the Prompt Emission of GRB100418A
We have observed the prompt emission of GRB 100418A, from its beginning by the MAXI/SSC (0.7-7 keV) on board the International Space Station followed by the Swift/XRT (0.3-10 keV) observation. The light curve can be fitted by a combination of a power law component and an exponential component (decay constant is $31.6\pm 1.6$). The X-ray spectrum is well expressed by the Band function with $E_{\rm p}\leq$8.3 keV. This is the brightest GRB showing a very low value of $E_{\rm p}$. It is also consistent with the Yonetoku-relation ($E_{\rm p}$-$L_{\rm p}$) while it is not clear with the Amati-relation ($E_{\rm p}$-$E_{\rm iso}$).

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Jochen Greiner, last update: 15-Jul-2015 [Disclaimer]