//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13696 SUBJECT: GRB 120821A: a long GRB detected by INTEGRAL DATE: 12/08/21 14:47:21 GMT FROM: Sandro Mereghetti at IASF/CNR 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 ===================================================================== Sandro Mereghetti INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica - Milano Tel. +39-02-23699323 Fax +39-02-2666017 via Bassini 15, I-20133 Milano, ITALY sandro@iasf-milano.inaf.it http://www.iasf-milano.inaf.it/~sandro/personal.html =========================================================================== //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13697 SUBJECT: GRB 120821A: GROND upper limits DATE: 12/08/22 09:47:54 GMT FROM: Patricia Schady at MPE/Swift 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13698 SUBJECT: GRB 120821A: Swift/UVOT Upper Limits DATE: 12/08/22 11:38:06 GMT FROM: Samantha Oates at MSSL 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). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13699 SUBJECT: GRB 120821A: Swift/XRT observations DATE: 12/08/22 12:05:46 GMT FROM: Paolo D'Avanzo at INAF-OAB 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.