Gamma-ray Burst 120821A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Tue 21 Aug 12 13:23:49 UT
NOTICE_TYPE:    INTEGRAL Wakeup
TRIGGER_NUM:    6626,   Sub_Num: 1
GRB_RA:         255.2658d {+17h 01m 04s} (J2000),
                255.4859d {+17h 01m 57s} (current),
                254.3961d {+16h 57m 35s} (1950)
GRB_DEC:        -40.5016d {-40d 30' 05"} (J2000),
                -40.5194d {-40d 31' 09"} (current),
                -40.4288d {-40d 25' 43"} (1950)
GRB_ERROR:      3.23 [arcmin, radius, statistical only]
GRB_INTEN:      8.44 [sigma]
GRB_TIME:       48225.17 SOD {13:23:45.17} UT
GRB_DATE:       16160 TJD;   234 DOY;   12/08/21
SC_RA:          251.43 [deg] (J2000)
SC_DEC:         -43.08 [deg] (J2000)
SUN_POSTN:      151.02d {+10h 04m 05s}  +11.86d {+11d 51' 43"}
SUN_DIST:       108.63 [deg]   Sun_angle= -7.0 [hr] (East of Sun)
MOON_POSTN:     196.35d {+13h 05m 25s}  -10.64d {-10d 38' 06"}
MOON_DIST:       59.79 [deg]
GAL_COORDS:     345.31,  0.99 [deg] galactic lon,lat of the burst
ECL_COORDS:     258.29,-17.66 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Time_Scale=0.1599 and Time_Error=2.0000.  
COMMENTS:       Possibly real GRB event

red DSS finding chart ps-file

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Tue 21 Aug 12 13:23:55 UT
NOTICE_TYPE:    INTEGRAL Refined
TRIGGER_NUM:    6626,   Sub_Num: 2
GRB_RA:         255.2852d {+17h 01m 08s} (J2000),
                255.5053d {+17h 02m 01s} (current),
                254.4153d {+16h 57m 40s} (1950)
GRB_DEC:        -40.5188d {-40d 31' 07"} (J2000),
                -40.5365d {-40d 32' 10"} (current),
                -40.4460d {-40d 26' 45"} (1950)
GRB_ERROR:      2.67 [arcmin, radius, statistical only]
GRB_INTEN:      18.29 [sigma]
GRB_TIME:       48227.16 SOD {13:23:47.16} UT
GRB_DATE:       16160 TJD;   234 DOY;   12/08/21
SC_RA:          251.43 [deg] (J2000)
SC_DEC:         -43.08 [deg] (J2000)
SUN_POSTN:      151.02d {+10h 04m 05s}  +11.86d {+11d 51' 43"}
SUN_DIST:       108.64 [deg]   Sun_angle= -7.0 [hr] (East of Sun)
MOON_POSTN:     196.36d {+13h 05m 25s}  -10.64d {-10d 38' 07"}
MOON_DIST:       59.80 [deg]
GAL_COORDS:     345.30,  0.97 [deg] galactic lon,lat of the burst
ECL_COORDS:     258.31,-17.67 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Time_Scale=1.2799 and Time_Error=8.0000.  
COMMENTS:       Possibly real GRB event

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Tue 21 Aug 12 13:26:49 UT
NOTICE_TYPE:    INTEGRAL Refined
TRIGGER_NUM:    6626,   Sub_Num: 3
GRB_RA:         255.2652d {+17h 01m 04s} (J2000),
                255.4853d {+17h 01m 56s} (current),
                254.3952d {+16h 57m 35s} (1950)
GRB_DEC:        -40.5278d {-40d 31' 39"} (J2000),
                -40.5456d {-40d 32' 43"} (current),
                -40.4550d {-40d 27' 17"} (1950)
GRB_ERROR:      2.65 [arcmin, radius, statistical only]
GRB_INTEN:      19.73 [sigma]
GRB_TIME:       48229.78 SOD {13:23:49.78} UT
GRB_DATE:       16160 TJD;   234 DOY;   12/08/21
SC_RA:          251.43 [deg] (J2000)
SC_DEC:         -43.08 [deg] (J2000)
SUN_POSTN:      151.02d {+10h 04m 05s}  +11.86d {+11d 51' 40"}
SUN_DIST:       108.62 [deg]   Sun_angle= -7.0 [hr] (East of Sun)
MOON_POSTN:     196.38d {+13h 05m 32s}  -10.64d {-10d 38' 39"}
MOON_DIST:       59.76 [deg]
GAL_COORDS:     345.29,  0.98 [deg] galactic lon,lat of the burst
ECL_COORDS:     258.29,-17.69 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Time_Scale=10.0000 and Time_Error=10.0000.  
COMMENTS:       Possibly real GRB event

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Tue 21 Aug 12 14:32:32 UT
NOTICE_TYPE:    INTEGRAL Offline
TRIGGER_NUM:    6626,   Sub_Num: 4
GRB_RA:         255.2692d {+17h 01m 05s} (J2000),
                255.4893d {+17h 01m 57s} (current),
                254.3993d {+16h 57m 36s} (1950)
GRB_DEC:        -40.5211d {-40d 31' 15"} (J2000),
                -40.5389d {-40d 32' 19"} (current),
                -40.4483d {-40d 26' 53"} (1950)
GRB_ERROR:      2.00 [arcmin, radius, statistical only]
GRB_INTEN:      19.73 [sigma]
GRB_TIME:       48229.78 SOD {13:23:49.78} UT
GRB_DATE:       16160 TJD;   234 DOY;   12/08/21
SC_RA:          251.43 [deg] (J2000)
SC_DEC:         -43.08 [deg] (J2000)
SUN_POSTN:      151.06d {+10h 04m 15s}  +11.85d {+11d 50' 45"}
SUN_DIST:       108.59 [deg]   Sun_angle= -7.0 [hr] (East of Sun)
MOON_POSTN:     197.00d {+13h 08m 01s}  -10.85d {-10d 51' 02"}
MOON_DIST:       59.17 [deg]
GAL_COORDS:     345.29,  0.98 [deg] galactic lon,lat of the burst
ECL_COORDS:     258.29,-17.68 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Time_Scale=10.0000 and Time_Error=10.0000.  
COMMENTS:       refined_coordinates_after_offline_analysis

GCN Circular #13696
S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, R.Boissay (ISDC, Versoix), and J.Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report:
a long gamma ray burst lasting about 12 s has been detected by IBAS in the IBIS/ISGRI data at 13:23:45 UT of August 21
Its refined coordinates (J2000) are:
```
RA:   255.2692    [degrees]
DEC:  -40.5212   [degrees]
```
with an uncertainty of 2 arcmin (90% c.l.).
The burst has a fluence of about 3e-7 erg/cm2 (20-200 keV)
A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html
GCN Circular #13697
P. Schady (MPE Garching), S. Klose (TLS Tautenburg) and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 120821A (INTEGRAL trigger #6266; Mereghetti et al., GCN #13696) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile).
Observations started at 23:47 UT, 10.4 hours after the GRB trigger. They were performed at an average seeing of 1.1" and at an average airmass of 1.0.
The GROND JHK observations fully covered the INTEGRAL error circle, whereas the g'r'i'z observations covered ~60% of the error circle. We do not detect any obvious new source brighter than the detection limits of DSS2 and 2MASS within the area covered by the 2arcmin INTEGRAL error circle.
GCN Circular #13698
S. R. Oates (MSSL-UCL) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120821A 15ks after the INTEGRAL trigger (Mereghetti et al., GCN Circ. 13696). No optical afterglow consistent with the INTEGRAL position (Mereghetti et al., GCN Circ. 13696) 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 initial exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

u                17059        17241          179         >20.92
w1               16153        17053          886         >21.7
m2               15246        16146          886         >21.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 25.4 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #13699
P. D'Avanzo, A. Melandri, S. Campana (INAF-OAB) report on behalf of the Swift team:
The Swift XRT observed the error circle of the INTEGRAL-detected GRB 120821A (Mereghetti et al, GCN Circ. 13696) from 15.2 to 17.2 ks after the trigger. The data comprise 2.0 ks of Photon Counting (PC) mode data. No clear afterglow candidate is detected. We note however the presence of a very faint and low-significance source within the INTEGRAL error circle (Mereghetti et al, GCN Circ. 13696) at the following position: RA, Dec =255.25762, -40.51365 which is equivalent to:
```
RA (J2000): 17h 01m 01.83s
Dec (J2000): -40d 30' 49.1"
```
with an uncertainty of 6.7 arcsec (radius, 90% confidence).
The source has a count rate of (4.5 +/- 2.1) x 10^-3 cts/s. This corresponds to an observed 0.3-10 keV flux of (2.7 +/- 1.2) x 10^-13 erg/cm2/s (assuming a typical GRB spectrum with photon spectral index of 2). If we consider the Galactic absorption in this direction (1.1 x 10^22 cm^-2; Kalberla et al. 2005) this corresponds to an unabsorbed flux of (5.5 +/- 2.5) x 10^-12 erg/cm2/s. Given the limited statistics, it is not possible to determine whether the source is fading.

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Jochen Greiner, last update: 22-Aug-2012 [Disclaimer]