//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11277 SUBJECT: GRB 100915A: Swift detection of a likely burst DATE: 10/09/15 01:51:42 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT O. M. Littlejohns (U Leicester), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), A. Rowlinson (U Leicester), M. H. Siegel (PSU) and M. Stamatikos (OSU/NASA/GSFC) report on behalf of the Swift Team: At 01:31:05 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100915A (trigger=434178). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 315.648, +65.667 which is RA(J2000) = 21h 02m 36s Dec(J2000) = +65d 39' 60" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This is a BAT image-only trigger with significance reported on-board of 8.67 sigma. Ground processing of the BAT scaled map image indicates a slightly weaker, 6.4 sigma excess. As is typical for such triggers, there is nothing obvious in the raw light curve. We will need to wait for event-by-event data on the ground to clarify the nature of the light curve. The XRT began observing the field at 01:33:17.7 UT, 131.9 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 315.6937, 65.6731 which is equivalent to: RA(J2000) = 21h 02m 46.50s Dec(J2000) = +65d 40' 23.0" with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 71 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 consistent with the Galactic value of 2.27 x 10^21 cm^-2 (Kalberla et al. 2005). The initial flux in the 2.5 s image was 5.89e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 140 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 0.51. Burst Advocate for this burst is O. M. Littlejohns (oml2 AT star.le.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: 11279 SUBJECT: GRB 100915A: Enhanced Swift-XRT position DATE: 10/09/15 10:24:02 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 5278 s of XRT Photon Counting mode data and 9 UVOT images for GRB 100915A, 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 = 315.69440, +65.67303 which is equivalent to: RA (J2000): 21h 02m 46.66s Dec (J2000): +65d 40' 22.9" with an uncertainty of 1.6 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: 11280 SUBJECT: GRB 100915A: Swift-XRT refined analysis DATE: 10/09/15 11:37:28 GMT FROM: Owen Littlejohns at U of Leicester O. M. Littlejohns (U Leicester) reports on behalf of the Swift-XRT team: We have analysed 8.5 ks of XRT data for GRB 100915A (Littlejohns et al. GCN Circ. 11277), from 138 s to 18.8 ks after the BAT trigger. The data comprise 95 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 11279). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=0.9 (+0.6, -1.8). At T+320 s the decay steepens to an alpha of 2.4 (+0.6, -0.3). The light curve breaks again at T+1058 s to a decay with alpha=0.66 (+0.16, -5.16), before a final break at T+6126 s after which the decay index is 1.6 (+0.8, -0.3). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.37 (+0.21, -0.20). The best-fitting absorption column is 3.8 (+1.3, -1.1) x 10^21 cm^-2, in excess of the Galactic value of 2.3 x 10^21 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.74 (+/-0.18) and a best-fitting absorption column of 4.6 (+1.0, -0.9) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.5 x 10^-11 (8.2 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 1.6, the count rate at T+24 hours will be 1.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 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/00434178. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11281 SUBJECT: GRB 100915A: Swift-BAT refined analysis DATE: 10/09/15 13:06:38 GMT FROM: Scott Barthelmy at NASA/GSFC W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), O. M. Littlejohns (U Leicester), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (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 100915A (trigger #434178) (Littlejohns, et al., GCN Circ. 11277). The BAT ground-calculated position is RA, Dec = 315.664, 65.676 deg, which is RA(J2000) = 21h 02m 39.4s Dec(J2000) = +65d 40' 32.3" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 54%. The mask-weighted light curves shows two broad peaks, the first starting at ~T-90sec, peaking at ~T+5 sec, and ending at ~T+90 sec. The second, weaker peak starts at ~T+110, peaks at ~T+170 sec and ends at ~T+190 sec. T90 (15-350 keV) is 200 +- 31 sec (estimated error including systematics). The time-averaged spectrum from T-36.3 to T+72.2 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 2.88 +- 0.00, and Epeak of 265.2 +- 0.0 keV (chi squared 66.1 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.5 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+8.76 sec in the 15-150 keV band is 0.5 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.50 +- 0.23 (chi squared 73.1 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/434178/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11282 SUBJECT: GRB 100915A: Swift/UVOT Upper Limits DATE: 10/09/15 14:10:44 GMT FROM: Craig Swenson at PSU/Swift C. A. Swenson (PSU) and O. M. Littlejohns (U Leicester) report on behalf of the Swift/UVOT team. The Swift/UVOT began settled observations of the field of GRB 100915A 123s after the BAT trigger (Littlejohns et al., GCN Circ. 11277). No new source is found at the enhanced XRT position (Osborne et al., GCN Circ. 11279). The 3-sigma uppder limits for the finding chart (fc) and summed exposures are reported below: FILTER T_start(s) T_stop Exposure Mag/3UL =========================================================== white fc 140 290 147 >21.46 white 142 11637 1619 >22.83 v 123 13122 1057 >20.98 b 557 7343 467 >21.43 u fc 300 550 246 >20.68 u 300 7161 963 >21.52 uvw1 680 6956 491 >20.87 uvm2 1256 18902 2787 >21.79 uvw2 606 12544 1152 >21.50 The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.51 (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11283 SUBJECT: GRB 100915A: Correction to Swift-BAT refined analysis DATE: 10/09/15 14:56:36 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC) (i.e. the Swift-BAT team): We would like to make corrections to the BAT refined analysis of GRB 100915A (GCN Circ. 11281). The BAT time-averaged spectrum is best fit by a simple power-law (PL) model rather than a power-law with an exponential cutoff (CPL) model. We believe a low signal to noise in the observed spectrum of this burst causes a significant improvement in chi2 by a CPL model over a PL model. We would like to correct the 3rd paragraph of GCN Circ. 11281 to: "The time-averaged spectrum from T-36.3 to T+72.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.50 +- 0.24. The fluence in the 15-150 keV band is 1.5 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+8.76 sec in the 15-150 keV band is 0.5 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. " We apologize for possible inconvenience. We would like to thank Eleonora Troja for pointing this issue. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11285 SUBJECT: GRB 100915A: GRT Optical Observation DATE: 10/09/16 00:11:56 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (UMBC/GSFC), D. Donato (UMCP/GSFC), N. Gehrels (GSFC), T. Okajima (JHU/GSFC), Y. Urata (NCU), C.A. Wallace (FGCU) We observed the field of GRB 100915A detected by Swift (trigger #434178; Littlejohns et al., GCN Circ. 11277) with the 14-inch Goddard Robotic Telescope (GRT) located at the Goddard Geophysical and Astronomical Observatory (http://cddisa.gsfc.nasa.gov/ggao/). A total 423 images of 5 sec (200 images), 30 sec (80 images), 60 sec (120 images) and 100 sec (23 images) exposures were taken in the R filter starting from September 15 01:33:32 (UT) about 146 seconds after the trigger (70 seconds after the BAT position notice) and stopped on September 15 05:49:30 (UT). We do not detect the optical afterglow both in the individual images and the stacked image, which only combined good quality 418 images, inside the XRT position (Osborne et al., GCN #11279). The estimated five sigma upper limit of the combined image (total exposure of 12500 sec) is ~19.8 mag using the USNO-B1 catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11287 SUBJECT: GRB100915A: MITSuME Ishigakijima Optical upper limits DATE: 10/09/16 15:22:45 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ), K. Yanagisawa (OAO, 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 100915A (Littlejohns et al., GCN 11277) 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 10 10:46:01 UT (~9.2 h after the trigger). We did not find any new point source within the enhanced XRT error circle (Osborne et al., GCNC 11279) 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 ------------------------------------------------------ 0.40450 11:13:34 2760.0 >22.0 >21.5 >21.0 0.56696 15:07:30 4560.0 >22.5 >21.8 >21.1 ------------------------------------------------------ T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11292 SUBJECT: GRB 100915A: TAROT Calern observatory optical observations DATE: 10/09/19 07:42:30 GMT FROM: Alain Klotz at CESR-CNRS Klotz A. (CESR-OMP), Gendre B. (IASF), Boer M. (OHP-OAMP), Atteia J.L. (LATT-OMP) report: We imaged the field of GRB 100915A detected by SWIFT (trigger 434178) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France. The observations started 97s after the GRB trigger (20s after the notice). The elevation of the field decreased from 47 degrees above horizon and weather conditions were good. The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). Time sampling is 10 seconds / pixel. We do not detect any OT with a limiting magnitude of: t0+97s to t0+157s : R > 17.2 We co-added a series of exposures: t0+174s to t0+394s : R > 19.0 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: 11323 SUBJECT: GRB 100915 optical upper limit DATE: 10/10/09 01:08:30 GMT FROM: Alina Volnova at SAI MSU E. Klunko (ISTP), A. Volnova (SAI MSU), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of the Swift GRB 100915A (Littlejohns et al., GCN 11277) with AZT-33IK telescope of Sayan observatory (Mondy) on Sep. 15 between (UT) 14:02 - 16:54 under variable weather conditions and mean seeing of about  ~1.9". In the two stacked images of two epochs we do not detect any source in enhanced XRT error circle (Osborne et al. GCN 11279). The upper limits (3 sigma) of the two stacked images based on USNO-B1.0 field stars are the following: t-t0,d      filter    exp.,s  uplim 0.53437  R       15*60   23.2 0.60644  R       15*60   23.4