//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18578 SUBJECT: GRB 151111A: Swift detection of a burst DATE: 15/11/11 08:53:58 GMT FROM: Kim Page at U.of Leicester L. M. McCauley (PSU), P. A. Evans (U Leicester), H. A. Krimm (CRESST/GSFC/USRA), K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 08:33:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151111A (trigger=663074). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 56.828, -44.164 which is RA(J2000) = 03h 47m 19s Dec(J2000) = -44d 09' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single FRED-like structure with a duration of about 40 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 08:34:35.8 UT, 72.5 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 56.8452, -44.1615 which is equivalent to: RA(J2000) = 03h 47m 22.86s Dec(J2000) = -44d 09' 41.3" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 45 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 (1.07 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.6 (+1.82/-1.61) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 1.85e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 81 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 0.01. Burst Advocate for this burst is L. M. McCauley (marissamc AT swift.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: 18579 SUBJECT: GRB 151111A: Enhanced Swift-XRT position DATE: 15/11/11 13:39:52 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 639 s of XRT Photon Counting mode data and 1 UVOT images for GRB 151111A, 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 = 56.84455, -44.16154 which is equivalent to: RA (J2000): 03h 47m 22.69s Dec (J2000): -44d 09' 41.5" with an uncertainty of 1.8 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: 18580 SUBJECT: GRB 151111A: Swift-BAT refined analysis DATE: 15/11/11 14:23:50 GMT FROM: Hans Krimm at NASA-GSFC J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), L. M. McCauley (PSU), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (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 151111A (trigger #663074) (McCauley, et al., GCN Circ. 18578). The BAT ground-calculated position is RA, Dec = 56.850, -44.154 deg which is RA(J2000) = 03h 47m 24.0s Dec(J2000) = -44d 09' 12.9" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 80%. The mask-weighted light curve shows a single long FRED-shaped peak beginning at T-5 sec, peaking at T+0 sec and fading to background by T+140 sec. T90 (15-350 keV) is 76.93 +- 12.59 sec (estimated error including systematics). The time-averaged spectrum from T-5.62 to T+91.35 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.79 +- 0.45, and Epeak of 56.6 +- 9.2 keV (chi squared 98.19 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.7 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+0.52 sec in the 15-150 keV band is 1.0 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.76 +- 0.00 (chi squared 115.24 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/663074/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18581 SUBJECT: GRB 151111A: LCOGT-FTS afterglow observations DATE: 15/11/11 17:05:15 GMT FROM: Simone Dichiara at Ferrara U/Italy S. Dichiara (U. Ferrara, ICRANet), C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana) on behalf of a larger collaboration report: The 2-m LCOGT Faulkes Telescope South began observing Swift GRB 151111A (McCauley et al. GCN 18578) on November 11, 10:45 UT (2.2 hours after the burst trigger) with SDSS R and I filters under poor sky conditions. We do not detect any optical afterglow candidate within the enhanced Swift-XRT error circle (Goad et al. GCN 18579) with the following magnitudes: Mid Time Exposure Filter Magnitude (hours) (s) ------------------------------------------------------- 3.5 10x120 R > 20.5 4.2 9x120 I > 20.0 ------------------------------------------------------- Calibration is done against nearby USNOB-1 stars using R2 and I nominal magnitudes. We note in both filters the presence of a possible source of R~21 mag at the following position: RA(J2000)=03:47:22.75, DEC(J2000)=-44:09:43.6 (error radius of 1.5"). We caution that the detection is not significant, so we cannot rule out the possibility that it is a fluke. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18582 SUBJECT: GRB 151111A: Fermi GBM observation DATE: 15/11/11 21:23:12 GMT FROM: Elisabetta Bissaldi at U.Innsbruk/IAPP E.Bissaldi (INFN Bari) and P.N. Bhat (UAH) report on behalf of the Fermi GBM Team: "At 08:33:20.03 UT on 11 November 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 151111A (trigger 468923604 / 151111356), which was also detected by the Swift/BAT (McCauley et al. 2015, GCN 18578). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 50 degrees. The GBM light curve consists of a single FRED-like episode with a duration (T90) of about 40 s (50-300 keV). The time-averaged spectrum from T0-2 s to T0+30 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is 0.0 ± 0.2 and the cutoff energy, parameterized as Epeak, is 107 ± 8 keV. The event fluence (10-1000 keV) in this time interval is (2.05 ± 0.13)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.2 s in the 10-1000 keV band is 1.41 ± 0.17 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: 18583 SUBJECT: GRB 151111A: Swift-XRT refined Analysis DATE: 15/11/12 00:11:28 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), T.G.R. Roegiers (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and L.M. McCauley report on behalf of the Swift-XRT team: We have analysed 16 ks of XRT data for GRB 151111A (McCauley et al. GCN Circ. 18578), from 63 s to 45.5 ks after the BAT trigger. The data comprise 284 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 Goad et al. (GCN Circ. 18579). The late-time light curve (from T0+5.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.2 (+/-0.4). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.28 (+/-0.05). The best-fitting absorption column is 3.7 (+1.9, -1.7) x 10^20 cm^-2, in excess of the Galactic value of 1.1 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.74 (+0.19, -0.18) and a best-fitting absorption column of 5.0 (+4.8, -3.9) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.0 (+4.8, -3.9) x 10^20 cm^-2 Galactic foreground: 1.1 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.74 (+0.19, -0.18) If the light curve continues to decay with a power-law decay index of 1.2, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.8 x 10^-14 (8.4 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00663074. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18585 SUBJECT: GRB 151111A: GROND marginal detection of a afterglow candidate DATE: 15/11/12 04:42:46 GMT FROM: John Graham at MPE/Garching J. F. Graham, T. Schweyer, and J. Greiner (all MPE Garching) report: We observed the field of GRB 151111A (Swift trigger 663074; Page et al., GCN 18578) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 00:08:05 UT on November 12, about 16 hours after the GRB trigger. Consistent with the enhanced X-ray error circle (Evans et al., GCN 18579) and the LCOGT-FTS possible source (Dichiara et al., GCN 18581) we detect a faint source at coordinates RA, DEC (J2000) = 03:47:22.73, -44:09:43.3 with an error of 2". Due to high winds we were able to observe the target for only a limited period in conditions of extremity poor seeing (~3") and thick cirrus. We thus give the following preliminary AB magnitudes with statistical and estimated systematic errors. g: 23.25 ± 0.21 ± 1.0 r: 22.16 ± 0.14 ± 0.5 i: 20.89 ± 0.15 ± 0.5 At present we cannot decide if this is the afterglow. Further observations are currently precluded by high winds. We encourage additional observations from locations with better observing conditions. Magnitudes are calibrated against the USNO-B1.0 catalog and are not corrected for the Galactic extinction in the direction of the burst. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18587 SUBJECT: GRB 151111A: Swift/UVOT upper limits DATE: 15/11/12 13:57:55 GMT FROM: Massimiliano de Pasquale at IASF-Palermo M. De Pasquale, S. Emery (UCL-MSSL) and L. M. McCauley (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 151111A 81 s after the BAT trigger (McCauley et al., GCN Circ. 18578). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 18579) 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 first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 81 231 147 >20.9 u_FC 293 543 246 >19.7 white 81 6778 519 >21.7 v 622 7094 339 >19.7 b 549 6573 235 >20.6 u 293 6367 442 >19.7 w1 671 6163 216 >20.0 m2 5757 5957 197 >19.7 w2 772 6984 413 >20.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 18598 SUBJECT: GRB 151111A: GROND confirmation of the afterglow and photometric redshift estimate DATE: 15/11/13 18:01:27 GMT FROM: Jan Bolmer at MPE/Garching J. Bolmer, J. Graham, F. Knust and J. Greiner (all MPE Garching) report: We reobserved the field of GRB 151111A (Swift trigger 663074; Page et al., GCN 18578) simultaneously in g’r’i’z’JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 05:31:33 UT on November 13, about 1.9 days after the GRB trigger. The initially reported source at the coordinates of RA, Dec = 56.84483, -44.16201 (+/- 0.2“) (Graham et al. GCN 18585) has clearly faded (e.g. in the r’ band from 22.19 +/- 0.04 to 22.68 +/- 0.05 mag) and we thus conclude that this source is the optical afterglow of GRB 151111A. Furthermore, after correcting for the galactic foregorund E(B-V)=0.01 mag, and fitting a powerlaw model to the 7-cannel GROND SED from the first night, we derive a photometric redshift of z = 3.5 +/- 0.3, according to the g'-band dropout with g'-r’ = 1.3 mag.