//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10006 SUBJECT: GRB 091010: Swift-XRT position DATE: 09/10/10 20:24:43 GMT FROM: Raffaella Margutti at U. di Milano Bicocca R. Margutti (INAF-OAB) & C. Guidorzi (U. Ferrara) report on behalf of the Swift XRT team: We have analyzed the first orbit data (1.8 ks exposure) of the Swift ToO observation of the SuperAGILE detected (Donnarumma et al., GCN Circ. 10004; Feroci, GCN Circ 10005) burst GRB 091010. The Swift observation started on 2009 Oct 10 at 14:48:26 UT, about 43 ks after the SuperAGILE trigger. We detected a single, uncatalogued X-ray source within the SuperAGILE error box at RA, Dec =298.6661, -22.5181 which is equivalent to: RA (J2000): 19h54m39.86s Dec (J2000): -22:31:05.2 with an uncertainty of 4.3 arcsec (radius, 90% confidence). The source lies 72 arcsec from the SuperAGILE position. The source has a count rate of about 5.7E-02 count s^-1. At the moment it is not possible to determine whether the source is fading given the current statistics. Burst Advocate for this burst is R. Margutti (raffaella.margutti AT brera.inaf.it). 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.) This is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10007 SUBJECT: GRB 091010: Swift/UVOT Upper Limits DATE: 09/10/10 21:54:59 GMT FROM: Peter Curran at MSSL P.A. Curran (MSSL-UCL) and R. Margutti (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began ToO observations of the field of the SuperAGILE detected GRB 091010 (Donnarumma et al., GCN 10004) on 2009 Oct 10 at 14:48:26 UT. No optical afterglow consistent with the Swift XRT position (Margutti et al., GCN 10006) is detected in the UVOT exposures. Preliminary 3-sigma upper limits, using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627), for the exposures are: Filter Time(s) Exp(s) Mag -------------------------------------- wh 4.41e4 498 >21.36 v 4.47e4 609 >19.86 u 4.35e4 567 >20.48 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.10 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10008 SUBJECT: GRB 091010: GROND afterglow candidate DATE: 09/10/11 04:11:35 GMT FROM: Andrea Rossi at TLS Tautenburg A. Rossi (Tautenburg), A. Rau, P. Afonso and J. Greiner (all MPE), report on behalf of the GROND team: Starting October 10 at 23h45 UT (21.03hrs post-burst) GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile) imaged the field of GRB 091010 (Donnarumma et al., GCN #10004) simultaneously in the g'r'i'z'JHK bands. Within the Swift-XRT circle (Margutti et al., GCN #10006) we find a single source at: RA(J2000): 19:54:39.80 DEC(J2000): -22:31:03.9 with uncertainties of 0.5" in each coordinate. The object is detected in the r' band with a preliminary AB magnitude of ~22.2 calibrated against the GROND photometric zero point. No correction for Galactic foreground extinction of E(B-V)=0.14mag (Schlegel et al. 1998, Apj, 500, 525) was applied. Strongly variable sky conditions and high seeing >2.5 arcsec) prevent reliable detections in others bands. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10011 SUBJECT: GRB 091010 optical upper limits DATE: 09/10/11 11:29:01 GMT FROM: AAVSO GRB Network at AAVSO Arto Oksanen and Eric Southgate (The Hermitage Observatory, Sunshine Coast, QLD, Australia) report to the AAVSO International High Energy Network the following optical observations of the field of GRB 091010 (GCN Circ. #10004, Donnarumma et al.): A. Oksanen and E. Southgate report an upper limit of approximately CR=17.5 on the optical afterglow of GRB 091010 (GCN Circ. #10004, Donnarumma et al.). The afterglow upper limit was measured relative to the star USNO-B1.0 0674-0991959. A single, 120-second observation was made using an A&M 130-mm TMB APO with an SBIG ST2000 CCD camera and no filter. The mid-point of the exposure was 2009 October 10, 11:19:17 UT, approximately 8.6 hours after the SuperAGILE trigger. The entire error box of the burst centered on RA 19h 54m 40.51s , Dec -22d 32m 17.36s was imaged; no new sources were detected using visual comparison of the CCD image with the DSS2 R-band plate of the area. A stacked, 10 x 120-second image was also created from subsequent images of the field using the same camera. The midpoint of this image was 2009 October 10 11:47 UT, approximately 9.0 hours after the burst. This image was visually examined, and no candidate objects were found; the image extends to approximately the same depth as the DSS2 red plate. A FITS image of the initial observation is available at the following URL: ftp://ftp.aavso.org/grb/ArtoOksanen_GRB091010_2455115.12128_.fits The AAVSO thanks the Curry Foundation for its support of the AAVSO International High Energy Network. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10012 SUBJECT: GRB 091010: Enhanced XRT position DATE: 09/10/11 12:41:43 GMT FROM: Phil Evans at U of Leicester P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team: Using 3934 s of XRT Photon Counting mode data and 4 UVOT images, 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 = 298.66550, -22.51820 which is equivalent to: RA (J2000): 19 54 39.72 Dec (J2000): -22 31 05.7 with an uncertainty of 1.9 arcsec (radius, 90% confidence). This is consistent with the position of the candidate optical afterglow seen by GROND (Rossi et al. GCN Circ. 10008). 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 is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10013 SUBJECT: Konus-Wind observations of GRB 091010 DATE: 09/10/11 13:11:40 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 GRB 091010 (Donnarumma et al., GCN Circ. 10004; Feroci, GCN Circ 10005) triggered Konus-Wind at T0=09788.232 s UT (02:43:08.232). The burst light curve shows a multipeaked structure with a total duration of ~8 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB091010_T09788/ As observed by Konus-Wind the burst had a fluence of (9.4 ± 1.1)x10-6 erg/cm2, and a 64-ms peak flux measured from T0 + 2.240s of (8.3 ± 1.0)x10-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range). The time-integrated spectrum of the burst (from T0 to T0+8.448 s) is well fitted in the 20 keV - 2 MeV range by GRB (Band) model for which: the low-energy photon index alpha = -1.20 (-0.28, +0.35), the high energy photon index beta = -2.9(< -2.4), the peak energy Ep = 119(-17, +19) keV (chi2 = 55/59 dof). All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10014 SUBJECT: GRB 091010: RXTE detection DATE: 09/10/11 15:16:55 GMT FROM: Peter Curran at MSSL A.L. Watts, A. Patruno, M. van der Klis (U.v. Amsterdam), P. Casella (Southampton), P.A. Curran (MSSL-UCL), D. Altamirano, Y. Cavecchi, N. Degenaar, R. Kaur, M. Linares, P. Soleri, R. Wijnands, A. Kamble (U.v. Amsterdam) and N. Rea (ICE-CSIC/IEEC) report: RXTE observations taken at the time of the SuperAGILE detected burst GRB 091010 (Donnarumma et al., GCN Circ. 10004; Feroci, GCN Circ 10005) also recorded the event.  The RXTE PCA detected two strong flares in emission, the first coinciding with the SuperAGILE trigger time (02:43:09 UT) and the other 2s later.  Each flare lasted ~1s. There is also evidence for a third weaker flare 5s after the trigger. Peak count-rate (2-60 keV, 0.1s binning) for the first flare is 250 counts/s, and for the second flare is 500 counts/s. The RXTE lightcurve can be found at http://staff.science.uva.nl/~pgcasell/GRB091010 At the time RXTE was observing XTE J1751-305, with nominal pointing direction RA(J2000)  = 17h 51m 13.49s Dec(J2000) = -30d 39' 23.4" so was approximately 28 degrees off-axis from GRB 091010.  For this reason spectral and timing information will be degraded. Preliminary timing analysis reveals no significant periodic variability. The flares are not detected strongly below 30 keV.  Although bright, this GRB did not have an exceptionally high peak flux.  It is therefore perhaps a little surprising that RXTE was able to record this event so strongly given the offset angle. Reflections in the collimator may be responsible (see Laros et al. 1985). We would like to thank the SuperAGILE team for providing us with their lightcurve for GRB 091010, which enabled us to confirm the RXTE identification.  //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10017 SUBJECT: GRB 091010: Faulkes Telescope North observations DATE: 09/10/12 13:02:36 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), A. Gomboc (U. Ljubljana), D. Bersier, Z. Cano, S. Kobayashi, A. Melandri, C.J. Mottram, C.G. Mundell, R.J. Smith, I.A. Steele (Liverpool JMU), N.R. Tanvir (U. Leicester) on behalf of a large collaboration report: We began observing the SuperAGILE GRB 091010 (Donnarumma et al. GCN Circ. 10004) with the 2-m Faulkes Telescope North (FTN) on October 11, 04:54:49 UT (26.2 hours post burst) with the BVRi' filters. We clearly detect the GROND afterglow candidate (Rossi et al. GCN Circ. 10008) with the Ri' filters with the following magnitudes: Telescope Mid Time Exposure Filter Mag (hours) (s) ------------------------------------------------------- FTN 27.5 7x300 i' 22.11 +- 0.15 FTN 27.6 6x300 R 22.2 +- 0.2 ------------------------------------------------------- Calibration was performed against a nearby USNOB-1 star: RA(J2000), Dec(J2000)= 19:54:38.242, -22:31:27.11 assuming R2=14.89 and i'=15.02. Compared with GROND measurements, we cannot confirm any fading of the source due to the closeness in time between our observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10018 SUBJECT: GRB 091010: Fermi GBM observation DATE: 09/10/12 15:05:12 GMT FROM: David Gruber at MPE A. von Kienlin, E. Bissaldi and D. Gruber (all MPE) report on behalf of the Fermi GBM Team: "At 02:43:09.32 UT on 10 October 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 091010 (trigger 276835391 / 091010113), which was also detected by SuperAGILE (Donnarumma et al., GCN 10004). The GBM on-ground location is consistent with the Swift-XRT position (Margutti et al. 2009, GCN 10006 and Evans et al. 2009, GCN 10012). The angle from the Fermi LAT boresight is 55.7 degrees. Moreover, this burst was bright enough to result in a Fermi spacecraft repointing maneuver. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of multiple peaks with a duration (T90) of about 8.1 +/- 0.5 s (8-1000 keV). The time-averaged spectrum from T0-0.128 s to T0+8.064 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -1.11 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 150 (+6/-5) keV (C-stat 446 for 359 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.09 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.9 s in the 8-1000 keV band is 40.9 +/- 0.5 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: 10022 SUBJECT: GRB 091010: AGILE-MCAL measurement and GRID upper limit DATE: 09/10/13 15:44:40 GMT FROM: Martino Marisaldi at INAF-IASF M. Marisaldi, F. Fuschino (INAF/IASF Bologna), F. Longo, E. Moretti (INFN Trieste), A. Bulgarelli, F. Gianotti, M. Trifoglio, M. Galli, C. Labanti, G. Di Cocco (INAF/IASF Bologna), E. Del Monte, I. Donnarumma, Y. Evangelista, M. Feroci, F. Lazzarotto, L. Pacciani, P. Soffitta, E. Costa, I. Lapshov, M. Rapisarda, A. Argan, F. D'Ammando, G. Piano, G. Pucella, S. Sabatini, E. Striani, M. Tavani, A. Trois, V. Vittorini (INAF/IASF Roma), A. Chen, A. Giuliani, S. Mereghetti, P. Caraveo, F. Perotti (INAF/IASF Milano), A. Pellizzoni, M. Pilia (INAF/OA Cagliari), S. Vercellone (INAF/IASF Palermo), G. Barbiellini, E. Vallazza (INFN Trieste), A. Morselli, P. Picozza (INFN Roma-2), M. Prest (Universita` dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), P.W. Cattaneo, A. Rappoldi (INFN Pavia), S. Cutini, P. Giommi, C. Pittori, P. Santolamazza, F. Verrecchia (ASDC), L. Salotti (ASI) "The long GRB 091010 localized by SuperAGILE (Donnarumma et al., GCN 10004) triggered also the MCAL instrument onboard AGILE, sensitive in the energy range 330 keV - 100 MeV, at 02:43:10 UT (T0). As seen by MCAL the burst has a double-peaked light curve, with a duration of 3.5 s. The time integrated spectrum in the time interval [T0-1.5 s, T0+2.0 s] can be fit in the energy range 400 keV - 2 MeV with a single powerlaw with photon index -3.0 (-0.6, +0.8) (reduced chi2 = 1.09 with 9 d.o.f.). The estimated fluence is (1.40 +/- 0.3)x10-6 erg/cm2 in the same energy range. All reported errors are at the 90% confidence level. No significant emission is detected above 2 MeV. The photon index and fluence are consistent with those reported by Konus-Wind (Golenetskii et al., GCN 10013), when the different energy range is accounted for. No significant emission is detected by AGILE GRID. A 3-sigma Upper Limit for emission in the GRID energy range (E>30 MeV) in the same 3.5 seconds time interval used for MCAL analysis can be placed at 0.043 ph/cm2. Using a 60-seconds time interval starting from T0 the 3-sigma Upper Limit is 0.1 ph/cm2." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10023 SUBJECT: GRB 091010: Suzaku WAM observation of the prompt emission DATE: 09/10/15 09:56:22 GMT FROM: Masanori Ohno at ISAS/JAXA N. Vasquez (Tokyo Tech.), M. Ohno, M. Suzuki,M. Kokubun, T. Takahashi (ISAS/JAXA), K. Yamaoka (Aoyama Gakuin U.), N. Ohmori, E. Sonoda, K. Kono, H. Hayashi, A. Daikyuji, Y. Nishioka, K. Noda, M. Yamauchi (Univ. of Miyazaki), Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.), W. Iwakiri, M. Tashiro, Y. Terada, A. Endo, K. Onda, T. Sugasahara (Saitama U.), Y. Urata (NCU), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), Y. E. Nakagawa, T. Tamagawa (RIKEN), S. Hong (Nihon U.), S. Sugita (Nagoya U.)on behalf of the Suzaku WAM team, report: The long GRB 091010 (Fermi trigger #276835391/091010113, von Kienlin et al., GCN10018, SuperAGILE Donnarumma et al., GCN 10004) triggered the Suzaku Wide-band All-sky Monitor (WAM) in a energy range from 50 keV to 5 MeV at 02:43:09.50 UT (=T0). The observed light curve shows a multi-peaked structure, starting at T0 s and ending at T0+7s, with a total duration (T90) of 6.5 s. The fluence in 100 - 1000 keV was 6.22(+0.48,-0.42) x 10-6 erg/cm^2. The 1-s peak flux measured from T0+1 s was 9.91(+0.89,-1.03) photons/s/ cm^2 in the same energy range. Preliminary result shows that the time-averaged spectrum from T0-1s to T0+7s is well fitted by a single power-law with a photon index of 2.50 (+0.24,-0.22) (chi^2/d.o.f = 11.7/8). All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. The light curves for this burst are available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10024 SUBJECT: GRB 091010: Swift-XRT refined analysis DATE: 09/10/15 14:19:46 GMT FROM: Raffaella Margutti at U. di Milano Bicocca R. Margutti (INAF-OAB) reports on behalf of the Swift-XRT team: The Swift ToO observations of the SuperAGILE GRB 091010 (Donnarumma et al., GCN Circ. 10004; Feroci, GCN Circ. 10005) started on 2009 Oct 10th at 14:48:26 UT. The XRT data set consists of 9 ks exposure in PC mode. The UVOT-enhanced XRT position was given by Evans et al. in GCN Circ. 10012. The X-ray source reported by Margutti & Guidorzi, GCN Circ. 10006 has faded to a level of (2.4 +/- 1.0)e-3 count/sec, with a best fit power-law decay index of alpha=-1.4 +/- 0.6 . This source is thus confirmed as the afterglow of GRB 091010. The spectrum extracted in the time interval 43-50 ks contains about 170 photons and can be fitted using an absorbed power law model. Spectral channels have been grouped so as to have 5 counts per bin and then weighted using the Churazov method (Churazov et al. 1996). The best fit photon index is found to be 2.3 +/- 0.4. The spectrum shows evidence of absorption at the level of (1.9 +/- 0.1)e21 cm-2, in excess of the Galactic value in the direction of the burst which is 8.1e20 cm-2, Kalberla et al. 2005. The observed (unabsorbed) flux over this time interval is 1.5e-12 (2.8e-12) erg cm^-2 s^-1. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (6.6 x 10^-11) erg cm^-2 count^-1. All quoted errors are at 90% confidence level. The results of the xrt automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020116. This is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10027 SUBJECT: GRB 091010: optical afterglow candidate rejection DATE: 09/10/16 15:16:32 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), A. Melandri, C.G. Mundell, D. Bersier, Z. Cano, N.R. Clay, S. Kobayashi, C.J. Mottram, R.J. Smith, I.A. Steele (Liverpool JMU), A. Gomboc (U. Ljubljana), N.R. Tanvir (U. Leicester) on behalf of a large collaboration report: We re-observed the optical afterglow candidate (Rossi et al. GCN Circ. 10008) of the SuperAGILE GRB 091010 (Donnarumma et al. GCN Circ. 10004) with the 2-m Faulkes Telescope South (FTS) on October 16, 09:27:33 UT (6.3 days post burst) with the Ri' filters. The source is still clearly detected in both filters. Comparison with our previous values obtained at 1 day post burst (Guidorzi et al. GCN Circ. 10017) shows that the source did not fade appreciably. We derived an upper limit to the possible power-law decay index of alpha<0.5 (90% confidence) from 1 to 6 days post burst, flux~t^(-alpha). Given that a comparably shallow and long-lasting decay has never been observed, we can confidently rule out this source as the optical afterglow of GRB 091010. Telescope Mid Time Exposure Filter Mag (days) (s) ----------------------------------------------------- FTS 6.29 6x300 i' 22.2 +- 0.3 FTS 6.31 6x300 R 22.3 +- 0.3 ----------------------------------------------------- Calibration was the same as that used in our previous report (GCN Circ. 10017). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10030 SUBJECT: GRB 091010: optical obsevation DATE: 09/10/17 02:11:22 GMT FROM: Alexei Pozanenko at IKI, Moscow V. Rumyantsev (CrAO), E. Klunko (ISTP) and A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of SuperAGILE GRB 091010 (Donnarumma et al. GCN 10004) with Shajn telescope of CrAO on Oct. 12 between (UT) 16:55:18 - 18:09:40. In the XRT error circle (Margutti et al. GCN 10006) we detect a single object at coordinates (J2000) RA: 19 54 39.80 Dec: -22 31 04.71. The coordinates of the object coincide with OT candidate reported by Rossi et al. (GCN 1008). The photometry against nearby USNO-B1.0 stars (0674-0991940 RA:19 54 39.26 Dec: -22 31 29.7 R=18.18, 0674-0991922 RA:19 54 38.07 Dec: -22 31 12.4 R=17.27) is following: T0+ Filter, Exposure, mag., err. (d) (s) 2.62 R 71x60 22.40 +/- 0.17 Our photometry confirm the absence of variability of the OT candidate (Rossi et al.GCN 1008, Guidorzi et al.GCN 10027). However the object looks like extended in E-W direction, and can be a candidate in a host galaxy of GRB 091010. The combined image can be found in http://grb.rssi.ru/GRB091010/GRB091010_091012_R_ZTSh.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10057 SUBJECT: Konus-Wind observations of GRB 091010 DATE: 09/10/21 14:12:00 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 GRB 091020 (Racusin et al., GCN 10048; Palmer et al., GCN Circ 10051) triggered Konus-Wind at T0=77804.860s UT (21:36:44.860). The burst light curve shows a smooth structure with a total duration of ~40 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB091020_T77804/ As observed by Konus-Wind the burst had a fluence of (1.04 ± 0.21)x10-5 erg/cm2, and a 256-ms peak flux measured from T0 + 0.768s of (1.2 ± 0.2)x10-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range). The time-integrated spectrum of the burst (from T0 to T0+33.024 s) is well fitted in the 20 keV - 2 MeV range by GRB (Band) model for which: the low-energy photon index alpha = -0.93 (> -1.57), the high energy photon index beta = -1.9(-0.8 / +0.2), the peak energy Ep = 103(-68, +248) keV (chi2 = 62/60 dof). All the quoted values are preliminary. All the quoted errors are at the 90% confidence level. Assuming z = 1.71 (Dong Xu et al., GCN 10053) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 0.73, the isotropic energy release E_iso ~7.9x10^52 erg, the peak luminosity (L_iso)_max ~2.5x10^52 erg/s, and Ep_rest ~280 keV. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10128 SUBJECT: Fermi LAT Upper Limits on GRB 091010 DATE: 09/11/03 17:12:28 GMT FROM: Daniel Kocevski at UC Berkeley Daniel Kocevski (SLAC), Aurelien Bouvier (SLAC), Julie McEnery (NASA/GSFC), Jim Chiang (SLAC), Elena Moretti (INFN Trieste), Vlasios Vasileiou (NASA/GSFC & UMBC) and Frederic Piron (LPTA) report on behalf of the Fermi LAT team: We present the flux and fluence upper limits based on the non-detection of GRB 091010 (trigger 276835391 / 091010113) (GCN 10004, GCN 10018) by the Fermi Large Area Telescope (Fermi LAT) in the 0.1-300 GeV band. As reported by Kienlin et al. 2009, GCN 10018, GRB 091010 was well detected by the Fermi Gamma-ray Burst Monitor with a 1-sec peak photon flux in the 8-1000 keV band of 40.9 +/- 0.5 ph/s/cm^2 and was sufficiently bright to trigger a spacecraft repointing maneuver. The burst occurred 55.7 degrees off axis with respect to the LAT boresight. The subsequent repoint maneuver resulted in pointed observations starting 200 seconds post trigger and lasting for approximately 5 hours. No significant emission was detected in the LAT band during any of the time intervals in which the burst was in the LAT field of view. We use a Bayesian method (as described in Abdo et al. 2009: arXiv:0910.4192) to determine the 95% CL upper limits on the LAT energy flux and fluence for several time intervals with respect to the GRB trigger time (02:43:09.32 UT, October 10th 2009): Prompt Emission (T0 to T0+8.1s): 95% Energy Flux Upper Limit = 1.94e-7 erg/s/cm^2 95% Energy Fluence Upper Limit = 1.57e-06 erg/cm^2 Extended Emission Interval 1 (T0-200s to T0+200s): 95% Energy Flux Upper Limit = 4.35e-9 erg/s/cm^2 95% Energy Fluence Upper Limit = 1.74e-06 erg/cm^2 Extended Emission Interval 2 (T0 to T0+400s): 95% Energy Flux Upper Limit = 4.13e-9 erg/s/cm^2 95% Energy Fluence Upper Limit = 1.65e-066 erg/cm^2 Furthermore, the upper limit on the ratio between the 0.1-300 GeV to 8-1000 keV fluence (HE/LE) for the T0 to T0+8.1s interval is 0.14. The upper limit results presented above are preliminary. The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.