Gamma-ray Burst 160821A

(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:     Sun 21 Aug 16 20:34:49 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     709351,   Seg_Num: 0
GRB_RA:          171.248d {+11h 24m 59s} (J2000),
                 171.473d {+11h 25m 54s} (current),
                 170.567d {+11h 22m 16s} (1950)
GRB_DEC:         +42.343d {+42d 20' 35"} (J2000),
                 +42.252d {+42d 15' 05"} (current),
                 +42.618d {+42d 37' 05"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3726 [cnts]    Image_Peak=301 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       19729 [cnts]
BKG_TIME:        74055.25 SOD {20:34:15.25} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17621 TJD;   234 DOY;   16/08/21
GRB_TIME:        74070.16 SOD {20:34:30.16} UT
GRB_PHI:         -67.53 [deg]
GRB_THETA:        18.74 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     22.49 [sigma]
IMAGE_SIGNIF:    12.57 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +2 -100  +0 -81  +0 
SUN_POSTN:       151.33d {+10h 05m 18s}  +11.75d {+11d 45' 00"}
SUN_DIST:         35.19 [deg]   Sun_angle= -1.3 [hr] (East of Sun)
MOON_POSTN:       14.94d {+00h 59m 45s}   +3.42d {+03d 25' 20"}
MOON_DIST:       129.62 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      166.51, 66.74 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      153.07, 34.98 [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 = 228.94,20.42 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=493504474).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 21 Aug 16 20:34:53 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      46
TRIGGER_NUM:     493504474
GRB_RA:          168.383d {+11h 13m 32s} (J2000),
                 168.623d {+11h 14m 29s} (current),
                 167.660d {+11h 10m 38s} (1950)
GRB_DEC:         +55.017d {+55d 01' 00"} (J2000),
                 +54.926d {+54d 55' 33"} (current),
                 +55.289d {+55d 17' 21"} (1950)
GRB_ERROR:       17.32 [deg radius, statistical plus systematic]
GRB_INTEN:       97 [cnts/sec]
DATA_SIGNIF:     6.80 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        17621 TJD;   234 DOY;   16/08/21
GRB_TIME:        74070.04 SOD {20:34:30.04} UT
GRB_PHI:         210.00 [deg]
GRB_THETA:        30.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      1.09
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      91%  GRB
2nd_MOST_LIKELY:   6%  Solar Flare
DETECTORS:       0,0,0, 0,0,0, 1,1,0, 0,0,0, 0,0,
SUN_POSTN:       151.33d {+10h 05m 18s}  +11.75d {+11d 45' 00"}
SUN_DIST:         45.27 [deg]   Sun_angle= -1.2 [hr] (East of Sun)
MOON_POSTN:       14.94d {+00h 59m 45s}   +3.42d {+03d 25' 20"}
MOON_DIST:       117.73 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      148.74, 56.93 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      142.44, 44.89 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2016/bn160821857/quicklook/glg_lc_medres34_bn160821857.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 249.78,-24.27 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=709351).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 21 Aug 16 20:35:03 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      57
TRIGGER_NUM:     493504474
GRB_RA:          171.167d {+11h 24m 40s} (J2000),
                 171.396d {+11h 25m 35s} (current),
                 170.474d {+11h 21m 54s} (1950)
GRB_DEC:         +49.450d {+49d 27' 00"} (J2000),
                 +49.358d {+49d 21' 30"} (current),
                 +49.725d {+49d 43' 29"} (1950)
GRB_ERROR:       15.88 [deg radius, statistical plus systematic]
GRB_INTEN:       101 [cnts/sec]
DATA_SIGNIF:     10.60 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        17621 TJD;   234 DOY;   16/08/21
GRB_TIME:        74070.04 SOD {20:34:30.04} UT
GRB_PHI:         204.00 [deg]
GRB_THETA:        25.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.22
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      90%  GRB
2nd_MOST_LIKELY:   7%  Solar Flare
DETECTORS:       0,0,0, 0,0,0, 1,1,0, 0,0,0, 0,0,
SUN_POSTN:       151.33d {+10h 05m 18s}  +11.75d {+11d 45' 00"}
SUN_DIST:         41.11 [deg]   Sun_angle= -1.3 [hr] (East of Sun)
MOON_POSTN:       14.94d {+00h 59m 46s}   +3.42d {+03d 25' 22"}
MOON_DIST:       123.42 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      153.88, 62.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      148.49, 41.10 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2016/bn160821857/quicklook/glg_lc_medres34_bn160821857.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 249.78,-24.27 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=709351).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 21 Aug 16 20:35:07 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      56
TRIGGER_NUM:     493504474
GRB_RA:          169.850d {+11h 19m 24s} (J2000),
                 170.082d {+11h 20m 20s} (current),
                 169.152d {+11h 16m 36s} (1950)
GRB_DEC:         +48.650d {+48d 38' 60"} (J2000),
                 +48.559d {+48d 33' 32"} (current),
                 +48.924d {+48d 55' 25"} (1950)
GRB_ERROR:       10.83 [deg radius, statistical only]
DATA_SIGNIF:     8.80 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        17621 TJD;   234 DOY;   16/08/21
GRB_TIME:        74070.04 SOD {20:34:30.04} UT
GRB_PHI:         205.00 [deg]
GRB_THETA:        24.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4153 (Gnd S/W Version number)
SUN_POSTN:       151.33d {+10h 05m 18s}  +11.75d {+11d 44' 60"}
SUN_DIST:         39.98 [deg]   Sun_angle= -1.3 [hr] (East of Sun)
MOON_POSTN:       14.94d {+00h 59m 46s}   +3.42d {+03d 25' 23"}
MOON_DIST:       123.69 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      156.39, 62.07 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      148.06, 39.97 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2016/bn160821857/quicklook/glg_lc_medres34_bn160821857.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_493504474.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=709351).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 21 Aug 16 20:35:57 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     493504474
GRB_RA:          172.610d {+11h 30m 26s} (J2000),
                 172.834d {+11h 31m 20s} (current),
                 171.935d {+11h 27m 44s} (1950)
GRB_DEC:         +42.490d {+42d 29' 24"} (J2000),
                 +42.398d {+42d 23' 53"} (current),
                 +42.766d {+42d 45' 57"} (1950)
GRB_ERROR:       3.78 [deg radius, statistical only]
DATA_SIGNIF:     13.10 [sigma]
DATA_INTERVAL:   10.240 [sec]
GRB_DATE:        17621 TJD;   234 DOY;   16/08/21
GRB_TIME:        74070.04 SOD {20:34:30.04} UT
GRB_PHI:         194.00 [deg]
GRB_THETA:        19.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41531 (Gnd S/W Version number)
SUN_POSTN:       151.33d {+10h 05m 18s}  +11.75d {+11d 44' 59"}
SUN_DIST:         35.91 [deg]   Sun_angle= -1.4 [hr] (East of Sun)
MOON_POSTN:       14.95d {+00h 59m 48s}   +3.43d {+03d 25' 32"}
MOON_DIST:       129.99 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      164.71, 67.47 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      154.06, 35.59 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2016/bn160821857/quicklook/glg_lc_medres34_bn160821857.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_493504474.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.  
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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=709351).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 21 Aug 16 20:36:19 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      1
TRIGGER_NUM:     493504474
GRB_RA:          168.420d {+11h 13m 41s} (J2000),
                 168.650d {+11h 14m 36s} (current),
                 167.726d {+11h 10m 54s} (1950)
GRB_DEC:         +42.760d {+42d 45' 36"} (J2000),
                 +42.669d {+42d 40' 09"} (current),
                 +43.032d {+43d 01' 57"} (1950)
GRB_ERROR:       3.38 [deg radius, statistical only]
DATA_SIGNIF:     15.60 [sigma]
DATA_INTERVAL:   16.384 [sec]
GRB_DATE:        17621 TJD;   234 DOY;   16/08/21
GRB_TIME:        74070.04 SOD {20:34:30.04} UT
GRB_PHI:         204.00 [deg]
GRB_THETA:        18.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41531 (Gnd S/W Version number)
SUN_POSTN:       151.33d {+10h 05m 19s}  +11.75d {+11d 44' 59"}
SUN_DIST:         34.39 [deg]   Sun_angle= -1.2 [hr] (East of Sun)
MOON_POSTN:       14.95d {+00h 59m 49s}   +3.43d {+03d 25' 36"}
MOON_DIST:       128.13 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      168.34, 64.75 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      150.60, 34.35 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2016/bn160821857/quicklook/glg_lc_medres34_bn160821857.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_493504474.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.  
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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=709351).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 21 Aug 16 20:36:23 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     493504474
GRB_RA:          168.470d {+11h 13m 53s} (J2000),
                 168.700d {+11h 14m 48s} (current),
                 167.776d {+11h 11m 06s} (1950)
GRB_DEC:         +42.750d {+42d 45' 00"} (J2000),
                 +42.659d {+42d 39' 33"} (current),
                 +43.022d {+43d 01' 21"} (1950)
GRB_ERROR:       3.01 [deg radius, statistical only]
DATA_SIGNIF:     16.30 [sigma]
DATA_INTERVAL:   17.408 [sec]
GRB_DATE:        17621 TJD;   234 DOY;   16/08/21
GRB_TIME:        74070.04 SOD {20:34:30.04} UT
GRB_PHI:         204.00 [deg]
GRB_THETA:        18.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41531 (Gnd S/W Version number)
SUN_POSTN:       151.33d {+10h 05m 19s}  +11.75d {+11d 44' 59"}
SUN_DIST:         34.40 [deg]   Sun_angle= -1.2 [hr] (East of Sun)
MOON_POSTN:       14.95d {+00h 59m 49s}   +3.43d {+03d 25' 37"}
MOON_DIST:       128.16 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      168.32, 64.79 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      150.64, 34.36 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2016/bn160821857/quicklook/glg_lc_medres34_bn160821857.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_493504474.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.  
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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=709351).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 21 Aug 16 20:38:13 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     709351,   Seg_Num: 0
GRB_RA:          171.248d {+11h 24m 59s} (J2000),
                 171.473d {+11h 25m 54s} (current),
                 170.567d {+11h 22m 16s} (1950)
GRB_DEC:         +42.343d {+42d 20' 35"} (J2000),
                 +42.252d {+42d 15' 05"} (current),
                 +42.618d {+42d 37' 05"} (1950)
GRB_DATE:        17621 TJD;   234 DOY;   16/08/21
GRB_TIME:        74070.16 SOD {20:34:30.16} UT
TRIGGER_INDEX:   146
GRB_PHI:         -67.53 [deg]
GRB_THETA:        18.74 [deg]
DELTA_TIME:      -50.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     22.49 [sigma]
IMAGE_SIGNIF:    12.57 [sigma]
LC_URL:          sw00709351000msb.lc
SUN_POSTN:       151.33d {+10h 05m 19s}  +11.75d {+11d 44' 57"}
SUN_DIST:         35.19 [deg]   Sun_angle= -1.3 [hr] (East of Sun)
MOON_POSTN:       14.97d {+00h 59m 53s}   +3.43d {+03d 25' 58"}
MOON_DIST:       129.59 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:      166.51, 66.74 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      153.07, 34.98 [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 = 228.94,20.42 [deg].

GCN Circular #19830
M. H. Siegel (PSU), S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Swift Team:
At 20:34:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160821A (trigger=709351). Swift did not slew due to Sun observing constraint. The BAT on-board calculated location is RA, Dec 171.248, +42.343, which is
```
   RA(J2000)  =  11h 24m 59s
   Dec(J2000) = +42d 20' 35"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows several small peaks and then a large peak at ~T+130 sec with a total duration of at least 160 sec. The peak count rate was ~24,000 counts/sec (15-350 keV), at ~138 sec after the trigger.
Due to a Sun observing constraint, Swift cannot slew to the BAT position until 10:53 UT on 2016 September 29. There will thus be no XRT or UVOT data for this trigger before this time.
Burst Advocate for this burst is M. H. Siegel (siegel AT swift.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 Circular #19831
**J. McEnery, J. Racusin (NASA/GSFC) and Francesco Longo (INFN/Trieste) report on behalf of the Fermi-LAT team:
At 20:36:44.33 on August 21, 2016, Fermi-LAT triggered on high-energy emission from GRB 160821A, also detected by GBM (trigger 493504474/ GRB160821857), and Swift-BAT (Siegel et al., GCN 19830).
The onboard location is
RA, Dec = 172.5, 43.0 (J2000)
with an error radius of 0.5 deg (90% containment, systematic error only). This was 17 deg from the LAT boresight at the time of the trigger.
Onboard LAT GRB detections are relatively rare, and imply that this GRB is exceptionally bright at high energy gamma-rays. We strongly encourage follow-up observations.
The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo@trieste.infn.it ).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #19832
Gendre B. (UVI - Etelman Obs.), Klotz A., Turpin D., Atteia J.L. (CNRS-OMP-IRAP), Boer, M., Laugier, R. (CNRS-ARTEMIS) report:
We imaged the field of GRB 160821A detected by SWIFT (trigger 709351) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France.
The observations started 29.31min after the GRB trigger. The elevation of the field decreased from 10 degrees above horizon and weather conditions were fair.
We detect a new fading source in the error box given by SWIFT (Siegel et al., GCNC 19830) at the following position (+/- 3 arcsec):
```
RA(J2000.0) = 11h 25m 01.6s
DEC(J2000.0) +42d 20' 05"
```
OT was R~15.4 at 29.31min after GRB. Due to the brightness of the event, we encourage any follow-up.
Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction.
N.B. Galactic coordinates are lon=166.5065 lat=+66.7370 and the galactic extinction in R band is 0.1 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S.
This message may be cited.
GCN Circular #19835
M. Stanbro (UAH) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 20:34:30.04 UT on 21 August 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160821A (trigger 493504474 / 160821857), which was also detected by the Swift/BAT (Siegel et al. 2016, GCN 19830) and by the LAT (McEnery et al. 2016, GCN 19831). The GBM on-ground location is consistent with the Swift position.
The GBM light curve shows/consists of several episodes and a bright burst with a duration (T90) of about 43 s (50-300 keV). The time-averaged spectrum from T0-4.1 s to T0+194.6 s is best fit by a Band function with Epeak = 968 +/- 16 keV, alpha = -1.08 +/- 0.00, and beta = -2.38 +/- 0.03
The event fluence (10-1000 keV) in this time interval is (550.3 +/- 1.39)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+135.7 s in the 10-1000 keV band is 123.1 +/- 0.7 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #19836
M. Arimoto (Waseda U./Tokyo Tech), M. Axelsson (KTH Stockholm), F. Dirirsa (U. Johannesburg) and F. Longo (INFN/Trieste) report on behalf of the Fermi-LAT team: We report the on-ground localization and analysis of GRB 160821A, which triggered an onboard LAT detection (McEnery et al., GCN 19831). All times are relative to the initial GBM trigger (Stanbro et al., GCN 19835). The best LAT on-ground location is found to be: RA, Dec = 171.3, 42.3 deg (J2000) with an error radius of 0.08 deg (90 % containment, statistical error only). This is fully compatible with the position of the prompt emission detected by Swift/BAT (Siegel et al., GCN 19830). This was 17 deg from the LAT boresight at the time of the GBM trigger and triggered an autonomous repoint of the spacecraft.
More than 50 photons above 100 MeV and 4 photons above 1 GeV were detected within 245s, before the spacecraft entered the SAA. The GRB did not come back into the Fermi-LAT FoV until T0 + 1380s.
The LAT emission was coincident with the bright pulse observed by GBM at ~T0+135 s. The highest-energy photon is a 4.7 GeV event which is observed ~212 seconds after the GBM trigger.
The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo@trieste.infn.it).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #19840
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. H. Siegel (PSU), 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 160821A (trigger #709351) (Siegel, et al. GCN Circ. 19830). The BAT ground-calculated position is RA, Dec = 171.254, 42.345 deg which is
```
  RA(J2000)  =  11h 25m 00.9s
  Dec(J2000) = +42d 20' 43.0"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 79%.
The mask-weighted light curve shows a complex structure with many overlapping pulses that starts at ~T-3 s and extends beyond T+117s, when the the burst went out of the BAT FOV due to a pre-planned slew. The burst flux was rising during the slew, so it is possible that the BAT detector missed the peak emission. The main peak that is visible in the BAT light curve occurs at ~T+114 s.
The time-averaged spectrum from T-2.61 to T+115.17 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.52 +- 0.06. The fluence in the 15-150 keV band is 7.2 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+113.51 sec in the 15-150 keV band is 2.8 +- 0.6 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/709351/BA/
GCN Circular #19842
A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration, very bright GRB 160821A (Swift detection: Siegel et al., GCN 19830; Fermi LAT detection: McEnery et al., GCN 19831, Arimoto et al., GCN 19836; Fermi GBM observation: Stanbro et al., GCN 19835) triggered Konus-Wind at T0=74179.687 s UT (20:36:19.687).
The burst light curve shows a weak emission starting at ~T0-113 s followed by the bright main episode at ~T0. A total duration of the burst is ~320 s. The emission is seen up to ~10 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB160821_T74179/
As observed by Konus-Wind, the burst had a fluence of 1.17(-0.03,+0.03)x10^-3 erg/cm2, and a 64-ms peak flux, measured from T0+22.320 s, of 1.06(-0.13,+0.13)x10^-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+99.328 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.00(-0.02,+0.02), the high energy photon index beta = -1.99(-0.04,+0.04), the peak energy Ep = 710(-44,+47) keV (chi2 = 212/88 dof)
The spectrum near the maximum count rate (measured from T0+22.272 to T0+22.528 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.84(-0.10,+0.12), the high energy photon index beta = -1.89(-0.29,+0.17), the peak energy Ep = 1074(-326,+431) keV (chi2 = 54/57 dof)
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN Circular #19865
P. S. Marrocchesi (U of Siena), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), and the CALET collaboration:
The long-duration GRB 160821A (Siegel et al., GCN Circ. 19830; McEnery et al., GCN Circ. 19831; Stanbro et al., GCN Circ. 19835; INTEGRAL-SPI/ACS trigger #7537) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 20:36:21.91 on 21 August 2016. The burst signal was seen by all CGBM instruments. Note that the CGBM trigger time is 111 sec after the trigger time of Swift/BAT. This is because the CGBM triggered at the bright main peak of the burst (Markwardt et al. GCN Circ. 19840).
The light curve of the SGM shows a bright peak with several overlapping pulses. The emission starts from T sec, peaks at T+24 sec and ends at T+80 sec. There is a hint of the emission in the SGM light curve around the trigger time of Swift/BAT. The T90 duration measured by the SGM data is 35.1 +- 0.8 sec (40-1000 keV).
The light curve is available at
http://cgbm.calet.jp/cgbm_trigger/flight/1155846835/
The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.
GCN Circular #19867
V. Bhalerao (IUCAA), V. Kumar (IUCAA), D. Bhattacharya (IUCAA), A. R. Rao (TIFR), S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:
The bright long GRB160821A (Barthelmy et al., GCN Circ. 19830) was detected using the CsI veto detectors on Astrosat CZTI (Bhalerao et al., arXiv:1608.03408). The primary CZTI detectors were disabled as the satellite was passing through the South Atlantic Anomaly at that time.
The source was clearly detected in the 40-200 keV energy range. The light curve shows a single peak, with the strongest peak at 20:36:45.00 UT, 133 seconds after BAT Trigger at 20:34:28 UT. The time delay arises from detection of the main peak of the burst, and the timing is consistent with the Fermi LAT (McEnery et al., GCN 19831) and CALET (Marrocchesi et al., GCN 19865). The peak count rate in the CsI detectors was 11200 counts/sec above the background (four quadrants summed together), with a total of 149300 counts. The local mean background count rate was 1400 counts/sec. Using cumulative rates, we measure a T90 of 42 secs.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb . CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.
GCN Circular #19893
K. P. Mooley, T. D. Staley, R. P. Fender (Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D. Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, C. Rumsey, P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester)
The AMI Large Array triggered on the Swift alert for GRB 160821A (Siegel et al., GCN 19830) as part of the 4pisky program, and subsequent follow up observations were obtained up to 10 days post-burst. Our observations at 15 GHz on 2016 Aug 22.55, Aug 23.56, Aug 25.56, and Aug 29.56 (UT) do not reveal any transient radio source within the BAT error circle (Markwardt et al., GCN 19840), with 3sigma upper limits of 87 uJy, 108 uJy, 108 uJy, and 102 uJy respectively.
We thank the AMI staff for scheduling these observations. The AMI-GRB database is a log of all GRB follow up observations with the AMI, and is available at http://4pisky.org/ami-grb/.
GCN Circular #20007
Soulier J.-F. (Observatoire de Maisoncelles, France) repports:
I imaged the field of GRB 160821A detected by SWIFT (trigger 709351) with the Newtonian 30cm F/3.8 telescope located at the Maisoncelles observatory, France (IAU C10).
I detected the optical transcient described by Gendre et al. (GCNC 19832) at the following position (+/- 0.5 arcsec):
```
RA(J2000.0) = 11h 25m 01.83s
DEC(J2000.0) = +42d 20' 06.5"

Filter  T_start(d)   T_stop(d)  Exp(s)     R
None    0.992        1.008      1440       18.6
None    4.992        4.008      1440      >20
```
Taking account for the magnitude provided by Gendre et al. (GCNC 19832) I derived an optical decay alpha=0.78 for the first day.
Magnitudes were estimated with the nearby UCAC-4 stars and are not corrected for galactic dust extinction.

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Jochen Greiner, last update: 07-Oct-2016 [Disclaimer]