Gamma-ray Burst 180311A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:04:40 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     813721,   Seg_Num: 0
GRB_RA:            3.433d {+00h 13m 44s} (J2000),
                   3.658d {+00h 14m 38s} (current),
                   2.814d {+00h 11m 15s} (1950)
GRB_DEC:         -54.479d {-54d 28' 43"} (J2000),
                 -54.378d {-54d 22' 39"} (current),
                 -54.757d {-54d 45' 24"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       22617 [cnts]    Image_Peak=495 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   453     E_range: 15-50 keV
BKG_INTEN:       160119 [cnts]
BKG_TIME:        64939.39 SOD {18:02:19.39} UT
BKG_DUR:         64 [sec]
GRB_DATE:        18188 TJD;    70 DOY;   18/03/11
GRB_TIME:        65029.24 SOD {18:03:49.24} UT
GRB_PHI:         -24.81 [deg]
GRB_THETA:        22.47 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.00 [sigma]
IMAGE_SIGNIF:    8.58 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +1  -1  +0  +0 -61  +0 
SUN_POSTN:       351.84d {+23h 27m 21s}   -3.52d {-03d 31' 15"}
SUN_DIST:         51.76 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.82d {+19h 07m 18s}  -19.96d {-19d 57' 52"}
MOON_DIST:        66.28 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.54,-61.79 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      333.29,-49.52 [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 = 178.26,-5.60 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:07:19 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     813721,   Seg_Num: 0
GRB_RA:            3.433d {+00h 13m 44s} (J2000),
                   3.658d {+00h 14m 38s} (current),
                   2.814d {+00h 11m 15s} (1950)
GRB_DEC:         -54.479d {-54d 28' 43"} (J2000),
                 -54.378d {-54d 22' 39"} (current),
                 -54.757d {-54d 45' 24"} (1950)
GRB_DATE:        18188 TJD;    70 DOY;   18/03/11
GRB_TIME:        65029.24 SOD {18:03:49.24} UT
TRIGGER_INDEX:   453
GRB_PHI:         -24.81 [deg]
GRB_THETA:        22.47 [deg]
DELTA_TIME:      -24.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.00 [sigma]
IMAGE_SIGNIF:    8.58 [sigma]
LC_URL:          sw00813721000msb.lc
SUN_POSTN:       351.84d {+23h 27m 22s}   -3.52d {-03d 31' 13"}
SUN_DIST:         51.76 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.85d {+19h 07m 23s}  -19.96d {-19d 57' 49"}
MOON_DIST:        66.27 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.54,-61.79 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      333.29,-49.52 [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 = 178.26,-5.60 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:08:30 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.431d {+00h 13m 44s} (J2000)
POINT_DEC:       -54.456d {-54d 27' 22"} (J2000)
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65304.51 SOD {18:08:24.51} UT,   275.3 [sec] since BAT Trigger Time
COUNTS:          10    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        3    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:     Sun 11 Mar 18 18:12:21 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.431d {+00h 13m 43s} (J2000)
POINT_DEC:       -54.457d {-54d 27' 23"} (J2000)
POINT_ROLL:      345.195d
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65309.08 SOD {18:08:29.08} UT,   279.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.359
N_STARS:         20
X_OFFSET:        332 [pixels]
Y_OFFSET:        617 [pixels]
X_MAX:           1291 [pixels]
Y_MAX:           1576 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    11
SL_URL:          sw00813721000msufc0279.fits
SUN_POSTN:       351.84d {+23h 27m 22s}   -3.52d {-03d 31' 08"}
SUN_DIST:         51.74 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.89d {+19h 07m 34s}  -19.96d {-19d 57' 44"}
MOON_DIST:        66.24 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.56,-61.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      333.31,-49.50 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:12:38 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.431d {+00h 13m 43s} (J2000)
POINT_DEC:       -54.457d {-54d 27' 23"} (J2000)
POINT_ROLL:      345.195d
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65309.08 SOD {18:08:29.08} UT,   279.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.359
N_STARS:         20
X_OFFSET:        332 [pixels]
Y_OFFSET:        617 [pixels]
X_MAX:           1291 [pixels]
Y_MAX:           1576 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    11
SL_URL:          sw00813721000msufc0279.fits
SUN_POSTN:       351.84d {+23h 27m 22s}   -3.52d {-03d 31' 08"}
SUN_DIST:         51.74 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.89d {+19h 07m 34s}  -19.96d {-19d 57' 43"}
MOON_DIST:        66.24 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.56,-61.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      333.31,-49.50 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:12:47 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     813721,   Seg_Num: 0
GRB_RA:            3.3903d {+00h 13m 33.67s} (J2000),
                   3.6147d {+00h 14m 27.53s} (current),
                   2.7709d {+00h 11m 05.00s} (1950)
GRB_DEC:         -54.4916d {-54d 29' 29.7"} (J2000),
                 -54.3905d {-54d 23' 25.8"} (current),
                 -54.7696d {-54d 46' 10.5"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65329.00 SOD {18:08:49.00} UT,   299.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       351.84d {+23h 27m 22s}   -3.52d {-03d 31' 07"}
SUN_DIST:         51.77 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.89d {+19h 07m 35s}  -19.96d {-19d 57' 43"}
MOON_DIST:        66.22 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.59,-61.77 [deg] galactic lon,lat of the burst
ECL_COORDS:      333.25,-49.51 [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:     Sun 11 Mar 18 18:13:52 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.431d {+00h 13m 43s} (J2000)
POINT_DEC:       -54.457d {-54d 27' 23"} (J2000)
ROLL:            345.195d
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65309.08 SOD {18:08:29.08} UT,   279.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     542484529
X_OFFSET:        651 [pixels]
Y_OFFSET:        936 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       811
Y_GRB_POS:       1096
BINNING_INDEX:   1
IM_URL:          sw00813721000msuni0300.fits
SUN_POSTN:       351.84d {+23h 27m 23s}   -3.52d {-03d 31' 06"}
SUN_DIST:         51.74 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.90d {+19h 07m 37s}  -19.96d {-19d 57' 42"}
MOON_DIST:        66.24 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.56,-61.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      333.31,-49.50 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:14:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.431d {+00h 13m 43s} (J2000)
POINT_DEC:       -54.457d {-54d 27' 23"} (J2000)
ROLL:            345.195d
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65309.08 SOD {18:08:29.08} UT,   279.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     542484529
X_OFFSET:        651 [pixels]
Y_OFFSET:        936 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       811
Y_GRB_POS:       1096
BINNING_INDEX:   1
IM_URL:          sw00813721000msuni0300.fits
SUN_POSTN:       351.84d {+23h 27m 23s}   -3.52d {-03d 31' 06"}
SUN_DIST:         51.74 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.91d {+19h 07m 37s}  -19.96d {-19d 57' 42"}
MOON_DIST:        66.24 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.56,-61.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      333.31,-49.50 [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 #22468
K. L. Page (U Leicester), A. Deich (PSU), S. W. K Emery (UCL-MSSL), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 18:03:49 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180311A (trigger=813721). Swift slewed to the burst after a brief delay to clear the Earth limb observing contraint. The BAT on-board calculated location is RA, Dec 3.433, -54.479 which is
```
   RA(J2000) = 00h 13m 44s
   Dec(J2000) = -54d 28' 43"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex peak structure with a duration of about 30 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~4 sec after the trigger.
The XRT began observing the field at 18:08:24.5 UT, 275.3 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 3.39027, -54.49162 which is equivalent to:
```
   RA(J2000)  = 00h 13m 33.66s
   Dec(J2000) = -54d 29' 29.8"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 100 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.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.59 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.9 (+3.32/-2.86) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 279 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 26% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:21:04 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.427d {+00h 13m 43s} (J2000)
POINT_DEC:       -54.458d {-54d 27' 26"} (J2000)
POINT_ROLL:      345.200d
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65888.33 SOD {18:18:08.33} UT,   859.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.964
N_STARS:         64
X_OFFSET:        92 [pixels]
Y_OFFSET:        377 [pixels]
X_MAX:           1531 [pixels]
Y_MAX:           1816 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    9
SL_URL:          sw00813721000msufc0859.fits
SUN_POSTN:       351.85d {+23h 27m 24s}   -3.52d {-03d 31' 00"}
SUN_DIST:         51.74 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.97d {+19h 07m 52s}  -19.96d {-19d 57' 34"}
MOON_DIST:        66.20 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.57,-61.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      333.31,-49.50 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:21:19 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.427d {+00h 13m 43s} (J2000)
POINT_DEC:       -54.458d {-54d 27' 26"} (J2000)
POINT_ROLL:      345.200d
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65888.33 SOD {18:18:08.33} UT,   859.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.964
N_STARS:         64
X_OFFSET:        92 [pixels]
Y_OFFSET:        377 [pixels]
X_MAX:           1531 [pixels]
Y_MAX:           1816 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    9
SL_URL:          sw00813721000msufc0859.fits
SUN_POSTN:       351.85d {+23h 27m 24s}   -3.52d {-03d 30' 59"}
SUN_DIST:         51.74 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.97d {+19h 07m 53s}  -19.96d {-19d 57' 34"}
MOON_DIST:        66.20 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.57,-61.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      333.31,-49.50 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:21:39 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     813721,   Seg_Num: 0
GRB_RA:            3.3875d {+00h 13m 33.00s} (J2000),
                   3.6119d {+00h 14m 26.86s} (current),
                   2.7680d {+00h 11m 04.33s} (1950)
GRB_DEC:         -54.4913d {-54d 29' 28.6"} (J2000),
                 -54.3902d {-54d 23' 24.7"} (current),
                 -54.7693d {-54d 46' 09.4"} (1950)
GRB_ERROR:       2.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65329.00 SOD {18:08:49.00} UT,   299.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       351.85d {+23h 27m 24s}   -3.52d {-03d 30' 59"}
SUN_DIST:         51.77 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.97d {+19h 07m 53s}  -19.96d {-19d 57' 33"}
MOON_DIST:        66.17 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.59,-61.77 [deg] galactic lon,lat of the burst
ECL_COORDS:      333.24,-49.51 [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:     Sun 11 Mar 18 18:22:30 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.427d {+00h 13m 43s} (J2000)
POINT_DEC:       -54.458d {-54d 27' 26"} (J2000)
ROLL:            345.200d
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65888.33 SOD {18:18:08.33} UT,   859.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     542485108
X_OFFSET:        651 [pixels]
Y_OFFSET:        936 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       811
Y_GRB_POS:       1096
BINNING_INDEX:   1
IM_URL:          sw00813721000msuni0880.fits
SUN_POSTN:       351.85d {+23h 27m 24s}   -3.52d {-03d 30' 58"}
SUN_DIST:         51.74 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.98d {+19h 07m 55s}  -19.96d {-19d 57' 32"}
MOON_DIST:        66.19 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.57,-61.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      333.31,-49.50 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Mar 18 18:22:36 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     813721,   Seg_Num: 0
POINT_RA:          3.427d {+00h 13m 43s} (J2000)
POINT_DEC:       -54.458d {-54d 27' 26"} (J2000)
ROLL:            345.200d
IMG_START_DATE:  18188 TJD;    70 DOY;   18/03/11
IMG_START_TIME:  65888.33 SOD {18:18:08.33} UT,   859.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     542485108
X_OFFSET:        651 [pixels]
Y_OFFSET:        936 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       811
Y_GRB_POS:       1096
BINNING_INDEX:   1
IM_URL:          sw00813721000msuni0880.fits
SUN_POSTN:       351.85d {+23h 27m 24s}   -3.52d {-03d 30' 58"}
SUN_DIST:         51.74 [deg]   Sun_angle= -0.8 [hr] (East of Sun)
MOON_POSTN:      286.98d {+19h 07m 55s}  -19.96d {-19d 57' 32"}
MOON_DIST:        66.19 [deg]
MOON_ILLUM:      29 [%]
GAL_COORDS:      314.57,-61.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      333.31,-49.50 [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 #22469
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 180311A, we find an enhanced XRT position of the afterglow: RA, Dec: 3.3872, -54.4914 which is equivalent to:
```
   RA (J2000)  = 00 13 32.93
   Dec (J2000) = -54 29 29.0
```
with an uncertainty of 2.1 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/813721.
Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular #22470
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 3908 s of XRT Photon Counting mode data and 5 UVOT images for GRB 180311A, 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 = 3.38761, -54.49145 which is equivalent to:
```
RA (J2000): 00h 13m 33.03s
Dec (J2000): -54d 29' 29.2"
```
with an uncertainty of 1.7 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 #22473
A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB) and K.L. Page report on behalf of the Swift-XRT team:
We have analysed 8.3 ks of XRT data for GRB 180311A (Page et al. GCN Circ. 22468), from 284 s to 20.1 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 22469).
The light curve can be modelled with an initial power-law decay with an index of alpha=3.1 (+0.9, -0.6), followed by a break at T+636 s to an alpha of 0.57 (+0.10, -0.09).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.07 (+0.20, -0.19). The best-fitting absorption column is 5.5 (+4.3, -3.7) x 10^20 cm^-2, in excess of the Galactic value of 1.6 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.1 x 10^-11 (3.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     5.5 (+4.3, -3.7) x 10^20 cm^-2
Galactic foreground: 1.6 x 10^20 cm^-2
Excess significance: 1.7 sigma
Photon index:	     2.07 (+0.20, -0.19)
```
If the light curve continues to decay with a power-law decay index of 0.57, the count rate at T+24 hours will be 0.012 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.6 x 10^-13 (4.2 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/00813721.
This circular is an official product of the Swift-XRT team.
GCN Circular #22474
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), K. L. Page (U Leicester), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180311A (trigger #813721) (Page et al., GCN Circ. 22468). The BAT ground-calculated position is RA, Dec = 3.379, -54.491 deg which is
```
  RA(J2000)  =  00h 13m 31.0s
  Dec(J2000) = -54d 29' 26.6"
```
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 94%.
The mask-weighted light curve shows a single-peaked structure that starts at ~ T0, peaks at ~T+3 s, and ends at ~T+26 s. T90 (15-350 keV) is 23.0 +- 8.7 sec (estimated error including systematics).
The time-averaged spectrum from T-0.2 to T+26.6 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.78 +- 0.29. The fluence in the 15-150 keV band is 3.3 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+2.88 sec in the 15-150 keV band is 0.6 +- 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/813721/BA/
GCN Circular #22475
F. E. Marshall (NASA/GSFC) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180311A 280 s after the BAT trigger (Page et al., GCN Circ. 22468). No optical afterglow consistent with the enhanced XRT position (Goad et al. GCN Circ. 22470) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           280          430          147         >20.3
white              280         6742          589         >21.2
v                  437         7155          333         >19.4
b                  536         8600          488         >20.9
u                  511         7770          561         >20.5
w1                 486         7565          330         >20.2
m2                7160         7360          197         >20.3
w2                1187         6950          255         >20.5
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).

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Jochen Greiner, last update: 12-Mar-2018 [Disclaimer]