//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13618 SUBJECT: Swift Trigger 530581: GRB 120811A or a galactic transient DATE: 12/08/11 02:57:33 GMT FROM: Scott Barthelmy at NASA/GSFC B.-B. Zhang (PSU), S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA) and D. M. Palmer (LANL) report on behalf of the Swift Team: At 02:35:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located a possible GRB (120811A, trigger=530581). Swift did not slew to the location. The BAT on-board calculated location is RA, Dec 257.183, -22.736 which is RA(J2000) = 17h 08m 44s Dec(J2000) = -22d 44' 08" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 30 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. This source was matched to a source 4U 1708-23 (== X Oph X-2) in the on-board catalog, with an offset from the catalog position of 6 arcminutes. However, the latest position available is from the 1972 UHURU catalog, which has a large position uncertainty consistent with this offset. At this time we cannot determine whether this is a GRB, the catalogued 4U 1708-23, or some previously-unknown Galactic transient. Burst Advocate for this burst is B.-B. Zhang (bbzhang AT psu.edu). 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: 13620 SUBJECT: IPN Triangulation of short hard GRB 120811B DATE: 12/08/11 12:31:20 GMT FROM: Dmitry Svinkin at Ioffe Institute S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, K. Hurley on behalf of the IPN, V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi GBM team, A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, report: The short hard GRB 120811B has been observed by Fermi (GBM: trigger 366337233), Konus-Wind, INTEGRAL (SPI-ACS), and Swift (BAT), so far, at about 1230 s UT (00:20:30). We have triangulated the burst to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 43.719 (02h 54m 53s) -30.233 (-30d 13' 58") Corners: 43.568 (02h 54m 16s) -28.355 (-28d 21' 19") 43.930 (02h 55m 43s) -27.828 (-27d 49' 40") 43.853 (02h 55m 25s) -32.184 (-32d 11' 04") 43.457 (02h 53m 50s) -32.775 (-32d 46' 30") --------------------------------------------- The error box area is 1.39 sq. deg, and its maximum dimension is 4.96 deg. This box can be improved. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB120811_T01231/IPN/ The time history and spectrum will be given in a forthcoming GCN Circular. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13621 SUBJECT: Konus-Wind observation of GRB 120811B DATE: 12/08/11 13:28:20 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 short-duration hard GRB 120811B (IPN localization: Golenetskii at al., GCN 13620) triggered Konus-Wind at T0=01231.575s UT (00:20:31.575) The light curve shows a double pulse, a total duration of the burst is ~0.33 s. The emission is seen up to ~6 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB120811_T01231/ As observed by Konus-Wind the burst had a fluence of 4.6(-0.9,+1.0)x10-6 erg/cm2, and a 16-ms peak flux, measured from T0, of 2.8(-0.6,+0.7)x10-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The spectrum of the burst (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 7 MeV range by a power law with exponential cutoff model, for which alpha = -0.14 (-0.28, +0.35), and Ep = 1130(-230, +310) keV, chi2 = 13.6/24 dof. All the quoted results are preliminary. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13622 SUBJECT: GRB 120811C: Swift detection of a burst with an optical counterpart DATE: 12/08/11 15:52:41 GMT FROM: Scott Barthelmy at NASA/GSFC B. N. Barlow (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), D. Grupe (PSU), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and B.-B. Zhang (PSU) report on behalf of the Swift Team: At 15:34:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120811C (trigger=530689). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 199.709, +62.291 which is RA(J2000) = 13h 18m 50s Dec(J2000) = +62d 17' 29" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single bright peak with a duration of about 35 sec. The peak count rate was ~7000 counts/sec (15-350 keV), at ~6 sec after the trigger. The XRT began observing the field at 15:36:00.8 UT, 68.7 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 199.6833, 62.3027 which is equivalent to: RA(J2000) = +13h 18m 43.99s Dec(J2000) = +62d 18' 09.7" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 60 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 2.5 s image was 2.97e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 75 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 13:18:43.81 = 199.68253 DEC(J2000) = +62:18:02.7 = 62.30076 with a 90%-confidence error radius of about 0.75 arc sec. This position is 7.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.40 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03. Burst Advocate for this burst is B. N. Barlow (bnb2 AT psu.edu). 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: 13623 SUBJECT: GRB 120811C: MASTER-Amur observations of fading OT DATE: 12/08/11 20:32:22 GMT FROM: Denis Denisenko at SAI MSU D. Denisenko, E. Gorbovskoy, V. Lipunov, V. Kornilov, D. Kuvshinov, A. Belinski, N. Tyurina, N. Shatskiy, P. Balanutsa, D. Zimnukhov, A. Kuznetsov, V.V. Chazov, A. Sankovich Lomonosov Moscow State University, Sternberg Astronomical Institute V. Yurkov, Yu. Sergienko, D. Varda, E. Sinyakov Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, A.V. Parhomenko, D. Dormidontov, V. Sennik Kislovodsk Solar Station of the Pulkovo Observatory V. Krushinski, I. Zalozhnich, A. Popov, A. Bourdanov, A. Punanova Ural Federal University H. Levato, C. Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) C. Mallamaci, C. Lopez, F. Podest Observatorio Astronomico Felix Aguilar (OAFA) report: MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Blagoveschensk was pointed to GRB 120811C (Barlow et al., GCN 13622) 665 sec after GRB time, at 2012-08-11 15:45:57 UT. Observations were performed simultaneously in two tubes with mutually perpendicular polarizations. First two pairs of images were obtained with 130 and 160 sec exposures, followed by the set of 180-sec exposures. On our images we find the fading optical transient at the coordinates: R.A. (J2000) = 13 18 44.01 Dec. (J2000) = +62 18 02.7 which are consistent with the position of UVOT candidate afterglow reported in GCN 13622. Photometry of GRB 120811C afterglow was performed using SDSS J131828.08+621651.3 (r=14.74) as the reference star. To improve the signal-to-noise ratio, images were combined by four. The resulting magnitudes of the afterglow in the Western tube with a better image quality (FWHM=2.6-3.2") are listed in the Table below. ---------------------------------------------- T_mid UT | T-T0, s | Exptime | Mag. | Mag.err ---------+---------+---------+-------+-------- 15:51:48 | 1016 | 650 | 18.4 | 0.10 16:04:46 | 1794 | 720 | 18.9 | 0.17 16:18:37 | 2625 | 720 | 19.3 | 0.27 16:32:27 | 3455 | 720 | 19.0 | 0.24 16:46:16 | 4284 | 720 | <19.5 | N/A 17:00:04 | 5112 | 720 | <19.5 | N/A ---------------------------------------------- The detailed analysis of the complete data set is continuing. This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13624 SUBJECT: GRB 120811C: TAROT Calern observatory optical observations DATE: 12/08/11 21:03:08 GMT FROM: Alain Klotz at CESR-CNRS Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR), Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report: We imaged the field of GRB 120811C detected by SWIFT (trigger 530689) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 3.98h after the GRB trigger. The elevation of the field decreased from 50 degrees above horizon and weather conditions were good. We co-added a series of exposures but we do not find any optical transcient at the afterglow position (Barlow et al. GCNC 13622, Denisenko et al. GCNC 13623): ------------------------------- T-T0 start | T-T0 End | Mag. | -----------+----------+-------+ 246 min | 313 min | >19.5 | ------------------------------- Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13625 SUBJECT: GRB 120811C: Enhanced Swift-XRT position DATE: 12/08/11 21:13:09 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1291 s of XRT Photon Counting mode data and 2 UVOT images for GRB 120811C, 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 = 199.68285, +62.30068 which is equivalent to: RA (J2000): 13h 18m 43.88s Dec (J2000): +62d 18' 02.4" with an uncertainty of 1.7 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: 13626 SUBJECT: GRB 120811C: RTT150 optical observations DATE: 12/08/11 21:53:06 GMT FROM: Rodion Burenin at IKI, Moscow A. Galeev (Kazan Federal University), I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (Kazan Federal University), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.) report: We observed the field of the Swift-BAT GRB 120811C (Barlow et al. GCN 13622) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey), starting at 11 Aug, 18:52 UT, i.e. approximately 3.3 hours after the burst, using TFOSC instrument. We made a serie of 300-600s images in R and V. The afterglow is detected at the position: RA=13:18:43.83, DEC=62:18:02.6 (J2000) with positional error about 0.1 arcsec, which is consistent with that measured by UVOT and MASTER (Denisenko et al., GCN 13623). We measured the afterglow magnitude as m_R=20.00+-0.05 (calibrated relative to USNO-B1 stars). Observations are continuing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13627 SUBJECT: Improved IPN error box for short hard GRB 120811B DATE: 12/08/11 22:11:15 GMT FROM: Dmitry Svinkin at Ioffe Institute S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, K. Hurley, and J. Goldsten, on behalf of the MESSENGER GRNS GRB team, V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi GBM team, A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on behalf of the Swift-BAT team, report: This burst (GCN 13620) was also observed by MESSENGER (GRNS). We have triangulated it to an improved, but still preliminary 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 43.658 (02h 54m 38s) -31.675 (-31d 40' 29") Corners: 43.770 (02h 55m 05s) -32.366 (-32d 21' 59") 43.820 (02h 55m 17s) -31.614 (-31d 36' 51") 43.545 (02h 54m 11s) -30.978 (-30d 58' 42") 43.495 (02h 53m 59s) -31.735 (-31d 44' 06") --------------------------------------------- The error box area is 734 sq. arcmin, and its maximum dimension is 84 arcmin. This error box is fully contained within the previous IPN error box (GCN 13620). This box can be further improved. An updated triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB120811_T01231/IPN/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13628 SUBJECT: GRB 120811C: Redshift from OSIRIS/GTC DATE: 12/08/11 23:14:09 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC C. C. Thoene (IAA-CSIC), A. de Ugarte Postigo (IAA-CSIC, DARK), J. Gorosabel, R. Sanchez-Ramirez (IAA-CSIC) and J. P. U. Fynbo (DARK) G. Gomez Velarde (GTC) report on behalf of a larger collaboration: We observed the afterglow of GRB 120811C (Barlow et al., GCN 13622) with OSIRIS at the 10.4m GTC telescope starting at UT 22:07 (6.5 hr after the burst) for a total exposure time of 2400s. We used grism 1000B covering the wavelength range between 3700 and 7800 Angstrom. Despite Calima, the continuum is clearly detected and the spectrum shows strong Ly alpha and Ly beta absorption as well as a number of absorption lines (SII, SiII, OI, CII, CIV, SiIV, AlII, AlIII, NiII, ZnII and SiII*) at a common redshift of z=2.671. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13629 SUBJECT: GRB 120811C: Swift/UVOT Detection DATE: 12/08/12 01:58:39 GMT FROM: Paul Kuin at MSSL P. Kuin, S. R. Oates (MSSL-UCL) and B.N. Barlow (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 120811C 76 s after the BAT trigger (Barlow et al., GCN Circ. 13622). A source consistent with the XRT position Evans et al., GCN Circ. 13625 is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 13:18:43.82 = 199.68258 (deg.) Dec (J2000) = +62:18:02.8 = 62.30077 (deg.) with an estimated uncertainty of 0.52 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 76 226 147 18.59 +/- 0.05 v 620 1243 78 18.49 +/- 0.19 b 544 739 39 18.95 +/- 0.19 u 288 538 246 18.61 +/- 0.09 w1 670 1464 97 >20.0 m2 819 1439 78 >20.5 w2 595 1219 78 >19.7 The absence of a detection in the uv bands is consistent with the reported redshift from Thoene et al., GCN Circ. 13628. The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13630 SUBJECT: GRB 120811C: Swift-XRT refined Analysis DATE: 12/08/12 06:52:03 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), O.M. Littlejohns (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. Maselli (INAF-IASFPA), M.C. Stroh (PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester) and B.N. Barlow report on behalf of the Swift-XRT team: We have analysed 6.5 ks of XRT data for GRB 120811C (Barlow et al. GCN Circ. 13622), from 56 s to 40.2 ks after the BAT trigger. The data comprise 137 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 Evans et al. (GCN. Circ 13625). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.12 (+0.13, -0.14). At T+224 s the decay flattens to an alpha of 0.44 (+0.12, -0.27) before breaking again at T+1468 s to a final decay with index alpha=1.06 (+0.19, -0.09). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.74 (+0.14, -0.13). The best-fitting absorption column is 1.08 (+0.22, -0.20) x 10^21 cm^-2, in excess of the Galactic value of 2.1 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.00 (+/-0.15) and a best-fitting absorption column of 8.8 (+3.4, -3.1) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 8.8 (+3.4, -3.1) x 10^20 cm^-2 Galactic foreground: 2.1 x 10^20 cm^-2 Excess significance: 3.6 sigma Photon index: 2.00 (+/-0.15) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00530689. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13631 SUBJECT: GRB 120811C: Bassano Bresciano Observatory optical observations DATE: 12/08/12 07:26:59 GMT FROM: Ulisse Quadri at Bassano Bresciano Obs U.Quadri, L.Strabla and R.Girelli, A.Quadri report: We imaged the field of GRB 120811C detected by SWIFT(trigger 530689) with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy. The observations started 266min. after the GRB trigger,with our schmidt telescope D=320 mm F/D=3.1. Weather conditions were good. We co-added a series of 30 exposures. We did not found any optical counterpart in the error box of the XRTcandidate (Barlow et al. GCNC 13622). Start End Vlim 266min 326min 19.2 Magnitudes were estimated with the UCAC-3 The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13632 SUBJECT: GRB 120811C: NOT redshift DATE: 12/08/12 11:54:19 GMT FROM: Dong Xu at Weizmann Inst J. P. U. Fynbo (DARK/NBI), D. Xu (WIS), P. Jakobsson (U. Iceland), D. Armstrong (U. Warwick), R. Cardenes (NOT) report on behalf of a larger collaboration: We observed the optical afterglow of GRB 120811C (Barlow et al., GCN 13622) using the 2.5m Nordic Optical Telescope (NOT) equipped with ALFOSC. Spectroscopic observations started at 21:58 UT on 2012-08-11 (i.e., 6.4 hr after the BAT trigger) with exposure time of 3x1800s, covering the wavelength range of ~3800A to ~8000A. The afterglow was detected in each of the 1800s frames though the weather was dusty to a certain degree. The spectrum exhibits a clear Damped Lyman Alpha (DLA) absorption feature at about 4460A. Redward of Lyman alpha the spectrum shows quite a few significant absorption lines, including Si II, O I, C II, C IV, Si IV, all at a common redshift of z=2.67, in good agreement with the measurement in Thoene at al. (GCN 13628). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13633 SUBJECT: GRB 120811A: Swift-BAT refined analysis DATE: 12/08/12 12:26:25 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), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU), B.-B. Zhang (PSU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 120811A (trigger #530581) (Zhang, et al., GCN Circ. 13618). The BAT ground-calculated position is RA, Dec = 257.184, -22.735 deg, which is RA(J2000) = 17h 08m 44.1s Dec(J2000) = -22d 44' 06.7" with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%. The mask-weighted light curve shows two overlapping peaks starting at ~T-20 sec, peaking at ~T+2 sec, ending at ~T+25 sec with a flat section out to ~T+160 sec. T90 (15-350 keV) is 166 +- 52 sec (estimated error including systematics). The time-averaged spectrum from T-14.16 to T+169.06 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.95 +- 0.20. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.43 sec in the 15-150 keV band is 1.0 +- 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/530581/BA/ While the BAT lightcurve and spectral results are consistant with a GRB origin for this trigger, given that the galactic coordinates are (lon,lat)=(0.6,10.3) deg, we cannot rule out a galactic source origin. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13634 SUBJECT: GRB 120811C: Swift-BAT refined analysis DATE: 12/08/12 13:43:42 GMT FROM: Scott Barthelmy at NASA/GSFC H. A. Krimm (GSFC/USRA), B. N. Barlow (PSU), S. D. Barthelmy (GSFC), T. Sakamoto (GSFC/UMBC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 120811C (trigger #530689) (Barlow, et al., GCN Circ. 13622). The BAT ground-calculated position is RA, Dec = 199.690, 62.297 deg, which is RA(J2000) = 13h 18m 45.5s Dec(J2000) = +62d 17' 50.3" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 89%. The mask-weighted light curve shows a nearly symmetric peak starting at ~T-10 sec, peaking at ~T+6 sec, and ending at ~T+40 sec. T90 (15-350 keV) is 26.8 +- 3.7 sec (estimated error including systematics). The time-averaged spectrum from T-9.7 to T+42.9 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.40 +- 0.30, and Epeak of 42.9 +- 5.7 keV (chi squared 59.5 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.0 +- 0.3 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+5.27 sec in the 15-150 keV band is 4.1 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.04 +- 0.06 (chi squared 74.5 for 57 d.o.f.). 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/530689/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13635 SUBJECT: GRB 120811C: MASTER-Tunka OT observations DATE: 12/08/13 07:05:34 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, D.Zimnukhov, A.Kuznetsov, V.V.Chazov, A.Kuznetsov, A.Sankovich Sternberg Astronomical Institute, Moscow State University V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, Kourovka Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA) MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Tunka was pointed to the GRB120811C (Barlow et al., GCN 13622) 40 sec s after notice time and 676 sec after GRB time at 2012-08-11 15:46:08.449 UT. On our first (130s exposure) set we have found OT within SWIFT-BAT error-box in two polarizations. The preliminary robotic photometry (m=0.2B + 0.8R, Usno B magnitudes) is: datetime coord2000 Band mag error 2012-08-11 15:46:08.449 13h 18m 43.90s , +62d 18m 02s.1 P| 17.3 0.2 2012-08-11 15:46:09.684 13h 18m 43.86s , +62d 18m 02s.3 P- 17.2 0.1 2012-08-11 15:49:12.268 13h 18m 43.76s , +62d 18m 02s.3 P| 17.6 0.2 2012-08-11 15:49:12.282 13h 18m 43.93s , +62d 18m 02s.6 P- 17.6 0.2 2012-08-11 15:52:52.452 13h 18m 43.75s , +62d 18m 01s.8 P| 17.8 0.2 So, MASTER-Net have simultaneous optical observations in four polarizations (see Denisenko et al., GCN 13623) of GRB120811C. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13636 SUBJECT: GRB 120811C: RTT150 optical observations DATE: 12/08/13 17:29:30 GMT FROM: Rodion Burenin at IKI, Moscow A. Galeev (Kazan Federal University), I. Khamitov (TUG), I. Bikmaev, N. Sakhibullin (Kazan Federal University), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.) report: We continued the observations of the field of the Swift-BAT GRB 120811C (Barlow et al. GCN 13622, Galeev et al., GCN 13626) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey). The second epoch observations were started at 12 Aug, 18:38 UT, i.e. approximately 27.05 hours after the burst. We made a serie of 300s images in R using TFOSC instrument. The afterglow was clearly detected in the combined image. Using USNO-B1 stars as reference, we estimated the afterglow magnitude as m_R=22.3+-0.2. Fitting this point together with the data from RTT150 first epoch observations (Galeev et al., GCN 13626), gives the power law decay with index alpha = 1.04 +- 0.05, consistent with late time decay in X-rays, as it was observed with XRT (Evans et al., GCN 13630). When all RTT150 data are compared with the data of MASTER telescopes (Denisenko et al., GCN 13623, Ivanov et al., 13635), the power law break at few hours time scale is found, approximately consistent with the position of second break observed in X-rays with XRT (Evans et al., GCN 13630). However, better cross-calibration between RTT and MASTER photometry should be done for more reliable light curve modelling. The light curve and direct images of the field can be found at: http://hea.iki.rssi.ru/grb/120811c/indexeng.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13637 SUBJECT: GRB 120811C: EVLA Observations DATE: 12/08/13 20:49:36 GMT FROM: Tanmoy Laskar at Harvard U T. Laskar, A. Zauderer and E. Berger (Harvard) report: "We observed the position of GRB 120811C (Barlow et al. GCN 13622) with the EVLA at 2012 Aug 11.79 UT (1.14 days after the burst). No significant radio emission is detected at the enhanced Swift-XRT position (Evans et al. GCN 13625), the UVOT position (Kuin et al. GCN 13629) or optical position (Denisenko et al. GCN 13623; Galeev et al. GCN 13626; Ivanov et al. GCN 13635), to a three-sigma upper limit of 76 uJy at 6.0 GHz." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13641 SUBJECT: GRB 120811A: Swift/XRT-UVOT Obseravations DATE: 12/08/14 15:57:21 GMT FROM: Binbin Zhang at PSU B.-B. Zhang (PSU), S. R. Oates (UCL-MSSL), K. L. Page (U Leicester), P.A. Evans (U. Leicester), D. N. Burrows (PSU), J. R. Cummings (GSFC/UMBC), J. A. Kennea (PSU),H. A. Krimm (GSFC/USRA), E. Helder (PSU) and S. D. Barthelmy (GSFC) report on behalf of the Swift-XRT and Swift-UVOT team: We report further Swift XRT-UVOT observations of GRB 120811A (Zhang et al, GCN 13618). We performed 9.1 ks follow-up XRT observations of the field at T0+1.6 hr, T0+0.27 day, T0+0.94 days and T0+3.1 days (where T0 = 2012 Aug 11 at 02:35:18 UT ), in order to determine whether or not the X-ray source had faded. We find a fading source with count rates in the 0.3-10 keV band as follows : T-T0 Count Rate (5.8+/-0.2)x10^3 s 0.05+/-0.01 count/s (2.2+/-0.01)x10^4 s 0.02+/-0.01 count/s (8.1+/-0.03)x10^4 s 0.02+/-0.001 count/s (2.7+/-0.2)x10^5 s < 0.005 count/s The data are entirely in Photon Counting (PC) mode. Using 1227 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 257.16542, -22.71054 , which is equivalent to: RA (J2000): 17h 08m 39.70s Dec(J2000): -22d 42' 38.0" with an uncertainty of 2.8 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=0.31 (+0.13, -0.12). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+/-0.5). The best-fitting absorption column is 7.4 (+4.2, -3.0) x 10^21 cm^-2, in excess of the Galactic value of 1.5 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.5 x 10^-11 (9.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.4 (+4.2, -3.0) x 10^21 cm^-2 Galactic foreground: 1.5 x 10^21 cm^-2 Excess significance: 3.2 sigma Photon index: 1.9 (+/-0.5) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00530581. The fact that the XRT source is fading suggests that Swift trigger 530581 (Zhang et al., GCN Circ. 13618) is most likely a GRB. The Swift/UVOT began settled observations of the field of GRB 120811A 5627 s after the BAT trigger (Zhang et al., GCN Circ. 13618). No optical afterglow consistent with the XRT position 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 white 6243 6443 197 > 20.7 v 6654 6853 197 > 19.1 b 6038 7593 313 > 20.2 u 5832 7468 393 > 20.0 uvw1 5627 7263 393 > 19.9 uvw2 6449 6649 197 > 19.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.77 in the direction of the burst (Schlegel et al. 1998). This circular is an official product of the Swift-XRT and Swift-UVOT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13642 SUBJECT: GCN for GRB 120811C DATE: 12/08/14 20:33:25 GMT FROM: Peter Jenke at MSFC Peter Jenke (MSFC/NPP) reports on behalf of the Fermi GBM Team: "At 15:34:55.09 UT on 11 August 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120811C (trigger 366392098 / 120811649) which was also detected by the Swift/BAT (Barthelmy et al. 2012, GCN 13622). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 133 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 14.3 s (50-300 keV). The time-averaged spectrum from T0-6.14 s to T0+10.24 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.71 +/- 0.20 and the cutoff energy, parameterized as Epeak, is 54 +/- 3 keV. The event fluence (10-1000 keV) in this time interval is (2.98 +/- 0.08)E-06 ergs/cm^2. The 1-sec peak photon flux measured starting from T0+3.072 s in the 10-1000 keV band is 5.9304 +/- 0.55 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: 13644 SUBJECT: GRB 120811B: Fermi GBM observation DATE: 12/08/15 02:22:29 GMT FROM: Shaolin Xiong at UAH Shaolin Xiong (UAH) and Chip Meegan (USRA) report on behalf of the Fermi GBM Team: "At 00:20:31.288 UT on 11 August 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120811B (trigger 366337233 / 120811014), which was also located by the IPN (S. Golenetskii et al. 2012, GCN 13627). The GBM on-ground location is consistent with the IPN position. The angle from the Fermi LAT boresight is 85 degrees. The GBM light curve consists of two pulses with a duration (T90) of about 0.448 s (50-300 keV). The time-averaged spectrum from T0-0.064 s to T0+0.384 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.29 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 1294 +/- 145 keV. The event fluence (10-1000 keV) in this time interval is (2.45 +/- 0.10)E-6 erg/cm^2. The 64 ms peak photon flux measured starting from T0+0.064 s in the 10-1000 keV band is 21.0 +/- 1.3 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: 13679 SUBJECT: GRB 120811C: optical observations DATE: 12/08/18 22:18:42 GMT FROM: Alexei Pozanenko at IKI, Moscow L. Elenin (KIAM), A. Volnova (SAI MSU), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 120811C (Barlow et al., GCN 13622) with 0.45-m telescope of ISON-NM observatory starting on Aug. 12 (UT) 03:25:07. We took several unfiltered images of 30 s exposures. The optical afterglow (Denisenko et al., GCN 13623) is marginally detected in co-added frames at coordinates (J2000) 13:18:43.98 +62:18:03.4 with uncertainty of 0.5 arcsec in both coordinates. A preliminary photometry of co-added frames is based on the USNO-B1.0 (R2) nearby stars is following: T_start, T0+, Exposure, OT, UL (3 sigma) (UT) mid, d (s) 03:25:07 0.5095 1800 21.5 +/-0.5 21.2 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13693 SUBJECT: GRB 120811C: optical observations DATE: 12/08/20 15:14:34 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Litvinenko (UBAI), A. Volnova (SAI MSU), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of GRB 120811C (Barlow et al., GCN 13622) with 0.4-m telescope of ISON-Kitab observatory starting on Aug. 11 (UT) 15:53:49. We took several unfiltered images of 30 s exposures. The optical afterglow (Denisenko et al., GCN 13623) is clearly detected in single initial frames. A photometry of some co-added frames is based on the SDSS stars SDSS id RA Dec R J131912.45+621444.3 13 19 12,453 +62 14 44,35 16.63 J131815,89+621830,6 13 18 15,896 +62 18 30,67 16.64 is following: T_start, T0+, Exposure, OT, (UT) mid, d (s) 15:53:49 0.01392 4x30 17,90 +/-0.13 15:56:05 0.01569 5x30 17.95 +/-0.13 15:58:55 0.01841 10x30 18.20 +/-0.10 16:04:35 0.02356 15x30 18.45 +/-0.11 16:13:06 0.03145 25x30 18.40 +/-0.07