Gamma-ray Burst 220408A

(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 08 Apr 22 05:46:16 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1101675,   Seg_Num: 0
GRB_RA:          202.402d {+13h 29m 36s} (J2000),
                 202.636d {+13h 30m 33s} (current),
                 201.875d {+13h 27m 30s} (1950)
GRB_DEC:         +47.061d {+47d 03' 41"} (J2000),
                 +46.947d {+46d 56' 48"} (current),
                 +47.319d {+47d 19' 09"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2353 [cnts]    Image_Peak=198 [image_cnts]
TRIGGER_DUR:     0.512 [sec] 
TRIGGER_INDEX:   124     E_range: 25-100 keV
BKG_INTEN:       20165 [cnts]
BKG_TIME:        20747.07 SOD {05:45:47.07} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19677 TJD;    98 DOY;   22/04/08
GRB_TIME:        20764.22 SOD {05:46:04.22} UT
GRB_PHI:         146.94 [deg]
GRB_THETA:        37.10 [deg]
SOLN_STATUS:     0x2001010D
RATE_SIGNIF:     28.56 [sigma]
IMAGE_SIGNIF:    12.80 [sigma]
MERIT_PARAMS:     +0  +0 +125  -1  +2  +2  +0  +0 +58  +0
SUN_POSTN:        16.96d {+01h 07m 50s}   +7.21d {+07d 12' 22"}
SUN_DIST:        125.61 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.78d {+06h 31m 08s}  +26.91d {+26d 54' 42"}
MOON_DIST:        79.94 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.82, 68.70 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      175.19, 50.80 [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 position matches one of the nearby galaxy sources in the on-board catalog!  
COMMENTS:        This matches a source in the on-board catalog: Num=12104=NGC5194,   delta=0.141 [deg].  
COMMENTS:        This matches a source in the ground catalog: NGC5194,   delta=0.141 [deg].  
COMMENTS:        The position is inside the galaxy NGC5194 (of total mag=8.40 and dia=11.00 arcmin).  
COMMENTS:        There is a 0.03% probability that this would happen by chance coincidence.
COMMENTS:        This is a GRB in nearby galaxy or it is noise.  
COMMENTS:        This trigger occurred at longitude,latitude = 282.59,17.61 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=671089569).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 08 Apr 22 05:46:28 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      51
TRIGGER_NUM:     671089569
GRB_RA:          193.883d {+12h 55m 32s} (J2000),
                 194.137d {+12h 56m 33s} (current),
                 193.312d {+12h 53m 15s} (1950)
GRB_DEC:         +46.600d {+46d 36' 00"} (J2000),
                 +46.480d {+46d 28' 47"} (current),
                 +46.871d {+46d 52' 14"} (1950)
GRB_ERROR:       13.62 [deg radius, statistical plus systematic]
GRB_INTEN:       255 [cnts/sec]
DATA_SIGNIF:     11.40 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        19677 TJD;    98 DOY;   22/04/08
GRB_TIME:        20764.41 SOD {05:46:04.41} UT
GRB_PHI:         199.00 [deg]
GRB_THETA:        55.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      1.11
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      98%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 0,1,0, 0,0,1, 0,0,
SUN_POSTN:        16.96d {+01h 07m 50s}   +7.21d {+07d 12' 22"}
SUN_DIST:        126.26 [deg]   Sun_angle= -11.8 [hr] (East of Sun)
MOON_POSTN:       97.78d {+06h 31m 08s}  +26.91d {+26d 54' 42"}
MOON_DIST:        74.91 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      120.82, 70.51 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      168.33, 47.07 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220408240/quicklook/glg_lc_medres34_bn220408240.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 129.53,20.83 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1101675).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 08 Apr 22 05:46:46 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      61
TRIGGER_NUM:     671089569
GRB_RA:          189.320d {+12h 37m 17s} (J2000),
                 189.586d {+12h 38m 21s} (current),
                 188.722d {+12h 34m 53s} (1950)
GRB_DEC:         +43.850d {+43d 51' 00"} (J2000),
                 +43.728d {+43d 43' 40"} (current),
                 +44.125d {+44d 07' 30"} (1950)
GRB_ERROR:       7.88 [deg radius, statistical only]
DATA_SIGNIF:     11.60 [sigma]
DATA_INTERVAL:   1.024 [sec]
GRB_DATE:        19677 TJD;    98 DOY;   22/04/08
GRB_TIME:        20764.41 SOD {05:46:04.41} UT
GRB_PHI:         194.00 [deg]
GRB_THETA:        56.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        16.96d {+01h 07m 50s}   +7.21d {+07d 12' 22"}
SUN_DIST:        128.63 [deg]   Sun_angle= -11.5 [hr] (East of Sun)
MOON_POSTN:       97.79d {+06h 31m 09s}  +26.91d {+26d 54' 42"}
MOON_DIST:        72.98 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      131.71, 73.04 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      166.69, 43.01 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220408240/quicklook/glg_lc_medres34_bn220408240.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_671089569.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(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1101675).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 08 Apr 22 05:48:04 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.426d {+13h 29m 42s} (J2000)
POINT_DEC:       +47.068d {+47d 04' 06"} (J2000)
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  20873.18 SOD {05:47:53.18} UT,   109.0 [sec] since BAT Trigger Time
COUNTS:          42    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2                                                  
COMMENTS:        SWIFT-XRT Nack Position.
COMMENTS:        Algorithm did not converge; too many iterations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 08 Apr 22 05:50:13 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1101675,   Seg_Num: 0
GRB_RA:          202.402d {+13h 29m 36s} (J2000),
                 202.636d {+13h 30m 33s} (current),
                 201.875d {+13h 27m 30s} (1950)
GRB_DEC:         +47.061d {+47d 03' 41"} (J2000),
                 +46.947d {+46d 56' 48"} (current),
                 +47.319d {+47d 19' 09"} (1950)
GRB_DATE:        19677 TJD;    98 DOY;   22/04/08
GRB_TIME:        20764.22 SOD {05:46:04.22} UT
TRIGGER_INDEX:   124
GRB_PHI:         146.94 [deg]
GRB_THETA:        37.10 [deg]
DELTA_TIME:      44.00 [sec]
TRIGGER_DUR:     0.512 [sec] 
SOLN_STATUS:     0x10D
RATE_SIGNIF:     28.56 [sigma]
IMAGE_SIGNIF:    12.80 [sigma]
LC_URL:          sw01101675000msb.lc
SUN_POSTN:        16.96d {+01h 07m 51s}   +7.21d {+07d 12' 25"}
SUN_DIST:        125.61 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.82d {+06h 31m 16s}  +26.91d {+26d 54' 43"}
MOON_DIST:        79.92 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.82, 68.70 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      175.19, 50.80 [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 matches a source in the on-board catalog.  
COMMENTS:        This matches a source in the ground catalog: NGC5194,   delta=0.141 [deg].  
COMMENTS:        The position is inside the galaxy NGC5194 (of total mag=8.40 and dia=11.00 arcmin).  
COMMENTS:        There is a 0.03% probability that this would happen by chance coincidence.  
COMMENTS:        This is not a GRB.  
COMMENTS:        This is an interesting source.  
COMMENTS:        This trigger occurred at longitude,latitude = 282.59,17.61 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 08 Apr 22 05:50:54 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.427d {+13h 29m 42s} (J2000)
POINT_DEC:       +47.068d {+47d 04' 06"} (J2000)
POINT_ROLL:      6.660d
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  20876.73 SOD {05:47:56.73} UT,   112.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.539
N_STARS:         68
X_OFFSET:        356 [pixels]
Y_OFFSET:        483 [pixels]
X_MAX:           1315 [pixels]
Y_MAX:           1442 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw01101675000msufc0112.fits
SUN_POSTN:        16.96d {+01h 07m 51s}   +7.21d {+07d 12' 26"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.82d {+06h 31m 18s}  +26.91d {+26d 54' 43"}
MOON_DIST:        79.93 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.78, 68.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.20, 50.82 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 08 Apr 22 05:52:07 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.427d {+13h 29m 42s} (J2000)
POINT_DEC:       +47.068d {+47d 04' 06"} (J2000)
ROLL:            6.660d
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  20876.73 SOD {05:47:56.73} UT,   112.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     671089705
X_OFFSET:        675 [pixels]
Y_OFFSET:        802 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       835
Y_GRB_POS:       962
BINNING_INDEX:   1
IM_URL:          sw01101675000msuni0141.fits
SUN_POSTN:        16.96d {+01h 07m 51s}   +7.21d {+07d 12' 27"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.84d {+06h 31m 21s}  +26.91d {+26d 54' 43"}
MOON_DIST:        79.92 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.78, 68.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.20, 50.82 [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 08 Apr 22 05:51:11 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.427d {+13h 29m 42s} (J2000)
POINT_DEC:       +47.068d {+47d 04' 06"} (J2000)
POINT_ROLL:      6.660d
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  20876.73 SOD {05:47:56.73} UT,   112.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.539
N_STARS:         68
X_OFFSET:        356 [pixels]
Y_OFFSET:        483 [pixels]
X_MAX:           1315 [pixels]
Y_MAX:           1442 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw01101675000msufc0112.fits
SUN_POSTN:        16.96d {+01h 07m 51s}   +7.21d {+07d 12' 26"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.83d {+06h 31m 19s}  +26.91d {+26d 54' 43"}
MOON_DIST:        79.92 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.78, 68.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.20, 50.82 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #31847
The Fermi GBM team reports the detection of a likely LONG GRB
At 05:46:04 UT on 8 Apr 2022, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 220408A (trigger 671089569.40531 / 220408240).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 192.9, Dec = 49.7 (J2000 degrees, equivalent to J2000 12h 51m, 49d 42'), with a statistical uncertainty of 6.5 degrees.
The angle from the Fermi LAT boresight is 52.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220408240/quicklook/glg_skymap_all_bn220408240.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220408240/quicklook/glg_healpix_all_bn220408240.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220408240/quicklook/glg_lc_medres34_bn220408240.gif

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 08 Apr 22 05:51:41 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1101675,   Seg_Num: 0
GRB_RA:          202.4171d {+13h 29m 40.10s} (J2000),
                 202.6514d {+13h 30m 36.34s} (current),
                 201.8899d {+13h 27m 33.58s} (1950)
GRB_DEC:         +47.0684d {+47d 04' 06.2"} (J2000),
                 +46.9539d {+46d 57' 14.0"} (current),
                 +47.3263d {+47d 19' 34.5"} (1950)
GRB_ERROR:       4.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  20880.00 SOD {05:48:00.00} UT,   115.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        16.96d {+01h 07m 51s}   +7.21d {+07d 12' 27"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.83d {+06h 31m 20s}  +26.91d {+26d 54' 43"}
MOON_DIST:        79.92 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.80, 68.69 [deg] galactic lon,lat of the burst
ECL_COORDS:      175.20, 50.81 [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:     Fri 08 Apr 22 05:59:24 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.428d {+13h 29m 43s} (J2000)
POINT_DEC:       +47.069d {+47d 04' 08"} (J2000)
POINT_ROLL:      6.662d
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  21089.46 SOD {05:51:29.46} UT,   325.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.516
N_STARS:         190
X_OFFSET:        116 [pixels]
Y_OFFSET:        243 [pixels]
X_MAX:           1555 [pixels]
Y_MAX:           1682 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw01101675000msufc0325.fits
SUN_POSTN:        16.97d {+01h 07m 52s}   +7.21d {+07d 12' 34"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.90d {+06h 31m 37s}  +26.91d {+26d 54' 45"}
MOON_DIST:        79.88 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.78, 68.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.20, 50.82 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 08 Apr 22 06:00:30 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.428d {+13h 29m 43s} (J2000)
POINT_DEC:       +47.069d {+47d 04' 08"} (J2000)
ROLL:            6.662d
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  21089.46 SOD {05:51:29.46} UT,   325.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     671089918
X_OFFSET:        675 [pixels]
Y_OFFSET:        802 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       835
Y_GRB_POS:       962
BINNING_INDEX:   1
IM_URL:          sw01101675000msuni0354.fits
SUN_POSTN:        16.97d {+01h 07m 53s}   +7.21d {+07d 12' 35"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.91d {+06h 31m 39s}  +26.91d {+26d 54' 46"}
MOON_DIST:        79.87 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.78, 68.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.20, 50.82 [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 08 Apr 22 05:59:38 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.428d {+13h 29m 43s} (J2000)
POINT_DEC:       +47.069d {+47d 04' 08"} (J2000)
POINT_ROLL:      6.662d
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  21089.46 SOD {05:51:29.46} UT,   325.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.516
N_STARS:         190
X_OFFSET:        116 [pixels]
Y_OFFSET:        243 [pixels]
X_MAX:           1555 [pixels]
Y_MAX:           1682 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw01101675000msufc0325.fits
SUN_POSTN:        16.97d {+01h 07m 52s}   +7.21d {+07d 12' 34"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.91d {+06h 31m 37s}  +26.91d {+26d 54' 45"}
MOON_DIST:        79.88 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.78, 68.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.20, 50.82 [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 08 Apr 22 06:00:44 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.428d {+13h 29m 43s} (J2000)
POINT_DEC:       +47.069d {+47d 04' 08"} (J2000)
ROLL:            6.662d
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  21089.46 SOD {05:51:29.46} UT,   325.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     671089918
X_OFFSET:        675 [pixels]
Y_OFFSET:        802 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       835
Y_GRB_POS:       962
BINNING_INDEX:   1
IM_URL:          sw01101675000msuni0354.fits
SUN_POSTN:        16.97d {+01h 07m 53s}   +7.21d {+07d 12' 35"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.92d {+06h 31m 40s}  +26.91d {+26d 54' 46"}
MOON_DIST:        79.87 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.78, 68.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.20, 50.82 [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 #31848
R. Caputo (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
At 05:46:04 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220408A (trigger=1101675). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 202.402, +47.061 which is
```
   RA(J2000) = 13h 29m 36s
   Dec(J2000) = +47d 03' 41"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 5 sec. The peak count rate was ~3500 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 05:47:53.1 UT, 109.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 202.41670, 47.06870 which is equivalent to:
```
   RA(J2000)  = 13h 29m 40.01s
   Dec(J2000) = +47d 04' 07.3"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 45 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.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.98 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.6 (+4.76/-3.79) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 112 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	13:29:39.72 = 202.41548
  DEC(J2000) = +47:04:09.5  =  47.06931
```
with a 90%-confidence error radius of about 0.91 arc sec. This position is 5.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 20.76 with a 1-sigma error of about 0.22. No correction has been made for the expected extinction corresponding to E(B-V) of 0.042.
We note that this GRB is in a direction near to that of M51, the Whirlpool Galaxy, although well outside of its optical disk. Determining whether this is a coincidence will require further study.
Burst Advocate for this burst is R. Caputo (regina.caputo 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/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 08 Apr 22 06:14:05 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1101675,   Seg_Num: 0
GRB_RA:          202.4167d {+13h 29m 40.00s} (J2000),
                 202.6510d {+13h 30m 36.24s} (current),
                 201.8895d {+13h 27m 33.49s} (1950)
GRB_DEC:         +47.0689d {+47d 04' 08.0"} (J2000),
                 +46.9544d {+46d 57' 15.8"} (current),
                 +47.3268d {+47d 19' 36.3"} (1950)
GRB_ERROR:       3.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  20880.00 SOD {05:48:00.00} UT,   115.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        16.98d {+01h 07m 55s}   +7.21d {+07d 12' 48"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       98.04d {+06h 32m 09s}  +26.91d {+26d 54' 49"}
MOON_DIST:        79.79 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.80, 68.69 [deg] galactic lon,lat of the burst
ECL_COORDS:      175.19, 50.81 [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:     Fri 08 Apr 22 05:52:15 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1101675,   Seg_Num: 0
POINT_RA:        202.427d {+13h 29m 42s} (J2000)
POINT_DEC:       +47.068d {+47d 04' 06"} (J2000)
ROLL:            6.660d
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  20876.73 SOD {05:47:56.73} UT,   112.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     671089705
X_OFFSET:        675 [pixels]
Y_OFFSET:        802 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       835
Y_GRB_POS:       962
BINNING_INDEX:   1
IM_URL:          sw01101675000msuni0141.fits
SUN_POSTN:        16.96d {+01h 07m 51s}   +7.21d {+07d 12' 27"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.84d {+06h 31m 21s}  +26.91d {+26d 54' 43"}
MOON_DIST:        79.92 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.78, 68.69 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.20, 50.82 [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:     Fri 08 Apr 22 05:53:31 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1101675,   Seg_Num: 0
GRB_RA:          202.4154d {+13h 29m 39.69s} (J2000),
                 202.6497d {+13h 30m 35.93s} (current),
                 201.8882d {+13h 27m 33.17s} (1950)
GRB_DEC:         +47.0693d {+47d 04' 09.4"} (J2000),
                 +46.9548d {+46d 57' 17.2"} (current),
                 +47.3272d {+47d 19' 37.7"} (1950)
GRB_ERROR:       0.9 [arcsec radius, statistical only]
GRB_MAG:         20.76 +/- 0.22 [mag]
FILTER:          10, White
IMG_START_DATE:  19677 TJD;    98 DOY;   22/04/08
IMG_START_TIME:  20873.00 SOD {05:47:53.00} UT,   108.8 [sec] since BAT Trigger Time
SUN_POSTN:        16.96d {+01h 07m 51s}   +7.21d {+07d 12' 28"}
SUN_DIST:        125.60 [deg]   Sun_angle= 11.6 [hr] (West of Sun)
MOON_POSTN:       97.85d {+06h 31m 24s}  +26.91d {+26d 54' 44"}
MOON_DIST:        79.90 [deg]
MOON_ILLUM:      40 [%]
GAL_COORDS:      104.80, 68.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      175.19, 50.81 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN Circular #31849
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) started inspect of the Fermi GRB 220408A ( Fermi GBM team, GCN 31847) errorbox 3978 sec after notice time and 4007 sec after trigger time at 2022-04-08 06:52:52 UT, with upper limit up to 17.7 mag. The observations began at zenith distance = 18 deg. The sun altitude is -51.3 deg.
The galactic latitude b = 68 deg., longitude l = 122 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1936539
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    4098 | 2022-04-08 06:52:52 |         MASTER-OAGH | (13h 25m 40.01s , +47d 07m 29.9s) |   C |   180 | 16.5 |        
    4098 | 2022-04-08 06:52:52 |         MASTER-OAGH | (13h 26m 12.76s , +46d 40m 00.5s) |   C |   180 | 17.7 |        
    4299 | 2022-04-08 06:56:13 |         MASTER-OAGH | (13h 25m 46.29s , +47d 06m 27.0s) |   C |   180 | 15.9 |        
    4299 | 2022-04-08 06:56:13 |         MASTER-OAGH | (13h 26m 19.51s , +46d 38m 57.5s) |   C |   180 | 17.4 |        
    4501 | 2022-04-08 06:59:35 |         MASTER-OAGH | (13h 25m 41.42s , +47d 05m 24.8s) |   C |   180 | 16.2 |        
    4501 | 2022-04-08 06:59:35 |         MASTER-OAGH | (13h 26m 14.91s , +46d 37m 55.1s) |   C |   180 | 17.7 |        
    4702 | 2022-04-08 07:02:56 |         MASTER-OAGH | (13h 25m 46.46s , +47d 05m 45.0s) |   C |   180 | 16.6 |        
    4702 | 2022-04-08 07:02:56 |         MASTER-OAGH | (13h 26m 19.98s , +46d 38m 15.0s) |   C |   180 | 17.7 |        
    4904 | 2022-04-08 07:06:18 |         MASTER-OAGH | (13h 25m 43.83s , +47d 06m 57.3s) |   C |   180 | 16.7 |        
    4904 | 2022-04-08 07:06:18 |         MASTER-OAGH | (13h 26m 17.35s , +46d 39m 27.8s) |   C |   180 | 17.7 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #31850
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to the Swift GRB 220408A (Caputo et al., GCN 31848; see also Fermi/GBM detection, GCN 31847) starting at 06:30:47 UT, ~44 min after the burst. Observations were performed with a sequence in the clear (roughly R), V, and I filters, and the exposure time was 20s per image. We did not detect the optical afterglow reported by UVOT (Caputo et al., GCN 31848) in any of our single images. We marginally detected the afterglow in the coadd image in clear band, which we measured its brightness of 21.4 +/- 0.3 mag at ~53 min after the burst, calibrated to the Pan-STARRS1 catalog.
GCN Circular #31851
S. Campana (INAF - Osservatorio astronomico di Brera) reports
that Chandra serendipitously observed the location of GRB 220408A (Caputo et al. 2022, GCN 31848; Fermi team 2022, GCN 31847). The UVOT position (Caputo et al. 2022) falls at the edge of the S4 chip of ACIS-S. The obsid 23474 observation lasted 36.6 ks and was taken on Dec 21, 2020. No source is visible at this position. We run srcflux (under CIAO 4.13 and CALDB 4.9.7) and derive a 3-sigma upper limit of 0.000206 c/s (2.38E-05,0.000432) on the 0.5-7 keV count rate. Assuming a power law photon index of 2 and a column density of 2x10^20 cm^-2, we derive an upper limit on the 0.5-7 keV unabsorbed flux of 2.1e-14 erg/cm2/s. If the GRB were at the M51 distance (8.58 Mpc), this translates into an upper limit on the 0.5-7 keV luminosity of 1.8e38 erg/s.
GCN Circular #31852
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 1138 s of XRT Photon Counting mode data and 2 UVOT images for GRB 220408A, 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 = 202.41658, +47.06912 which is equivalent to:
```
RA (J2000): 13h 29m 39.98s
Dec (J2000): +47d 04' 08.8"
```
with an uncertainty of 2.0 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 #31853
S.Q. Jiang, S.Y. Fu, X. Liu, D. Xu (NAOC), Z.P. Zhu (NAOC, HUST), L.P. Xin, J.Y. Wei, G.W. Li (NAOC) report on behalf of a larger collaboration:
We observed the field of GRB 220408A detected by Swift (Caputo et al., GCN 31848) and Fermi (Fermi GBM team, GCN 31847) using the Xinglong-2.16m telescope equipped with the BFOSC camera. Observations were carried out starting at 12:02:32 UT on 2022-04-08 (i.e., 6.27 hr since the BAT trigger), and 9x400 s frames in the R-band were obtained.
The previously reported optical counterpart (e.g., Caputo et al., GCN 31848; Zheng & Filippenko, GCN 31850) is not detected in our stacked image, down to a limiting magnitude of R ~ 20.7 (Vega) at 6.79 hr post-burst, calibrated with the nearby SDSS field.
GCN Circular #31855
S. R. Oates (U.Birmingham) and R. Caputo (GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 220408A 112 s after the BAT trigger (Caputo et al., GCN Circ. 31848). A source consistent with the XRT position (Beardmore et al., GCN Circ. 31852) is detected in the initial white UVOT exposure only.
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 (FC)         112          262          147        20.30 +/- 0.22
white              605	        799          40        >21.4
v                  655	        675          19        >19.3
b                  581	        774          39        >20.7
u                  325	        575         246        >20.2
w1                 704	        724          19        >17.9
m2                 679	        699          19        >17.4
w2                 631	        650          19        >17.7
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.042 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #31856
E. Bissaldi (Politecnico and INFN Bari) reports on behalf of the Fermi GBM Team:
"At 05:46:04.41 UT on 8 April 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220408A (trigger 671089569/ 220408240), which was also detected by the Swift/BAT (Caputo et al. 2022, GCN 31848). The Fermi GBM Final Real-time Localization (GCN 31847) is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 57 degrees.
The GBM light curve consists of a multipeaked emission episode with a duration (T90) of about 20 s (50-300 keV). The time-averaged spectrum from T0-0.8 s to T0+6.7 s is well fit by a power law function with an exponential high-energy cutoff. The power law index is -0.72 +/- 0.14 and the cutoff energy, parameterized as Epeak, is 48.8 +/- 2.3 keV.
The event fluence (10-1000 keV) in this time interval is (1.33 +/- 0.05)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.4 s in the 10-1000 keV band is 7.7 +/-0.3 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 #31857
H. Kumar (IITB), V. Swain (IITB), R. Norbu (IAO), V. Bhalerao (IITB), G. C. Anupama (IIA), S. Barway (IIA) report on behalf of the GIT team:
We observed GRB 220408A detected by Fermi-GBM (GCN #31847) and Swift-BAT (R. Caputo et al., GCN #31848) with 0.7m GROWTH-India Telescope (GIT). We obtained multiple 300-sec exposures in the r' filter and did not detect the afterglow in our stacked images. The obtained upper limits follow as:
```
---------------------------------------------------------------------------------
 JD (mid) | T_mid-T0(hrs) | Exposure (sec) | Filter | Lim_mag (5-sigma) |
---------------------------------------------------------------------------------
2459678.21683 | 11.43 | 3000(stacked) | r' | > 21.94
---------------------------------------------------------------------------------
```
The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.
The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
GCN Circular #31859
Y.-D. Hu, E. Fernandez-Garcia, T.-R. Sun, A. J. Castro-Tirado, R. Sanchez-Ramirez and M.D. Caballero-Garcia (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar and I. Carrasco (UMA), I. H. Park (SKKU) on behalf of a larger collaboration, report:
Following the detection of GRB 220408A by both Swift (Caputo et al. GCNC 31848) and Fermi (Fermi GBM team, GCNC 31847), the 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically responded to the burst on Apr 8 at 06:14 UT (i.e. ~ 28 min after trigger). In the co-added image (5 frames x 60 s exposure, clear filter), the optical afterglow is weakly detected with R = 21.1 +/- 0.3 mag at the position reported by UVOT (Caputo et al. GCNC 31848) and within the XRT error box (Beardmore et al. GCNC 31852). This is consistent with other optical detections previously reported by UVOT (Caputo et al. GCNC 31848, Oates et al. GCNC 31855) and KAIT (Zheng et al. GCNC 31850) and the upper limits provided by MASTER (Lipunov et al. GCNC 31849), Xinglong-2.16m (Jiang et al. GCNC 21853) and GIT (Kumar et al. GCNC 31857). Further observations are ongoing.
We thank the staff at San Pedro Martir Observatory for their excellent support.
GCN Circular #31861
P.A. Evans (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and R. Caputo report on behalf of the Swift-XRT team:
We have analysed 7.5 ks of XRT data for GRB 220408A (Caputo et al. GCN Circ. 31848), from 93 s to 63.6 ks after the BAT trigger. The data comprise 10 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 31852).
The light curve can be modelled with an initial power-law decay with an index of alpha=0.46 (+0.16, -0.17), followed by a break at T+2306 s to an alpha of 1.37 (+0.16, -0.15).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.94 (+0.23, -0.22). The best-fitting absorption column is 1.8 (+0.8, -0.7) x 10^21 cm^-2, in excess of the Galactic value of 2.0 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 3.6 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.8 (+0.8, -0.7) x 10^21 cm^-2
Galactic foreground: 2.0 x 10^20 cm^-2
Excess significance: 3.8 sigma
Photon index:	     1.94 (+0.23, -0.22)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01101675.
This circular is an official product of the Swift-XRT team.
GCN Circular #31862
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (College of Marin) report on behalf of a larger collaboration:
We observed Swift (Caputo et al. GCN 31848) and Fermi (Fermi GBM team, GCN 31847) GRB220408A with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on April 9, from 06:30 to 06:57 UT (corresponding to 0.63 to 1.18 hours from the GRB trigger time) with the Bessel R and I filters.
We performed a series of 3x300s exposures in I and R bands. We detect an optical counterpart within the XRT enhanced error region (Beardmore et al., GCN 31852) in both bands, consistent with other optical detections (Caputo et al. GCNC 31848, Zheng et al. GCNC 31850, Oates et al. GCNC 31855). The following magnitudes are calculated using the USNO-B.1 catalog as reference:
```
R=21.66+/-0.17
I=19.63+/-0.11
```
These magnitudes are not corrected for galactic extinction.
R.S. is funded by NSF AST grant #1831682
GCN Circular #31864
Z. Zhu (NAO/CAS, HUST), D. Xu, S.Y. Fu (NAOC/CAS), D. B. Malesani (Radboud Univ and DAWN/NBI), A. de Ugarte Postigo (Obs. Cote d'Azur), A. J. Levan (Radboud univ.), M. Aron (NOT), report on behalf of a larger collaboration:
We observed the field of GRB 220408A detected by Swift (Caputo et al., GCN 31848) and Fermi (Fermi GBM team, GCN 31847) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out starting at 03:53:08 UT on 2022-04-09 (i.e., 0.92 day since the BAT trigger), and 6x300 s frames in the SDSS r-band were obtained.
The previously reported optical counterpart (e.g., Caputo et al., GCN 31848; Zheng & Filippenko, GCN 31850; Oates et al., GCN 31855; Hu et al., GCN 31859; Strausbaugh & Cucchiara, GCN 31862) is detected in our stacked image with r = 24.1 +/- 0.1 AB, calibrated against nearby stars from the Pan-STARRS catalog.
We note that this field was covered by an image taken in 2007 with CFHT. Consistent with the UVOT coordinates, a faint source is visible with r = 24.5 +/- 0.2 (AB). While the S/N is not large, and we cannot conclusively determine whether this object is extended, it is a viable host galaxy candidate, suggesting a distance to the GRB much larger than M51.
We encourage spectroscopic observations of this Northern target to conclusively measure.
GCN Circular #31865
P. Minaev (IKI), A. Pozanenko (IKI) report on behalf of GRB IKI FuN:
We analysed GRB 220408A detected by Fermi (Fermi GBM team, GCN 31847; Bissaldi et al., GCN 31856), by Swift (GCN Caputo et al., GCN 31848). Using publicly available data of GBM/Fermi we estimate the duration T_90 = 32.3 +/- 2.5 s in (7 - 150) keV energy band. We performed spectral analysis in a time interval of (-1, 22) s since GBM trigger, the best fit is obtained for Band model with following parameters: E_p = 36.5 +/- 5.0 keV, alpha = -0.50 +/- 0.35, beta = -2.5 +/- 0.2. The fluence of F = (2.0 +/- 0.2)E-6 erg/cm**2 is obtained in 10 - 1000 keV energy band. Using T_90,i - EH diagram [1,2] we can classify the burst as type II (long) and find the minimal possible redshift value of z = 0.03, which is excluding possible association with M51 galaxy and confirming larger distance of GRB 220408A (Zhu et., GCN 31864).
The T_90,i - EH diagram can be found in http://grb.rssi.ru/GRB220408A/GRB220408A_EHD.png
```
[1] - Minaev et al., MNRAS, 492, 1919, 2020
[2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020
```
GCN Circular #31867
Gregory S.H. Paek (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Taewoo Kim (DOAO), Jinguk Seo (SAO), Yuji Urata (NCU), Hyun-Il Sung (KASI) on behalf of a larger collaboration
We searched for the optical counterpart of GRB 220408A possibly associated with M51 (Caputo et al., and GCN #31848; Fermi/GBM detection, GCN #31847) with the 1-m class telescopes in Lemonsan Optical Astronomy Observatory (LOAO), Deokheung Optical Astronomy Observatory (DOAO), and Seoul National University Astronomy Observatory (SAO), facilities of the GW EM-Counterpart Korean Observatory (GECKO).
We observed the center of UVOT localization (RA, Dec = 202.41548, +47.06931) +2.94 hours after the report, but could not find any detection. We calibrated flux with the PANSTARRS catalog and used an AB magnitude system. Depth means 5 sigma upper limit for a point source detection. The magnitudes are not corrected for galactic extinction.
```
------------------- ----------- ---------- ----=------ ------ -----------
---------- -----
DATE-OBS[UTC]       JD          t-t0[days] t-t0[hours] FILTER Observatory
EXPTIME[s] DEPTH
------------------- ----------- ---------- ----=------ ------ -----------
---------- -----
2022-04-08T11:29:38 2459677.979 0.239      5.7         R      LOAO
 180s*12    21.42
2022-04-08T15:44:59 2459678.156 0.416      10.0        V      SAO
 180s*21    19.75
2022-04-08T15:57:20 2459678.165 0.424      10.2        R      DOAO
 300s*37    21.90
2022-04-08T16:58:50 2459678.208 0.467      11.2        R      SAO
180s*21    19.77
```
Gravitational-wave EM Counterpart Korean Observatory (GECKO) is a network of 10+ 0.5m to 1m class telescopes over the world.
GCN Circular #31868
Amit Kumar, Rahul Gupta, Amit K. Ror, Nikita Rawat, Dimple, Ankur Ghosh, Amar Aryan, Brajesh Kumar, Shashi B. Pandey and Kuntal Misra (ARIES) report:
We observed the field of the Swift-BAT (Caputo et al., GCN 31848) and Fermi-GBM (GBM Team, GCN 31847) detected GRB 220408A with the 1.3m Devasthal Fast Optical Telescope (DFOT) located at Devasthal observatory of Aryabhatta Research Institute of Observational Sciences (ARIES), India. We started the observations on 2022-04-08 at 16:27:57 UT, i.e., ~10.698 hours after the GBM trigger. We have observed 300s*23 frames in each Bessel R and I filters. We stacked the images after the pre-processing and alignment. We did not detect the optical afterglow at the Swift-XRT position (Beardmore et al., GCN 31852) in our stacked images; see also Caputo et al., GCN 31848; Zheng & Filippenko, GCN 31850; Jiang et al., GCN 31853; Oates & Caputo, GCN 31855; Kumar et al., GCN 31857; Hu et al., GCN 31859; Strausbaugh et al., GCN 31862; Zhu et al., GCN 31864; and Gregory et al., GCN 31867.
We obtain the following 3-sigma upper limits in the stacked images.
```
Date Start_UT T_start-T0 (hour) Filter Exp time(s) Limiting magnitude
====================================================
2022-04-08 16:27:57 ~10.698 R 300s*23 >22.5
2022-04-08 18:29:56 ~12.731 I  300s*23 >22.1
```
The magnitudes are not corrected for the Galactic extinction in the burst direction. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue.
During our observations, the moon phase and its distance were ~45% and ~55-66 degrees, respectively, which affected our deeper limits significantly; see Kumar et al. 2021, JAA, arXiv:2111.13018 ( https://ui.adsabs.harvard.edu/abs/2000A%26A...363..705M/abstract) for the sky brightness of the Devasthal site w.r.t. the moon phase and distance.
Assuming a typical temporal flux decay index of the early afterglows (alpha~0.7), the extrapolated brightness at the epoch of our observation is consistent with the quoted non-detection. Deeper observations using the larger facilities will be useful to establish the fast decaying nature of the burst and to investigate for this burst to happen in any distant/background galaxy rather than Whirlpool Galaxy (M51a).
This message may be cited.
GCN Circular #31870
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Eleonora Troja (GSFC), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz (UCSC), Jes�s Gonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM), Harvey Moseley (GSFC), Rosa L. Becerra (UNAM), Simone Dichiara (UMD), and Oc�lotl L�pez (UNAM) report:
We observed the field of GRB 220408A (Caputo et al., GCN Circ. 31848) with the Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson Telescope at the Observatorio Astron�mico Nacional on Sierra San Pedro M�rtir from 2022/04 9.13 to 2022/04 9.49 UTC (20.98 to 29.45 hours after the BAT trigger), obtaining a total of 3.27 hours exposure in the r and i bands and 2.10 hours exposure in the Z, Y, J, and H bands.
For a source within the Swift-XRT error circle, in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following weak detection and 3-sigma upper limits:
```
  r	> 23.76
  i	> 23.45
  Z	> 21.36
  Y	> 22.04
  J	> 21.79
  H	= 21.27 +/- 0.23
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We note that while we have a formal detection in H, the large errors call it into doubt.
Our limit in r is consistent with the fainter and slightly earlier detection at r = 24.1 reported by Zhu et al. (GCN Circ. 31864).
We thank the staff of the Observatorio Astron�mico Nacional in San Pedro M�rtir.
GCN Circular #31874
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Caputo (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT team):
Using the data set from T-119 to T+183 sec from the recent telemetry downlink, we report further analysis of BAT GRB 220408A (trigger #1101675) (Caputo, et al., GCN Circ. 31848). The BAT ground-calculated position is RA, Dec = 202.399, 47.065 deg which is
```
    RA(J2000)  =  13h 29m 35.7s
    Dec(J2000) = +47d 03' 55.4"
```
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 34%.
The mask-weighted light curve shows a multi-peaked structure that starts at T-2 s and peaks at T+3 s. There is a weak emission which peaks at T+17 s. T90 (15-350 keV) is 17.25 +- 1.10 sec (estimated error including systematics).
The time-averaged spectrum from T-0.55 to T+18.26 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.19 +- 0.57, and Epeak of 35.3 +- 8.8 keV (chi squared 62.40 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+2.48 sec in the 15-150 keV band is 4.9 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.14 +- 0.13 (chi squared 72.77 for 57 d.o.f.). 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/1101675/BA/
GCN Circular #31875
B. O'Connor (UMD, GWU), S.B. Cenko (UMD,NASA-GSFC), E. Troja (UTV), S. Dichiara (PSU), A. Kutyrev (UMD,NASA-GSFC), S. Veilleux (UMD)
We observed GRB 220408A with the Large Monolithic Imager (LMI) on the 4.3m Lowell Discovery Telescope (LDT). Observations began on April 9, 2022 at 06:25:23 UT in r-band (~1.03 d after the GRB). At the location of the optical counterpart (Caputo et al., GCN 31848), we marginally detect a source with magnitude r~24.5 +/- 0.3 AB mag. This is likely dominated by the contribution from the host galaxy (Zhu et al., GCN 31864), and is consistent with fading of the earlier detection by Zhu et al. (GCN 31864).
Magnitudes are calibrated against the PS1 catalog and are not corrected for Galactic extinction.
We thank the staff of the Lowell Discovery Telescope for assistance with these observations.
GCN Circular #31884
S. Beradze (AbAO), U. Bhardwaj (GRAPPA), T. Culino (ESILV), P. Hello (IJCLAB), M. Masek (FZU), G. Raaijmakers (GRAPPA), Y. Rajabov (UBAI), T. Sadibekova (AIM/CEA-UPS), F. Z. Guo (THU), X. F. Wang (THU/BJP), Y. Zhu (NAOC), J. Zhang (NAOC), D. A. Kann (HETH/IAA-CSIC), K. Noysena (TRT-SRO), C. Rinner (OUCA), Z. Benkhaldoun (OUCA), J. Zhu (BJP), X. Song (BJP), S. Antier (OCA/Artemis), P. A. Duverne (IJCLAB), A. Simon (Kyiv Univ), A. Baransky (Kyiv Univ) and V. Godunova (IC ICAMER) report on behalf of GRANDMA collaboration:
The GRANDMA telescope network responded to the alert of GRB 220408A (Caputo et al. GCNC 31848). The first observations started 0.63 h after the SWIFT BAT trigger time.
We did not detect the optical afterglow within the first 24 h. Upper limits are given in the AB system, at 3-sigma.
```
T-T0(hr)| MJD��� | Observatory� | Exposure| Filter | Upp. Lim. (AB)
___________________________________________________________________________
0.63 |59677.26659|KNC-T19������ |9*300 s� |� V ��� �� |�� 17.7
1.82 |59677.31602|SRO���������� |7*60 s�� |� R ��� �� |�� 19.8
6.27 |59677.50176|Xinglong-2.16m|9*400 s� |� Rc��� �� |�� 20.3
8.45 |59677.59259|BJP/ALi-50��� |21*20 s� |� Clear |�� 21.4
14.89|59677.86076|MOSS��������� |45*60 s� |� Clear |�� 20.3
18.76|59678.02215|KNC-HAO������ |23*180 s |� Lumen |�� 20.6
```
These upper limits are consistent with previous reports of detections by UVOT (Caputo et al. GCNC 31848, Oates et al. GCNC 31855), KAIT (Zheng et al. GCNC 31850), LCO (R. Strausbaugh et al. GCNC 31862), NOT (Zhu et al. GCNC 31864), RATIR (Watson et al. GCNC 31870), and LDT (B. O'Connor et al. GCNC 31875), and the upper limits provided by MASTER (Lipunov et al. GCNC 31849), Xinglong-2.16m (Jiang et al. GCNC 31853), GIT (Kumar et al. GCNC 31857), LOAO/SAO/DOAO (Paek et al. GCNC 31867), and 1.3m DFOT (Kumar et al. GCNC 31868).
The SRO, Xinglong-2.16m, and Ali-50 data have been calibrated with four stars from the Pan-STARRS catalog, using the transformations by Lupton (2005) and using Rc values for the Clear Al-50 observation. The MOSSm KNC-T19 and KNC-HAO images have been calibrated using field stars from the PanSTARRS-DR1 catalog, measured 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/).
GCN Circular #31893
H. Kumar (IITB), V. Swain (IITB), R. Norbu (IAO), G. C. Anupama (IIA), S. Barway (IIA), V. Bhalerao (IITB), A. Dutta (IIA), R. Gupta (ARIES), K. Misra (ARIES), D. Panchal (ARIES), S.B. Pandey (ARIES), D.K. Sahu (IIA) report on behalf of the HCT team:
We observed GRB 220408A detected by the Fermi-GBM (GCN # 31847), Swift-BAT (R. Caputo et al., GCN #31848) and optical afterglow discovered by Swift-UVOT (GCN #31848) with the 2.0m Himalayan Chandra Telescope (HCT) of the Indian Astronomical Observatory (IAO). We obtained multiple exposures in the Rc and Ic filters. We did not detect any new source in our stacked image at the afterglow location.
The obtained upper limit follows as:
-------------------------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Exposure (sec) | Filter | Lim_mag (5-sigma) |
-------------------------------------------------------------------------
2459678.203981 | 11.13 | 300 x 3 (stacked) | Rc | > 22.51 |
2459678.225509 | 11.64 | 300 x 3 (stacked) | Ic | > 22.46 |
-------------------------------------------------------------------------
Our upper limits are consistent with results from R. Caputo et al. (GCN #31848), W. Zheng and A.V. Filippenko (GCN #31850), S.Q. Jiang et al. (GCN #3185), S.R. Oates & R. Caputo (GCN #31855), H. Kumar et al. (GCN #31857), Y.-D. Hu et al. (GCN #31859), R. Strausbaugh et al. (GCN #31862), Z. Zhu et al. (GCN #31864), G.S.H. Paek et al. (GCN #31867), A. Kumar et al. (GCN #31868), A.M. Watson et al. (GCN #31870), B. O'Connor et al. (GCN #31875), S. Beradze et al. (GCN #31884).
The magnitudes are in the AB system of magnitude, calibrated against PanSTARRS (Flewelling et al., 2018) using Lupton's transformation equations available at http://classic.sdss.org/dr4/algorithms/sdssUBVRITransform.html#Lupton2005. The magnitudes are not corrected for galactic extinction.
These observations were carried out under the ToO program HCT-2022-C1-P14 (PI: Harsh Kumar). We thank the HCT staff for their support during the observations. The Indian Astronomical Observatory is operated by the Indian Institute of Astrophysics, Bengaluru, India.
GCN Circular #32327
K. Noonan (UVI), P. Gokuldass (Florida Institute of Technology), N. Orange (OrangeWave Innovative Science, LLC), K. Smith (UVI), D. Morris (UVI) report:
We observed the field of GRB220408A (Caputo et al., GCN 31848) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 04-08-2022 starting at 23:53:07.963 UT (T+18.7 hrs). We performed a series of exposures in the R filter with a total exposure of 6180 s. The weather conditions were partly cloudy during the hours of observation with an average airmass of 1.5.
We detect no new source within the enhanced XRT position error circle (A.P. Beardmore et al., 31852), consistent with other non-detections ( Zheng & Filippenko, GCN 31850; Jiang et al., GCN 31853; Kumar et al., GCN 31857; and Gregory et al., GCN 31867) and report the following 5-sigma upper limit:
T_mid ||Exposure ||Filter ||Limit
T+ 19.5 hrs ||6180s ||R ||>20.8
The limit is estimated from comparison to nearby USNO B1 stars and is not corrected for Galactic extinction. The VIRT is still in the commissioning phase.
We acknowledge financial support from NASA MUREP MIRO award 80NSSC21M0001, NASA EPSCoR award 80NSSC19M0060, and NSF EiR award 1901296.This message can be cited.

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