Gamma-ray Burst 200416A

(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:     Thu 16 Apr 20 07:05:34 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     966554,   Seg_Num: 0
GRB_RA:          335.691d {+22h 22m 46s} (J2000),
                 335.957d {+22h 23m 50s} (current),
                 335.035d {+22h 20m 08s} (1950)
GRB_DEC:          -7.530d {-07d 31' 47"} (J2000),
                  -7.427d {-07d 25' 36"} (current),
                  -7.783d {-07d 46' 58"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1769 [cnts]    Image_Peak=140 [image_cnts]
TRIGGER_DUR:     0.512 [sec] 
TRIGGER_INDEX:   43     E_range: 25-100 keV
BKG_INTEN:       17585 [cnts]
BKG_TIME:        25503.21 SOD {07:05:03.21} UT
BKG_DUR:         8 [sec]
GRB_DATE:        18955 TJD;   107 DOY;   20/04/16
GRB_TIME:        25517.17 SOD {07:05:17.17} UT
GRB_PHI:         -168.20 [deg]
GRB_THETA:        47.06 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     21.65 [sigma]
IMAGE_SIGNIF:    10.19 [sigma]
MERIT_PARAMS:     +1  +0  +0  -1  +2  +0  +0  +0 -61  +0 
SUN_POSTN:        24.83d {+01h 39m 19s}  +10.32d {+10d 18' 57"}
SUN_DIST:         51.79 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.51d {+21h 02m 01s}  -20.31d {-20d 18' 38"}
MOON_DIST:        23.62 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.06,-49.71 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      334.73,  2.41 [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 = 59.19,-20.64 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=608713522).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 16 Apr 20 07:05:43 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     608713522
GRB_RA:          341.200d {+22h 44m 48s} (J2000),
                 341.464d {+22h 45m 51s} (current),
                 340.550d {+22h 42m 12s} (1950)
GRB_DEC:          -5.933d {-05d 55' 59"} (J2000),
                  -5.826d {-05d 49' 34"} (current),
                  -6.196d {-06d 11' 46"} (1950)
GRB_ERROR:       16.02 [deg radius, statistical plus systematic]
GRB_INTEN:       200 [cnts/sec]
DATA_SIGNIF:     8.00 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        18955 TJD;   107 DOY;   20/04/16
GRB_TIME:        25517.38 SOD {07:05:17.38} UT
GRB_PHI:          45.00 [deg]
GRB_THETA:        90.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      1.77
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      75%  Distant Particles
2nd_MOST_LIKELY:  13%  GRB
DETECTORS:       0,0,1, 0,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:        24.83d {+01h 39m 19s}  +10.32d {+10d 18' 57"}
SUN_DIST:         46.10 [deg]   Sun_angle= 2.9 [hr] (West of Sun)
MOON_POSTN:      315.51d {+21h 02m 02s}  -20.31d {-20d 18' 37"}
MOON_DIST:        29.06 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       62.32,-53.19 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      340.40,  1.87 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200416295/quicklook/glg_lc_medres34_bn200416295.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 125.63,-25.55 [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=966554).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Apr 20 07:07:06 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     966554,   Seg_Num: 0
POINT_RA:        335.683d {+22h 22m 44s} (J2000)
POINT_DEC:        -7.542d {-07d 32' 30"} (J2000)
IMG_START_DATE:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25617.14 SOD {07:06:57.14} UT,   100.0 [sec] since BAT Trigger Time
COUNTS:          8    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Apr 20 07:09:09 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     966554,   Seg_Num: 0
GRB_RA:          335.691d {+22h 22m 46s} (J2000),
                 335.957d {+22h 23m 50s} (current),
                 335.035d {+22h 20m 08s} (1950)
GRB_DEC:          -7.530d {-07d 31' 47"} (J2000),
                  -7.427d {-07d 25' 36"} (current),
                  -7.783d {-07d 46' 58"} (1950)
GRB_DATE:        18955 TJD;   107 DOY;   20/04/16
GRB_TIME:        25517.17 SOD {07:05:17.17} UT
TRIGGER_INDEX:   43
GRB_PHI:         -168.20 [deg]
GRB_THETA:        47.06 [deg]
DELTA_TIME:      45.00 [sec]
TRIGGER_DUR:     0.512 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.65 [sigma]
IMAGE_SIGNIF:    10.19 [sigma]
LC_URL:          sw00966554000msb.lc
SUN_POSTN:        24.83d {+01h 39m 19s}  +10.32d {+10d 18' 60"}
SUN_DIST:         51.79 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.54d {+21h 02m 09s}  -20.30d {-20d 18' 15"}
MOON_DIST:        23.59 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.06,-49.71 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      334.73,  2.41 [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 = 59.19,-20.64 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Apr 20 07:12:51 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     966554,   Seg_Num: 0
POINT_RA:        335.683d {+22h 22m 44s} (J2000)
POINT_DEC:        -7.543d {-07d 32' 32"} (J2000)
POINT_ROLL:      70.633d
IMG_START_DATE:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25619.37 SOD {07:06:59.37} UT,   102.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        8.322
N_STARS:         21
X_OFFSET:        508 [pixels]
Y_OFFSET:        449 [pixels]
X_MAX:           1467 [pixels]
Y_MAX:           1408 [pixels]
DET_THRESH:      25
PHOTO_THRESH:    16
SL_URL:          sw00966554000msufc0102.fits
SUN_POSTN:        24.83d {+01h 39m 20s}  +10.32d {+10d 19' 03"}
SUN_DIST:         51.81 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.57d {+21h 02m 17s}  -20.30d {-20d 17' 50"}
MOON_DIST:        23.55 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.04,-49.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      334.72,  2.40 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Apr 20 07:11:18 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     966554,   Seg_Num: 0
GRB_RA:          335.6990d {+22h 22m 47.76s} (J2000),
                 335.9650d {+22h 23m 51.60s} (current),
                 335.0429d {+22h 20m 10.29s} (1950)
GRB_DEC:          -7.5182d {-07d 31' 05.5"} (J2000),
                  -7.4151d {-07d 24' 54.5"} (current),
                  -7.7713d {-07d 46' 16.5"} (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:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25666.00 SOD {07:07:46.00} UT,   148.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        24.83d {+01h 39m 20s}  +10.32d {+10d 19' 02"}
SUN_DIST:         51.78 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.56d {+21h 02m 13s}  -20.30d {-20d 18' 00"}
MOON_DIST:        23.59 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.09,-49.72 [deg] galactic lon,lat of the burst
ECL_COORDS:      334.74,  2.42 [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:     Thu 16 Apr 20 07:13:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     966554,   Seg_Num: 0
POINT_RA:        335.683d {+22h 22m 44s} (J2000)
POINT_DEC:        -7.543d {-07d 32' 32"} (J2000)
POINT_ROLL:      70.633d
IMG_START_DATE:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25619.37 SOD {07:06:59.37} UT,   102.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        8.322
N_STARS:         21
X_OFFSET:        508 [pixels]
Y_OFFSET:        449 [pixels]
X_MAX:           1467 [pixels]
Y_MAX:           1408 [pixels]
DET_THRESH:      25
PHOTO_THRESH:    16
SL_URL:          sw00966554000msufc0102.fits
SUN_POSTN:        24.83d {+01h 39m 20s}  +10.32d {+10d 19' 03"}
SUN_DIST:         51.81 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.57d {+21h 02m 17s}  -20.30d {-20d 17' 48"}
MOON_DIST:        23.55 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.04,-49.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      334.72,  2.40 [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:     Thu 16 Apr 20 07:14:28 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     966554,   Seg_Num: 0
POINT_RA:        335.683d {+22h 22m 44s} (J2000)
POINT_DEC:        -7.543d {-07d 32' 32"} (J2000)
ROLL:            70.633d
IMG_START_DATE:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25619.37 SOD {07:06:59.37} UT,   102.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     608713644
X_OFFSET:        827 [pixels]
Y_OFFSET:        768 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       987
Y_GRB_POS:       928
BINNING_INDEX:   1
IM_URL:          sw00966554000msuni0127.fits
SUN_POSTN:        24.83d {+01h 39m 20s}  +10.32d {+10d 19' 05"}
SUN_DIST:         51.81 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.58d {+21h 02m 20s}  -20.29d {-20d 17' 39"}
MOON_DIST:        23.54 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.04,-49.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      334.72,  2.40 [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:     Thu 16 Apr 20 07:23:01 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     966554,   Seg_Num: 0
POINT_RA:        335.684d {+22h 22m 44s} (J2000)
POINT_DEC:        -7.544d {-07d 32' 36"} (J2000)
ROLL:            70.631d
IMG_START_DATE:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25831.50 SOD {07:10:31.50} UT,   314.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     608713856
X_OFFSET:        827 [pixels]
Y_OFFSET:        768 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       987
Y_GRB_POS:       928
BINNING_INDEX:   1
IM_URL:          sw00966554000msuni0339.fits
SUN_POSTN:        24.84d {+01h 39m 21s}  +10.32d {+10d 19' 12"}
SUN_DIST:         51.81 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.66d {+21h 02m 38s}  -20.28d {-20d 16' 42"}
MOON_DIST:        23.47 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.04,-49.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      334.72,  2.40 [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:     Thu 16 Apr 20 07:23:14 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     966554,   Seg_Num: 0
POINT_RA:        335.684d {+22h 22m 44s} (J2000)
POINT_DEC:        -7.544d {-07d 32' 36"} (J2000)
ROLL:            70.631d
IMG_START_DATE:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25831.50 SOD {07:10:31.50} UT,   314.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     608713856
X_OFFSET:        827 [pixels]
Y_OFFSET:        768 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       987
Y_GRB_POS:       928
BINNING_INDEX:   1
IM_URL:          sw00966554000msuni0339.fits
SUN_POSTN:        24.84d {+01h 39m 21s}  +10.32d {+10d 19' 12"}
SUN_DIST:         51.81 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.66d {+21h 02m 39s}  -20.28d {-20d 16' 41"}
MOON_DIST:        23.47 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.04,-49.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      334.72,  2.40 [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 #27591
P. A. Evans (U Leicester), V. D'Elia (SSDC), J.D. Gropp (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
At 07:05:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200416A (trigger=966554). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 335.691, -7.530 which is
```
   RA(J2000) = 22h 22m 46s
   Dec(J2000) = -07d 31' 47"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 10 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 07:06:57.1 UT, 99.9 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 335.69906, -7.51816 which is equivalent to:
```
   RA(J2000)  = 22h 22m 47.77s
   Dec(J2000) = -07d 31' 05.4"
```
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 51 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 (6.54 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2 (+3.00/-2.56) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 102 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	22:22:47.83 = 335.69929
  DEC(J2000) = -07:31:05.9  =  -7.51831
```
with a 90%-confidence error radius of about 0.75 arc sec. This position is 1.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 16.47 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.06.
Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). 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:     Thu 16 Apr 20 07:21:25 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     966554,   Seg_Num: 0
POINT_RA:        335.684d {+22h 22m 44s} (J2000)
POINT_DEC:        -7.544d {-07d 32' 36"} (J2000)
POINT_ROLL:      70.631d
IMG_START_DATE:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25831.50 SOD {07:10:31.50} UT,   314.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        3.578
N_STARS:         75
X_OFFSET:        268 [pixels]
Y_OFFSET:        209 [pixels]
X_MAX:           1707 [pixels]
Y_MAX:           1648 [pixels]
DET_THRESH:      16
PHOTO_THRESH:    9
SL_URL:          sw00966554000msufc0314.fits
SUN_POSTN:        24.84d {+01h 39m 21s}  +10.32d {+10d 19' 11"}
SUN_DIST:         51.81 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.65d {+21h 02m 35s}  -20.28d {-20d 16' 53"}
MOON_DIST:        23.48 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.04,-49.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      334.72,  2.40 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Apr 20 07:21:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     966554,   Seg_Num: 0
POINT_RA:        335.684d {+22h 22m 44s} (J2000)
POINT_DEC:        -7.544d {-07d 32' 36"} (J2000)
POINT_ROLL:      70.631d
IMG_START_DATE:  18955 TJD;   107 DOY;   20/04/16
IMG_START_TIME:  25831.50 SOD {07:10:31.50} UT,   314.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        3.578
N_STARS:         75
X_OFFSET:        268 [pixels]
Y_OFFSET:        209 [pixels]
X_MAX:           1707 [pixels]
Y_MAX:           1648 [pixels]
DET_THRESH:      16
PHOTO_THRESH:    9
SL_URL:          sw00966554000msufc0314.fits
SUN_POSTN:        24.84d {+01h 39m 21s}  +10.32d {+10d 19' 11"}
SUN_DIST:         51.81 [deg]   Sun_angle= 3.3 [hr] (West of Sun)
MOON_POSTN:      315.65d {+21h 02m 35s}  -20.28d {-20d 16' 52"}
MOON_DIST:        23.48 [deg]
MOON_ILLUM:      37 [%]
GAL_COORDS:       55.04,-49.72 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      334.72,  2.40 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #27592
E. Bissaldi (Politecnico and INFN Bari) reports on behalf of the Fermi GBM Team:
"At 07:05:17.38 UT on 16 April 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 200416A (trigger 608713522 /200416295), which was also detected by the Swift/BAT (Evans et al. 2020, GCN 27591). The trigger was initially misclassified as a particle event by the flight software. The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 92 degrees.
The GBM light curve shows a double-peaked emission episode with a duration (T90) of about 9 s (50-300 keV). The time-averaged spectrum from T0-2 s to T0+6 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.87 +/- 0.15 and the cutoff energy, parameterized as Epeak, is 74 +/- 6 keV.
The event fluence (10-1000 keV) in this time interval is (1.43 +/- 0.08)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 6.5 +/- 0.3 ph/s/cm^2.
A Band function fits the spectrum equally well with Epeak= 64 +/- 9 keV, alpha = -0.66 +/- 0.24 and beta = -2.5 +/- 0.3.
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 #27594
P. A. Evans (U Leicester) reports on behalf of the Swift-XRT team:
We have analysed 677 s of XRT data for GRB 200416A (Evans et al. GCN Circ. 27591), from 84 s to 773 s after the BAT trigger. The data comprise 43 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 = 335.6986, -7.5179 which is equivalent to:
```
RA (J2000): 22 22 47.66
Dec(J2000): -07 31 04.3
```
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=2.9 (+/-0.5), followed by a break at T+167 s to an alpha of 0.25 (+0.18, -0.25).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.86 (+0.22, -0.20). The best-fitting absorption column is 9.6 (+6.3, -3.1) x 10^20 cm^-2, consistent with the Galactic value of 6.5 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 (4.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     9.6 (+6.3, -3.1) x 10^20 cm^-2
Galactic foreground: 6.5 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.86 (+0.22, -0.20)
```
The GRB entered Swift's Moon-proximity observing constraint shortly after the trigger, and will not be observable until early on Monday April 20th; observations are planned for that time. The light curve appears to be in the plateau phase common to X-ray afterglows and is expected to break to a steeper decay at some point within the next ~24 hours, so we do not attempt to predict the flux at T0+24 hours.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00966554.
This circular is an official product of the Swift-XRT team.
GCN Circular #27601
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), P. A. Evans (U Leicester) H. A. Krimm (NSF), S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200416A (trigger #966554) (P. A. Evans et al., GCN Circ. 27591). The BAT ground-calculated position is RA, Dec = 335.691, -7.525 deg which is
```
   RA(J2000)  =  22h 22m 45.8s
   Dec(J2000) = -07d 31' 29.5"
```
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 33%.
The mask weighted light curve shows multi-peaked structure. The overall structure starts at ~T-2 s and lasts till ~T+6 s. T90 (15-350 keV) is 5.04 +- 0.73 sec (estimated error including systematics).
The time-averaged spectrum from T-1.31 to T+4.69 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.76 +- 0.15. The fluence in the 15-150 keV band is 8.7 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.05 sec in the 15-150 keV band is 3.8 +- 0.5 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/966554/BA/
GCN Circular #27602
GRB 200416A: Swift/UVOT Detection
K. K. Simpson (PSU) and P. A. Evans (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 200416A 102 s after the BAT trigger (Evans et al., GCN Circ. 27591). A source consistent with the XRT position (Evans GCN Circ. 27594) is detected in the initial UVOT exposures.
The preliminary UVOT position is:
```
    RA  (J2000) =  22:22:47.84 = 335.69934 (deg.)
    Dec (J2000) = -07:31:06.0  =  -7.51833 (deg.)
```
with an estimated uncertainty of 0.43 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              102          252          147         16.57 +/- 0.03
v                  644          664           19         17.05 +/- 0.32
b                  570          590           20         17.48 +/- 0.20
u                  314          564          246         16.44 +/- 0.04
w1                 694          714           20         16.59 +/- 0.23
m2                 668          688           19        >16.3
w2                 620          640           19        >17.5
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.06 in the direction of the burst (Schlegel et al. 1998).

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Jochen Greiner, last update: 18-Apr-2020 [Disclaimer]