//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9850 SUBJECT: GRB 090831: Fermi GBM detection DATE: 09/08/31 10:11:30 GMT FROM: Arne Rau at MPE Arne Rau (MPE) reports on behalf of the Fermi GBM Team: "At 07:36:36.58 UT on 31 August 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090831 (trigger 273396998 / 090831317). The on-ground calculated location, using the GBM trigger data, is RA = 145.1, DEC = 51.0 (J2000 degrees, equivalent to 09 h 40m m, +51 d 00 '), with an uncertainty of 1.9 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 107 degrees. This burst was also independently detected by INTEGRAL SPI-ACS. The GBM light curve consists of two structured main pulses with a duration (T90) of about 69.1 s (8-1000 keV). The time-averaged spectrum from T+0.0 s to T0+47.7 s is best fit by a power law function with an exponential high energy cutoff. The power law index is -1.57 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 399.6 +/- 86.2 keV (chi squared 443 for 415 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.66 +/- 0.05)E-05 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+8.784 s in the 8-1000 keV band is 9.4 +/- 0.4 ph/s/cm^2. A Band function fits the spectrum equally well (chi squared 441 for 414 d.o.f.) with Epeak= 243.8 +/- 85.3 keV, alpha = -1.52 +/- 0.06 and beta = -1.96 +/- 0.14. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9851 SUBJECT: GRB 090831B: Swift detection of a possible burst DATE: 09/08/31 18:26:54 GMT FROM: David Palmer at LANL M. De Pasquale (UCL-MSSL), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), P. A. Evans (U Leicester), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), M. Stamatikos (OSU/NASA/GSFC), R. L. C. Starling (U Leicester) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 18:01:14 UT, the Swift Burst Alert Telescope (BAT) triggered and located possible GRB 090831B (trigger=361477). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 3.619, +27.970 which is RA(J2000) = 00h 14m 29s Dec(J2000) = +27d 58' 12" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows nothing significant as is typical for an image trigger. The XRT began observing the field at 18:03:44.9 UT, 149.9 seconds after the BAT trigger. No source was detected in the promptly available XRT data. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White filter starting 153 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 25% of the BAT 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 BAT 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 0.03. Due to the lack of detection by XRT, we cannot confirm that this is a true astrophysical source. Further analysis of the downlinked data (available in ~3 hours) will be required. Burst Advocate for this burst is M. De Pasquale (mdp 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: 9852 SUBJECT: GRB 090831: MAXI GSC detection DATE: 09/08/31 19:22:52 GMT FROM: Nobuyuki Kawai at Tokyo Tech M. Matsuoka (JAXA), S. Miyoshi, M. Nakajima, H. Negoro, R. Ishiwata (Nihon Univ.), K. Kawasaki, S. Ueno, H. Tomida, M. Suzuki, M. Ishikawa (JAXA), T. Mihara, M. Kohama, Y.E. Nakagawa, M. Sugizaki, T. Yamamoto (RIKEN), N. Kawai, M. Morii, K. Sugimori (Tokyo Tech), A. Yoshida, K. Yamaoka, S. Nakahira (Aoyama G. Univ.), H. Tsunemi, M. Kimura (Osaka Univ.), Y. Ueda, N. Isobe, S. Eguchi and K. Hiroi (Kyoto Univ.) report on behalf of the MAXI team: The Gas Slit Camera (GSC) of MAXI, the all-sky X-ray monitor on the ISS, detected a bright X-ray source at the position consistent with GRB 090831 (Rau et al, GCN 9850) in the energy range of 2-30 keV. The nominal location of the source as measured by GSC is (R.A., Dec.) = (145.4 deg, +51.4 deg) = (09:41:36, +51:24:00) (J2000) with an estimated systematic uncertainty of about 1 degree. The source was detected for 60 seconds during the transit of GSC over the source starting approximately at 07:36:35 UT on 31 August 2009, very close to the Fermi GBM trigger time. The X-ray flux at the peak of the transit was about 3 Crab. There are significant time structure within the transit light curve, which would be simply triangular for a steady source. The all-sky image and the transit light curve is shown at the MAXI web site http://maxi.riken.jp/ in the "News" section. MAXI is currently in the commissioning phase that runs for three months. The systematic uncertainty in localization will be significantly improved with the progress of the alignment calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9853 SUBJECT: GRB 090831B, RIMOTS optical upper limits DATE: 09/08/31 20:02:34 GMT FROM: Kenta Kono at Miyazaki U K.Kono, A.Daikyuji, E.Sonoda, N.Ohmori, H.hayasi, K.Noda, Y.Nisioka, M.Yamauchi (University of Miyazaki) We have observed the field covering the error circle of GRB 090831B (Swift trigger 361477, GCN 9851, M. De Pasquale et al.) with the unfiltered CCD camera on the 30-cm telescope at University of Miyazaki. The observation was started 18:03:42 UT, about 2.5 min after the Swift trigger time. We have compared our data of 30 sec exposures with the USNO-A2.0 catalog, There is no new source at the reported position. (GCN 9851, M. De Pasquale et al.) the upper limits are as follows: -------------------------------------------------------------- Start(UT) End(UT) Num. of frames Limit (mag.) -------------------------------------------------------------- 18:03:42 18:04:12 1 15.4 18:03:42 18:40:05 27 17.2 --------------------------------------------------------------- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9854 SUBJECT: GRB 090831C: Swift detection of a burst DATE: 09/08/31 21:42:30 GMT FROM: Scott Barthelmy at NASA/GSFC P. Schady (MSSL-UCL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), A. Rowlinson (U Leicester), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC) and M. A. Stark (PSU) report on behalf of the Swift Team: At 21:30:25 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090831C (trigger=361489). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 108.278, -25.100 which is RA(J2000) = 07h 13m 07s Dec(J2000) = -25d 06' 00" 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 10 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~3 sec after the trigger. The XRT began observing the field at 21:32:23.5 UT, 117.5 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 108.29307, -25.11934 which is equivalent to: RA(J2000) = 07h 13m 10.34s Dec(J2000) = -25d 07' 09.6" with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 85 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 3.24e+21 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White filter starting 120 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Results from the 2.7'x2.7' sub-image are not available at this time. The coverage of the XRT error circle by the 8'x8' region for the list of sources generated on-board is uncertain because the large number of sources filled the available telemetry. No correction has been made for the expected extinction corresponding to E(B-V) of 0.38. Burst Advocate for this burst is P. Schady (ps 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: 9855 SUBJECT: GRB 090831C: Enhanced Swift-XRT position DATE: 09/09/01 02:31:50 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 3607 s of XRT Photon Counting mode data and 3 UVOT images for GRB 090831C, 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 = 108.29453, -25.11859 which is equivalent to: RA (J2000): 07h 13m 10.69s Dec (J2000): -25d 07' 06.9" 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, arXiv:0812.3662). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9857 SUBJECT: GRB 090831C: Swift XRT Refined Analysis DATE: 09/09/01 07:03:06 GMT FROM: Antonia Rowlinson at U.of Leicester A. Rowlinson (U. Leicester) and P. Schady (MSSL-UCL) report on behalf of the Swift-XRT team: We have analysed 8.4 ks of XRT data for GRB 090831C (Schady et al. GCN Circ. 9854), from 121 s to 21.8 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 9855). The light curve has two flares at T+186 s and T+440 s, while the underlying decay can be modelled with a power-law decay with a decay index of alpha=0.83 (+0.17, -0.11). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.84 (+0.21, -0.15). The best-fitting absorption column is 3.254 (+1.001, -0.014) x 10^21 cm^-2, consistent with the Galactic value of 3.2 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 4.9 x 10^-11 (7.2 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 0.83, the count rate at T+24 hours will be 0.0029 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.4 x 10^-13 (2.1 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00361489. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9858 SUBJECT: GRB 090831B: MITSuME optical upper limits DATE: 09/09/01 09:35:30 GMT FROM: Michitoshi Yoshida at Okayama Astrophysical Obs M. Yoshida, D. Kuroda, K. Yanagisawa, Y. Shimizu, S. Nagayama, H. Toda (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 090831B (De Pasquale et al. GCN 9851) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2009-08-31 18:03:21 UT (2m 7s after the burst). We did not find any new point source in the BAT error circle reported by De Pasquale et al. (GCN 9851) in all the three bands. Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration. #PDAY MID-UT T-EXP g' Rc Ic -------------------------------------------------- 0.00505 18:09:49 540.0 >19.0 >18.8 >18.1 0.03482 18:52:41 4200.0 >19.9 >19.7 >19.0 -------------------------------------------------- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9859 SUBJECT: GRB090831C: Swift/UVOT upper limits DATE: 09/09/01 10:42:09 GMT FROM: Patricia Schady at MSSL/Swift P. Schady (MSSL-UCL) reports on behalf of the Swift/UVOT team. The Swift/UVOT began settled observations of the field of GRB 090831C 121s after the BAT trigger (Schady et al., GCN Circ 9854). No new source is detected within the XRT error circle (Evans et al., GCN Circ 9855) in any of the individual or combined UVOT filters. The 3-sigma upper limits of detecting a source at the position of the X-ray afterglow in the first white band finding chart (fc) observation and in consecutive coadded observations for each of the UVOT filters are as follows: Filter T_start(s) T_stop(s) Exp(s) Mag 3-sig UL wh (fc) 121 270 147 > 20.78 wh 561 1183 206 > 20.73 vv 610 1060 58 > 18.47 bb 536 1159 58 > 19.30 uu 279 1134 285 > 19.95 w1 660 1109 58 > 18.74 m2 635 1084 58 > 18.48 w2 586 1209 78 > 18.95 The values quoted above are not corrected for the Galactic extinction due to the large reddening of E(B-V) = 0.38 in the direction of the burst (Schlegel et al., 1998). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9860 SUBJECT: Swift Trigger 361477, called GRB090831B, is probably not real. DATE: 09/09/01 12:45:04 GMT FROM: Massimiliano de Pasquale at MSSL-UCL J.R. Cummings (NASA/UMBC), P.A. Evans (U. Leicester), J.A. Kennea (PSU), C. Pagani (PSU), and M. De Pasquale (MSSL/UCL) on behalf of the Swift team report: The ground analysis of BAT data from trigger 361477 (De Pasquale et al., GCN Circ. 9851) shows a very weak excess in the low energy bands only. The response is consistent with a somewhat unusually large noise fluctuation in the image domain caused by the presence of a bright source in the BAT partially coded field of view (Cyg-X1). The XRT observed the field for 3.23 ks between T0+150 s and T0+10 ks. The data are entirely in Photon Counting mode. We do not find any source in the field of view. A 3-sigma upper limit on covering the BAT onboard error circle is 2.7 x 10^-3 ct/sec. No new source is found in the UVOT white filter finding chart (153-303s after the trigger) inside the BAT error circle down to a 3 sigma upper limit of 20.9. We conclude that the trigger is unlikely to be due to a GRB or any other astrophysical source. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9861 SUBJECT: Konus-Wind observations of GRB 090831A DATE: 09/09/01 13:40:48 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: GRB 090831A (Rau, GCN 9850; Matsuoka et al., GCN 9852) triggered Konus-Wind at T0=27393.820 s UT (07:36:33.820) The burst started with a short (~250 ms) spike which resembles a classical short/hard GRB. The spike is followed by a structured profile with a total duration of ~50 s. The Konus-Wind light curves of this GRB are available at http://www.ioffe.ru/LEA/GRBs/GRB090831_T27393/ As observed by Konus-Wind, the burst had a fluence of 1.33(-0.2,+0.25)x10-5 erg/cm2, and a 16-ms peak flux, measured from T0, of 9.3(-2.2,+3.2)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+49.408 s) is well fitted (in the 20 keV - 2 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with alpha = -1.53(-0.14,+0.16), and Ep = 253(-69,+162)keV (chi2 = 69/61 dof). Fitting by the GRB (Band) model yields to the same alpha and Ep values with the high energy photon index beta of -9 (< -2.1) The spectrum at the maximum count rate, measured from T0 to T0 + 0.256s (initial short pulse), is well fitted (in the 20 keV - 2 MeV range) by the GRB (Band) model with: alpha = -1.28(-0.3,+0.7), beta = -2.5( < -1.7), and Ep = 273(-212,+331)keV (chi2 = 12/22 dof). All the quoted values are preliminary. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9862 SUBJECT: GRB 090831C: GROND upper limits DATE: 09/09/01 18:45:16 GMT FROM: Thomas Kruehler at MPE/MPI F. Olivares, T. Kruehler and J. Greiner (all MPE Garching) report on behalf of the GROND team: We observed the field of GRB 090831C (Swift trigger #361489; Schady et al., GCN #9854) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at LaSilla Observatory (Chile). Observations started at 08:07 UT on September 1st, 2009, 10.6 hr after the burst. At this time the position of the burst was becoming visible above the pointing constraints of the telescope. Observations suffer from high airmass and large seeing of around 2". In stacked images of 74 min total integration time in griz and 60 min in JHK, we do not detect any object within the enhanced XRT error circle (Evans et al., GCN #9855), down to the following limiting magnitudes (all in the AB system): g' > 23.5 r' > 24.0 i' > 23.3 z' > 22.9 J > 21.4 H > 21.1 K > 20.0 These upper limits were derived using the GROND zeropoints and 2MASS field stars as reference and are not corrected for significant Galactic foreground extinction corresponding to a reddening of E(B-V)=0.38 mag (Schlegel et al., 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9863 SUBJECT: GRB 090831C BAT refined analysis DATE: 09/09/02 01:30:11 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), P. Schady (MSSL-UCL), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 090831 (trigger #361489) (Schady, et al., GCN Circ. 9854). The BAT ground-calculated position is RA, Dec = 108.294, -25.112 deg which is RA(J2000) = 07h 13m 10.6s Dec(J2000) = -25d 06' 44.0" with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 84%. The mask-weighted light curve shows a single roughly symmetrical peak. T90 (15-350 keV) is 3.3 +- 1.0 sec (estimated error including systematics). The time-averaged spectrum from T+0.6 to T+4.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.33 +- 0.29. The fluence in the 15-150 keV band is 1.5 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.94 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/361489/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9864 SUBJECT: GRB 090831A: IPN Triangulation DATE: 09/09/02 04:31:29 GMT FROM: Valerie Connaughton at MSFC S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team, V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi GBM team, K. Yamaoka, M. Ohno, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada, T. Murakami, K. Makishima, and Y. Hanabata on behalf of the Suzaku-WAM team, M. Suzuki, A. Yoshida, N. Kawai, S. Nakahira, Y.E. Nakagawa, M. Kohama and M. Matsuoka on behalf of the MAXI team and A. von Kienlin, G. Lichti, A. Rau, and K. Hurley on behalf of the INTEGRAL SPI-ACS GRB team, report: GRB 090831A, reported in GCN 9850 (Rau) as Fermi/GBM trigger 273396998 / 090831317, and as a MAXI event in GCN 9852 (Matsuoka et al.), and as a Konus event in GCN 9861 (Golenetskii et al.), was also detected by Suzaku-WAM and INTEGRAL (SPI-ACS). We have triangulated this burst to a Konus-GBM annulus centered at RA(2000)=155.584 (10h 22m 20s) Dec(2000)=+3.772 (+3d 46' 21"), with a radius of 49.244 ± 0.177 deg (3 sigma). The Konus-WAM annulus is centered at RA(2000)=155.807 (10h 23m 14s) Dec=+3.771 (+3d 46' 16"), with a radius of 49.210 ± 0.249 deg (3 sigma). The Konus-SPI-ACS annulus is centered at RA(2000)=156.539 (10h 26m 09s) Dec(2000)=-3.361 (-3d 21' 41"), with radius of 56.520 ± 0.412 deg (3 sigma). A map is posted at http://www.ioffe.ru/LEA/GRBs/GRB090831_T27393/IPN/ showing the GBM best-fit position (blue star), the MAXI localization circle and best-fit position (pink star), and the IPN annuli (solid lines with centers dot-dashed). The shaded area shows the intersection of the Konus-GBM annulus with the 1-deg MAXI localization circle. The maximum distance between points on this overlapping region is 1.47 deg, at coordinates RA, Dec = 143.985 (09h 35m 56s) +51.878 (+51d 52' 40") and 146.304 (09h 45m 13s) +52.229 (+52d 13' 46"). The area of this region is 0.160 sq. deg. This map will also be posted at http://ssl.berkeley.edu/ipn3/090831A. The IPN localization may be improved. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9900 SUBJECT: GRB 090831A: Suzaku WAM observation of the prompt emission DATE: 09/09/05 07:59:58 GMT FROM: Norisuke Ohmori at Miyazaki U N. Ohmori, K. Noda, E. Sonoda, K. Kono, H. Hayashi, A. Daikyuji, Y. Nishioka, M. Yamauchi (Univ. of Miyazaki), M. Ohno, M. Suzuki, M. Kokubun, T. Takahashi (ISAS/JAXA), K. Yamaoka, S. Sugita (Aoyama Gakuin U.), Y. E. Nakagawa, T. Tamagawa (RIKEN), S. Hong (Nihon U.), N. Vasquez (Tokyo Tech.), 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), on behalf of the Suzaku WAM team, report: The long GRB 090831A (Fermi-GBM trigger 273396998 / 090831317; Arne et al., GCN 9850, MAXI-GSC; Matsuoka et al., GCN 9852) triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 07:36:36.472 UT (=T0). The observed light curve shows main three peaks starting at T0s, ending at T0+10s, followed by a long weak tail seen up to T0+48s. The total T90 duration is about 53 seconds. The fluence in 100 - 1000 keV was 6.8 (-1.8, +1.0)x10-6 erg/cm2. The 1-s peak flux measured from T0+4 s was 1.8 (-0.2, +0.3) photons/cm2/s in the same energy range. Preliminary result shows that the time-averaged spectrum from T0 s to T0+48 s is well fitted by a power-law with exponential cutoff model: dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) with alpha 0.89(-0.91, +0.65), and Epeak 286(-57, +88) keV (chi2/d.o.f. = 93/80). All the quoted errors are at statistical 90% confidence level, in which the systematic uncertainties are not included. The light curves for this burst is available at: http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html