EAFON GRB follow-up Yuji Urata 浦田裕次 Saitama Univ/ASIAA NCU ( ~) Y. Qiu, J.Y Hu, J.Wei, W. Zheng, J.S. Deng, M. Zhai, X. Liping (National Astronomical Observatory, China)

Out line ① Introduction of EAFON ② Prompt optical observation by WIDGET ③ Continuous monitoring results ④ Ongoing constructions New telescopes Pan-STARRS ⑤ Summary

Brief summary and merit of EAFON Established at 2004 Fill in the East Asian blank for Optical follow-ups Kiso, Japan experience for HETE-2 China, Japan, Korea, Taiwan collaboration (1)Introduction of EAFON

Around HETE-2 launch (Early 2001) There was no telescopes for Optical follow-ups in east Asian region! CFHT 5 (+1)telescopes in EA 1(+1) telescope in USA 1 unique instrument in Japan Ultra Wide FOV. 64 x 64 degree High Time resolution Automatic Operations Beijing 2, 1, 0.8 m Kiso 2001 ～ Lulin 2003 ～ Beijing 2004 ～ WIDGET 2004 ～ LOAO(1m) BOAO1.8m 2005~ 2006~ 2007~ Yunnan2.4m 2m will be available from 2009 PanSTARRs

Brief summary and merit of EAFON Established at 2004 Fill in the East Asian blank for Optical follow-ups Kiso, Japan experience for HETE-2 China, Japan, Korea, Taiwan collaboration Reduce weather risk in East Asian region Good weather ratio 40~50% at each site Fastest response time 76 Xinglong 108 follow-up observations using 8 telescopes plus 1 unique instrument Prompt optical observations by WIDGET Continuous monitoring (1)Introduction of EAFON

Since CCD cameras and 1 mount 64 x 64 degree Fully automatic operation Provide several GB/night (2) WIDGET : Prompt Optical observations Site : Kiso, Japan 32° ヘルクレス座 へびつかい座 かんむり座 てんびん座 木星 さそり座 いて座 たて座 Milky way Galactic Center

(2) WIDGET:System summary and observation list System upgrading (limiting mag R~12, 5s exposure) 9 Simultaneous Observations (ratio 2~3 events / year)

(2) Prompt obs : GRB080319B Trigger time 2008/03/19 06:12:49 (UT) → 15:12:49 (JST) : ~afternoon tea time at Japan USA : weather monitor detected the flash ! Big Dipper 北斗七星 V=6.7±0.2

LOAO, Lulin, CFHT monitoring (0.04~80days) 80 days (3-1) GRB080319B (3) Continuous Monitoring αo = 1.28±0.01 No Jet break ~ 80days Jet opening angle : Θ>12 deg No jet break (~80 days after the burst) Not so wide e.g. GRB (tj~400day, α=1.29±0.03, θ~67deg) ◯ EAFON □Gemini obs. X-ray break1 X-ray break2 X-ray break3 No breaks with X-ray αx=1.85 αx=1.17 αx= days ◯ EAFON □Gemini obs. According to αo-αx relation For external shock testing (e.g. Urata et al. 2007), OK Rejected

(3-2) Ep - Eγiso relation : GRB071010B Suzaku/WAM & Swift/BATJoint fitting (3) Continuous Monitoring GRB071010B is the one of the best sample in Swift era - Ep estimation from Swift/BAT and Suzaku/WAM - Longer dense optical afterglow monitoring TAOS, LOAO, Lulin Epeak = 50.9 keV Ep-Eγiso Expected jet break time : days Another outlier : GRB Urata et al. 2007, Shirasaki et al Θ~10° Optical (R-band) LC Single PL Possible break ~8days

(3-3) Normal decay phase Pre-Swift era, the standard external shock model successfully explain late phase (~1day) optical afterglows (e.g. Panaitescu & Kumar 2001, Urata et al. 2003) Recent X-ray & Optical analysis claim that X-ray and optical come from different emission regions. (e.g. Huang, Urata et al ApJL) Pre-Swift era, the standard external shock model successfully explain late phase (~1day) optical afterglows (e.g. Panaitescu & Kumar 2001, Urata et al. 2003) Recent X-ray & Optical analysis claim that X-ray and optical come from different emission regions. (e.g. Huang, Urata et al ApJL) Simple testing method is needed to evaluate the standard external shock model. (3) Continuous Monitoring

Simple testing for external shock model There are four ways, (1)αx-βx (Liang et al Swift era) (2)αo-βo (Sari et al HETE-2 era) (3)βx-βo (Jakobsson et al Swift era) βo, fairly depends on the assumed dust model βx, Swift/XRT statistic is not good for normal decay phase to estimate spectral β. (4)αo-αx (This work, Urata et al 2007) “s” is the ambient matter density parameter (0<s). Thus -1/4 <αo-αx. ( n ∝ r -s) (3) Continuous Monitoring

Samples & Event selection criteria (1)Swift event – (~200 events) (2)Clear normal decay phase in X-ray X-ray movie events (~100 events) (3)Simultaneous optical observations (~14 events) Optical movie events Large part of data come from EAFON There are 14 GRBs that have good coverage with X-ray and optical bands at the normal decay phase. (3) Continuous Monitoring

Sample table Our EAFON observation is efficient. (3) Continuous Monitoring

αo – αx relation The classical external-shock model predicts αo – αx = -1/4 (solid line) and 1/4 (dashed line) for the uniform ISM (s=0) and for the wind medium (s=2) cases, respectively. R-band decay index αo as a function of the X-ray decay index αx in the normal decay phase. Four events out of 14 violate the limit at more than 3σlevel Standard afterglow Outlier (3) Continuous Monitoring

Summary of normal decay Tested the external-shock model using the late time simultaneous optical and X-ray For selected 14 best samples, four events violate the limit at more than 3σ level Totally, the external shock models cannot explain all of events (need improve or new model) Outlier maybe capable of the internal shock origin Urata et al., ApJ Letter 668, L95, (2007 )

(4-1) New Telescopes Lulin 2m telescope (First light ~2009) Multi-color camera, NIR instrument Kiso 30cm Robotic telescope with WIDGET (This autumn) 2m LOT TAOS (Hung et al) Kiso 30cm Robotic Telescope Automatic control Roof is ready. Telescope system is under testing. Lulin 2-m telescope (4) Ongoing constructions

(4-2) Pan-STARRS NCU, Taiwan (EAFON site), is one of the member. PS1 (2008~) Observe entire sky visible at Hawaii every 7~10 days 2000~3000 transients & variable sources per night (including new type transient) Some follow-ups will be done by the frame work of EAFON. (4) Ongoing constructions

Summary EAFON was established at 2004 Filled in East Asian Optical follow-up blank Performing significant observations 108 follow-ups GRB080319B etc Two new telescopes are under construction for further GRB follow-ups & other transients

Range of αo – αx for individual events The classical external-shock model predicts αo – αx = -1/4 (solid line) and 1/4 (dashed line) for the uniform ISM (s=0) and for the wind medium (s=2) cases, respectively. External-Shock Outlier

GRB071010B Amati

East Asian GRB Follow-up Network Prompt optical observation by WIDGET Continuous monitoring Multi-color observations Reduce weather risk in East Asian region Good weather ratio 40~50% at each site East Asia has rainy season…. Fastest response time

GRB071010B Epeak-Eγiso Expected jet break time : days (2) Continuous Monitoring Another outlier : GRB Urata et al. 2007, Shirasaki et al Θ~10°

Follow-up 望遠鏡 の観測可能領域 WIDGET の観測可能 領域 他の大型望遠鏡 の観測可能領域 GRB GRB GRB050525a GRB GRB GRB050502a