Gamma-ray Burst 180316A

(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:     Fri 16 Mar 18 04:57:53 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     814677,   Seg_Num: 0
GRB_RA:          265.436d {+17h 41m 45s} (J2000),
                 265.668d {+17h 42m 40s} (current),
                 264.800d {+17h 39m 12s} (1950)
GRB_DEC:          +0.737d {+00d 44' 11"} (J2000),
                  +0.729d {+00d 43' 43"} (current),
                  +0.760d {+00d 45' 37"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       7455 [cnts]    Image_Peak=253 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   271     E_range: 50-350 keV
BKG_INTEN:       62672 [cnts]
BKG_TIME:        17811.36 SOD {04:56:51.36} UT
BKG_DUR:         24 [sec]
GRB_DATE:        18193 TJD;    75 DOY;   18/03/16
GRB_TIME:        17845.09 SOD {04:57:25.09} UT
GRB_PHI:          42.77 [deg]
GRB_THETA:        38.87 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.51 [sigma]
IMAGE_SIGNIF:    9.43 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +3  +0  +0  +0  +0  +0 
SUN_POSTN:       355.92d {+23h 43m 41s}   -1.77d {-01d 45' 53"}
SUN_DIST:         90.28 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.16d {+22h 48m 38s}   -9.86d {-09d 51' 47"}
MOON_DIST:        76.82 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.46, 15.80 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      265.00, 24.10 [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 = 29.84,-18.87 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 16 Mar 18 04:59:27 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     814677,   Seg_Num: 0
GRB_RA:          265.4290d {+17h 41m 42.95s} (J2000),
                 265.6609d {+17h 42m 38.62s} (current),
                 264.7922d {+17h 39m 10.12s} (1950)
GRB_DEC:          +0.7497d {+00d 44' 58.9"} (J2000),
                  +0.7418d {+00d 44' 30.5"} (current),
                  +0.7734d {+00d 46' 24.3"} (1950)
GRB_ERROR:       6.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       6.14e-10 [erg/cm2/sec]
GRB_SIGNIF:      5.19 [sigma]
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  17940.53 SOD {04:59:00.53} UT,   95.4 [sec] since BAT Trigger Time
TAM[0-3]:        327.66 237.23 261.65 243.61
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       355.92d {+23h 43m 42s}   -1.76d {-01d 45' 52"}
SUN_DIST:         90.29 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.17d {+22h 48m 41s}   -9.86d {-09d 51' 33"}
MOON_DIST:        76.84 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.47, 15.82 [deg] galactic lon,lat of the burst
ECL_COORDS:      264.99, 24.11 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.91 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 16 Mar 18 04:59:37 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     814677,   Seg_Num: 0
GRB_RA:          265.4290d {+17h 41m 42.9s} (J2000),
                 265.6609d {+17h 42m 38.6s} (current),
                 264.7922d {+17h 39m 10.1s} (1950)
GRB_DEC:          +0.7497d {+00d 44' 58.9"} (J2000),
                  +0.7418d {+00d 44' 30.5"} (current),
                  +0.7734d {+00d 46' 24.3"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       27 [cnts]
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  17940.53 SOD {04:59:00.53} UT,   95.4 [sec] since BAT Trigger Time
CENTROID_X:      355.75,  raw= 356  [pixels]
CENTROID_Y:      308.85,  raw= 309  [pixels]
ROLL:            91.79 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   24.64
GRB_POS_XRT_Z:   116.33
IMAGE_URL:       sw00814677000msxps_rw.img
SUN_POSTN:       355.92d {+23h 43m 42s}   -1.76d {-01d 45' 51"}
SUN_DIST:         90.29 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.17d {+22h 48m 41s}   -9.86d {-09d 51' 31"}
MOON_DIST:        76.84 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.47, 15.82 [deg] galactic lon,lat of the burst
ECL_COORDS:      264.99, 24.11 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 16 Mar 18 04:59:46 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     814677,   Seg_Num: 0
GRB_RA:          265.4290d {+17h 41m 42.9s} (J2000),
                 265.6609d {+17h 42m 38.6s} (current),
                 264.7922d {+17h 39m 10.1s} (1950)
GRB_DEC:          +0.7497d {+00d 44' 58.9"} (J2000),
                  +0.7418d {+00d 44' 30.5"} (current),
                  +0.7734d {+00d 46' 24.3"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       27 [cnts]
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  17940.53 SOD {04:59:00.53} UT,   95.4 [sec] since BAT Trigger Time
CENTROID_X:      355.75,  raw= 356  [pixels]
CENTROID_Y:      308.85,  raw= 309  [pixels]
ROLL:            91.79 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   24.64
GRB_POS_XRT_Z:   116.33
IMAGE_URL:       sw00814677000msxps_rw.img
SUN_POSTN:       355.92d {+23h 43m 42s}   -1.76d {-01d 45' 51"}
SUN_DIST:         90.29 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.17d {+22h 48m 41s}   -9.86d {-09d 51' 30"}
MOON_DIST:        76.85 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.47, 15.82 [deg] galactic lon,lat of the burst
ECL_COORDS:      264.99, 24.11 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 16 Mar 18 05:01:14 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     814677,   Seg_Num: 0
GRB_RA:          265.436d {+17h 41m 45s} (J2000),
                 265.668d {+17h 42m 40s} (current),
                 264.800d {+17h 39m 12s} (1950)
GRB_DEC:          +0.737d {+00d 44' 11"} (J2000),
                  +0.729d {+00d 43' 43"} (current),
                  +0.760d {+00d 45' 37"} (1950)
GRB_DATE:        18193 TJD;    75 DOY;   18/03/16
GRB_TIME:        17845.09 SOD {04:57:25.09} UT
TRIGGER_INDEX:   271
GRB_PHI:          42.77 [deg]
GRB_THETA:        38.87 [deg]
DELTA_TIME:      -11.00 [sec]
TRIGGER_DUR:     2.048 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.51 [sigma]
IMAGE_SIGNIF:    9.43 [sigma]
LC_URL:          sw00814677000msb.lc
SUN_POSTN:       355.93d {+23h 43m 42s}   -1.76d {-01d 45' 50"}
SUN_DIST:         90.28 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.19d {+22h 48m 44s}   -9.85d {-09d 51' 16"}
MOON_DIST:        76.85 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.46, 15.80 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      265.00, 24.10 [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 = 29.84,-18.87 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 16 Mar 18 05:02:03 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.462d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.742d {+00d 44' 30"} (J2000)
POINT_ROLL:      91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  17949.59 SOD {04:59:09.59} UT,   104.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.345
N_STARS:         190
X_OFFSET:        244 [pixels]
Y_OFFSET:        642 [pixels]
X_MAX:           1203 [pixels]
Y_MAX:           1601 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00814677000msufc0104.fits
SUN_POSTN:       355.93d {+23h 43m 42s}   -1.76d {-01d 45' 49"}
SUN_DIST:         90.25 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.19d {+22h 48m 46s}   -9.85d {-09d 51' 08"}
MOON_DIST:        76.83 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 16 Mar 18 05:02:18 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.462d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.742d {+00d 44' 30"} (J2000)
POINT_ROLL:      91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  17949.59 SOD {04:59:09.59} UT,   104.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.345
N_STARS:         190
X_OFFSET:        244 [pixels]
Y_OFFSET:        642 [pixels]
X_MAX:           1203 [pixels]
Y_MAX:           1601 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00814677000msufc0104.fits
SUN_POSTN:       355.93d {+23h 43m 42s}   -1.76d {-01d 45' 49"}
SUN_DIST:         90.25 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.19d {+22h 48m 47s}   -9.85d {-09d 51' 05"}
MOON_DIST:        76.83 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 16 Mar 18 05:03:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.462d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.742d {+00d 44' 30"} (J2000)
ROLL:            91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  17949.59 SOD {04:59:09.59} UT,   104.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     542869170
X_OFFSET:        564 [pixels]
Y_OFFSET:        962 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       724
Y_GRB_POS:       1122
BINNING_INDEX:   1
IM_URL:          sw00814677000msuni0125.fits
SUN_POSTN:       355.93d {+23h 43m 42s}   -1.76d {-01d 45' 47"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.21d {+22h 48m 50s}   -9.85d {-09d 50' 51"}
MOON_DIST:        76.85 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 16 Mar 18 05:03:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.462d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.742d {+00d 44' 30"} (J2000)
ROLL:            91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  17949.59 SOD {04:59:09.59} UT,   104.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     542869170
X_OFFSET:        564 [pixels]
Y_OFFSET:        962 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       724
Y_GRB_POS:       1122
BINNING_INDEX:   1
IM_URL:          sw00814677000msuni0125.fits
SUN_POSTN:       355.93d {+23h 43m 42s}   -1.76d {-01d 45' 47"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.21d {+22h 48m 50s}   -9.85d {-09d 50' 50"}
MOON_DIST:        76.85 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 16 Mar 18 05:07:11 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.463d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.744d {+00d 44' 38"} (J2000)
POINT_ROLL:      91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18161.76 SOD {05:02:41.76} UT,   316.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.522
N_STARS:         74
X_OFFSET:        244 [pixels]
Y_OFFSET:        642 [pixels]
X_MAX:           1203 [pixels]
Y_MAX:           1601 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00814677000msufc0316.fits
SUN_POSTN:       355.93d {+23h 43m 43s}   -1.76d {-01d 45' 44"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.24d {+22h 48m 57s}   -9.84d {-09d 50' 19"}
MOON_DIST:        76.87 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 16 Mar 18 05:07:26 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.463d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.744d {+00d 44' 38"} (J2000)
POINT_ROLL:      91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18161.76 SOD {05:02:41.76} UT,   316.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.522
N_STARS:         74
X_OFFSET:        244 [pixels]
Y_OFFSET:        642 [pixels]
X_MAX:           1203 [pixels]
Y_MAX:           1601 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00814677000msufc0316.fits
SUN_POSTN:       355.93d {+23h 43m 43s}   -1.76d {-01d 45' 44"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.24d {+22h 48m 57s}   -9.84d {-09d 50' 16"}
MOON_DIST:        76.87 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 16 Mar 18 05:08:33 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.463d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.744d {+00d 44' 38"} (J2000)
ROLL:            91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18161.76 SOD {05:02:41.76} UT,   316.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     542869382
X_OFFSET:        564 [pixels]
Y_OFFSET:        962 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       724
Y_GRB_POS:       1122
BINNING_INDEX:   1
IM_URL:          sw00814677000msuni0337.fits
SUN_POSTN:       355.93d {+23h 43m 43s}   -1.76d {-01d 45' 43"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.25d {+22h 48m 59s}   -9.84d {-09d 50' 06"}
MOON_DIST:        76.88 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 Circular #22500
A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), A. Deich (PSU), D. M. Palmer (LANL) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 04:57:25 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180316A (trigger=814677). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 265.436, +0.737 which is
```
   RA(J2000) = 17h 41m 45s
   Dec(J2000) = +00d 44' 11"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 20 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 04:59:00.5 UT, 95.4 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 265.4290, 0.7497 which is equivalent to:
```
   RA(J2000)  = +17h 41m 42.96s
   Dec(J2000) = +00d 44' 58.9"
```
with an uncertainty of 6.1 arcseconds (radius, 90% containment). This location is 52 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 104 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 0.27.
Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.inaf.it). 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 16 Mar 18 05:08:42 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.463d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.744d {+00d 44' 38"} (J2000)
ROLL:            91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18161.76 SOD {05:02:41.76} UT,   316.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     542869382
X_OFFSET:        564 [pixels]
Y_OFFSET:        962 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       724
Y_GRB_POS:       1122
BINNING_INDEX:   1
IM_URL:          sw00814677000msuni0337.fits
SUN_POSTN:       355.93d {+23h 43m 43s}   -1.76d {-01d 45' 43"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.25d {+22h 49m 00s}   -9.83d {-09d 50' 04"}
MOON_DIST:        76.89 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 16 Mar 18 05:15:53 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.463d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.744d {+00d 44' 37"} (J2000)
POINT_ROLL:      91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18715.01 SOD {05:11:55.01} UT,   869.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.825
N_STARS:         190
X_OFFSET:        4 [pixels]
Y_OFFSET:        402 [pixels]
X_MAX:           1443 [pixels]
Y_MAX:           1841 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    14
SL_URL:          sw00814677000msufc0869.fits
SUN_POSTN:       355.93d {+23h 43m 44s}   -1.76d {-01d 45' 35"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.31d {+22h 49m 14s}   -9.82d {-09d 48' 56"}
MOON_DIST:        76.94 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 16 Mar 18 05:16:09 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.463d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.744d {+00d 44' 37"} (J2000)
POINT_ROLL:      91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18715.01 SOD {05:11:55.01} UT,   869.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.825
N_STARS:         190
X_OFFSET:        4 [pixels]
Y_OFFSET:        402 [pixels]
X_MAX:           1443 [pixels]
Y_MAX:           1841 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    14
SL_URL:          sw00814677000msufc0869.fits
SUN_POSTN:       355.93d {+23h 43m 44s}   -1.76d {-01d 45' 35"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.31d {+22h 49m 15s}   -9.82d {-09d 48' 53"}
MOON_DIST:        76.95 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 16 Mar 18 05:16:32 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     814677,   Seg_Num: 0
GRB_RA:          265.4289d {+17h 41m 42.93s} (J2000),
                 265.6608d {+17h 42m 38.59s} (current),
                 264.7921d {+17h 39m 10.09s} (1950)
GRB_DEC:          +0.7482d {+00d 44' 53.5"} (J2000),
                  +0.7403d {+00d 44' 25.1"} (current),
                  +0.7719d {+00d 46' 18.9"} (1950)
GRB_ERROR:       2.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18498.00 SOD {05:08:18.00} UT,   652.9 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       355.93d {+23h 43m 44s}   -1.76d {-01d 45' 35"}
SUN_DIST:         90.30 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.32d {+22h 49m 16s}   -9.81d {-09d 48' 49"}
MOON_DIST:        76.98 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.47, 15.81 [deg] galactic lon,lat of the burst
ECL_COORDS:      264.99, 24.11 [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 16 Mar 18 05:17:40 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.463d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.744d {+00d 44' 37"} (J2000)
ROLL:            91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18715.01 SOD {05:11:55.01} UT,   869.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     542869935
X_OFFSET:        563 [pixels]
Y_OFFSET:        961 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       723
Y_GRB_POS:       1121
BINNING_INDEX:   1
IM_URL:          sw00814677000msuni0890.fits
SUN_POSTN:       355.94d {+23h 43m 45s}   -1.76d {-01d 45' 34"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.32d {+22h 49m 18s}   -9.81d {-09d 48' 39"}
MOON_DIST:        76.96 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 16 Mar 18 05:17:48 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     814677,   Seg_Num: 0
POINT_RA:        265.463d {+17h 41m 51s} (J2000)
POINT_DEC:        +0.744d {+00d 44' 37"} (J2000)
ROLL:            91.789d
IMG_START_DATE:  18193 TJD;    75 DOY;   18/03/16
IMG_START_TIME:  18715.01 SOD {05:11:55.01} UT,   869.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     542869935
X_OFFSET:        563 [pixels]
Y_OFFSET:        961 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       723
Y_GRB_POS:       1121
BINNING_INDEX:   1
IM_URL:          sw00814677000msuni0890.fits
SUN_POSTN:       355.94d {+23h 43m 45s}   -1.76d {-01d 45' 34"}
SUN_DIST:         90.26 [deg]   Sun_angle= 6.0 [hr] (West of Sun)
MOON_POSTN:      342.33d {+22h 49m 18s}   -9.81d {-09d 48' 37"}
MOON_DIST:        76.96 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:       25.48, 15.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      265.03, 24.10 [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 #22501
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 180316A, we find an enhanced XRT position of the afterglow: RA, Dec: 265.4289, 0.7483 which is equivalent to:
```
   RA (J2000)  = 17 41 42.94
   Dec (J2000) = +00 44 54.0
```
with an uncertainty of 2.1 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/814677.
Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular #22502
V. Lipunov, N.Tyurina, V.Kornilov, E.Gorbovskoy, P.Balanutsa, V.Vladimirov, A.Krylov, I.Gorbunov, A.Kuznetsov, V.Chazov, D. Kuvshinov, D.Zimnukhov (Lomonosov Moscow State University, SAI),
R. Rebolo, M. Serra-Ricart (The Instituto de Astrofisica de Canarias),
R.Podesta, C.Lopez, F. Podesta (Observatorio Astronomico Felix Aguilar (OAFA),National University of San Juan, Argentina),
H. Levato, C. Saffe (Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE), San Juan, Argentina),
D.Buckley, S. Potter (South African Astronomical Observatory),
O.Gres, N.M.Budnev (Irkutsk State University),
A. Tlatov, V.Senik, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory)
V.Yurkov, A.Gabovich, Yu.Sergienko (Blagoveschensk Educational State University, Blagoveschensk),
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in IAC was pointed to the GRB180316A (Melandri et al GCN22500) 15 sec after notice time and 44 sec after trigger time at 2018-03-16 04:58:09 UT.
There is new changing OT at SWIFT XRT (Evans et al. GCN 22501) coordinates 17 41 42.94 +00 44 54.0
The 5-sigma upper limit on the first 10s image is 17.06mag The message may be cited.
====================================================================
The observations made on zenit distance = 42 degrees, galaxy latitude b = 15 degree. The moon ( 2 % bright part) below the horizon (The altitude of the Moon is -22 degree ). The sun altitude is -30.4 degree. The object can be observed till sunrise at 2018-03-16 07:14:55
GCN Circular #22503
V. Lipunov, N.Tyurina, V.Kornilov, E.Gorbovskoy, P.Balanutsa, V.Vladimirov, A.Krylov, I.Gorbunov, A.Kuznetsov, V.Chazov, D. Kuvshinov, D.Zimnukhov (Lomonosov Moscow State University, SAI),
R. Rebolo, M. Serra-Ricart (The Instituto de Astrofisica de Canarias),
R.Podesta, C.Lopez, F. Podesta (Observatorio Astronomico Felix Aguilar (OAFA),National University of San Juan, Argentina),
H. Levato, C. Saffe (Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE), San Juan, Argentina),
D.Buckley, S. Potter (South African Astronomical Observatory),
O.Gres, N.M.Budnev (Irkutsk State University),
A. Tlatov, V.Senik, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory)
V.Yurkov, A.Gabovich, Yu.Sergienko (Blagoveschensk Educational State University, Blagoveschensk),
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in IAC was pointed to the GRB180316A (Melandri et al GCN22500) 15 sec after notice time and 44 sec after trigger time at 2018-03-16 04:58:09 UT .
There is OT(GCN 22502) as the GRB counterpart coordinates (17h 41m 42s.82, + 00d 44m 53s.6 ) error =+-0.5"
The automatical OT light curve available at http://master.sai.msu.ru/static/OT/LC_GRB180316A.png
The message may be cited.
====================================================================
The observations made on zenit distance = 42 degrees, galaxy latitude b = 15 degree. The moon ( 2 % bright part) below the horizon (The altitude of the Moon is -22 degree ). The sun altitude is -30.4 degree. The object can be observed till sunrise at 2018-03-16 07:14:55
GCN Circular #22504
P. Schady and S. Steinmassl (both MPE) report:
We observed the field of GRB 180316A (Swift trigger 814677; Melandri et al., GCN #22500) 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 06:46 UT on March 16, 1.8 hours after the GRB trigger. They were performed at an average seeing of 1.5" and at an average airmass of 1.5.
We clearly detect the NIR/optical transient of GRB 180316A within the enhanced XRT position (Evans et al., GCN #22501), in agreement with the optical transient detected with MASTER (Lipunov et al., GCN #22502, #22503). Based on the first 4 minutes of exposure, we measure the following magnitudes (all in AB system):
```
g' = 19.4 +/- 0.1 mag
r' = 19.0 +/- 0.1 mag
i' = 18.9 +/- 0.1 mag
z' = 18.8 +/- 0.1 mag
J = 18.2 +/- 0.1 mag
H = 18.0 +/- 0.1 mag
K = 17.8 +/- 0.2 mag
```
Given magnitudes are calibrated against GROND zeropoints in g'r'i'z' and 2MASS field stars in JHK, and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.24 in the direction of the burst (Schlafly & Finkbeiner 2011).
We acknowledge the excellent support from the TiO and the current observer at the 2.2m in La Silla, Sam Kim and Charlotte Brand.
GCN Circular #22507
R. Martone, C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (= U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a l= arge collaboration report:
We observed the field of Swift GRB180316A (Melandri et al., GCN 22500) on= March 16, from 07:38 to 07:59 UT (mid time of 0.12 days post burst) with= a 1-m unit LCO telescope in Cerro Tololo in the SDSS r=E2=80=99 i' filte= rs. We detect the optical afterglow (Lipunov et al., GCN 22502; Schady an= d Steinmassl, GCN 22504) with the following magnitudes:
```
Mid time since GRB     Exp        Filter         Magnitude
(days)                 (s)
-------------------------------------------------------------
0.11                   4x120      SDSS-R         19.04 +- 0.05
0.12                   4x120      SDSS-I         18.88 +- 0.05
-------------------------------------------------------------
```
as calibrated against nearby SDSS stars.
GCN Circular #22508
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 4963 s of XRT Photon Counting mode data and 8 UVOT images for GRB 180316A, 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 = 265.42854, +0.74813 which is equivalent to:
```
RA (J2000): 17h 41m 42.85s
Dec (J2000): +00d 44' 53.3"
```
with an uncertainty of 1.4 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 #22509
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of GRB 180316A (Melandri, et al., GCN 22500) 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 2018/03 16.39 to 2018/03 16.52 UTC (4.34 to 7.49 hours after the BAT trigger), obtaining a total of 2.29 hours exposure in the r and i bands.
The afterglow is well-detected within the Swift-XRT error circle (Evans, et al., GCN 22501). In comparison with the USNO-B1 catalog, we obtain:
```
  r = 20.07 +/- 0.02
  i = 19.87 +/- 0.02
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The source appears so fade in flux with time as t^(-1.4+/-0.1).
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro M=E1rtir.
GCN Circular #22510
A. A. Breeveld (UCL-MSSL) and A. Melandri (INAF-OAB) report on behalf of=20 the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180316A=20 105 s after the BAT trigger (Melandri et al., GCN Circ. 22500). A fading source consistent with the enhanced XRT position (Evans et al.=20 GCN Circ. 22508) and the optical transient reported by Lipunov et al.=20 (GCN Circ. 22503), Shady & Steinmassl (GCN Circ. 22504) and Martone et=20 al. (GCN Circ. 22507), Butler et al. (GCN Circ. 22509) is detected in=20 the initial UVOT exposures.
The preliminary UVOT position is:
```
     RA  (J2000) =3D  17:41:42.87 =3D 265.42861 (deg.)
     Dec (J2000) =3D +00:44:53.7  =3D   0.74824 (deg.)
```
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT=20 photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for=20 the finding chart (white_fc) and early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white_fc           105          254          147         16.27 =B1 0.03
white              596          616           20         17.40 =B1 0.11
v                  646          839           39         17.15 =B1 0.18
b                  572          592           20         17.40 =B1 0.15
u                  317          566          246         16.44 =B1 0.04
w1                 695        22410         1175        >20.4
m2               12527        12578           50        >19.2
w2                 622         6753          255        >19.5
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) =3D 0.28 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #22511
S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU) and A. Melandri report on behalf of the Swift-XRT team:
We have analysed 6.1 ks of XRT data for GRB 180316A (Melandri et al. GCN Circ. 22500), from 101 s to 28.6 ks after the BAT trigger. The data comprise 534 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 22501).
The late-time light curve (from T0+4.4 ks) can be modelled with an initial power-law decay with an index of alpha=-0.0 (+/-0.6), followed by a break at T+8729 s to an alpha of 2.1 (+/-0.3).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.94 (+0.07, -0.04). The best-fitting absorption column is 2.038 (+0.286, -0.012) x 10^21 cm^-2, consistent with the Galactic value of 2.0 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.05 (+/-0.16) and a best-fitting absorption column of 3.3 (+/-0.7) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (5.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     3.3 (+/-0.7) x 10^21 cm^-2
Galactic foreground: 2.0 x 10^21 cm^-2
Excess significance: 3.2 sigma
Photon index:	     2.05 (+/-0.16)
```
If the light curve continues to decay with a power-law decay index of 2.1, the count rate at T+24 hours will be 2.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-13 (1.7 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/00814677.
This circular is an official product of the Swift-XRT team.
GCN Circular #22512
J. R. Cummings (CPI), S. D. Barthelmy (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), A. Melandri (INAF-OAB), 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+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180316A (trigger #814677) (Melandri et al., GCN Circ. 22500). The BAT ground-calculated position is RA, Dec = 265.422, 0.737 deg which is
```
  RA(J2000)  =  17h 41m 41.3s 
  Dec(J2000) = +00d 44' 14.3" 
```
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 29%.
The mask-weighted light curve shows a main structure with several overlapping pulses that starts at ~ T-15 s and ends at ~ T+30 s. The major peak occurs at ~ T+1 s. In addition, there are some weak emission before the main structure that starts at ~ T-80 s, and a weak tail afterward that lasts until ~ T+40 s. T90 (15-350 keV) is 87.0 +- 20.6 sec (estimated error including systematics).
The time-averaged spectrum from T-79.73 to T+37.27 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.46 +- 0.12. The fluence in the 15-150 keV band is 4.9 +- 0.4 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+1.27 sec in the 15-150 keV band is 3.3 +- 0.5 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
GCN Circular #22514
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of GRB 180316A (Melandri,, et al., GCN 22500) 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 2018/03 17.39 to 2018/03 17.52 UTC (28.35 to 31.55 hours after the BAT trigger), obtaining a total of 2.36 hours exposure in the r and i bands.
The optical afterglow (e.g., Lipunov, et al., GCN 22502) is again cleanly detected. In comparison with the USNO-B1 catalog, we obtain:
```
  r = 20.23 +/- 0.02
  i = 19.93 +/- 0.01
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. These magnitudes are comparable to those reported for RATIR for 2018/03.16 (Butler, et al., GCN 22509). During that observation, the afterglow was fading strongly. We again observe the afterglow to be fading, as t^(-0.7+/-0.3), and we infer that the afterglow may have brightened between our epochs, at a time around 1 day after the GRB.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro M=E1rtir.
GCN Circular #22516
A. Volnova (IKI), A. Kusakin (FAPHI), A. Pozanenko (IKI), I. Reva (FAPHI), E. Mazaeva (IKI), M. Krugov (FAPHI) report on behalf of larger GRB follow-up collaboration:
We observed the field of GRB GRB 180316A (Melandri et al., GCN 22500) with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting on Mar. 17 (UT) 23:19:40. We obtained several images in R-filter. The optical afterglow (Lipunov et al., GCN 22502; Schady et al. GCN 22504; Martone et al. GCN 22507; Butler et al., GCN 22509; Breeveld et al. GCN 22510) is marginally detected in a stacked image. Preliminary photometry of the field is following.
```
Date        UT start t-T0     Filter Exp.    OT    Err.  UL
                      (mid, days)     (s)

2018-03-17  23:19:40 1.78280  R      36*60   21.5  0.5   21.0
```
The photometry is based on several nearby USNO-B1.0 stars.
GCN Circular #22517
K. L. Murata, R. Itoh, T. Yoshii, Y. Tachibana, S. Harita, K. Morita, T. Ozawa, H. Mamiya, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 180316A (A. Melandri et al., GCN Circular #22500) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Okayama Astrophysical Observatory, Japan.
The observation started on 16:19:04 UT. We did not find any new point source within enhanced XRT circle (P.A. Evans et al., GCN Circular #22508) in all three bands. We obtained following limits for the magnitudes.
```
T0+[hour]    MID-UT      T-EXP[sec]    g'       Rc        Ic
------------------------------------------------------------
12.22       19:44:32      1980     >17.3     >17.4     >17.4
------------------------------------------------------------

T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
We used GSC2.3 catalog for flux calibration.
GCN Circular #22518
K. L. Murata, R. Itoh, T. Yoshii, Y. Tachibana, S. Harita, K. Morita, T. Ozawa, H. Mamiya, K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 180316A (A. Melandri et al., GCN Circular #22500) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 16:39:08 UT. We did not find any new point source within enhanced XRT circle (P.A. Evans et al., GCN Circular #22508) in all three bands. We obtained following limits for the magnitudes.
```
T0+[hour]    MID-UT      T-EXP[sec]    g'       Rc        Ic
------------------------------------------------------------
11.71       18:28:36      11620     >20.6     >19.7     >18.9
------------------------------------------------------------

T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
We used GSC2.3 catalog for flux calibration.
GCN Circular #22519
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga= (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of GRB 180316A (Melandri et al., GCN 22500) 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 2018/03 19.38 to 2018/03 19.52 UTC (76.23 to 79.44 hours after the BAT trigger), obtaining a total of 2.44 hours exposure in the r and i bands.
For a source within the Swift-XRT error circle, in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following 3-sigma upper limits:
```
 r	> 23.72
 i	> 23.59
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro M=E1rtir.
GCN Circular #22548
A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 180316A (Swift detection of a burst: Melandri et al., GCN 22500; Cummings et al., GCN 22512) triggered Konus-Wind at T0=3D17845.869 s UT (04:57:25.869).
The burst light curve shows a single emission episode which starts at ~T0-13 s and has a total duration of ~29 s. The emission is seen up to ~1.2 MeV.
As observed by Konus-Wind, the burst had a fluence of 1.43(-0.21,+0.38)x10^-5 erg/cm2, and a 64-ms peak energy flux, measured from T0+2.976 s, of 2.77(-1.16,+1.49)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst (measured from T0 to T0+16.640 s) is best fit in the 20 keV - 1.2 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with=A0 alpha =3D -1.23(-0.23,+0.27), and Ep =3D 439(-139,+424) keV (chi2 =3D 74/60 dof). Fitting by the GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -1.87 (chi2 =3D 74/59 dof).
The spectrum near the peak count rate (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 2 MeV range by a power law with exponential cutoff model with=A0 alpha =3D -1.19(-0.22,+0.26), and Ep =3D 498(-165,+498) keV (chi2 =3D 54/61 dof). Fitting by the GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -1.75 (chi2 =3D 53/60 dof).
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180316_T17845/
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.

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Jochen Greiner, last update: 26-Mar-2018 [Disclaimer]