Gamma-ray Burst 180331B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE


TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:39:16 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     820513,   Seg_Num: 0
GRB_RA:          196.820d {+13h 07m 17s} (J2000),
                 196.999d {+13h 08m 00s} (current),
                 196.328d {+13h 05m 19s} (1950)
GRB_DEC:         +61.725d {+61d 43' 30"} (J2000),
                 +61.628d {+61d 37' 40"} (current),
                 +61.992d {+61d 59' 31"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       7525 [cnts]    Image_Peak=250 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   264     E_range: 25-100 keV
BKG_INTEN:       69352 [cnts]
BKG_TIME:        56283.28 SOD {15:38:03.28} UT
BKG_DUR:         24 [sec]
GRB_DATE:        18208 TJD;    90 DOY;   18/03/31
GRB_TIME:        56319.32 SOD {15:38:39.32} UT
GRB_PHI:         -67.56 [deg]
GRB_THETA:        34.35 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.67 [sigma]
IMAGE_SIGNIF:    9.48 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +2  +0  +0  +0 +40  +0 
SUN_POSTN:        10.00d {+00h 40m 00s}   +4.30d {+04d 18' 15"}
SUN_DIST:        113.85 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.25d {+12h 53m 00s}   -0.89d {-00d 53' 36"}
MOON_DIST:        62.59 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.30 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      153.65, 59.60 [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 = 51.62,-4.01 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:42:17 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     820513,   Seg_Num: 0
GRB_RA:          196.820d {+13h 07m 17s} (J2000),
                 196.999d {+13h 08m 00s} (current),
                 196.328d {+13h 05m 19s} (1950)
GRB_DEC:         +61.725d {+61d 43' 30"} (J2000),
                 +61.628d {+61d 37' 40"} (current),
                 +61.992d {+61d 59' 31"} (1950)
GRB_DATE:        18208 TJD;    90 DOY;   18/03/31
GRB_TIME:        56319.32 SOD {15:38:39.32} UT
TRIGGER_INDEX:   264
GRB_PHI:         -67.56 [deg]
GRB_THETA:        34.35 [deg]
DELTA_TIME:      76.00 [sec]
TRIGGER_DUR:     2.048 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.67 [sigma]
IMAGE_SIGNIF:    9.48 [sigma]
LC_URL:          sw00820513000msb.lc
SUN_POSTN:        10.00d {+00h 40m 00s}   +4.31d {+04d 18' 18"}
SUN_DIST:        113.85 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.27d {+12h 53m 06s}   -0.90d {-00d 54' 12"}
MOON_DIST:        62.60 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.30 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      153.65, 59.60 [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 = 51.62,-4.01 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:49:48 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.807d {+13h 07m 14s} (J2000)
POINT_DEC:       +61.704d {+61d 42' 13"} (J2000)
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  56983.01 SOD {15:49:43.01} UT,   663.7 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:52:31 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.807d {+13h 07m 14s} (J2000)
POINT_DEC:       +61.704d {+61d 42' 13"} (J2000)
POINT_ROLL:      7.409d
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  56987.19 SOD {15:49:47.19} UT,   667.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.342
N_STARS:         17
X_OFFSET:        652 [pixels]
Y_OFFSET:        491 [pixels]
X_MAX:           1611 [pixels]
Y_MAX:           1450 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00820513000msufc0667.fits
SUN_POSTN:        10.01d {+00h 40m 02s}   +4.31d {+04d 18' 28"}
SUN_DIST:        113.87 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.37d {+12h 53m 28s}   -0.94d {-00d 56' 13"}
MOON_DIST:        62.60 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      153.68, 59.58 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:52:44 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.807d {+13h 07m 14s} (J2000)
POINT_DEC:       +61.704d {+61d 42' 13"} (J2000)
POINT_ROLL:      7.409d
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  56987.19 SOD {15:49:47.19} UT,   667.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.342
N_STARS:         17
X_OFFSET:        652 [pixels]
Y_OFFSET:        491 [pixels]
X_MAX:           1611 [pixels]
Y_MAX:           1450 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00820513000msufc0667.fits
SUN_POSTN:        10.01d {+00h 40m 02s}   +4.31d {+04d 18' 28"}
SUN_DIST:        113.87 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.37d {+12h 53m 28s}   -0.94d {-00d 56' 15"}
MOON_DIST:        62.61 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      153.68, 59.58 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:53:37 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     820513,   Seg_Num: 0
GRB_RA:          196.7801d {+13h 07m 07.22s} (J2000),
                 196.9592d {+13h 07m 50.20s} (current),
                 196.2877d {+13h 05m 09.05s} (1950)
GRB_DEC:         +61.7264d {+61d 43' 35.0"} (J2000),
                 +61.6292d {+61d 37' 45.0"} (current),
                 +61.9933d {+61d 59' 35.8"} (1950)
GRB_ERROR:       4.6 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  57006.00 SOD {15:50:06.00} UT,   686.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        10.01d {+00h 40m 02s}   +4.31d {+04d 18' 29"}
SUN_DIST:        113.84 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.38d {+12h 53m 30s}   -0.94d {-00d 56' 26"}
MOON_DIST:        62.63 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.67, 55.30 [deg] galactic lon,lat of the burst
ECL_COORDS:      153.63, 59.59 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:53:53 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.807d {+13h 07m 14s} (J2000)
POINT_DEC:       +61.704d {+61d 42' 13"} (J2000)
ROLL:            7.409d
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  56987.19 SOD {15:49:47.19} UT,   667.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     544204207
X_OFFSET:        971 [pixels]
Y_OFFSET:        810 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1131
Y_GRB_POS:       970
BINNING_INDEX:   1
IM_URL:          sw00820513000msuni0688.fits
SUN_POSTN:        10.01d {+00h 40m 02s}   +4.31d {+04d 18' 29"}
SUN_DIST:        113.87 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.38d {+12h 53m 31s}   -0.94d {-00d 56' 29"}
MOON_DIST:        62.61 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      153.68, 59.58 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:54:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.807d {+13h 07m 14s} (J2000)
POINT_DEC:       +61.704d {+61d 42' 13"} (J2000)
ROLL:            7.409d
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  56987.19 SOD {15:49:47.19} UT,   667.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     544204207
X_OFFSET:        971 [pixels]
Y_OFFSET:        810 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1131
Y_GRB_POS:       970
BINNING_INDEX:   1
IM_URL:          sw00820513000msuni0688.fits
SUN_POSTN:        10.01d {+00h 40m 02s}   +4.31d {+04d 18' 29"}
SUN_DIST:        113.87 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.38d {+12h 53m 31s}   -0.94d {-00d 56' 30"}
MOON_DIST:        62.61 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      153.68, 59.58 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:56:44 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.805d {+13h 07m 13s} (J2000)
POINT_DEC:       +61.700d {+61d 42' 01"} (J2000)
POINT_ROLL:      7.407d
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  57194.24 SOD {15:53:14.24} UT,   874.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.422
N_STARS:         41
X_OFFSET:        412 [pixels]
Y_OFFSET:        251 [pixels]
X_MAX:           1851 [pixels]
Y_MAX:           1690 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00820513000msufc0874.fits
SUN_POSTN:        10.01d {+00h 40m 03s}   +4.31d {+04d 18' 32"}
SUN_DIST:        113.87 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.40d {+12h 53m 37s}   -0.95d {-00d 57' 02"}
MOON_DIST:        62.61 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.33 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      153.68, 59.58 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:56:59 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.805d {+13h 07m 13s} (J2000)
POINT_DEC:       +61.700d {+61d 42' 01"} (J2000)
POINT_ROLL:      7.407d
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  57194.24 SOD {15:53:14.24} UT,   874.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.422
N_STARS:         41
X_OFFSET:        412 [pixels]
Y_OFFSET:        251 [pixels]
X_MAX:           1851 [pixels]
Y_MAX:           1690 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00820513000msufc0874.fits
SUN_POSTN:        10.01d {+00h 40m 03s}   +4.31d {+04d 18' 32"}
SUN_DIST:        113.87 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.40d {+12h 53m 37s}   -0.95d {-00d 57' 05"}
MOON_DIST:        62.61 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.33 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      153.68, 59.58 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:57:18 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     820513,   Seg_Num: 0
GRB_RA:          196.7829d {+13h 07m 07.89s} (J2000),
                 196.9620d {+13h 07m 50.87s} (current),
                 196.2905d {+13h 05m 09.73s} (1950)
GRB_DEC:         +61.7271d {+61d 43' 37.5"} (J2000),
                 +61.6299d {+61d 37' 47.6"} (current),
                 +61.9940d {+61d 59' 38.3"} (1950)
GRB_ERROR:       2.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  57006.00 SOD {15:50:06.00} UT,   686.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        10.01d {+00h 40m 03s}   +4.31d {+04d 18' 33"}
SUN_DIST:        113.84 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.41d {+12h 53m 38s}   -0.95d {-00d 57' 09"}
MOON_DIST:        62.64 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.67, 55.30 [deg] galactic lon,lat of the burst
ECL_COORDS:      153.63, 59.59 [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:     Sat 31 Mar 18 15:57:57 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.805d {+13h 07m 13s} (J2000)
POINT_DEC:       +61.700d {+61d 42' 01"} (J2000)
ROLL:            7.407d
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  57194.24 SOD {15:53:14.24} UT,   874.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     544204414
X_OFFSET:        971 [pixels]
Y_OFFSET:        810 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1131
Y_GRB_POS:       970
BINNING_INDEX:   1
IM_URL:          sw00820513000msuni0895.fits
SUN_POSTN:        10.01d {+00h 40m 03s}   +4.31d {+04d 18' 33"}
SUN_DIST:        113.87 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.41d {+12h 53m 39s}   -0.95d {-00d 57' 17"}
MOON_DIST:        62.62 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.33 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      153.68, 59.58 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Mar 18 15:58:03 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     820513,   Seg_Num: 0
POINT_RA:        196.805d {+13h 07m 13s} (J2000)
POINT_DEC:       +61.700d {+61d 42' 01"} (J2000)
ROLL:            7.407d
IMG_START_DATE:  18208 TJD;    90 DOY;   18/03/31
IMG_START_TIME:  57194.24 SOD {15:53:14.24} UT,   874.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     544204414
X_OFFSET:        971 [pixels]
Y_OFFSET:        810 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1131
Y_GRB_POS:       970
BINNING_INDEX:   1
IM_URL:          sw00820513000msuni0895.fits
SUN_POSTN:        10.01d {+00h 40m 03s}   +4.31d {+04d 18' 33"}
SUN_DIST:        113.87 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      193.41d {+12h 53m 39s}   -0.96d {-00d 57' 18"}
MOON_DIST:        62.62 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      119.64, 55.33 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      153.68, 59.58 [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 #22573
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), A. Deich (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU), K. L. Page (U Leicester) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 15:38:39 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180331B (trigger=820513). Swift executed a delayed slewed due to an observing constraint. The BAT on-board calculated location is RA, Dec 196.820, +61.725, which is
```
   RA(J2000)  =  13h 07m 17s
   Dec(J2000) = +61d 43' 30"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 8 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 15:49:43.0 UT, 663.7 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 196.7829, 61.7271 which is equivalent to:
```
   RA(J2000)  = 13h 07m 07.91s
   Dec(J2000) = +61d 43' 37.5"
```
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This location is 63 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. No spectrum from the promptly downlinked event data is yet available to determine the column density.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 667 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 0.01.
Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular #22575
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1501 s of XRT Photon Counting mode data and 2 UVOT images for GRB 180331B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 196.78337, +61.72625 which is equivalent to:
```
RA (J2000): 13h 07m 8.01s
Dec (J2000): +61d 43' 34.5"
```
with an uncertainty of 1.8 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 #22576
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180331B (trigger #820513) (Lien et al., GCN Circ. 22573). The BAT ground-calculated position is RA, Dec = 196.781, 61.735 deg which is
```
  RA(J2000)  =  13h 07m 07.6s
  Dec(J2000) = +61d 44' 05.9"
```
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 30%.
The mask-weighted light curve shows a double-peaked structure that starts at ~T-20 s and ends at ~T+140 s. The two peaks occur at ~T-20 s and ~T+1 s, respectively. T90 (15-350 keV) is 147.0 +- 33.1 sec (estimated error including systematics).
The time-averaged spectrum from T-22.03 to T+142.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.48 +- 0.22. The fluence in the 15-150 keV band is 1.9 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.97 sec in the 15-150 keV band is 2.8 +- 0.3 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/820513/BA/
GCN Circular #22577
A. Volnova (IKI), A. Pozanenko (IKI), E. Mazaeva (IKI), R. Inasaridze (AbAO), V. Ayvazian (AbAO), O. Kvaratskhelia (AbAO), G. Kapanadze (AbAO), I. Molotov (KIAM), report on behalf of larger GRB follow-up collaboration:
We observed the field of GRB 180331B (Lien et al., GCN 22573) with AS-32 (0.7m) telescope of Abastumani Observatory starting on Mar. 31 (UT) 17:49:41. We do not detect any object within enhanced XRT position (Goad et al., GCN 22575). Preliminary photometry of the field is following.
```
Date        UT start   t-T0      Filter Exp.   OT    Err. UL
                      (mid, days)        (s)

2018-03-31  17:49:41   0.11370   CR     38*60  n/d   n/d  22.3
```
The photometry is based on nearby USNO-B1.0 stars (R2 magnitude).
GCN Circular #22578
P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), A. D'Ai (INAF-IASFPA) and report on behalf of the Swift-XRT team: report on behalf of the Swift-XRT team:
We have analysed 6.6 ks of XRT data for GRB 180331B, from 671 s to 25.2 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay index of alpha=0.30 (+/-0.04).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.80 (+0.13, -0.12). The best-fitting absorption column is 8.7 (+3.5, -3.2) x 10^20 cm^-2, in excess of the Galactic value of 1.6 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     8.7 (+3.5, -3.2) x 10^20 cm^-2
Galactic foreground: 1.6 x 10^20 cm^-2
Excess significance: 3.7 sigma
Photon index:	     1.80 (+0.13, -0.12)
```
If the light curve continues to decay with a power-law decay index of 0.30, the count rate at T+24 hours will be 0.082 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x 10^-12 (3.5 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/00820513.
This circular is an official product of the Swift-XRT team.
GCN Circular #22579
N. P. M. Kuin (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180331B 668 s after the BAT trigger (Lien et al., GCN Circ. 22573). No optical afterglow consistent with the XRT position Goad er al., (GCN Circ. 22575) is detected in the initial UVOT exposures, consistent with the report of Volnova et al. (GCN Circ. 22577). Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           668          818          147         >21.2
white              668         2066          412         >21.8
v                 1056         2115          136         >19.2
b                 1156         2041          117         >20.3
u                 1130         2016          117         >20.3
w1                 849         1992           78         >20.2
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).

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Jochen Greiner, last update: 01-Apr-2018 [Disclaimer]