//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9829 SUBJECT: GRB 090820: Fermi GBM Detection of a bright burst. DATE: 09/08/20 06:58:15 GMT FROM: Valerie Connaughton at MSFC Valerie Connaughton (UAH) reports on behalf of the Fermi GBM Team: "At 00:38:16.19 UT on 20 August 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090820027 (trigger 272421498 / 090820027). The on-ground calculated location, using the GBM trigger data, is RA = 87.7, DEC = 27.0 (J2000 degrees, equivalent to 05h 51 m, 27 d 00 '), with an uncertainty of 1.0 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 108 degrees. Although this burst was bright enough to result in a Fermi spacecraft repointing maneuver and ensuing pointed observations of the burst position, Earth avoidance constraints prevented such a maneuver until 3100 sec after the burst trigger. The light curve shows GBM triggered on a weak precursor, followed by a bright pulse beginning 30 s later and lasting a further 30 s. The time-averaged spectrum from T0+28 s to T0+60 s is best fit by a Band function with Epeak = 215 +/- 3 keV, alpha = -0.69 +/- 0.01, and beta = -2.61 - 0.05. The event fluence (8-1000 keV) in this time interval is (6.6 +/- 0.1)E-5 erg/cm^2. The 1-sec peak photon flux measured starting from T0+34 s in the 8-1000 keV band is about 58 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9830 SUBJECT: GRB 090820: MASTER-Net optical polarization observations DATE: 09/08/20 16:35:57 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov Sternberg Astronomical Institute, Moscow State University K.Ivanov, S.Yazev Irkutsk State University A. Tlatov, A.V. Parhomenko, Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalognih, T.Kopytova Ural State University, Kourovka There are 6 MASTER Very Wide Field cameras located at Kislovodsk and Irkutsk with common FOW = 2000 + 1680 square degrees (http://observ.pereplet.ru/). Four MASTER Very Wide Field Cameras located at Kislovodsk (4 Carl Zeiss Planar T* 85/1.4 ZF, 4x420 square degrees, 11 Mpx, 22" per pix with 4 polarizers) responded to the bright GRB 090820 (Fermi TRIGGER_NUM:272421498, V. Connaughton, GCN 9829), producing images beginning 9 s after the GRB Time (first alert notice). We took 1300 images with 5 sec exposition in different polarizations. Individual images have limiting magnitudes~11. Our unfiltered images are calibrated relative to Tycho stars (V) and very close to V band. Other observations are required for independ error box elaboration. The reduction is continued. The message may be cited. mailto: lipunov@sai.msu.ru //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9833 SUBJECT: GRB 090820: detection of a strong burst by RT-2 on board CORONAS PHOTON DATE: 09/08/24 06:34:33 GMT FROM: Sandip K. Chakrabarti at S.N. Bose Nat. Centre for Basic Sci. GRB 090820: RT-2 detection of a strong burst S. K. Chakrabarti, A. Nandi, D. Debnath, T. C. Kotoch (ICSP, Kolkata, India), A. R. Rao, J. P. Malkar, M. K. Hingar, V. K. Agrawal (TIFR, Mumbai, India), T. R. Chidambaram, P. Vinod, S. Sreekumar (VSSC, Thiruvananthapuram, India), Y. D. Kotov, A. S. Buslov, V. N. Yurov, V. G. Tyshkevich, A. I. Arkhangelskij, R. A.Zyatkov (MephI, Moscow, Russia) report: The RT-2 Experiment onboard the CORONAS-PHOTON satellite has detected GRB 090820 (FERMI, Trigger No.- 272421498, V. Connaughton, GCN 9829) which is triggered at T0 = 00h 38m 16s (UT) (Onboard processor switch/toggle to Flare mode from Quiet mode). The satellite was in the GOOD/LIGHT mode with Earth latitude = -64.09 and longitude = 169.11. with GOOD time observation of 600 sec starting at 00h 29m 16sec (UT) and ending at 00h 39m 16sec (UT). After 30 sec, the satellite completely entered into BAD mode of high charge particle region. The GRB light curve shows a simple profile of a strong emission peak at T0+34 sec with a weak precursor (T0). The time duration of the brightest emission is around 19 sec with ~1100 cts/sec. Both RT-2/S and RT-2/G detectors have registered this burst profile in the energy band of 15 - 1000 keV with strongest emission in the energy range of above 100 keV to 330 keV. It is also noted that the burst width decreases with the increase in the energy band, a quite natural phenomena of GRB burst profile. This analysis is preliminary. Analysis of time resolved spectral data is going on, however the light curve is available at the web-site: http://csp.res.in/rt2_files/grb090820-lc.html