Gamma-ray Burst 180727A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 27 Jul 18 14:15:52 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     554393733
GRB_RA:           13.017d {+00h 52m 04s} (J2000),
                  13.218d {+00h 52m 52s} (current),
                  12.474d {+00h 49m 54s} (1950)
GRB_DEC:         -57.633d {-57d 37' 59"} (J2000),
                 -57.533d {-57d 31' 56"} (current),
                 -57.905d {-57d 54' 16"} (1950)
GRB_ERROR:       11.67 [deg radius, statistical plus systematic]
GRB_INTEN:       181 [cnts/sec]
DATA_SIGNIF:     8.20 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        18326 TJD;   208 DOY;   18/07/27
GRB_TIME:        51328.81 SOD {14:15:28.81} UT
GRB_PHI:          99.00 [deg]
GRB_THETA:        60.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      1.69
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      85%  GRB
2nd_MOST_LIKELY:  14%  Generic SGR
DETECTORS:       0,1,0, 0,0,0, 0,0,0, 1,0,0, 0,0,
SUN_POSTN:       126.85d {+08h 27m 24s}  +19.13d {+19d 07' 53"}
SUN_DIST:        118.67 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:      303.96d {+20h 15m 52s}  -19.37d {-19d 22' 26"}
MOON_DIST:        62.66 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      302.77,-59.49 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      336.63,-55.38 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2018/bn180727594/quicklook/glg_lc_medres34_bn180727594.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 140.55,2.05 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 27 Jul 18 14:16:06 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      59
TRIGGER_NUM:     554393733
GRB_RA:           14.490d {+00h 57m 58s} (J2000),
                  14.695d {+00h 58m 47s} (current),
                  13.937d {+00h 55m 45s} (1950)
GRB_DEC:         -51.740d {-51d 44' 23"} (J2000),
                 -51.640d {-51d 38' 23"} (current),
                 -52.010d {-52d 00' 35"} (1950)
GRB_ERROR:       6.67 [deg radius, statistical only]
DATA_SIGNIF:     9.00 [sigma]
DATA_INTERVAL:   1.024 [sec] 
GRB_DATE:        18326 TJD;   208 DOY;   18/07/27
GRB_TIME:        51328.81 SOD {14:15:28.81} UT
GRB_PHI:         104.00 [deg]
GRB_THETA:        64.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4153 (Gnd S/W Version number)
SUN_POSTN:       126.85d {+08h 27m 24s}  +19.13d {+19d 07' 53"}
SUN_DIST:        118.56 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      303.97d {+20h 15m 52s}  -19.37d {-19d 22' 25"}  
MOON_DIST:        63.04 [deg] 
MOON_ILLUM:      100 [%]
GAL_COORDS:      300.51,-65.36 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      344.15,-51.45 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2018/bn180727594/quicklook/glg_lc_medres34_bn180727594.gif
POS_MAP_URL:      http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_554393733.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.
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.

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 27 Jul 18 14:16:51 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.678d {+23h 06m 43s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 58"} (J2000)
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51400.38 SOD {14:16:40.38} UT
COUNTS:          11    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.

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 27 Jul 18 14:19:42 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.679d {+23h 06m 43s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 57"} (J2000)
POINT_ROLL:      129.511d
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51404.95 SOD {14:16:44.95} UT
FILTER:          10, White
BKG_MEAN:        4.065
N_STARS:         19
X_OFFSET:        404 [pixels]
Y_OFFSET:        681 [pixels]
X_MAX:           1363 [pixels]
Y_MAX:           1640 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    9
SL_URL:          sw00850231000msufc554393804.fits
SUN_POSTN:       126.85d {+08h 27m 24s}  +19.13d {+19d 07' 51"}
SUN_DIST:        128.34 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.00d {+20h 16m 00s}  -19.37d {-19d 22' 11"}
MOON_DIST:        52.47 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.12,-50.20 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      314.38,-50.94 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 27 Jul 18 14:20:11 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.679d {+23h 06m 43s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 57"} (J2000)
POINT_ROLL:      129.511d
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51404.95 SOD {14:16:44.95} UT
FILTER:          10, White
BKG_MEAN:        4.065
N_STARS:         19
X_OFFSET:        404 [pixels]
Y_OFFSET:        681 [pixels]
X_MAX:           1363 [pixels]
Y_MAX:           1640 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    9
SL_URL:          sw00850231000msufc554393804.fits
SUN_POSTN:       126.85d {+08h 27m 24s}  +19.13d {+19d 07' 51"}
SUN_DIST:        128.34 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.00d {+20h 16m 01s}  -19.37d {-19d 22' 09"}
MOON_DIST:        52.47 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.12,-50.20 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      314.38,-50.94 [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 27 Jul 18 14:22:35 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.679d {+23h 06m 43s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 57"} (J2000)
ROLL:            129.511d
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51404.95 SOD {14:16:44.95} UT
FILTER:          10, White
EXPOSURE_ID:     554393826
X_OFFSET:        723 [pixels]
Y_OFFSET:        1000 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       883
Y_GRB_POS:       1160
BINNING_INDEX:   1
IM_URL:          sw00850231000msuni554393826.fits
SUN_POSTN:       126.85d {+08h 27m 25s}  +19.13d {+19d 07' 49"}
SUN_DIST:        128.34 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.02d {+20h 16m 06s}  -19.37d {-19d 22' 00"}
MOON_DIST:        52.46 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.12,-50.20 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      314.38,-50.94 [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 27 Jul 18 14:22:46 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.679d {+23h 06m 43s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 57"} (J2000)
ROLL:            129.511d
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51404.95 SOD {14:16:44.95} UT
FILTER:          10, White
EXPOSURE_ID:     554393826
X_OFFSET:        723 [pixels]
Y_OFFSET:        1000 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       883
Y_GRB_POS:       1160
BINNING_INDEX:   1
IM_URL:          sw00850231000msuni554393826.fits
SUN_POSTN:       126.85d {+08h 27m 25s}  +19.13d {+19d 07' 49"}
SUN_DIST:        128.34 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.02d {+20h 16m 06s}  -19.37d {-19d 22' 00"}
MOON_DIST:        52.46 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.12,-50.20 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      314.38,-50.94 [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 27 Jul 18 14:23:55 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.683d {+23h 06m 44s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 58"} (J2000)
POINT_ROLL:      129.507d
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51618.45 SOD {14:20:18.45} UT
FILTER:          7, U
BKG_MEAN:        0.107
N_STARS:         15
X_OFFSET:        164 [pixels]
Y_OFFSET:        441 [pixels]
X_MAX:           1603 [pixels]
Y_MAX:           1880 [pixels]
DET_THRESH:      4
PHOTO_THRESH:    2
SL_URL:          sw00850231000msufc554394018.fits
SUN_POSTN:       126.85d {+08h 27m 25s}  +19.13d {+19d 07' 48"}
SUN_DIST:        128.34 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.03d {+20h 16m 08s}  -19.37d {-19d 21' 55"}
MOON_DIST:        52.46 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.12,-50.20 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      314.38,-50.94 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 27 Jul 18 14:24:14 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.683d {+23h 06m 44s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 58"} (J2000)
POINT_ROLL:      129.507d
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51618.45 SOD {14:20:18.45} UT
FILTER:          7, U
BKG_MEAN:        0.107
N_STARS:         15
X_OFFSET:        164 [pixels]
Y_OFFSET:        441 [pixels]
X_MAX:           1603 [pixels]
Y_MAX:           1880 [pixels]
DET_THRESH:      4
PHOTO_THRESH:    2
SL_URL:          sw00850231000msufc554394018.fits
SUN_POSTN:       126.85d {+08h 27m 25s}  +19.13d {+19d 07' 48"}
SUN_DIST:        128.34 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.04d {+20h 16m 09s}  -19.37d {-19d 21' 53"}
MOON_DIST:        52.46 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.12,-50.20 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      314.38,-50.94 [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 27 Jul 18 14:25:05 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.683d {+23h 06m 44s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 58"} (J2000)
ROLL:            129.507d
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51618.45 SOD {14:20:18.45} UT
FILTER:          7, U
EXPOSURE_ID:     554394039
X_OFFSET:        723 [pixels]
Y_OFFSET:        1000 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       883
Y_GRB_POS:       1160
BINNING_INDEX:   1
IM_URL:          sw00850231000msuni554394040.fits
SUN_POSTN:       126.85d {+08h 27m 25s}  +19.13d {+19d 07' 48"}
SUN_DIST:        128.34 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.04d {+20h 16m 11s}  -19.36d {-19d 21' 50"}
MOON_DIST:        52.46 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.12,-50.20 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      314.38,-50.94 [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 27 Jul 18 14:25:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     850231,   Seg_Num: 0
POINT_RA:        346.683d {+23h 06m 44s} (J2000)
POINT_DEC:       -63.066d {-63d 03' 58"} (J2000)
ROLL:            129.507d
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51618.45 SOD {14:20:18.45} UT
FILTER:          7, U
EXPOSURE_ID:     554394039
X_OFFSET:        723 [pixels]
Y_OFFSET:        1000 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       883
Y_GRB_POS:       1160
BINNING_INDEX:   1
IM_URL:          sw00850231000msuni554394040.fits
SUN_POSTN:       126.85d {+08h 27m 25s}  +19.13d {+19d 07' 48"}
SUN_DIST:        128.34 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.05d {+20h 16m 11s}  -19.36d {-19d 21' 49"}
MOON_DIST:        52.46 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.12,-50.20 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      314.38,-50.94 [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 27 Jul 18 14:31:54 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     850231,   Seg_Num: 0
GRB_RA:          346.6653d {+23h 06m 39.67s} (J2000),
                 346.9495d {+23h 07m 47.88s} (current),
                 345.8942d {+23h 03m 34.59s} (1950)
GRB_DEC:         -63.0505d {-63d 03' 01.7"} (J2000),
                 -62.9499d {-62d 56' 59.4"} (current),
                 -63.3210d {-63d 19' 15.4"} (1950)
GRB_ERROR:       3.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18326 TJD;   208 DOY;   18/07/27
IMG_START_TIME:  51430.00 SOD {14:17:10.00} UT
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       126.86d {+08h 27m 26s}  +19.13d {+19d 07' 44"}
SUN_DIST:        128.36 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:      304.10d {+20h 16m 25s}  -19.36d {-19d 21' 23"}
MOON_DIST:        52.43 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      321.15,-50.21 [deg] galactic lon,lat of the burst
ECL_COORDS:      314.39,-50.92 [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 Circular #23043
A. P. Beardmore (U Leicester), S. B. Cenko (GSFC), P. A. Evans (U Leicester), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU), M. H. Siegel (PSU), R. L. C. Starling (U Leicester) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 14:15:28 UT, the Swift Burst Alert Telescope triggered and located GRB180727A (Trigger #850231). Due to a telemetry gap, very little BAT information is immediately available. The BAT light curve showed a single-peaked structure with a duration of about 1.5 sec. The peak count rate was ~5500 counts/sec (15-350 keV), at ~0 sec after the trigger. The burst does not seem to show significant emission above 100 keV. The full BAT information will be available after the next ground downlink.
Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 346.66536, -63.05052 which is equivalent to:
```
   RA(J2000)  = 23h 06m 39.69s
   Dec(J2000) = -63d 03' 01.9"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment).
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (2.10 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.5 (+3.98/-2.45) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the white filter. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.2 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 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02.
We note this GRB was also detected by the GBM on Fermi, and their automated light curve analysis indicates it is likely to be a short GRB.
Burst Advocate for this burst is A. P. Beardmore (apb 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/too.html.)
GCN Circular #23044
P. Veres (UAH) reports on behalf of the Fermi GBM Team:
"At 14:15:28.81 UT on 27 July 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180727A (trigger 554393733 / 180727594) which was also detected by Swift (Beardmore et al., GCN 23043). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 46 degrees.
The GBM light curve consists of a single pulse with a duration (T90) of about 1.1 s (50-300 keV).
The time-averaged spectrum from T0-0.19 s to T0+0.83 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is 0.14 +/- 0.28 and the cutoff energy, parameterized as Epeak, is 69 +/- 4 keV.
The event fluence (10-1000 keV) in this time interval is (3.32 +/- 0.18)E-7 erg/cm^2. The 64-msec peak photon flux measured starting from T0+0.45 s in the 10-1000 keV band is 7.2 +/- 1.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #23045
V. D'Elia (ASDC), D.N. Burrows (PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), Z. Liu (NAOC / U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB) and A.P. Beardmore report on behalf of the Swift-XRT team:
We have analysed 5.9 ks of XRT data for GRB 180727A (Beardmore et al. GCN Circ. 23043), from 58 s to 80.1 ks after the BAT trigger. The data comprise 24 s in Windowed Timing (WT) mode (the first 7 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 503 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 346.66632, -63.05183 which is equivalent to:
```
RA (J2000): 23h 06m 39.92s
Dec(J2000): -63d 03' 06.6"
```
with an uncertainty of 1.7 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay index of alpha=2.4 (+0.3, -0.4).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+/-0.4). The best-fitting absorption column is 2.1 (+1.8, -1.4) x 10^21 cm^-2, in excess of the Galactic value of 2.1 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 3.9 x 10^-11 (5.0 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.1 (+1.8, -1.4) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^20 cm^-2
Excess significance: 2.2 sigma
Photon index:	     1.9 (+/-0.4)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00850231.
This circular is an official product of the Swift-XRT team.
GCN Circular #23047
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), 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+200 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180727A (trigger #850231) (Beardmore et al., GCN Circ. 23043). The BAT ground-calculated position is RA, Dec = 346.639, -63.066 deg which is
```
    RA(J2000)  =  23h 06m 33.3s
    Dec(J2000) = -63d 03' 57.9"
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 85%.
The mask-weighted light curve shows a single peak of duration ~1 second, peaking at T+0 sec. T90 (15-350 keV) is 1.1 +- 0.2 sec (estimated error including systematics).
The time-averaged spectrum from T-0.1 to T+1.3 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.59 +- 0.51, and Epeak of 67.6 +- 14.8 keV (chi squared 43.23 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.7 +- 0.2 x 10^-7 erg/cm2 and the 1-sec peak flux measured from T-0.05 sec in the 15-150 keV band is 3.6 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.60 +- 0.11 (chi squared 57.46 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
The duration and hardness of this burst are consistent with the general BAT short GRB distribution.
The results of the batgrbpoduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/850231/BA/
GCN Circular #23062
F. E. Marshall (NASA/GSFC) and A. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180727A 77 s after the BAT trigger (Beardmore et al., GCN Circ. 23043). No optical afterglow consistent with the enhanced XRT position (D'Elia et al., GCN Circ. 23045) 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) exposures and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            77          227          147         >20.9
u_FC               290          303           12         >18.4
white             4280         5915          393         >21.7
v                 4690         6312          379         >19.6
b                 4075         5710          393         >21.2
u                 5305         5505          197         >20.3
uvw1              5101         5301          197         >20.0
uvm2              4895         5095          197         >21.0
uvw2              4485         6122          393         >21.4
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #23072
J. P. Norris (BSU), Y. Kawakubo (AGU), T. Sakamoto (AGU), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), A. Y. Lien (GSFC/UMBC)
We report the spectral lag analysis for GRB 180727A (Beardmore et al., GCN Circ. 23043; Lien et al., GCN Circ. 23047) based on the BAT data. The lag analysis finds a lag of 80 +- 27 ms for the 50-100 keV to 15-25 keV band. Despite the short T90 duration (1.1 +- 0.2 s), the lag value is consistent with that of long GRBs.
photometric redshift z = 1.95 +0.49 -0.57
of host-galaxy: A. E. Nugent et al. 2022, ApJ, 940, 57

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Jochen Greiner, last update: 12-Jan-2023 [Disclaimer]