GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 1 可視・ X 線・ γ 線同時観測で探る γ 線バース ト (Exploring GRBs through Optical, X- ray and Gamma-ray Observations) November 27, 2008 Tsunefumi Mizuno (Hiroshima Univ.) Yasushi Fukazawa, Koji Kawabata, Hideaki Katagiri, Yoshitaka Hanabata (Hiroshima Univ.), Goro Sato, Masanori Ohno (ISAS/JAXA) Hiroyasu Tajima (SLAC) on behalf of the Fermi GBM/LAT Collaboration Contribution to the Conference “Deciphering the Ancient Universe with Gamma-Ray Bursts” at Mitaka, Tokyo, Japan (Nov 27-29, 2008)

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 2 Introduction Multiwavelength Observation to explorer GRB phenomena  Fermi LAT and GBM 7 decades of energy coverage (8 keV-300 GeV) High sensitivity imaging in GeV band (>100 MeV) Spectral cutoff (  -factor), GeV excess (hadronic origin?), etc.  Suzaku WAM Largest Aeff in keV, large FOV (~2  ) “best friend” to Fermi LAT/GBM; better constrain of the spectral parameter, spectral-lag analysis, time-resolved spectroscoy.  Kanata Optical Telescope 1.5 m diameter & very fast driving speed (5deg/sec) HOWPol is about to ready Polarimetry of optical afterglow to constrain the magnetic field structure.

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 3 The Fermi Observatory Large Area Telescope (LAT) Large Field of View (>2.4 sr) views entire sky every 3 hrs in wide energy range (20 MeV GeV) Gamma-ray Burst Monitor (GBM) Views entire unocculted sky 12 NaI detectors: 8 keV - 1 MeV 2 BGO detectors: 150 keV - 30 MeV LAT+GBM=> more than 7 energy decades! (For detail, see talk by K. Asano’s in this afternoon) ~200 GRBs/year expected by the GBM

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 4 Fermi Launch !! (photo taken by M. Ohno) Launch from Cape Canaveral Air Station 11 June 2008 at 12:05 PM EDT Circular orbit, 565 km altitude (96 min period), 25.6 deg inclination. Operation Onboard processing (GBM): alerts and updates to GCN with localization. LAT ground processing (5-12 hours): updates location and the spectrum/flux. Scientists serve as “Burst Advocator” (for GBM and LAT individually)  LAT BAs cover 24hrs/day and 7days/week by an international collaboration. They continuously check the GCN Notice and perform the analysis of LAT data.  In Japan, ISAS/JAXA, Tokyo Institute of Technology and Hiroshima Univ. are involved in BA. See talk by R. Sato for detail.

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 5 GRBs Detected by Fermi Sep. 18, 2008 “Fermi/GBM Data Now Available” ( bin//W3Browse/w3table.pl?Action=Detailed%20Mission&Observatory=fermi)  32 GRBs from Sep. 12 th to Nov. 19 th (~0.5/day, as expected before the launch)  11 GRBs are also detected by Suzaku WAM 3 LAT GRBs  GRB080825C (<35sec, 14 photons in 100MeV-1GeV)  GRB080916C (<100sec, 14 photons above GeV) see K. Asano’s talk  GRB081024B (short GRB, up to 3 GeV. GCN Circular #8407)

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 6 GRB081024B by Fermi Nicola Omodei On behalf of the Fermi LAT Collaboration The Fermi LAT telescope detected an increased count rate at 2008/10/24 (21:22:41), associated with a GRB detected also by the Fermi GBM (Trigger number: ). The location of the GRB reported by Fermi LAT data ground analysis is: Ra=322.9, Dec= which corresponds to Ra (J2000) = 21:31:36.00 Dec (J200) = 21:12:14.4 within a statistical uncertainty of 0.16 degrees (68% containment radius). The emission from this point source was seen up to 3 GeV, in the first 5 seconds after the trigger. The Fermi LAT point of contact for this burst is Nicola Omodei 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. This message can be cited. LAT GCN Circular # LAT photos above 100 MeV The first short GRB with emission above GeV (possible exception of GRB930131; Sommer et al. 1994).  Joint analysis of GBM/LAT data is important and is underway by Fermi GBM/LAT team.

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 7 Detailed GBM Light Curve NaI ( keV) NaI ( keV) NaI ( keV) BGO ( keV) Background subtracted light curves, with s bin width (to make them match with WAM light curves) 3 time regions could be specified (colored areas) Only below ~100 keV, two pulses are clearly separated.  possible soft lag of the 2 nd pulse. 2 nd pulse is shorter in high energy band.  possible spectral evolution (s)

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 8 GBM Spectra of GRB081024B NaI & BGO fit by a single power-law model: index ~ 1.0 +/- 0.1 Interval1 ( s) Interval2 ( s) Interval3 ( s) Apparent cutoff not seen up to 1 MeV Possible spectral evolution  In interval 3, spectrum softens and shows deficit of photons below 30 keV. Statistics-limited analysis with preliminary detector responses. Further analysis using more accurate responses is underway. single PL-fit: Index ~ 0.9 +/- 0.2 single PL-fit: Index~ / Preliminary

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 9 Suzaku WAM also Detected the GRB WAM TH0( keV) WAM TH1( keV) WAM TH2( keV) WAM TH3( keV) Barycentric correction not applied yet counts/significance in s (stat error only)  TH0: 75(3.3  )  TH1: 178(7.6  )  TH2: 85(3.2  )  TH3:139(3.9  ) Above 100 keV, factor of ~2 higher counts and slightly better significance than GBM => WAM/GBM joint analysis could improve the spectral fit (s)

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 10 HOWPol on Kanata Telescope (1) (Hiroshima One-shot Wide-field Polarimeter) CCD dewer Focus adj. stage Focal mask exchanger Collimator lens Camera lens Filter exchanger Prism exchanger Shutter and pupil Polarmetric unit exchanger １露出型偏光撮像（広視野 7’×7’ 、 狭視野 1’×15’ ） 2008 年 7 月 日  ファーストライト  効率測定： B: 7%, V: 19%, R: 27%, I: 25% ( 大気含む ) 2008 年 11 月 4 日～  広視野用偏光プリズム導入  定常試験観測開始 器械偏光 ~4% （第三鏡による偏光面回転のみで 0.4% 精度で の補正が可能、他の依存性調査中）

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 11 HOWPol on Kanata Telescope (2) 1000 秒 Akerlof & Heather (2007) Statistics of 108 Swift GRBs 40% で光学残光 うち t=1000 秒換算での等級が 14 等,16 等,18 等より明るいもの 0.9%,4.6%,16.7% 4 年間観測を続けると  1000 秒後でも 16 等より明るい サンプルを１個 /4 年 ( s の間で偏光の変化を追う )  200s で 16 等より明るいサンプ ルを 3-4 個 (10 分露出で偏光測定 ) => 年 1 個程度の偏光観測を期待 仮定： 発見レート 100 個 / 年 高度係数 0.33 (>20 度） 夜間係数 0.4 晴天係数 年 12 月～ ＧＲＢアラート対応観測開始 ⇒バーストから 100 秒以内の偏光観測開始めざす 1 分露出時 10 分露出時 Δp=0.2% 偏光測定 限界 200 秒

GRB_Fermi-WAM-Kanata_2008Nov.ppt Tsunefumi Mizuno 12 Summary Fermi GBM detects ~0.5GRB/day, as expected before the launch. Now the GBM data is publicly available. Three LAT GRBs above 100 MeV  Two long (GRB080825C, GRB080916C) and one short (GRB081024B). GRB081024B is the first short GRB with photons above 1 GeV.  LAT detected photons up to 3 GeV  In GBM band, we observed a “hint” of the soft lag below 100 keV and the spectral evolution in the 2 nd pulse. (preliminary statement)  Detailed analysis is underway by GBM/LAT team. Suzaku-WAM has largest Aeff in keV and is the best friend of Fermi GBM/LAT  Simultaneous detection of GRB081024B. Better statistics above 100 keV. HOWPol on Kanata Telescope is about to ready  Study the magnetic filed of external shock. ~1GRB/year is expected.