//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12288 SUBJECT: GRB 110820A: Swift detection of a burst DATE: 11/08/20 17:55:18 GMT FROM: Scott Barthelmy at NASA/GSFC E. Troja (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU), E. Sonbas (GSFC/USRA/Adiyaman Univ.) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 17:38:27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110820A (trigger=501095). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 343.335, +70.305 which is RA(J2000) = 22h 53m 20s Dec(J2000) = +70d 18' 20" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 10 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 17:39:46.8 UT, 79.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 343.1911, 70.2974 which is equivalent to: RA(J2000) = 22h 52m 45.86s Dec(J2000) = +70d 17' 50.5" with an uncertainty of 2.3 arcseconds (radius, 90% containment). This location is 177 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 consistent with the Galactic value of 3.34 x 10^21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 250 seconds with the U filter starting 139 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. Data from the list of sources generated on-board are not available at this time. No correction has been made for the expected extinction corresponding to E(B-V) of 0.55. Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 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.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12289 SUBJECT: GRB 110820A: MASTER-NET observations DATE: 11/08/20 18:05:47 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs K.Ivanov, V.A.Poleshchuk, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev,E.Konstantinov, Irkutsk State University E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zimnukhov, M. Kornilov, A.Kuznetsov, D.Zimnukhov, M. Kornilov, A.Sankovich Sternberg Astronomical Institute, Moscow State University A. Tlatov, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalozhnich, T.Kopytova, A. Popov Ural State University, Kourovka V.Yurkov, Yu.Sergienko, D.Varda, I.Kudelina Blagoveschensk Educational State University, Blagoveschensk MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Tunka(Siberia) was pointed to the GRB110820A 45 sec after notice time and 133 sec after GRB time at 2011-08-20 17:40:40.275 UT in two polarizations. On our first (30s exposure) set we haven`t found optical transient within SWIFT error-box. The 5-sigma upper limit has been about 16.5 mag The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12290 SUBJECT: GRB 110820A: CrAO optical upper limit DATE: 11/08/20 22:17:57 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Rumyantsev, K. Antoniuk (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 110820A (Troja et al., GCN 12288) with AZT-11 telescope of CrAO between Aug. 20 (UT) 18:23 - 19:21. Within the XRT error box (Troja et al., GCN 12288) we do not detect any source. The photometry is based on the USNO B1.0 star 1602-0161058 (22:52:45.06 +70:17:17.5) assuming R=18.23: T0+ Filter, Exposure, OT, Upper Limit (3 sigma) (mid, d) (s) 0.0520 R 20x180 n/d 21.6 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12291 SUBJECT: GRB 110820A: Enhanced Swift-XRT position DATE: 11/08/20 23:52:19 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1200 s of XRT Photon Counting mode data and 2 UVOT images for GRB 110820A, 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 = 343.19224, +70.29848 which is equivalent to: RA (J2000): 22h 52m 46.14s Dec (J2000): +70d 17' 54.5" with an uncertainty of 2.3 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12292 SUBJECT: GRB 110820A: Swift-BAT refined analysis DATE: 11/08/21 01:52:10 GMT FROM: Scott Barthelmy at NASA/GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), E. Troja (NASA/GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-119 to T+296 sec from recent telemetry downlinks, we report further analysis of BAT GRB 110820A (trigger #501095) (Troja, et al., GCN Circ. 12288). The BAT ground-calculated position is RA, Dec = 343.203, 70.298 deg, which is RA(J2000) = 22h 52m 48.8s Dec(J2000) = +70d 17' 51.2" with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%. The mask-weighted light curve shows two main peaks. The first started at ~T-5 sec, peaking at ~T+2 sec, and ending at ~T+35 sec. The second starts at ~T+195 sec, peaking at ~T+230, and ending at ~T+285 sec. T90 (15-350 keV) is 256 +- 50 sec (estimated error including systematics). The time-averaged spectrum from T-7.07 to T+264.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.92 +- 0.28. The fluence in the 15-150 keV band is 8.2 +- 1.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.43 sec in the 15-150 keV band is 0.4 +- 0.1 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/501095/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12293 SUBJECT: GRB110820A: MITSuME Ishigakijima Optical Upper Limits DATE: 11/08/21 02:32:56 GMT FROM: Daisuke Kuroda at OAO/NAOJ $B3'MM(B $B9uED$G$9!#(B $B:rHU$N(BGRB110820A$B$N@P3@Eg$N7k2L$G$9!#(B $B2V;3$5$s$,4QB,$r$7$F$/$l$^$7$?!#(B D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ), K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 110820A (Troja et al., GCNC 12288) with the optical three color (g', Rc and Ic) CCD camera attached to the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory. The observation started on 17:47:41 UT (~9 min after the burst). We did not find any new point source within the enhanced XRT error circle (Beardmore et al., GCNC 12291) in all the three bands. Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration. #T0+[day] MID-UT T-EXP[sec] g' Rc Ic ---------------------------------------------------- 0.04719 18:46:24 5280.0 >20.6 >21.3 >19.9 ---------------------------------------------------- T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12294 SUBJECT: GRB 110820A: Swift-XRT refined Analysis DATE: 11/08/21 06:32:35 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester) and E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 110820A (Troja et al. GCN Circ. 12288), from 82 s to 24.5 ks after the BAT trigger. The data comprise 121 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 12291). The first snapshot of data is dominated by a large flare, also detected by the BAT (Palmer et al. GCN Circ. 12292). After around 750 s, the light curve decay can be fitted with index alpha=0.28 (+0.13, -0.15). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.32 (+0.07, -0.06). The best-fitting absorption column is 6.1 (+/-0.5) x 10^21 cm^-2, in excess of the Galactic value of 3.3 x 10^21 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.80 (+0.20, -0.26) and a best-fitting absorption column of 4.7 (+/-1.3) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.1 x 10^-11 (7.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.7 (+/-1.3) x 10^21 cm^-2 Galactic foreground: 3.3 x 10^21 cm^-2 Excess significance: 5.9 sigma Photon index: 1.80 (+0.20, -0.26) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00501095. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12295 SUBJECT: GRB 110820A: CQUEAN izY Observation DATE: 11/08/21 08:14:40 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Won-Kee Park (CEOU/Seoul National Univ), Soojong Pak, Giseon Baek, and Youngseok Oh (Kyunghee University) We observed GRB 100820A (Troja et al. GCN 12288) with i,z,and Y-filters using CQUEAN camera (the Camera for QUasars in the Early uNiverse) on the 2.1m telescope at the McDonald observatory. The observation started at 2010 August 21, 05:12:48 UT, about 11.5 hrs after the BAT trigger. In a stacked i-band image (3 x 300 sec), we identify a faint object within the error circle of the enhanced XRT position (Beardmore et al. GCN 12291). The position of the i-band source is RA=22:52:49.49 Dec=70:17:53.6 with a positional error of ~0.5". We are carrying our further observations to examine variability of the source. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12296 SUBJECT: GRB 110820A: i-band finding chart + correction to 12295 DATE: 11/08/21 08:22:26 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Won-Kee Park (CEOU/Seoul National Univ), Soojong Pak, Giseon Baek, and Youngseok Oh (Kyunghee University) The finding chart of the i-band image reported in Im et al. (GCN 12295) is available at http://astro.snu.ac.kr/~mim/grb110820a.html We also make a correction to the year of the observation reported in GCN 12295. It should be 2011, not 2010. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12297 SUBJECT: GRB 110820A: Position udpate + 2nd epoch data DATE: 11/08/21 11:58:19 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Won-Kee Park (CEOU/Seoul National Univ), Soojong Pak, Giseon Baek, and Youngseok Oh (Kyunghee University) We revise the position of the afterglow candidate to be RA=22:52:46.49 Dec=70:17:53.6 with a positional error of ~0.5". The 2nd set of i-band images were taken 3 hrs after the 1st set (Im et al. GCN 12295). Our analysis of the data shows no significant fading of the object (dm < 0.1 mag) during that time span. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12298 SUBJECT: GRB 110820A: Swift/UVOT Upper Limits DATE: 11/08/22 14:20:06 GMT FROM: Stefan Immler at NASA/GSFC S. Immler (NASA/CRESST/GSFC) and E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 110820A 139 s after the BAT trigger (Troja et al., GCN Circ. 12288). No optical afterglow consistent with the enhanced XRT position (Beardmore et al., GCN Circ. 12291) and the position of the optical afterglow candidate Myungshin et al., GCN Circ. 12297) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u_FC 139 389 246 >20.6 v 445 24186 1395 >21.1 b 394 12987 932 >22.0 u 139 18761 2181 >21.8 w1 494 18331 2155 >21.8 m2 469 24536 1716 >20.6 w2 420 23272 1396 >21.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.55 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12299 SUBJECT: IPN triangulation of GRB 110820B (very long duration, extremely intense) DATE: 11/08/22 22:40:43 GMT FROM: Valentin Pal'shin at Ioffe Inst K. Hurley and J. Goldsten, on behalf of the MESSENGER NS GRB team, S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline, on behalf of the Konus-Wind team, S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, and W. Hajdas, on behalf of the RHESSI GRB team, report: On 2011 August 20 at about 21:27:50 UT, an extremely intense, very long duration GRB was observed by Konus-Wind, MESSENGER, RHESSI, and Swift (BAT) (outside the coded field of view). We have triangulated it to a preliminary, 3 sigma error box whose area is 0.212 sq. deg. and whose coordinates are: ------------------------------------------------ RA(2000), deg Dec(2000), deg ------------------------------------------------ Center: 157.583 (10h 30m 20s) -54.605 (-54d 36' 16") Corners: 159.392 (10h 37m 34s) -54.329 (-54d 19' 45") 156.617 (10h 26m 28s) -54.836 (-54d 50' 09") 155.769 (10h 23m 05s) -54.841 (-54d 50' 27") 158.541 (10h 34m 10s) -54.362 (-54d 21' 44") ------------------------------------------------ Some improvement to this error box is possible. The time history and spectrum will be given in a forthcoming GCN Circular. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12300 SUBJECT: GRB 110820A: MASTER-NET first hour observations DATE: 11/08/23 06:09:31 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zimnukhov, M. Kornilov, A.Kuznetsov, D.Zimnukhov, M. Kornilov, A.Sankovich Sternberg Astronomical Institute, Moscow State University O. Gres, K.Ivanov, V.A.Poleshchuk, S.Yazev, N.M.Budnev, O.Chuvalaev Irkutsk State University A. Tlatov, A. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalozhnich, T.Kopytova, A. Popov Ural State University, Kourovka E. Sinyakov, V.Yurkov, Yu.Sergienko, D.Varda, I.Kudelina Blagoveschensk Educational State University, Blagoveschensk MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Tunka(Siberia) was pointed to the GRB110820A 45 sec after notice time and 133 sec after GRB time at 2011-08-20 17:40:40.275 UT in two polarizations on one in each tube. During the analysis of the data of the first hour of observation following results have been received: T-T(GRB) T-T(GRB) T-T(GRB) Exptime Limit Filter Coadd start[s] stop[s] mean [s] [s] (5-sigma) --------------------------------------------------------------- 133 163 148 30 16.4 P_ no 133 163 148 30 16.5 P| no 133 2797 1465 2040 19.3 P_ 14 133 2797 1465 2040 19.6 P| 14 133 2797 1465 4080 19.9 P|+P_ 28 Image in filter P_+P| available here http://observ.pereplet.ru/images/evgeny/GRB110820A.jpg The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12301 SUBJECT: Konus-Wind observation of GRB 110820B DATE: 11/08/23 09:34:20 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The long hard extremely intense GRB 110820B (localized by IPN: Hurley et al., GCN 12299) triggered Konus-Wind at T0=77268.054s UT (21:27:48.054) The event light curve shows two major bursting episodes separated by ~100 s. A weaker and softer emission is observed at the time between the two main pulses. The total duration of the burst is ~200s. 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/GRB110820_T77268/ As observed by Konus-Wind the burst had a fluence of (2.5 ± 0.3)x10-4 erg/cm2, and a 64-ms peak flux, measured from T0+3.136 s, of (2.6 ± 0.4)x10-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+191.488 s) is best fitted in the 20 keV - 10 MeV range by the GRB (Band) model, for which: the low-energy photon index alpha = -1.22 (-0.05, +0.06), the high energy photon index beta = -2.1 (-0.3, +0.2), the peak energy Ep = 481(-83, +90) keV, chi2 = 69/84 dof. The spectrum at the maximum count rate (measured from T0+0.256 to T0+3.840 s) is best fitted in the 20 keV - 10 MeV range by the GRB (Band) model, for which: the low-energy photon index alpha = -0.55 (-0.09, +0.09), the high energy photon index beta = -2.5 (-0.4, +0.2), the peak energy Ep = 483(-53, +60) keV, chi2 = 81/84 dof. All the quoted results are preliminary. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12306 SUBJECT: GRB 110820A, the review of the sky area in plate archives DATE: 11/08/26 16:36:37 GMT FROM: Valentyna Golovnya at Main Astro Obs,Kyiv V.V. Golovnya (Main Astro Obs, Kyiv) report: We have undertaken the review of the sky area in vicinity of GRB 110820A (Beardmore GCN Circ.12091) on astronegatives, collected in Ukrainian NAS Main astronomical observatory plate archive (1976-1996). All the plates with the possible object appearance are digitized using Microtek ScanMaker 9800XL TMA and Epson Expression 10000XL flatbed scanners and have been placed into Golosiiv Plate Archive database DBGPA with open access to them. The list of plates is given in the table: YYYYMMDD TimeUT --Plates-- Exp. LimMag Star USNOA2 19830903.220221 GUA040C000207 16.0 15.75 1575-05316204 19841020.183916 GUA040C000521A 16.0 15.75 1575-05316204 Plates: the plate's identifier in GUA040C archive of DWA (D/F=400/2000, M=103"/mm) of the Ukrainian NAS Main Astro obs in Kyiv (Marsden's number - 83)[1]. Exp. - Duration of the maximum exposure (minutes). LimMag - Limited V mag, derived in the 15 minutes area around the location given in Beardmore et al. GCN Circ.12091: RA(J2000): 22h 52m 46.14s, Dec(J2000): +70d 17' 54.5" Star USNOA2 - Comparison star. The preview images of 2 areas together with the 15x15 min.of arc area from SkyMap can be found in http://gua.db.ukr-vo.org/img/grb/110820A/index.html The images with full resolution are available via e-mail on demand. References: 1.L.Pakuliak DATABASE of GOLOSIIV PLATE ARCHIVE (DBGPA V2.0), http://gua.db.ukr-vo.org //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12321 SUBJECT: GRB 110820A: optical upper limit DATE: 11/09/02 14:33:04 GMT FROM: Alina Volnova at SAI MSU Volnova (SAI MSU), E. Litvinenko (UBAI), I. Molotov (Institute of Applied Mathematics), A. Pozanenko (IKI) We observed the field of the Swift GRB 110820A (Troja et al., GCN 12288) with 40-cm telescope ORI-40 of Kitab ISON observatory on Aug. 20 starting on 17:48:45 UT, i.e. 15.5 minutes after the BAT trigger. On the stacked image we do not detect any source within the enhanced XRT error box (Beardmore et al., GCN 12291). The photometry is based on the USNO B1.0 star USNO-B1.0 1603-0160240, (J2000) RA = 22:52:56.89 Dec = +70:18:37.5, assuming R 17.19: Tstart UT, T0+, Filter, Exposure, OT, Upper Limit (3 sigma) (mid, d) (s) 17:48:45 0.01072 R 5*120 n/d 19.2 17:48:45 0.02734 R 28*120 n/d 19.6 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12707 SUBJECT: GRB 110820A: optical observations in Maidanak observatory DATE: 11/12/20 12:49:33 GMT FROM: Alina Volnova at SAI MSU A. Volnova (SAI MSU), M. Ibrahimov (UBAI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 110820A (Troja et al., GCN 12288) with AZT-22 telescope of Maidanak observatory on Aug. 20 starting on 21:54:54 UT in R band. We took 6 frames with exposure of 300 seconds under good weather condition and seeing (FWHM) of about 0.7". On the stacked image we do not detect the source reported by Im et al. (GCNs 12295, 12297). The photometry is based on the USNO B1.0 star USNO-B1.0 1603-0160240, (J2000) RA = 22:52:56.89 Dec = +70:18:37.5, assuming R =17.19: Tstart UT, T0+, Filter, Exposure, OT, Upper Limit (3 sigma) (mid, d) (s) 21:54:54 0.18924 R 6*300 n/d 22.5