Gamma-ray Burst 180720C

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Jul 18 22:25:16 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     848932,   Seg_Num: 0
GRB_RA:          265.623d {+17h 42m 30s} (J2000),
                 265.913d {+17h 43m 39s} (current),
                 264.844d {+17h 39m 23s} (1950)
GRB_DEC:         -26.584d {-26d 35' 01"} (J2000),
                 -26.591d {-26d 35' 28"} (current),
                 -26.561d {-26d 33' 37"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4022 [cnts]    Image_Peak=228 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       22991 [cnts]
BKG_TIME:        80618.70 SOD {22:23:38.70} UT
BKG_DUR:         8 [sec]
GRB_DATE:        18319 TJD;   201 DOY;   18/07/20
GRB_TIME:        80637.64 SOD {22:23:57.64} UT
GRB_PHI:          -2.02 [deg]
GRB_THETA:        19.23 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     18.60 [sigma]
IMAGE_SIGNIF:    9.38 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +0  +0  +1 +84  +0 
SUN_POSTN:       120.25d {+08h 01m 00s}  +20.53d {+20d 31' 45"}
SUN_DIST:        148.05 [deg]   Sun_angle= -9.7 [hr] (East of Sun)
MOON_POSTN:      220.76d {+14h 43m 01s}  -10.23d {-10d 13' 51"}
MOON_DIST:        45.57 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:        1.64,  1.82 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      266.08, -3.20 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
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 = 35.97,20.39 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(4.0<100sec) coincident with the FERMI_GBM event (trignum=553818238).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 20 Jul 18 22:24:26 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     553818238
GRB_RA:          275.933d {+18h 23m 44s} (J2000),
                 276.265d {+18h 25m 04s} (current),
                 275.038d {+18h 20m 09s} (1950)
GRB_DEC:         -42.600d {-42d 36' 00"} (J2000),
                 -42.589d {-42d 35' 19"} (current),
                 -42.627d {-42d 37' 35"} (1950)
GRB_ERROR:       17.63 [deg radius, statistical plus systematic]
GRB_INTEN:       80 [cnts/sec]
DATA_SIGNIF:     7.20 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        18319 TJD;   201 DOY;   18/07/20
GRB_TIME:        80633.15 SOD {22:23:53.15} UT
GRB_PHI:         208.00 [deg]
GRB_THETA:        95.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.60
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      92%  GRB
2nd_MOST_LIKELY:   3%  Distant Particles
DETECTORS:       0,0,0, 0,0,0, 0,0,1, 0,0,1, 0,0,
SUN_POSTN:       120.25d {+08h 01m 00s}  +20.53d {+20d 31' 45"}
SUN_DIST:        150.14 [deg]   Sun_angle= -10.4 [hr] (East of Sun)
MOON_POSTN:      220.75d {+14h 43m 00s}  -10.23d {-10d 13' 43"}
MOON_DIST:        57.97 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      351.59,-13.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      274.62,-19.26 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2018/bn180720933/quicklook/glg_lc_medres34_bn180720933.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 115.15,-17.30 [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 20 Jul 18 22:24:17 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     553818238
GRB_RA:          263.450d {+17h 33m 48s} (J2000),
                 263.711d {+17h 34m 51s} (current),
                 262.748d {+17h 30m 59s} (1950)
GRB_DEC:         -12.617d {-12d 37' 00"} (J2000),
                 -12.628d {-12d 37' 41"} (current),
                 -12.583d {-12d 34' 59"} (1950)
GRB_ERROR:       18.57 [deg radius, statistical plus systematic]
GRB_INTEN:       89 [cnts/sec]
DATA_SIGNIF:     4.70 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        18319 TJD;   201 DOY;   18/07/20
GRB_TIME:        80633.15 SOD {22:23:53.15} UT
GRB_PHI:         186.00 [deg]
GRB_THETA:       120.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.00
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:     100%  Below horizon
2nd_MOST_LIKELY:   0%  n/a
DETECTORS:       0,0,0, 0,0,0, 0,0,1, 0,0,1, 0,0,
SUN_POSTN:       120.25d {+08h 01m 00s}  +20.53d {+20d 31' 45"}
SUN_DIST:        144.18 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      220.75d {+14h 42m 59s}  -10.23d {-10d 13' 41"}
MOON_DIST:        42.14 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:       12.53, 10.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      263.50, 10.67 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2018/bn180720933/quicklook/glg_lc_medres34_bn180720933.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 115.15,-17.30 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

 
TITLE:           GCN/SWIFT NOTICE 
NOTICE_DATE:     Fri 20 Jul 18 22:26:03 UT 
NOTICE_TYPE:     Swift-XRT Nack-Position 
TRIGGER_NUM:     848932,   Seg_Num: 0 
POINT_RA:        265.652d {+17h 42m 36s} (J2000) 
POINT_DEC:       -26.569d {-26d 34' 09"} (J2000) 
IMG_START_DATE:  18319 TJD;   201 DOY;   18/07/20 
IMG_START_TIME:  80734.82 SOD {22:25:34.82} UT,   97.2 [sec] since BAT Trigger Time 
COUNTS:          35    Min_needed= 20 
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec] 
PH2_ITER:        4    Max_iter_allowed= 4 
ERROR_CODE:      2 
COMMENTS:        SWIFT-XRT Nack Position.   
COMMENTS:        Algorithm did not converge; too many iterations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Jul 18 22:28:06 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     848932,   Seg_Num: 0
GRB_RA:          265.623d {+17h 42m 30s} (J2000),
                 265.913d {+17h 43m 39s} (current),
                 264.844d {+17h 39m 23s} (1950)
GRB_DEC:         -26.584d {-26d 35' 01"} (J2000),
                 -26.591d {-26d 35' 28"} (current),
                 -26.561d {-26d 33' 37"} (1950)
GRB_DATE:        18319 TJD;   201 DOY;   18/07/20
GRB_TIME:        80637.64 SOD {22:23:57.64} UT
TRIGGER_INDEX:   146
GRB_PHI:          -2.02 [deg]
GRB_THETA:        19.23 [deg]
DELTA_TIME:      26.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     18.60 [sigma]
IMAGE_SIGNIF:    9.38 [sigma]
LC_URL:          sw00848932000msb.lc
SUN_POSTN:       120.25d {+08h 01m 01s}  +20.53d {+20d 31' 43"}
SUN_DIST:        148.04 [deg]   Sun_angle= -9.7 [hr] (East of Sun)
MOON_POSTN:      220.78d {+14h 43m 07s}  -10.24d {-10d 14' 19"}
MOON_DIST:        45.54 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:        1.64,  1.82 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      266.08, -3.20 [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 = 35.97,20.39 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Jul 18 22:29:20 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     848932,   Seg_Num: 0
POINT_RA:        265.652d {+17h 42m 36s} (J2000)
POINT_DEC:       -26.569d {-26d 34' 09"} (J2000)
POINT_ROLL:      266.634d
IMG_START_DATE:  18319 TJD;   201 DOY;   18/07/20
IMG_START_TIME:  80737.86 SOD {22:25:37.86} UT,   100.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.164
N_STARS:         190
X_OFFSET:        607 [pixels]
Y_OFFSET:        383 [pixels]
X_MAX:           1566 [pixels]
Y_MAX:           1342 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00848932000msufc0100.fits
SUN_POSTN:       120.25d {+08h 01m 01s}  +20.53d {+20d 31' 43"}
SUN_DIST:        148.07 [deg]   Sun_angle= -9.7 [hr] (East of Sun)
MOON_POSTN:      220.79d {+14h 43m 10s}  -10.24d {-10d 14' 31"}
MOON_DIST:        45.56 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:        1.67,  1.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      266.11, -3.19 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Jul 18 22:29:34 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     848932,   Seg_Num: 0
POINT_RA:        265.652d {+17h 42m 36s} (J2000)
POINT_DEC:       -26.569d {-26d 34' 09"} (J2000)
POINT_ROLL:      266.634d
IMG_START_DATE:  18319 TJD;   201 DOY;   18/07/20
IMG_START_TIME:  80737.86 SOD {22:25:37.86} UT,   100.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.164
N_STARS:         190
X_OFFSET:        607 [pixels]
Y_OFFSET:        383 [pixels]
X_MAX:           1566 [pixels]
Y_MAX:           1342 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00848932000msufc0100.fits
SUN_POSTN:       120.25d {+08h 01m 01s}  +20.53d {+20d 31' 42"}
SUN_DIST:        148.07 [deg]   Sun_angle= -9.7 [hr] (East of Sun)
MOON_POSTN:      220.79d {+14h 43m 10s}  -10.24d {-10d 14' 33"}
MOON_DIST:        45.55 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:        1.67,  1.81 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      266.11, -3.19 [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 20 Jul 18 22:29:54 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     848932,   Seg_Num: 0
GRB_RA:          265.6351d {+17h 42m 32.42s} (J2000),
                 265.9244d {+17h 43m 41.86s} (current),
                 264.8555d {+17h 39m 25.32s} (1950)
GRB_DEC:         -26.6302d {-26d 37' 48.7"} (J2000),
                 -26.6378d {-26d 38' 16.0"} (current),
                 -26.6071d {-26d 36' 25.6"} (1950)
GRB_ERROR:       5.8 [arcsec radius, statistical plus systematic, 90% containment]    
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18319 TJD;   201 DOY;   18/07/20
IMG_START_TIME:  80759.00 SOD {22:25:59.00} UT,   121.4 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       120.25d {+08h 01m 01s}  +20.53d {+20d 31' 42"}
SUN_DIST:        148.05 [deg]   Sun_angle= -9.7 [hr] (East of Sun)
MOON_POSTN:      220.79d {+14h 43m 11s}  -10.24d {-10d 14' 36"}
MOON_DIST:        45.55 [deg] 
MOON_ILLUM:      62 [%] 
GAL_COORDS:        1.61,  1.79 [deg] galactic lon,lat of the burst
ECL_COORDS:      266.09, -3.25 [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 #22982
S. J. LaPorte (PSU), P. A. Evans (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. J. Moss (George Washington University), B. Sbarufatti (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 22:23:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible GRB 180720C or Galactic transient (trigger=848932). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 265.623, -26.584 which is
```
   RA(J2000) = 17h 42m 30s
   Dec(J2000) = -26d 35' 01"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 30 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 22:25:34.8 UT, 97.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 265.63486, -26.63041 which is equivalent to:
```
   RA(J2000)  = 17h 42m 32.37s
   Dec(J2000) = -26d 37' 49.5"
```
with an uncertainty of 5.7 arcseconds (radius, 90% containment). This location is 171 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.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (6.76 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.7 (+3.01/-2.29) x 10^22 cm^-2 (90% confidence).
We note that the detected source is at the edge of the reduced field of view available with the promptly down linked data. Because of that the accuracy of the position could be lower than stated.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 100 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 none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the large, but uncertain, extinction expected.
While the BAT and XRT data are consistent with a GRB, because of the proximity to the Galactic Center, at present we cannot rule out a Galactic transient nature for the source.
Burst Advocate for this burst is S. J. LaPorte (extragsam AT gmail.com). 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 #22987
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 2824 s of XRT Photon Counting mode data and 7 UVOT images for GRB 180720C, 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 = 265.63557, -26.62903 which is equivalent to:
```
RA (J2000): 17h 42m 32.54s
Dec (J2000): -26d 37' 44.5"
```
with an uncertainty of 1.9 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 #22990
O.J. Roberts (USRA/NASA) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 22:23:53.15 UT on 20 July 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 180720C (trigger 553818238 / 180720933), which was also detected by Swift (S.J. LaPorte et al. 2018, GCN 22982). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time using the Swift-XRT position is 111 degrees.
The GBM light curve consists of broad, single peak with a duration (T90) of about 23 s (50-300 keV). The time-averaged spectrum from T0-6.1 to T0+17.4 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -1.12 +/- 0.08 and the cutoff energy, parameterized as Epeak, is 583 +/- 161 keV.
The event fluence (10-1000 keV) over this time interval is (2.83 +/- 0.05)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.3 s in the 10-1000 keV band is 2.8 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #22991
C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a large collaboration report:
The 2-m robotic Liverpool Telescope automatically began observing Swift GRB 180720C (LaPorte et al. GCN 22982) on July 20, 22:28:18 UT (261 seconds after the GRB trigger time) with the RINGO3 polarimeter and the IO:O camera in the SDSS-R filter. Within the enhanced Swift-XRT error circle (Evans et al. GCN 22987) we do not find any uncatalogued object down to r'>20.4 mag at a mid time of 47 minutes post GRB with a 3x10s exposure, as calibrated against nearby Pan-STARRS objects.
GCN Circular #22992
S. R. Oates (U. Warwick) and S. J. LaPorte (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180720C 100 s after the BAT trigger (LaPorte et al., GCN Circ. 22982). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 22987) 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)         100         250          147           >20.3
white              100         5490         541           >21.0    
u (FC)             312         425          111           >19.2
u                  312         11199       1193           >20.6
v                  4263        5901         393           >19.1
b                  3646        11902       1072           >20.8
uvw1               4674        10285       1133           >20.3
uvm2               4469        6106         393           >19.7
uvw2               4058        5696         393           >19.8
```
The magnitudes in the table are not corrected for the Galactic extinction due to the significant reddening of E(B-V) = 2.11 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #23000
J. R. Cummings (CPI), S. D. Barthelmy (GSFC), H. A. Krimm (NSF/USRA), S. J. LaPorte (PSU), 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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180720C (trigger #848932) (LaPorte et al., GCN Circ. 22982). The BAT ground-calculated position is RA, Dec = 265.655, -26.634 deg which is
```
  RA(J2000)  =  17h 42m 37.1s
  Dec(J2000) = -26d 38' 02.5"
```
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%.
The mask-weighted light curve shows a main single-pulse structure that starts at ~T-20 s, peaks at ~T0, and ends at ~T+20 s. In addition, there are some weak emission prior to this main pulse, starting at ~T-150 s. T90 (15-350 keV) is 124.2 +- 32.7 sec (estimated error including systematics).
The time-averaged spectrum from T-150.52 to T+23.34 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.39 +- 0.13. The fluence in the 15-150 keV band is 2.4 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.27 sec in the 15-150 keV band is 1.1 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The temporal and spectral characteristics of this burst are consistent with those of a long GRB.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/848932/BA/
GCN Circular #23003
A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), Z. Liu (NAOC / U. Leicester) and S.J. LaPorte report on behalf of the Swift-XRT team:
We have analysed 7.2 ks of XRT data for GRB 180720C (LaPorte et al. GCN Circ. 22982), from 105 s to 69.3 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 22987).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.59 (+/-0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.1 (+0.6, -0.5). The best-fitting absorption column is 2.8 (+1.2, -1.0) x 10^22 cm^-2, in excess of the Galactic value of 6.8 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 6.7 x 10^-11 (1.7 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.8 (+1.2, -1.0) x 10^22 cm^-2
Galactic foreground: 6.8 x 10^21 cm^-2
Excess significance: 3.7 sigma
Photon index:	     2.1 (+0.6, -0.5)
```
If the light curve continues to decay with a power-law decay index of 0.59, the count rate at T+24 hours will be 6.3 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.2 x 10^-13 (1.1 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00848932.
This circular is an official product of the Swift-XRT team.
GCN Circular #23009
E. Gorbovskoy, V.Lipunov, N.Tiurina, V. Lipunov, V.Kornilov, A.Kuznetsov, V.Chazov, I. Gorbunov, D.Zimnukhov, D.Kuvshinov, P.Balanutsa, V.Vladimirov, D.Vlasenko Lomonosov Moscow State University,SAI
D. Buckley, South African Astronomical Observatory (SAAO)
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias (IAC)
A. Tlatov, V.Senik, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
R. Podesta, F. Podesta, C. Lopez, C.Francile Observatorio Astronomico Felix Aguilar (OAFA)
H.Levato, Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
O. Gres, N.M.Budnev , Yu.Ishmuhametova Irkutsk State University (ISU)
A. Gabovich, V. Yurkov, Yu. Sergienko Blagoveschensk Educational State University (BSPU)
MASTER-Kislovodsk robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the GRB180720C 21 sec after notice time and 102 sec after trigger time at 2018-07-20 22:25:39 UT.
MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) was pointed to the GRB180720C 258 sec after notice time and 1668 sec after trigger time at 2018-07-20 22:56:57 UT.
MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the GRB180720C 30 sec after notice time and 111 sec after trigger time at 2018-07-20 22:25:48 UT.
MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the GRB180720C 21 sec after notice time and 102 sec after trigger time at 2018-07-20 22:25:39 UT.
We have a number of images on this observatories. The observations made very close to Galactic center (~ 1 degree). The upper limit on observaroties is about 18 mag.
The message may be cited.
GCN Circular #23016
C. Perez del Pulgar and A. Castellon (Univ. de Malaga), E. Fernandez-Garcia, Y. Hu, I. Carrasco and A. J. Castro-Tirado (IAA-CSIC), on behalf of a larger collaboration, report:
The 60cm BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Spain) automatically responded in 53s (and 132s after the GRB onset) to the Swift trigger of GRB 180720C (LaPorte et al., GCNC 22982). The first image (10s exposure, unfiltered) was obtained at 22:26:09 UT. At the position of the Swift X-ray afterglow (Evans et al. GCNC 22987), no optical afterglow is detected down 18 mag in this crowded field in the direction of the Galactic Center (i.e. high extinction towards the source is very likely present). This is consistent with the limits reported by Guidorzi et al. (GCNC 22991), Oates et al. (GCNC 22992) and Gorbovskoy et al. (GCNC 23009).
The message may be cited.

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Jochen Greiner, last update: 22-Jul-2018 [Disclaimer]