//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12031 SUBJECT: GRB 110521A: Swift detection of a burst DATE: 11/05/21 16:05:05 GMT FROM: David Palmer at LANL S. R. Oates (UCL-MSSL), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), J. M. Gelbord (PSU), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), C. B. Markwardt (NASA/GSFC), A. Melandri (INAF-OAB), P. T. O\'Brien (U Leicester), C. Pagani (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL) and E. Sonbas (GSFC/USRA/Adiyaman Univ.) report on behalf of the Swift Team: At 15:51:31.45 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110521A (trigger=453788). Swift slewed immediately to this burst. The BAT on-board calculated location is RA, Dec 120.144, +45.798, which is RA(J2000) = 08h 00m 35s Dec(J2000) = +45d 47' 53" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a few pulses with a total duration of about 20 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~8 sec after the trigger. The XRT began observing the field at 15:53:10.0 UT, 98.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 120.1327, 45.8264 which is equivalent to: RA(J2000) = 08h 00m 31.84s Dec(J2000) = +45d 49' 35.1" with an uncertainty of 2.3 arcseconds (radius, 90% containment). This location is 106 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (4.51 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 5.5 (+2.93/-2.35) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 8.07e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 104 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 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.09. Burst Advocate for this burst is S. R. Oates (sro AT mssl.ucl.ac.uk). 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: 12033 SUBJECT: GRB 110521A: MASTER synchronous and early optical observations limit DATE: 11/05/21 18:50:06 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs O. Gres, K.Ivanov, V.A.Poleshchuk, S.Yazev, N.M.Budnev, O.Chuvalaev Irkutsk State University V.Krushinski, I.Zalozhnich, A. Popov Ural State University, Kourovka 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.Sankovich Sternberg Astronomical Institute, Moscow State University A. Tlatov, A.V. Parhomenko, D. Dormidontov,V. Senik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, 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 GRB110521A (Oates et al., GCN Circ 12031) 32 sec s after notice time and 92 sec after GRB time at 2011-05-21 15:53:03.316 UT. On our first (20s exposure) set we haven`t found optical transient within SWIFT error-box . The 3-sigma upper limit has been about 16.0 mag The Swift erros box was inside FOV of the one of the 2 Very Wide Field Cameras (2x480 square degrees, 2x12 Mpixs). We have images before, during and after GRB . The 3-sigma upper limit has been about 12.0 mag each image (5 s exposition). The data reduction is continued. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12034 SUBJECT: GRB 110521A: Enhanced Swift-XRT position DATE: 11/05/21 21:41:09 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 428 s of XRT Photon Counting mode data and 1 UVOT images for GRB 110521A, 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 = 120.13290, +45.82658 which is equivalent to: RA (J2000): 08h 00m 31.90s Dec (J2000): +45d 49' 35.7" with an uncertainty of 1.9 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: 12035 SUBJECT: GRB 110521A: Swift-BAT refined analysis DATE: 11/05/21 22:10:48 GMT FROM: Scott Barthelmy at NASA/GSFC 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), S. R. Oates (UCL-MSSL), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+529 sec from recent telemetry downlinks, we report further analysis of BAT GRB 110521A (trigger #453788) (Oates, et al., GCN Circ. 12031). The BAT ground-calculated position is RA, Dec = 120.132, 45.818 deg, which is RA(J2000) = 08h 00m 31.7s Dec(J2000) = +45d 49' 05.3" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows several overlapping peaks starting at ~T_zero, with the maximum peak at ~T+8 sec, and ending at ~T+18 sec. There is a low significance tail out to around T+60 sec. T90 (15-350 keV) is 13.8 +- 3.3 sec (estimated error including systematics). The time-averaged spectrum from T+0.2 to T+18.8 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.90 +- 0.22. The fluence in the 15-150 keV band is 4.4 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+7.88 sec in the 15-150 keV band is 0.5 +- 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/453788/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12036 SUBJECT: GRB 110521A - NOT optical observation DATE: 11/05/22 00:54:55 GMT FROM: Steve Schulse at U. of Iceland S. Schulze (U. Iceland), D. Xu (WIS), P. Jakobsson (U. Iceland), T. Pursimo (NOT Observatory), report on behalf of a larger collaboration: We observed the field of GRB 110521A (Oates et al., GCN 12031) with the Nordic Opitcal Telescope (NOT) equipped with ALFOSC. We obtained 3x300 s R-band and 6x300 s I-band images. Observations started at 22:01 UT on May 21 (i.e., 6.1604 hrs after the burst). We do not detect any source in the stacked R-band and I-band images at the refined XRT position (Beardmore et al., GCN 12034). The limiting magnitudes are R ~ 24.4 mag at the mid-exposure time t = 6.285 hrs post-burst, and I ~ 23.8 mag at the mid-exposure time t = 6.745 hrs post-burst, calibrated with the #1358-0196725 star (R1 = 19.57, R2 = 19.58, and I =18.81) in the USNO B1 catalogue. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12038 SUBJECT: GRB 110521A: Swift-XRT refined analysis DATE: 11/05/22 09:18:34 GMT FROM: Kim Page at U.of Leicester O. M. Littlejohns (U. Leicester) and S. R. Oates (UCL-MSSL) reports on behalf of the Swift-XRT team: We have analysed 21 ks of XRT data for GRB 110521A (Oates et al. GCN Circ. 12031), from 87 s to 47.7 ks after the BAT trigger. The data comprise 61 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 12034). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.5 (+0.4, -0.3). At T+299 s the decay steepens to an alpha of 7.1 (+2.9, -1.3) before breaking again at T+529 s to a final decay with index alpha=1.0 (+0.5, -1.9). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.0 (+0.3, -0.6). The best-fitting absorption column is 4.3 (+1.5, -2.6) x 10^21 cm^-2, in excess of the Galactic value of 4.5 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.7 x 10^-11 (7.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.3 (+1.5, -2.6) x 10^21 cm^-2 Galactic foreground: 4.5 x 10^20 cm^-2 Excess significance: 2.7 sigma Photon index: 2.0 (+0.3, -0.6) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00453788. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12039 SUBJECT: GRB 110521A: Swift/UVOT Upper Limits DATE: 11/05/22 09:22:55 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 110521A 105 s after the BAT trigger (Oates et al., GCN Circ. 12031). No optical afterglow consistent with the XRT position (Beardmore et al., GCN Circ. 12034) 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 --------------------------------------------------------------- white_FC 105 255 147 >20.4 u_FC 263 513 246 >20.0 white 105 6615 766 >21.0 v 594 41254 2261 >20.5 b 519 30377 1766 >21.1 u 263 36155 3624 >21.7 w1 644 35466 3860 >22.0 m2 618 41934 3564 >22.3 w2 570 40340 2262 >22.3 -------------------------------------------------------------- The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.09 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 12040 SUBJECT: GRB 110521A: MASTER prompt optical limit DATE: 11/05/23 09:31:10 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.Sankovich Sternberg Astronomical Institute, Moscow State University O. Gres, K.Ivanov, V.A.Poleshchuk, S.Yazev, N.M.Budnev, O.Chuvalaev Irkutsk State University V.Krushinski, I.Zalozhnich, A. Popov Ural State University, Kourovka A. Tlatov, A.V. Parhomenko, D. Dormidontov,V. Senik Kislovodsk Solar Station of the Pulkovo Observatory V.Yurkov, Yu.Sergienko, I.Kudelina Blagoveschensk Educational State University, Blagoveschensk The Swift erros box has casually appeared inside FOV of the one of the 2 Very Wide Field Cameras (Gres et al., GCN Circ 12033). We have images before, during and after GRB . The 3-sigma upper limit has been about 12.0 mag (unfiltered, close to V) each image (5 s exposition). The upper limit of coadded images during 15 sec GRB is 12.7. The corresponding optical fluence less than 10^-9 erg/cm^2 The best-fitting absorption column is 4.3 (+1.5, -2.6) x 10^21 cm^-2, in excess of the Galactic value of 4.5 x 10^20 cm^-2 (Littlejohns et al., GCN Circ 12038). The fluence in the 15-150 keV band is 4.4 +- 0.5 x 10^-7 erg/cm2 (Barthelmy et al., GCN Circ 12035). So including ~2 mag absorption: Fluence_opt/Fluemce_gamma(15-150) < ~1/60 The video is available at http://observ.pereplet.ru/images/GRB110521A/grb110521A.gif . This message may be cited.