Gamma-ray Burst 220403B

(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 03 Apr 22 20:42:57 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1101053,   Seg_Num: 0
GRB_RA:          191.025d {+12h 44m 06s} (J2000),
                 189.879d {+12h 39m 31s} (current),
                 195.378d {+13h 01m 31s} (1950)
GRB_DEC:         +89.170d {+89d 10' 13"} (J2000),
                 +89.048d {+89d 02' 54"} (current),
                 +89.442d {+89d 26' 31"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4319 [cnts]    Image_Peak=300 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   137     E_range: 15-50 keV
BKG_INTEN:       24968 [cnts]
BKG_TIME:        74547.10 SOD {20:42:27.10} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19672 TJD;    93 DOY;   22/04/03
GRB_TIME:        74562.65 SOD {20:42:42.65} UT
GRB_PHI:         -144.99 [deg]
GRB_THETA:        34.24 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     18.68 [sigma]
IMAGE_SIGNIF:    12.67 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  +2  +0  +0  -8  +0 
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 02"}
SUN_DIST:         85.40 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.26d {+02h 49m 02s}  +15.57d {+15d 34' 21"}
MOON_DIST:        75.23 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.96 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       92.06, 66.71 [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 = 66.53,20.55 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(3.0<100sec) coincident with the FERMI_GBM event (trignum=670711364).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:43:03 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     670711364
GRB_RA:          290.867d {+19h 23m 28s} (J2000),
                 290.804d {+19h 23m 13s} (current),
                 291.003d {+19h 24m 01s} (1950)
GRB_DEC:         +71.550d {+71d 32' 60"} (J2000),
                 +71.594d {+71d 35' 39"} (current),
                 +71.451d {+71d 27' 02"} (1950)
GRB_ERROR:       11.27 [deg radius, statistical plus systematic]
GRB_INTEN:       102 [cnts/sec]
DATA_SIGNIF:     6.20 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        19672 TJD;    93 DOY;   22/04/03
GRB_TIME:        74559.05 SOD {20:42:39.05} UT
GRB_PHI:          96.00 [deg]
GRB_THETA:        25.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      1.81
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      85%  GRB
2nd_MOST_LIKELY:  13%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,1,0, 0,0,
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 02"}
SUN_DIST:         82.26 [deg]   Sun_angle= 5.5 [hr] (West of Sun)
MOON_POSTN:       42.26d {+02h 49m 03s}  +15.57d {+15d 34' 22"}
MOON_DIST:        81.75 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      103.00, 23.16 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       43.24, 81.10 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220403863/quicklook/glg_lc_medres34_bn220403863.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 178.95,2.93 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the SWIFT_BAT event (trignum=1101053).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:43:13 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     670711364
GRB_RA:          187.533d {+12h 30m 08s} (J2000),
                 187.640d {+12h 30m 34s} (current),
                 187.301d {+12h 29m 12s} (1950)
GRB_DEC:         +84.833d {+84d 49' 60"} (J2000),
                 +84.710d {+84d 42' 38"} (current),
                 +85.109d {+85d 06' 34"} (1950)
GRB_ERROR:       12.00 [deg radius, statistical plus systematic]
GRB_INTEN:       113 [cnts/sec]
DATA_SIGNIF:     10.80 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        19672 TJD;    93 DOY;   22/04/03
GRB_TIME:        74559.05 SOD {20:42:39.05} UT
GRB_PHI:         101.00 [deg]
GRB_THETA:        45.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      2.02
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      76%  GRB
2nd_MOST_LIKELY:  23%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,1,0, 0,0,
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 03"}
SUN_DIST:         89.72 [deg]   Sun_angle= -11.6 [hr] (East of Sun)
MOON_POSTN:       42.26d {+02h 49m 03s}  +15.57d {+15d 34' 24"}
MOON_DIST:        78.80 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      123.50, 32.27 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      103.04, 66.70 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220403863/quicklook/glg_lc_medres34_bn220403863.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 178.95,2.93 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the SWIFT_BAT event (trignum=1101053).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:43:22 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     670711364
GRB_RA:          154.090d {+10h 16m 22s} (J2000),
                 154.688d {+10h 18m 45s} (current),
                 152.707d {+10h 10m 50s} (1950)
GRB_DEC:         +80.350d {+80d 20' 60"} (J2000),
                 +80.238d {+80d 14' 18"} (current),
                 +80.599d {+80d 35' 56"} (1950)
GRB_ERROR:       5.88 [deg radius, statistical only]
DATA_SIGNIF:     11.20 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        19672 TJD;    93 DOY;   22/04/03
GRB_TIME:        74559.05 SOD {20:42:39.05} UT
GRB_PHI:         102.00 [deg]
GRB_THETA:        51.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 03"}
SUN_DIST:         92.13 [deg]   Sun_angle= -9.4 [hr] (East of Sun)
MOON_POSTN:       42.26d {+02h 49m 03s}  +15.57d {+15d 34' 26"}
MOON_DIST:        78.33 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      130.25, 34.46 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      108.17, 61.09 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220403863/quicklook/glg_lc_medres34_bn220403863.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_670711364.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(3.0<100sec) coincident with the SWIFT_BAT event (trignum=1101053).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:44:59 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1101053,   Seg_Num: 0
GRB_RA:          191.5991d {+12h 46m 23.7s} (J2000),
                 190.3617d {+12h 41m 26.8s} (current),
                 196.3083d {+13h 05m 13.9s} (1950)
GRB_DEC:         +89.1817d {+89d 10' 54.1"} (J2000),
                 +89.0600d {+89d 03' 36.0"} (current),
                 +89.4527d {+89d 27' 09.7"} (1950)
GRB_ERROR:       6.5 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       29 [cnts]
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74658.94 SOD {20:44:18.94} UT,   96.3 [sec] since BAT Trigger Time
CENTROID_X:      275.28,  raw= 275  [pixels]
CENTROID_Y:      281.31,  raw= 281  [pixels]
ROLL:            357.93 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -39.57
GRB_POS_XRT_Z:   -75.71
IMAGE_URL:       sw01101053000msxps_rw.img
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 04"}
SUN_DIST:         85.39 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.28d {+02h 49m 06s}  +15.58d {+15d 34' 45"}
MOON_DIST:        75.22 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.96, 27.95 [deg] galactic lon,lat of the burst
ECL_COORDS:       92.03, 66.71 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:45:02 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1101053,   Seg_Num: 0
GRB_RA:          191.5991d {+12h 46m 23.7s} (J2000),
                 190.3617d {+12h 41m 26.8s} (current),
                 196.3083d {+13h 05m 13.9s} (1950)
GRB_DEC:         +89.1817d {+89d 10' 54.1"} (J2000),
                 +89.0600d {+89d 03' 36.0"} (current),
                 +89.4527d {+89d 27' 09.7"} (1950)
GRB_ERROR:       6.5 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       29 [cnts]
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74658.94 SOD {20:44:18.94} UT,   96.3 [sec] since BAT Trigger Time
CENTROID_X:      275.28,  raw= 275  [pixels]
CENTROID_Y:      281.31,  raw= 281  [pixels]
ROLL:            357.93 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -39.57
GRB_POS_XRT_Z:   -75.71
IMAGE_URL:       sw01101053000msxps_rw.img
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 04"}
SUN_DIST:         85.39 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.28d {+02h 49m 07s}  +15.58d {+15d 34' 46"}
MOON_DIST:        75.22 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.96, 27.95 [deg] galactic lon,lat of the burst
ECL_COORDS:       92.03, 66.71 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:44:49 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1101053,   Seg_Num: 0
GRB_RA:          191.5991d {+12h 46m 23.78s} (J2000),
                 190.3617d {+12h 41m 26.80s} (current),
                 196.3083d {+13h 05m 13.98s} (1950)
GRB_DEC:         +89.1817d {+89d 10' 54.1"} (J2000),
                 +89.0600d {+89d 03' 36.0"} (current),
                 +89.4527d {+89d 27' 09.7"} (1950)
GRB_ERROR:       6.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       4.65e-10 [erg/cm2/sec]
GRB_SIGNIF:      5.38 [sigma]
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74658.94 SOD {20:44:18.94} UT,   96.3 [sec] since BAT Trigger Time
TAM[0-3]:        327.73 237.15 261.74 243.65
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 04"}
SUN_DIST:         85.39 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.28d {+02h 49m 06s}  +15.58d {+15d 34' 43"}
MOON_DIST:        75.22 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.96, 27.95 [deg] galactic lon,lat of the burst
ECL_COORDS:       92.03, 66.71 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.85 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:46:16 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1101053,   Seg_Num: 0
GRB_RA:          191.025d {+12h 44m 06s} (J2000),
                 189.879d {+12h 39m 31s} (current),
                 195.378d {+13h 01m 31s} (1950)
GRB_DEC:         +89.170d {+89d 10' 13"} (J2000),
                 +89.048d {+89d 02' 54"} (current),
                 +89.442d {+89d 26' 31"} (1950)
GRB_DATE:        19672 TJD;    93 DOY;   22/04/03
GRB_TIME:        74562.65 SOD {20:42:42.65} UT
TRIGGER_INDEX:   137
GRB_PHI:         -144.99 [deg]
GRB_THETA:        34.24 [deg]
DELTA_TIME:      45.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     18.68 [sigma]
IMAGE_SIGNIF:    12.67 [sigma]
LC_URL:          sw01101053000msb.lc
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 05"}
SUN_DIST:         85.40 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.29d {+02h 49m 09s}  +15.58d {+15d 35' 00"}
MOON_DIST:        75.22 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.96 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       92.06, 66.71 [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 = 66.53,20.55 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:47:16 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.876d {+12h 43m 30s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 37"} (J2000)
POINT_ROLL:      357.920d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74667.93 SOD {20:44:27.93} UT,   105.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.697
N_STARS:         75
X_OFFSET:        552 [pixels]
Y_OFFSET:        528 [pixels]
X_MAX:           1511 [pixels]
Y_MAX:           1487 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01101053000msufc0105.fits
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 06"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.30d {+02h 49m 11s}  +15.59d {+15d 35' 12"}
MOON_DIST:        75.22 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:47:29 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.876d {+12h 43m 30s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 37"} (J2000)
POINT_ROLL:      357.920d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74667.93 SOD {20:44:27.93} UT,   105.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.697
N_STARS:         75
X_OFFSET:        552 [pixels]
Y_OFFSET:        528 [pixels]
X_MAX:           1511 [pixels]
Y_MAX:           1487 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01101053000msufc0105.fits
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 07"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.30d {+02h 49m 11s}  +15.59d {+15d 35' 15"}
MOON_DIST:        75.22 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 20:54:55 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.970d {+12h 43m 53s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 35"} (J2000)
POINT_ROLL:      358.013d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74880.17 SOD {20:48:00.17} UT,   317.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.455
N_STARS:         34
X_OFFSET:        648 [pixels]
Y_OFFSET:        540 [pixels]
X_MAX:           1607 [pixels]
Y_MAX:           1499 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    3
SL_URL:          sw01101053000msufc0317.fits
SUN_POSTN:        12.96d {+00h 51m 51s}   +5.55d {+05d 33' 14"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.36d {+02h 49m 26s}  +15.61d {+15d 36' 42"}
MOON_DIST:        75.20 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #31820
N. J. Klingler (GSFC/UMBC/CRESSTII), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), J.D. Gropp (PSU), H. A. Krimm (NSF), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), T. M. Parsotan (GSFC/UMBC/CRESSTII) and T. Sakamoto (AGU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 20:42:42 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220403B (trigger=1101053). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 191.025, +89.170 which is
```
   RA(J2000) = 12h 44m 06s
   Dec(J2000) = +89d 10' 13"
```
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 30 sec and a possible precursor just before. The peak count rate was ~2800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 20:44:18.9 UT, 96.3 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 191.50031, 89.18362 which is equivalent to:
```
   RA(J2000)  = 12h 46m 00.07s
   Dec(J2000) = +89d 11' 01.0"
```
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 54 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 https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.20 x 10^21 cm^-2 (Willingale et al. 2013).
The initial flux in the 2.5 s image was 4.65e-10 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 105 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	12:45:53.30 = 191.47207
  DEC(J2000) = +89:11:06.6  =  89.18518
```
with a 90%-confidence error radius of about 0.67 arc sec. This position is 6.0 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.80 with a 1-sigma error of about 0.17. No correction has been made for the expected extinction corresponding to E(B-V) of 0.208.
Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu). 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/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 03 Apr 22 20:56:01 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.970d {+12h 43m 53s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 35"} (J2000)
ROLL:            358.013d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74880.17 SOD {20:48:00.17} UT,   317.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     670711709
X_OFFSET:        968 [pixels]
Y_OFFSET:        860 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1128
Y_GRB_POS:       1020
BINNING_INDEX:   1
IM_URL:          sw01101053000msuni0346.fits
SUN_POSTN:        12.96d {+00h 51m 52s}   +5.55d {+05d 33' 15"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.37d {+02h 49m 28s}  +15.62d {+15d 36' 55"}
MOON_DIST:        75.20 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 20:55:11 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.970d {+12h 43m 53s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 35"} (J2000)
POINT_ROLL:      358.013d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74880.17 SOD {20:48:00.17} UT,   317.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.455
N_STARS:         34
X_OFFSET:        648 [pixels]
Y_OFFSET:        540 [pixels]
X_MAX:           1607 [pixels]
Y_MAX:           1499 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    3
SL_URL:          sw01101053000msufc0317.fits
SUN_POSTN:        12.96d {+00h 51m 51s}   +5.55d {+05d 33' 14"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.36d {+02h 49m 27s}  +15.61d {+15d 36' 45"}
MOON_DIST:        75.20 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 20:56:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.970d {+12h 43m 53s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 35"} (J2000)
ROLL:            358.013d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74880.17 SOD {20:48:00.17} UT,   317.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     670711709
X_OFFSET:        968 [pixels]
Y_OFFSET:        860 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1128
Y_GRB_POS:       1020
BINNING_INDEX:   1
IM_URL:          sw01101053000msuni0346.fits
SUN_POSTN:        12.96d {+00h 51m 52s}   +5.55d {+05d 33' 15"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.37d {+02h 49m 29s}  +15.62d {+15d 36' 56"}
MOON_DIST:        75.20 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 20:48:43 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.876d {+12h 43m 30s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 37"} (J2000)
ROLL:            357.920d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74667.93 SOD {20:44:27.93} UT,   105.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     670711496
X_OFFSET:        968 [pixels]
Y_OFFSET:        860 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1128
Y_GRB_POS:       1020
BINNING_INDEX:   1
IM_URL:          sw01101053000msuni0134.fits
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 08"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.31d {+02h 49m 14s}  +15.59d {+15d 35' 29"}
MOON_DIST:        75.22 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 20:48:57 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.876d {+12h 43m 30s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 37"} (J2000)
ROLL:            357.920d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74667.93 SOD {20:44:27.93} UT,   105.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     670711496
X_OFFSET:        968 [pixels]
Y_OFFSET:        860 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1128
Y_GRB_POS:       1020
BINNING_INDEX:   1
IM_URL:          sw01101053000msuni0134.fits
SUN_POSTN:        12.96d {+00h 51m 50s}   +5.55d {+05d 33' 08"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.31d {+02h 49m 14s}  +15.59d {+15d 35' 32"}
MOON_DIST:        75.22 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 21:00:34 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.971d {+12h 43m 53s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 35"} (J2000)
POINT_ROLL:      358.014d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  75436.32 SOD {20:57:16.32} UT,   873.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.760
N_STARS:         144
X_OFFSET:        408 [pixels]
Y_OFFSET:        300 [pixels]
X_MAX:           1847 [pixels]
Y_MAX:           1739 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01101053000msufc0873.fits
SUN_POSTN:        12.97d {+00h 51m 52s}   +5.56d {+05d 33' 19"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.41d {+02h 49m 37s}  +15.63d {+15d 37' 48"}
MOON_DIST:        75.18 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 03 Apr 22 21:01:50 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.971d {+12h 43m 53s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 35"} (J2000)
ROLL:            358.014d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  75436.32 SOD {20:57:16.32} UT,   873.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     670712265
X_OFFSET:        967 [pixels]
Y_OFFSET:        859 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1127
Y_GRB_POS:       1019
BINNING_INDEX:   1
IM_URL:          sw01101053000msuni0902.fits
SUN_POSTN:        12.97d {+00h 51m 52s}   +5.56d {+05d 33' 20"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.42d {+02h 49m 40s}  +15.63d {+15d 38' 03"}
MOON_DIST:        75.18 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 21:00:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.971d {+12h 43m 53s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 35"} (J2000)
POINT_ROLL:      358.014d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  75436.32 SOD {20:57:16.32} UT,   873.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.760
N_STARS:         144
X_OFFSET:        408 [pixels]
Y_OFFSET:        300 [pixels]
X_MAX:           1847 [pixels]
Y_MAX:           1739 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01101053000msufc0873.fits
SUN_POSTN:        12.97d {+00h 51m 52s}   +5.56d {+05d 33' 19"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.41d {+02h 49m 38s}  +15.63d {+15d 37' 52"}
MOON_DIST:        75.18 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 21:01:58 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1101053,   Seg_Num: 0
POINT_RA:        190.971d {+12h 43m 53s} (J2000)
POINT_DEC:       +89.160d {+89d 09' 35"} (J2000)
ROLL:            358.014d
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  75436.32 SOD {20:57:16.32} UT,   873.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     670712265
X_OFFSET:        967 [pixels]
Y_OFFSET:        859 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1127
Y_GRB_POS:       1019
BINNING_INDEX:   1
IM_URL:          sw01101053000msuni0902.fits
SUN_POSTN:        12.97d {+00h 51m 52s}   +5.56d {+05d 33' 20"}
SUN_DIST:         85.41 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.42d {+02h 49m 40s}  +15.63d {+15d 38' 04"}
MOON_DIST:        75.18 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.97, 27.97 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       92.09, 66.71 [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 03 Apr 22 21:15:31 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1101053,   Seg_Num: 0
GRB_RA:          191.5035d {+12h 46m 00.84s} (J2000),
                 190.2751d {+12h 41m 06.01s} (current),
                 196.1872d {+13h 04m 44.93s} (1950)
GRB_DEC:         +89.1838d {+89d 11' 01.6"} (J2000),
                 +89.0621d {+89d 03' 43.5"} (current),
                 +89.4549d {+89d 27' 17.7"} (1950)
GRB_ERROR:       3.6 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74716.00 SOD {20:45:16.00} UT,   153.4 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        12.98d {+00h 51m 55s}   +5.56d {+05d 33' 33"}
SUN_DIST:         85.38 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.53d {+02h 50m 07s}  +15.68d {+15d 40' 43"}
MOON_DIST:        75.12 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.96, 27.94 [deg] galactic lon,lat of the burst
ECL_COORDS:       92.02, 66.71 [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:        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:     Sun 03 Apr 22 20:51:30 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1101053,   Seg_Num: 0
GRB_RA:          191.4720d {+12h 45m 53.28s} (J2000),
                 190.2456d {+12h 40m 58.93s} (current),
                 196.1526d {+13h 04m 36.62s} (1950)
GRB_DEC:         +89.1851d {+89d 11' 06.3"} (J2000),
                 +89.0634d {+89d 03' 48.1"} (current),
                 +89.4563d {+89d 27' 22.5"} (1950)
GRB_ERROR:       0.7 [arcsec radius, statistical only]
GRB_MAG:         19.79 +/- 0.17 [mag]
FILTER:          10, White
IMG_START_DATE:  19672 TJD;    93 DOY;   22/04/03
IMG_START_TIME:  74664.00 SOD {20:44:24.00} UT,   101.4 [sec] since BAT Trigger Time
SUN_POSTN:        12.96d {+00h 51m 51s}   +5.55d {+05d 33' 10"}
SUN_DIST:         85.38 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       42.33d {+02h 49m 19s}  +15.60d {+15d 36' 02"}
MOON_DIST:        75.19 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      122.96, 27.94 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       92.02, 66.71 [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 13.7 arcsec from the XRT position.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN Circular #31821
M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov) report:
We observed the position of the Swift-detected GRB 220403B (Klingler et al. GCNC 31820) with the D50 telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. Our observation started at 21:04 UT, i.e. 22 min after the initial trigger and was performed without a filter.
We detect the optical afterglow (Klingler et al. GCNC 31820) in a combined image with exp. mean time 31.3 min after trigger (exposed 21:05--21:22UT) with an AB magnitude RC = 19.02 +/- 0.04.
GCN Circular #31822
A. Nicuesa Guelbenzu, B. Stecklum, S. Klose, S. Melnikov, and U. Ludwig (all Tautenburg) report:
Tautenburg started observing the field of GRB 220403A (Klingler et al. GCN 31820) at 2022-04-03, 21:35:37 UT, using the 1.34m Schmidt telescope equipped with the TAUKAM 6k x 6k CCD camera. Observations are still ongoing.
At a mean time 21:36:07 UT for the optical transient discovered by Swift/UVOT, we measure the following magnitude:
r = 19.28 +/- 0.04 mag (AB),
calibrated against the Pan-STARRS catalog. Compared to the observations reported by Jelinek et al. (GCN 31821), the source is fading.
GCN Circular #31823
Z.P. Zhu (NAOC,HUST), S.Q. Jiang, X. Liu, S.Y. Fu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:
We observed the field of GRB 220403B detected by Swift (Klingler et al., GCN 31820) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. Observations started at 21:10:31 UT on 2022-04-03 (i.e., 27.8 min after the BAT trigger), and a series of 300 s frames were obtained in the Sloan r-filters.
The optical afterglow (Klingler et al., GCN 31820) is clearly detected in each of our images. The preliminary photometric analysis shows that the afterglow decays from r ~ 19.04 to r ~ 19.64 in 47 minutes, with a decay index of \alpha ~ 0.6 (F_t ~ t^-\alpha), calibrated the nearby PS1 stars.
Our measurement is consistent with that in other reports (Jelinek et al., GCN 31821; Nicuesa Guelbenzu et al., GCN 31822).
GCN Circular #31825
V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)
MASTER-OAGH robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the Swift GRB 220403B ( N. J. Klingler et al., GCN 31820) errorbox 20759 sec after notice time and 20778 sec after trigger time at 2022-04-04 02:29:01 UT, with upper limit up to 17.7 mag. Observations started at twilight. The observations began at zenith distance = 59 deg. The sun altitude is -11.3 deg.
The galactic latitude b = 28 deg., longitude l = 123 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1931497
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   20869 |         MASTER-OAGH |   C |   180 | 17.2 |        
   20869 |         MASTER-OAGH |   C |   180 | 17.7 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #31826
A Rossi (INAF-OAS) report on behalf of the CIBO collaboration:
We observed the field of GRB 220403B (Klingler et al., GCN 31820) simultaneously in the g',r',i' and z' bands with the LBC imager mounted on LBT (Mt Graham, AZ, USA). We obtained 10min of imaging at the midtime 04:02 UT on 2022-04-04, 0.3 days after the burst trigger. Observations were performed under good weather conditions with an average seeing of ~1.5".
We clearly detect the afterglow and we preliminary measure
r=20.9+-0.1 (AB system),
calibrated against Pan-STARRS field stars.
We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly A. Cardwell and S. Allanson in obtaining these observations.
GCN Circular #31827
A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester) and N.J. Klingler report on behalf of the Swift-XRT team:
We have analysed 6.3 ks of XRT data for GRB 220403B (Klingler et al. GCN Circ. 31820), from 86 s to 28.9 ks after the BAT trigger. The data comprise 50 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 191.4734, +89.1846 which is equivalent to:
```
RA (J2000): 12 45 53.62
Dec(J2000): +89 11 04.6
```
with an uncertainty of 3.5 arcsec (radius, 90% confidence).
The light curve can be modelled with an initial power-law decay with an index of alpha=4.4 (+/-0.4), followed by a break at T+229 s to an alpha of 0.35 (+0.04, -0.05).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.86 (+0.16, -0.14). The best-fitting absorption column is 1.47 (+0.51, -0.27) x 10^21 cm^-2, consistent with the Galactic value of 1.2 x 10^21 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 (4.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.47 (+0.51, -0.27) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.86 (+0.16, -0.14)
```
If the light curve continues to decay with a power-law decay index of 0.35, the count rate at T+24 hours will be 0.057 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.1 x 10^-12 (2.6 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/01101053.
This circular is an official product of the Swift-XRT team.
GCN Circular #31829
Rachel Hamburg (UAH) and Boyan Hristov (UAH) report on behalf of the Fermi GBM Team:
"At 20:42:39.05 UT on 03 April 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220403B (trigger 670711364 / 220403863), which was also detected by the Swift/BAT and the Swift/XRT (Klingler et al. 2022, GCN 31820). Additionally, the optical afterglow was detected by the Swift/UVOT (Klingler et al. 2022, GCN 31820), D50 (Jelinek et al. 2022, GCN 31821), Nanshan/NEXT (Zhu et al. 2022, GCN 31823) and LBT (Rossi 2022, GCN 31826).
The angle from the Fermi LAT boresight at the GBM trigger time is 43 degrees.
The GBM light curve shows broad rise with multiple peaks with a duration (T90) of about 28 s (50-300 keV).
The time-averaged spectrum from T0-6.1 s to T0+21.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 79 +/- 3 keV. The spectrum is also well fit by a Band function with Epeak = 70 +/- 5, alpha = -1.1 +/- 0.1, and beta = -2.6 +/- 0.2.
The event fluence (10-1000 keV) in this time interval is (5.2 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+7.6 s in the 10-1000 keV band is 4.3 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #31830
SUBJECT: GRB 220403B: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
B. Grossan (UCB, NU), T. Komesh (NU), Z. Maksut (NU), M. Krugov (FAI), E. Linder (UCB, NU), E. Abdikamalov (NU), K. Baigarin (NU), G. F. Smoot (HKUST, UCB, NU), report on behalf of the Energetic Cosmos Laboratory:
The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) observed the field of GRB 220403B 11 s after receipt an automated GCN / BAT position alert, observing in Sloan i' band, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14).
We started observations at 20:43:09 UT on 2022-04-03, 27 s after the BAT trigger. Observations were made in partially cloudy conditions starting at about 43 deg. target altitude. No source consistent with the XRT (A.P. Beardmore et al., GCN Circ.31827) was detected.� We report the following results:
```
start time��t-t0(s)� end time������� ULi'������ exposure_time (s)
---------� ----�  ---------  ����� ------     --------------------
20:43:09 ��� 27 � 20:44:09 �������� 17.6 ��������� 60
20:44:24 ��� 87 � 20:46:54 �������� 18.4 �������   150
```
start time is in UT. t-t0(s) gives the time since trigger, in seconds. UL i', gives the 5 sigma upper limit sensitivity in magnitudes, for images co-added to the given exposure time. The first row in the table corresponds to co-adds of an initial short exposure image sequence of 7.5 s. The second row corresponds to co-adds from a continuing series of 15 s exposures.� Calibration was done with the 2 bright Pan-STARRS catalog stars on our images.
We caution the reader that these are preliminary results, without color or other corrections. Please also note that times are approximate.
```
----------------------------------
NU = Nazarbayev University, Nur-Sultan, Kazakhstan
UCB = University of California, Berkeley, USA
HKUST = Hong Kong University of Science and Technology
FAI = Fesenkov Astrophysical Institute, Kazakhstan
```
The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan.
GCN Circular #31834
A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII) H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU) (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 220403B (trigger #1101053) (Klingler, et al., GCN Circ. 31820). The BAT ground-calculated position is RA, Dec = 190.974, 89.180 deg which is
```
    RA(J2000)  =  12h 43m 53.9s
    Dec(J2000) = +89d 10' 49.0"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 60%.
The mask-weighted light curve shows a bright peak structure that starts at T-19 s, peaks at T-1 s and ends at T+40 s. T90 (15-350 keV) is 27.0 +- 3.4 sec (estimated error including systematics).
The time-averaged spectrum from T-14.42 to T+27.96 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.94 +- 0.06. The fluence in the 15-150 keV band is 3.7 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.06 sec in the 15-150 keV band is 2.7 +- 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/1101053/BA/
GCN Circular #31837
N. Pankov (HSE), A. Zhornichenko (KIAM), A. Pozanenko (IKI), V. Agletdinov (KIAM), S. Belkin (IKI), Sh. Ehgamberdiev (UBAI) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 220403B (Klingler et al., GCN 31820) with Kitab RC-36 telescope in Clear filter. Observation started on April, 03 (UT) 21:23:55 and ended on April, 04 (UT) 00:00:11. We clearly detect the optical afterglow (Klingler et al., GCN 31820; Jelinek et al., GCN 31821; Zhu et al., GCN 31823; Rossi et al., GCN 31826; see also early upper limits in Lipunov et al., GCN 31825; Grossan et al., GCN 31830) in the combined images of an initial part of observations and do not detect it in the final part. Preliminary photometry of the combined images is following
```
  Date,      UT start, t-T0,   Exp.,  Filter, OT,    Err,  UL(3 sigma)
                     (mid, days)

2022-04-03  21:23:55 0.05178   40*60  CR      19.24  0.19   20.2
2022-04-03  22:30:39 0.10640   87*60  CR      n/d    n/d    20.5
```
The photometry is based on nearby USNO-B1.0 stars, R2 magnitude
```
USNO-B1.0_id R2
1791-0003982 16.77
1791-0003984 17.83
```
GCN Circular #31841
Y.-D. Hu, A. Sota, A. J. Castro-Tirado, T.-R. Sun, M. D. Caballero-Garcia, R. Sanchez-Ramirez and E. Fernandez-Garcia (IAA-CSIC), on behalf of a larger collaboration, report:
Following the detection of GRB 220403B by Swift (Klingler et al. GCNC 31820) and Fermi (Hamburg et al. GCNC 31829), we triggered the 1.5m OSN telescope in Granada (Spain) starting on Apr 4 at 02:49 UT (i.e. ~6.1 h post burst). A series of images in the I band with 60 s exposure were obtained in cloudy weather. In the co-added image of selected high S/N frames, the optical afterglow is weakly detected within the position reported by UVOT (Klingler et al. GCNC 31820) and XRT (Beardmore et al. GCNC 31827) with I=20.45+-0.30 at a median time of 03:20 UT, which is consistent with previous reports of detection by Jelinek et al. (GCNC 31821), Zhu et al. (GCNC 31823), Rossi et al. (GCNC 31826) and Pankov et al. (GCNC 31837), also upper limits by Lipunov et al. (GCNC 31825), Grossan et al. (GCNC 31830). Further observations are ongoing.
We thank the staff at OSN for their excellent support.
GCN Circular #31844
N. Pankov (HSE), A. Pozanenko (IKI), E. Klunko (ISTP), S. Belkin (IKI) report on behalf of GRB IKI FuN:
We observed the field of GRB 220403B (Klingler et al., GCN 31820) with AZT-33 telescope of Mondy observatory starting on April, 05 (UT) 15:00:54. We do not detect the optical afterglow (Klingler et al., GCN 31820; Jelinek et al., GCN 31821; Zhu et al., GCN 31823; Rossi et al., GCN 31826; Pankov et al., GCN 31837; Hu et al., GCN 31841; see also early upper limits in Lipunov et al., GCN 31825; Grossan et al., GCN 31830) in the combined image. Preliminary photometry of the combined image is following
```
  Date,      UT start, t-T0,   Exp.,  Filter, OT,    Err,  UL(3 sigma)
                     (mid, days)

2022-04-05  15:00:54 1.77723   20*120  R      n/d    n/d    23.2
```
The photometry is based on nearby USNO-B1.0 stars, R2 magnitude
```
USNO-B1.0_id R2
1791-0003982 16.77
1791-0003984 17.83
```
GCN Circular #31869
Amit Kumar Ror, Rahul Gupta, Amit Kumar, Dimple, Ankur Ghosh, Amar Aryan, Brajesh Kumar, S. B. Pandey, and Kuntal Misra (ARIES) report:
We observed the Swift-BAT and Fermi-GBM detected GRB 220403B (Klingler et al., GCN 31820; Hamburg et al., GCN 31829) with 1.3m Devasthal Fast Optical Telescope (DFOT) located at Devasthal observatory of Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2022-04-04 at ~ 17:32 UT, i.e., ~ 20.82 hours after the BAT trigger. We have taken multiple frames having an exposure time of 300 sec in the R filter. We stacked the images after the alignment. We did not detect the optical afterglow (Klingler et al., GCN 31820; Jelinek et al., GCN 31821; Zhu et al., GCN 31823; Lipunov et al., GCN 31825; Rossi GCN 31826; Pankov et al., GCN 31837; and Hu et al., GCN 31841) in our stacked image.
We obtain the following 3-sigma upper limit in the stacked image.
```
Date Start_UT T_start-T0 (hours) Filter  Exp time (sec)  Limiting magnitude

=============================================================
2022-04-04 17:32:01    ~20.82                 R        300 sec*24   > 21.6
```
The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog.
This circular may be cited.
GCN Circular #31876
N. J. Klingler (NASA-GSFC/UMBC/CRESST II) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 220403B 105 s after the BAT trigger (Klingler et al., GCN Circ. 31820). A source consistent with the XRT position is detected in the initial UVOT exposures.
The UVOT position is:
```
    RA  (J2000) =  12:45:53.46 = 191.47274 (deg.)
    Dec (J2000) = +89:11:06.5  =  89.18515 (deg.)
```
with an estimated uncertainty of 0.52 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              105          255          147         19.86 +/- 0.12
v                  647         1074           58        >18.6
b                  573          766           39        >19.3
u                  318          741          265         19.93 +/- 0.22
w1                 697          716           19        >18.9
w2                 797         1049           39        >19.9
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.208 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #31883
X. Song, J. Zhu (BJP), I. Tosta e Melo (INFN-LNS), J.-G. Ducoin (IAP), N. Guessoum (AUS), W. Corradi (LNA), T. Culino (OCA), E. Gurbanov (ShAO), E. Hesenov (ShAO), A. de Ugarte Postigo, S. Antier (OCA/Artemis), L. Wang, A. Iskandar (XAO), X. F. Wang (TSU/BJP), X. Zeng (CTGU), D. Marchais (KNC), P.A. Duverne, N. Leroy (IJCLAB), D. A. Kann (HETH/IAA-CSIC), A. Simon, A. Baransky (Kyiv univ), V. Godunova (IC ICAMER), report on behalf of GRANDMA collaboration:
The GRANDMA telescope network responded to the alert of GRB 220403B (Klingler et al., GCN 31820). The first observations started 8 min after the BAT trigger time.
We clearly detect the afterglow within the first hour. We also report our 3-sigma upper limits. Magnitudes are given in the AB system.
```
T-T0 (hr)| MJD�� | Obser.�� |Exposure| Filter | Mag +/- err� | Upp.Lim. (AB)
___________________________________________________________________________
0.13 |59672.86832| ALi-50�� | 5x20s� | Clear� | 18.4 +/- 0.1 | -
0.35 |59672.8775 | ALi-50�� | 20x20s | SDSS g'| 19.7 +/- 0.1 | -
0.48 |59672.88298| ALi-50�� | 20x20s | SDSS r'| 18.6 +/- 0.1 | -
17.67|59673.59939| SNOVA��� | 15x300s| Clear� |������ -����� | 19.4
24.72|59673.89285| KNC-T-CAT| 240x32s| Blue�� |������ -����� | 20.9
24.72|59673.89285| KNC-T-CAT| 240x32s| Green� |������ -����� | 20.9
24.72|59673.89285| KNC-T-CAT| 240x32s| Red��� |������ -����� | 19.9
```
These detections and limits are consistent with the detections and limits previously reported in Klingler et al. (GCN 31820), Jelinek et al. (GCN 31821),Nicuesa Guelbenzu et al. (GCN 31822), Zhu et al. (GCN 31823), Lipunov et al. (GCN 31825),� Rossi et al. (GCN, 31826), Grossan et al. (GCN 31830), Pankov et al. (GCN 31837, 31844), Hu et al. (GCN 31841), and Kumar et al. (GCN 31869).
The photometry of Ali-50 was performed using field stars from the PanSTARRs-DR1 catalog for images with SDSS g' and r' filters, and from the Gaia gmag catalog for images with no filters. The SNOVA and T-CAT data have been processed using field stars from the PanSTARRS-DR1 catalog and with the MUPHOTEN pipeline (Duverne et al. 2021).
GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).

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