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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)

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) Tsunefumi Mizuno Hiroshima Univ. 7 May 2009, Tokyo Tech, Japan. Outline. Fermi Gamma-ray Space Telescope Fermi LAT and GBM Burst Advocator GRBs seen by Fermi Overview GRB080916C GRB081024B

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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)

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  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) Tsunefumi Mizuno Hiroshima Univ. 7 May 2009, Tokyo Tech, Japan

  2. Outline • Fermi Gamma-ray Space Telescope • Fermi LAT and GBM • Burst Advocator • GRBs seen by Fermi • Overview • GRB080916C • GRB081024B • Kanata Telescope for GRB

  3. The Fermi Gamma-ray Space Telescope • Launch on 11 June 2008 • LAT (Large Area Telescope) • Energy range: 20 MeV-300 GeV • Effective Area: ~8000 cm2 • FOV: 2.4 sr (EGRET 0.5 sr) • Dead time: 26.5 ms (EGRET 100 ms) • GBM (GLAST Burst Monitor) • Consists of 12 NaI and 2 BGO detectors. • Energy range:8 keV – 30 MeV • Field of view: 9.5 str • Initial localization: <15 deg in 2s Spectrum more than 7 energy decades!!

  4. Burst Advocator • Scientists serve as “Burst Advocator” and cover 24 hrs/day and 7 dyas/week • Japanese B/A consists of young members from 3 institutes; • Masanori Ohno, Rie Sato (ISAS/JAXA), • Yoshitaka Hanabata, Takeshi Uehara and Hiromitsu Takahashi (Hiroshima Univ.), • Takeshi Nakamori, Takashi Shimokawabe (Tokyo Tech.) • Report on the LAT visibility and check the LAT data • Successfully issued GCN circular for GRB 090217 and GRB090323 which occurred during Japanese shift.

  5. Fermi Detection of GRBs GRB080825C (GCN8183, Bouvier et al.) GRB080916C* (GCN8246, Tajima et al.) (Abdo et al. 2009 Sci, 323, 1688) GRB081024B (GCN8407, Omodei et al.)(short GRB w/ GeV photons) GRB081215A (GCN8684, McEnery et al.) GRB090217 (GCN8903, Ohno et al.) GRB090323* (GCN9021, Ohno et al.) GRB090328* (GCN9044, McEnery et al.; GCN9077, Cutini et al.) • GBM : GRB detection rate is ~200/yr. (08/11/2008 – 03/10/2009 116 GCN Circulars) • LAT : 7 GRBs detected until May 2009 and notified to GCN Circulars. Detection rate is ~10/yr. 2 LAT GRBs w/ WAM detection 4 GRBs w/ GeV photons 3 GRBs w/ redshift (*) 2 GRBs w/ GCN by Japanease BA

  6. GRB080916C • z=4.35 +/- 0.15 (GROND; GCN8257) • More than 3000 LAT photons, 145 above 100 MeV and 14 above 1 GeV. Eh=13.2 GeV • Delayed & temporary extended (t>200s) HE emission 8-260 keV 260 keV-5 MeV LAT (all) >100 MeV >1 GeV

  7. Implications from GR080916C • Delayed & Extended HE emissions • Fitted by a single Band function. Eiso ~ 8.3 x 1054 ergs, highest ever observed. No conclusive evidence of extra component • Minimum bulk Lorentz factor840±40 (from opacity in bin-’b’) • EBL effect not included • Lorentz invariance violation • 13.2 GeV @ T0+16.5 s • MQG> (1.5±0.2) x 1018 GeV/c2, 1/10 of the Plank mass GRB080916C Planck mass Pulsar(Kaaret 99) GRB(Ellis 06) AGN(Biller 98) GRB(Boggs 04) AGN(Aharonian 08) min MQG (GeV) 1015 1016 1017 1018 1019

  8. GRB081024B • The first non-controversial short GRB w/ GeV photons • 11 photons above 100 MeV, Eh=3 GeV • no redshift • Single Band function, delayed HE onset & temporary extended HE emission (common feature among LAT GRBs?) • Gmin~100 (z=0.1), ~700 (z=3.0) (from opacity in bin-”b”) NaI 8 – 260 keV Preliminary! BGO 260 keV – 5 MeV LAT all events LAT > 100 MeV -4 -2 0 2 4 6 8 10

  9. HOWPol on Kanata Telescope(1) (Hiroshima One-shot Wide-field Polarimeter) １露出型偏光撮像（広視野 7’×7’、狭視野 1’×15’） Filter exchanger Prism exchanger Focus adj. stage Focal mask exchanger CCD dewer Collimator lens Shutter and pupil Camera lens Polarmetric unit exchanger • 2008年7月28-31日　ファーストライト • 検出効率： B: 8%, V: 20%, R: 30%, I: 28% (望遠鏡、大気込み) • 2008年11月4日～　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の補正で0.6%精度が達成） • 試験観測、超新星観測が主（GRBアラート対応観測はTRISPECで） • 2009年5月3日～　GRBアラート対応自動観測開始

  10. HOWPol on Kanata Telescope (2) • 2008年度中はHOWPolでのGRB観測は間に合わず • TRISPECでのGRB観測は9例、うち2例でdetected GRB t_start –t_end Satel. ⊿t comment -------------------------------------------------------------------- 080426 13:30:31-13:50:15 Swift, 428 s, Non-detection, shortburst 080506 17:49:26-19:22:30 Swift, 185 s, R=17.5-19.3 (Uehara+ in prep) 080810 13:16:23-19:39:17 Swift, 371 s, R=13.9-18.7 (Uehara+ in prep) 080905 12:01:32-12:58:06 Swift, 157 s, Non-detection 081012 13:16:17-14:06:13 Swift, 353 s, Non-detection 081211 15:22:22-15:40:37 Swift, 3.6 hr, Non-detection 081211B 15:47:29-15:49:02 Swift, 14.5 hr, Non-detection 081222 13:09:15-13:21:14 Swift, 8.3 hr, Non-detection 090217 14:20:13-16:00:17 Fermi, 9.4 hr, Cloudy, non-detection 090404 16:02:44-16:21:13 Swift, 374 s, Cloudy, non-detection 090410 18:48:50-19:01:18 Swift, 1.8 hr, Low-altitude, non-detection 090417B 15:31:49-15:38:18 Swift, 706 s, Non-detection 090418 12:35:35-12:38:19 Swift, 1.5 hr, Cloudy, non-detection 090426 12:54:09-13:28:22 Swift, 322 s, non-detection z=2.609 ⊿t は衛星のトリガーから露出開始（t_start）までの経過時間

  11. HOWPol on Kanata Telescope (3) GRB 080506：X線フレアと相関しない可視残光 GRB 080810：ゆっくりと青くなっていく可視残光 Ｘ線 可視・近赤外　　Ｘ線 TRISPEC観測 TRISPEC観測 緑　可視Ｖ 青　近赤Ｊ 水　近赤Ｋｓ • 2009年5月3日からGRB対応観測（但し狭視野モード用のウォラストンプリズムを視野マスク無しで使用するため背景スカイが4倍高くなり観測限界は悪い） • 2009-2010年度 公募研究「明るいガンマ線バースト初期残光の偏光分光測光同時モニター」にて広視野モード用のウォラストンプリズムを導入予定 (川端の講演)

  12. Summary • Fermi GBM detects ~0.5GRB/day and LAT ~10 GRBs/year • 7 LAT GRBs above 100 MeV • 4 GRBs w/ GeV photons, one short (GRB081024B) • 2 GRBs w/ WAM detection, 3 w/ redshift • GRB080916C w/ maximum Eiso ever observed • 14 photons > GeV, Gmin>=900, MQG>1.3x1018 GeV/c2 • GRB081024B is the first short GRB with photons above 1 GeV. • Gmin=100 (for z=0.1) and 700 (for z=3.0) • Single Band function, delayed HE onset and extended HE emission => common feature? • HOWPol on Kanata Telescope is now ready (on May 3, 2009) • 9 GRBs observed, 2 GRBs detected in 2008/4-2009/3 by TRISPEC

  13. Backup Slides

  14. Spectral Analysis Spectrum at T0+0.1 – T0+0.8s GBM 2nd pulse (including maximum energy photon of 3.0 GeV) can be fitted by a Band Function. Preliminary! • α= -0.9053 ± 0.203 • β= -1.993 ± 0.0768 • Ep = 819.2 ± 547.0 keV No strong evidence of additional high energy component. 10 103 104 105 102 106 (keV) (1MeV) (1GeV)

  15. Minimum Lorentz Factor Use interval b to derive Gamma minimum as described in GRB080916C paper (Abdo et al, 2009) and Asano-san’s talk. β= -1.993 ± 0.0768 Δt : The variability time scale = duration/2 = 0.35sec E0 : The maximum photon energy = 3.0GeV. Although z is uncertain, Γmin(z=0.1) ≒ 100, Γmin(z=3.0) ≒ 700

  16. HOWPol on Kanata Telescope (2) • 2008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 • 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(100-1000s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 200秒 1000秒 Δp=0.2% 偏光測定 限界 1分露出時 10分露出時 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0.4

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