Gamma-ray Burst 180404A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 04 Apr 18 00:45:56 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     821881,   Seg_Num: 0
GRB_RA:           83.564d {+05h 34m 15s} (J2000),
                  83.721d {+05h 34m 53s} (current),
                  83.133d {+05h 32m 32s} (1950)
GRB_DEC:         -37.170d {-37d 10' 10"} (J2000),
                 -37.159d {-37d 09' 30"} (current),
                 -37.202d {-37d 12' 06"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4635 [cnts]    Image_Peak=231 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   137     E_range: 15-50 keV
BKG_INTEN:       29134 [cnts]
BKG_TIME:        2723.27 SOD {00:45:23.27} UT
BKG_DUR:         8 [sec]
GRB_DATE:        18212 TJD;    94 DOY;   18/04/04
GRB_TIME:        2735.68 SOD {00:45:35.68} UT
GRB_PHI:          -8.78 [deg]
GRB_THETA:        32.49 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.85 [sigma]
IMAGE_SIGNIF:    8.76 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  -1  +0  +0 -20  +0 
SUN_POSTN:        13.08d {+00h 52m 20s}   +5.60d {+05d 36' 12"}
SUN_DIST:         78.23 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.70d {+15h 42m 48s}  -14.67d {-14d 40' 21"}
MOON_DIST:       121.84 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.98,-30.65 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       79.59,-60.38 [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 = 231.86,1.90 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 04 Apr 18 00:47:08 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.178d {-37d 10' 41"} (J2000)
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  2822.14 SOD {00:47:02.14} UT,   86.5 [sec] since BAT Trigger Time
COUNTS:          16    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:     Wed 04 Apr 18 00:49:29 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     821881,   Seg_Num: 0
GRB_RA:           83.564d {+05h 34m 15s} (J2000),
                  83.721d {+05h 34m 53s} (current),
                  83.133d {+05h 32m 32s} (1950)
GRB_DEC:         -37.170d {-37d 10' 10"} (J2000),
                 -37.159d {-37d 09' 30"} (current),
                 -37.202d {-37d 12' 06"} (1950)
GRB_DATE:        18212 TJD;    94 DOY;   18/04/04
GRB_TIME:        2735.68 SOD {00:45:35.68} UT
TRIGGER_INDEX:   137
GRB_PHI:          -8.78 [deg]
GRB_THETA:        32.49 [deg]
DELTA_TIME:      38.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.85 [sigma]
IMAGE_SIGNIF:    8.76 [sigma]
LC_URL:          sw00821881000msb.lc
SUN_POSTN:        13.08d {+00h 52m 20s}   +5.60d {+05d 36' 15"}
SUN_DIST:         78.23 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.73d {+15h 42m 56s}  -14.68d {-14d 40' 49"}
MOON_DIST:       121.85 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.98,-30.65 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       79.59,-60.38 [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 = 231.86,1.90 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 04 Apr 18 00:50:02 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.178d {-37d 10' 40"} (J2000)
POINT_ROLL:      286.545d
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  2825.45 SOD {00:47:05.45} UT,   89.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.615
N_STARS:         61
X_OFFSET:        562 [pixels]
Y_OFFSET:        588 [pixels]
X_MAX:           1521 [pixels]
Y_MAX:           1547 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00821881000msufc0089.fits
SUN_POSTN:        13.08d {+00h 52m 20s}   +5.60d {+05d 36' 16"}
SUN_DIST:         78.24 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.74d {+15h 42m 57s}  -14.68d {-14d 40' 53"}
MOON_DIST:       121.84 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.99,-30.65 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       79.60,-60.39 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.  
COMMENTS:        There is a bright star (mag=5.73) 7.66 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 04 Apr 18 00:50:20 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.178d {-37d 10' 40"} (J2000)
POINT_ROLL:      286.545d
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  2825.45 SOD {00:47:05.45} UT,   89.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.615
N_STARS:         61
X_OFFSET:        562 [pixels]
Y_OFFSET:        588 [pixels]
X_MAX:           1521 [pixels]
Y_MAX:           1547 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00821881000msufc0089.fits
SUN_POSTN:        13.08d {+00h 52m 20s}   +5.60d {+05d 36' 16"}
SUN_DIST:         78.24 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.74d {+15h 42m 57s}  -14.68d {-14d 40' 55"}
MOON_DIST:       121.84 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.99,-30.65 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       79.60,-60.39 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.  
COMMENTS:        There is a bright star (mag=5.73) 7.66 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 04 Apr 18 00:50:51 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     821881,   Seg_Num: 0
GRB_RA:           83.5490d {+05h 34m 11.76s} (J2000),
                  83.7063d {+05h 34m 49.52s} (current),
                  83.1183d {+05h 32m 28.38s} (1950)
GRB_DEC:         -37.1682d {-37d 10' 05.5"} (J2000),
                 -37.1569d {-37d 09' 24.9"} (current),
                 -37.2005d {-37d 12' 01.8"} (1950)
GRB_ERROR:       4.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  2869.00 SOD {00:47:49.00} UT,   133.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        13.09d {+00h 52m 20s}   +5.60d {+05d 36' 16"}
SUN_DIST:         78.22 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.74d {+15h 42m 58s}  -14.68d {-14d 41' 00"}
MOON_DIST:       121.86 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.97,-30.66 [deg] galactic lon,lat of the burst
ECL_COORDS:       79.57,-60.37 [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:     Wed 04 Apr 18 00:51:30 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.178d {-37d 10' 40"} (J2000)
ROLL:            286.545d
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  2825.45 SOD {00:47:05.45} UT,   89.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     544495646
X_OFFSET:        881 [pixels]
Y_OFFSET:        907 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1041
Y_GRB_POS:       1067
BINNING_INDEX:   1
IM_URL:          sw00821881000msuni0110.fits
SUN_POSTN:        13.09d {+00h 52m 21s}   +5.60d {+05d 36' 17"}
SUN_DIST:         78.24 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.75d {+15h 43m 00s}  -14.68d {-14d 41' 04"}
MOON_DIST:       121.84 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.99,-30.65 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       79.60,-60.39 [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:     Wed 04 Apr 18 00:51:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.178d {-37d 10' 40"} (J2000)
ROLL:            286.545d
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  2825.45 SOD {00:47:05.45} UT,   89.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     544495646
X_OFFSET:        881 [pixels]
Y_OFFSET:        907 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1041
Y_GRB_POS:       1067
BINNING_INDEX:   1
IM_URL:          sw00821881000msuni0110.fits
SUN_POSTN:        13.09d {+00h 52m 21s}   +5.60d {+05d 36' 17"}
SUN_DIST:         78.24 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.75d {+15h 43m 00s}  -14.69d {-14d 41' 06"}
MOON_DIST:       121.84 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.99,-30.65 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       79.60,-60.39 [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:     Wed 04 Apr 18 00:53:12 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     821881,   Seg_Num: 0
GRB_RA:           83.5484d {+05h 34m 11.61s} (J2000),
                  83.7057d {+05h 34m 49.37s} (current),
                  83.1176d {+05h 32m 28.23s} (1950)
GRB_DEC:         -37.1677d {-37d 10' 03.7"} (J2000),
                 -37.1564d {-37d 09' 23.1"} (current),
                 -37.2000d {-37d 12' 00.0"} (1950)
GRB_ERROR:       0.7 [arcsec radius, statistical only]
GRB_MAG:         19.39 +/- 0.16 [mag]
FILTER:          10, White
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  2822.00 SOD {00:47:02.00} UT,   86.3 [sec] since BAT Trigger Time
SUN_POSTN:        13.09d {+00h 52m 21s}   +5.61d {+05d 36' 19"}
SUN_DIST:         78.22 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.76d {+15h 43m 03s}  -14.69d {-14d 41' 17"}
MOON_DIST:       121.87 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.97,-30.66 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       79.56,-60.37 [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 #22589
J.D. Gropp (PSU), D. N. Burrows (PSU), A. Deich (PSU), C. Gronwall (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 00:45:35 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180404A (trigger=821881). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 83.564, -37.170 which is
```
   RA(J2000) = 05h 34m 15s
   Dec(J2000) = -37d 10' 10"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 50 sec. The peak count rate was ~1900 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 00:47:02.1 UT, 86.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 83.54900, -37.16824 which is equivalent to:
```
   RA(J2000)  = 05h 34m 11.76s
   Dec(J2000) = -37d 10' 05.7"
```
with an uncertainty of 4.2 arcseconds (radius, 90% containment). This location is 43 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. No spectrum from the promptly downlinked event data is yet available to determine the column density.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 89 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	05:34:11.63 =  83.54846
  DEC(J2000) = -37:10:03.9  = -37.16774
```
with a 90%-confidence error radius of about 0.65 arc sec. This position is 2.3 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.40 with a 1-sigma error of about 0.16. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04.
Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.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/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 04 Apr 18 00:58:41 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.182d {-37d 10' 53"} (J2000)
POINT_ROLL:      286.544d
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  3037.68 SOD {00:50:37.68} UT,   302.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.414
N_STARS:         86
X_OFFSET:        322 [pixels]
Y_OFFSET:        348 [pixels]
X_MAX:           1761 [pixels]
Y_MAX:           1787 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw00821881000msufc0301.fits
SUN_POSTN:        13.09d {+00h 52m 22s}   +5.61d {+05d 36' 24"}
SUN_DIST:         78.24 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.81d {+15h 43m 15s}  -14.70d {-14d 42' 00"}
MOON_DIST:       121.85 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.99,-30.65 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       79.60,-60.39 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 04 Apr 18 00:58:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.182d {-37d 10' 53"} (J2000)
POINT_ROLL:      286.544d
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  3037.68 SOD {00:50:37.68} UT,   302.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.414
N_STARS:         86
X_OFFSET:        322 [pixels]
Y_OFFSET:        348 [pixels]
X_MAX:           1761 [pixels]
Y_MAX:           1787 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw00821881000msufc0301.fits
SUN_POSTN:        13.09d {+00h 52m 22s}   +5.61d {+05d 36' 24"}
SUN_DIST:         78.23 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.81d {+15h 43m 15s}  -14.70d {-14d 42' 01"}
MOON_DIST:       121.85 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.99,-30.65 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       79.60,-60.39 [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:     Wed 04 Apr 18 00:59:16 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     821881,   Seg_Num: 0
GRB_RA:           83.5485d {+05h 34m 11.64s} (J2000),
                  83.7058d {+05h 34m 49.40s} (current),
                  83.1178d {+05h 32m 28.26s} (1950)
GRB_DEC:         -37.1683d {-37d 10' 05.8"} (J2000),
                 -37.1570d {-37d 09' 25.2"} (current),
                 -37.2006d {-37d 12' 02.2"} (1950)
GRB_ERROR:       2.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  2869.00 SOD {00:47:49.00} UT,   133.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        13.09d {+00h 52m 22s}   +5.61d {+05d 36' 24"}
SUN_DIST:         78.21 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.82d {+15h 43m 16s}  -14.70d {-14d 42' 04"}
MOON_DIST:       121.88 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.97,-30.66 [deg] galactic lon,lat of the burst
ECL_COORDS:       79.56,-60.37 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 04 Apr 18 00:59:51 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.182d {-37d 10' 53"} (J2000)
ROLL:            286.544d
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  3037.68 SOD {00:50:37.68} UT,   302.0 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     544495858
X_OFFSET:        881 [pixels]
Y_OFFSET:        907 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1041
Y_GRB_POS:       1067
BINNING_INDEX:   1
IM_URL:          sw00821881000msuni0322.fits
SUN_POSTN:        13.09d {+00h 52m 22s}   +5.61d {+05d 36' 25"}
SUN_DIST:         78.23 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.82d {+15h 43m 17s}  -14.70d {-14d 42' 08"}
MOON_DIST:       121.86 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.99,-30.65 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       79.60,-60.39 [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:     Wed 04 Apr 18 01:00:06 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     821881,   Seg_Num: 0
POINT_RA:         83.570d {+05h 34m 17s} (J2000)
POINT_DEC:       -37.182d {-37d 10' 53"} (J2000)
ROLL:            286.544d
IMG_START_DATE:  18212 TJD;    94 DOY;   18/04/04
IMG_START_TIME:  3037.68 SOD {00:50:37.68} UT,   302.0 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     544495858
X_OFFSET:        881 [pixels]
Y_OFFSET:        907 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1041
Y_GRB_POS:       1067
BINNING_INDEX:   1
IM_URL:          sw00821881000msuni0322.fits
SUN_POSTN:        13.09d {+00h 52m 22s}   +5.61d {+05d 36' 25"}
SUN_DIST:         78.23 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      235.82d {+15h 43m 18s}  -14.70d {-14d 42' 10"}
MOON_DIST:       121.86 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:      241.99,-30.65 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       79.60,-60.39 [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 #22591
J. Selsing (DARK/NBI), D. Malesani (DAWN/NBI and DARK/NBI), D.A. Kann (HETH/IAA-CSIC), N.R. Tanvir (Univ. Leicester) report on behalf of the Stargate consortium:
We observed the optical counterpart of GRB 180404A (Gropp et al., GCN 22589) using the ESO Very Large Telescope (VLT) UT2 equipped with the X-shooter spectrograph. Observations were carried out in robotic "rapid response mode" (RRM), initiated automatically following the X-ray localization notice.
In the 15-s r-band acquisition image, taken on 2018 Apr 4.0423 UT (15.3 min after the trigger), the afterglow is clearly detected, at coordinates (J2000):
```
RA = 05:34:11.67
Dec = -37:10:04.1
```
We measure a magnitude R = 18.64 +- 0.1 (Vega), calibrated against nearby USNO stars, where the error is dominated by the calibration scatter.
Several spectra were acquired. We report here on the exposure with mid epoch Apr 4.0495 UT (that is, 25.6 min after the GRB), with 600 s exposure time, and covering the wavelength range 3000-25000 AA. The afterglow continuum trace is clearly detected. Superposed on it, several absorption features are visible, which we identify as Al III, Fe II, Mg II, and Mg I, all at a common redshift redshift of z = 1.000.
We acknowledge excellent support from the observing staff at Paranal, in particular Stephane Brillant, Luca Sbordone, Andrea Mehner, and Jose Velasquez.
GCN Circular #22592
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 646 s of XRT Photon Counting mode data and 1 UVOT images for GRB 180404A, 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 = 83.54906, -37.16807 which is equivalent to:
```
RA (J2000): 05h 34m 11.77s
Dec (J2000): -37d 10' 05.1"
```
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 #22593
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, A.Kuznetsov, V.Chazov, I. Gorbunov, D. Vlasenko, D.Kuvshinov, P.Balanutsa Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University
R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA)
Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk
O. Gres, N.M. Budnev, O. Chuvalaev, Yu.Ishmuhametova Irkutsk State University
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
D. Buckley, S. Potter South African Astronomical Observatory
MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Argentina was pointed to the GRB180404A (Gropp et al. GCN 22589) 21 sec after notice time and 43 sec after trigger time at 2018-04-04 00:46:18 UT. On our first 10s exposure set we haven`t found optical transient with 17.4 5-sigma upper limit in SWIFT XRT error-box (ra=83.549 dec=-37.17 r=4.2").
MASTER auto-detection system detected OT with RA,Dec=5h 34m 11s.66, -37d 10m 03s.5 with unfiltered m_OT=19.8 on the summary image with 660s exposition started 2018-04-04 00:46:18.938UT, that was discovered by Swift (Gropp et al. GCN 22589) and confirmed by VLT (Selsing et al. GCN 22591)
====================================================================
The observations made on zenit distance = 42 degrees, galaxy latitude b = -30 degree. The moon (87 % bright part) below the horizon (The altitude of the Moon is -1 degree ). The sun altitude is -29.7 degree.
The message may be cited.
GCN Circular #22599
S. D. Barthelmy (GSFC), J. R. Cummings (CPI), J. D. Gropp (PSU), H. A. Krimm (NSF/USRA), A. Y. Lien (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-239 to T+654 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180404A (trigger #821881) (Gropp, et al., GCN Circ. 22589). The BAT ground-calculated position is RA, Dec = 83.540, -37.168 deg which is
```
    RA(J2000)  =  05h 34m 09.5s
    Dec(J2000) = -37d 10' 05.0"
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 82%.
The mask-weighted light curve shows a weak emission that starts at T-25 sec, followed by a bright peak which peaks at T+3 sec and ends at T+30 sec. T90 (15-350 keV) is 35.2 +- 5.3 sec (estimated error including systematics).
The time-averaged spectrum from T-20.7 to T+24.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.95 +- 0.12. The fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.99 sec in the 15-150 keV band is 1.3 +- 0.2 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/821881/BA/
GCN Circular #22602
A. Tohuvavohu (PSU), S. J. LaPorte (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), J.A. Kennea (PSU) and J.D. Gropp report on behalf of the Swift-XRT team:
We have analysed 3.9 ks of XRT data for GRB 180404A (Gropp et al. GCN Circ. 22589), from 90 s to 52.0 ks after the BAT trigger. The data comprise 26 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 22592).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.5 (+nan, -nan).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.62 (+0.27, -0.22). The best-fitting absorption column is consistent with the Galactic value of 3.1 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 4.1 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     3.1 (+/-5.1) x 10^20 cm^-2
Galactic foreground: 3.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.62 (+0.27, -0.22)
```
If the light curve continues to decay with a power-law decay index of 0.5, the count rate at T+24 hours will be 0.011 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.3 x 10^-13 (4.5 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00821881.
This circular is an official product of the Swift-XRT team.
GCN Circular #22603
C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell=20 (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a=20 large collaboration report:
We began observing Swift GRB180404A (Gropp et al. GCN 22589) on April 4,=20 09:30 UT (0.36 days post burst) with the LCO 2-m Faulkes Telescope South=20 unit in Siding Springs in the SDSS-R filter. We marginally detect the=20 optical afterglow (Gropp et al.; Selsing et al. GCN 22591) with the=20 following magnitude:
```
Mid time since GRB=A0=A0=A0=A0 Exp=A0=A0=A0=A0=A0=A0=A0 Filter=A0=A0=A0=A0=
=A0=A0=A0=A0 Magnitude
(days)=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 (s)
-------------------------------------------------------------
0.37=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 5x120=A0=A0=A0=
=A0=A0 SDSS-R=A0=A0=A0=A0=A0=A0=A0=A0 21.3 +- 0.3
-------------------------------------------------------------
```
as calibrated against nearby USNO UCAC4 objects.

GCN Circular #22605
M. H. Siegel (PSU) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180404A 90 s after the BAT trigger (Gropp et al., GCN Circ. 22589). A source consistent with the XRT position (Osborne et al. GCN Circ. 22592) is detected in the initial UVOT exposures.
The preliminary UVOT position is:

   RA  (J2000) =  05:34:11.64 =  83.54850 (deg.)
   Dec (J2000) = -37:10:03.9  = -37.16774 (deg.)

with an estimated uncertainty of 0.50 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 (fc)          90          240          147         19.47 +/- 0.09
white               90          770          180         19.34 +/ -0.10
white             45830       52026         1028        >21.66
v                  632         5179           99        >18.9
b                  558          750           39        >19.4
u (fc)              302         552          246         18.95 +/- 0.12
u                  303          726          265         18.95 +/ -0.14
w1                 682          701           19        >17.8
m2                 656          676           19        >17.4
w2                 607         5094          216         19.45 +/- 0.28

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998).

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Jochen Greiner, last update: 05-Apr-2018 [Disclaimer]