Gamma-Ray Burst Optical Observations with AST3 Xue-Feng Wu Xue-Feng Wu Chinese Center for Antarctic Astronomy, Chinese Center for Antarctic Astronomy, Purple Mountain Observatory, Purple Mountain Observatory, Chinese Academy of Sciences Chinese Academy of Sciences 2015, March 9, Hong Kong 2015, March 9, Hong Kong 2015 International Collaboration Meeting on Antarctic Survey Telescopes

Why GRB optical observations so important? Bloom et al., 2001, ApJ, 554, 678 Metzger et al., 1997, Nature, 387, 878 GRB z=0.835 (t~2.3day) host galaxy emission lines absorption lines in afterglow spectrum (t~6-11months) First of all, redshift! -> distance -> luminosity/energy

Importance of GRB optical observations (not complete) (not complete) 1. constraining the initial physical parameters of GRB fireballs – AST3! 2. diagnosing the circum-burst environments – AST3! 3. exploring the structure of GRB jets – AST3! 4. (long) GRB – supernova associations –AST3? 5. obtaining the host galaxy properties (morphology, star-forming, metallicity, etc.) 6. probing the high-redshift Universe (Pop III stars, re- ionization history) with high-z GRBs - KDUST 7. correlations, standard candles, cosmography? – AST3!

Constraining the initial physical parameters of GRB fireballs GRB central engine shocked ejecta - reverse shock shocked ISM -forward shock Akerlof et al., 1999, Nature, 398, 40 0 reverse shock forward shock Peak of reverse shock emission: -> initial Lorentz factor (usually ) -> ISM density (typically – 10 /cm^3)

Constraining the initial physical parameters of GRB fireballs GRB central engine shocked ejecta - reverse shock shocked ISM -forward shock Courtesy: David Coward, Zadko telescope Peak of forward shock emission: (Liang et al. 2010, for a large sample) -> initial Lorentz factor (usually ) -> ISM density (typically – 10 /cm^3) forward shock reverse shock too weak magnetized ejecta? GRB A

diagnosing the circum-burst environments GRB central engine ISM log n log R log t log flux shallower wind log R log flux log t log n n  R^-2 steeper forward shock

diagnosing the circum-burst environments GRB central engine reverse shockforward shock Light curve comparison ISM: more sharp Wind: more shallow

diagnosing the circum-burst environments free wind -> shocked regions -> ISM small wiggles/rebrightening in the light curve observational requirement: continuous and dense -> AST3, Yes! wind bubble of a Wolf-Rayet star Geng, Wu, Li, Huang & Dai, 2014, ApJ n(R) Afterglow light curves (theory)

exploring the structure of GRB jets jet break time -> jet angle -> true energy of GRB! jet signature Harrison et al (1999) two scenarios for jet breaks Woosley, Nature, 414, 853 (2001) Piran, Science, 295, 986 (2002)

exploring the structure of GRB jets Huang, Wu, Dai, Ma & Lu, 2004, ApJ GRB B Racusin, Karpov, Sokolowski, Granot, Wu, et al., 2008, Nature two-component jet model 1 st jet 2nd jet

 jet EpEp E ,jet Briggs et al et al. 1999; Ghirlanda et al. 2004; Dai et al Ghirlanda-Relation correlations, standard candles, cosmography?

Using Ghirlanda-Relation Dai et al correlations, standard candles, cosmography?

t jet EpEp E iso Briggs et al et al. 1999; Liang & Zhang 2005 Liang-Zhang Relation correlations, standard candles, cosmography?

14 Using Liang-Zhang Relation Wei, Wu, & Melia 2013, ApJ correlations, standard candles, cosmography?

GRB research with AST3 1.Regular GRB optical observation 2.GRB orphan afterglow survey 3.Merger-nova optical observation

regular GRB optical observation regular GRB optical observation I Prompt phase and early afterglow optical counterparts of prompt GRBs optical counterparts of prompt GRBs early optical afterglows early optical afterglows II Late optical observation light curve jet breaks light curve jet breaks origin of chromatic afterglows origin of chromatic afterglows III GRB-SN associations progenitors and explosion mechanisms progenitors and explosion mechanisms prompt/quick response (minutes to hours) deep limit magnitude

Long GRB optical afterglow lightcurves Kann, et al., 2010, ApJ, 720, 1513 MW dust extinction corrected AST3 limit magnitude

Peak Mag vs. Peak Time

orphan afterglow survey orphan afterglow prompt GRB afterglow I 、 off-axis GRBs ： jet, radiation is relativistic beamed off-axis ： on-axis ： II 、 failed GRBs ： less energetic (lower Lorentz factor), less gamma-ray released, even undetectable on-axis ： orphan afterglow jet decelerates beaming effect decreases true GRB rate ! true GRB energy !

Metzger & Berger, 2012 SGRB Multi-band transient ~hours, days, weeks, or even years Li-Paczyński Nova Opical flare ~ 1 day Ejecta-ISM shock Radio ~years Li & Paczyński, 1998 Nakar& Piran, 2011 Merger-nova optical observation: EM signals for a BH post-merger (NS-NS) product dimmer X-ray counterpart

Jet-ISM shock (Afterglow) Shocked ISM Ejecta SGRB Radio Optical X-ray Poynting flux MNS SGRB Late central engine activity ~Plateau & X-ray flare Magnetic Dissipation X-ray Afterglow 1000 ~10000 s Ejecta-ISM shock with Energy Injection (EI) Multi-band transient ~hours, days, weeks, or even years Gao, Ding, Wu, Zhang & Dai, 2013 Wu et al. 2014; Wang & Dai, 2013 Zhang, 2013 Merger-nova optical observation: EM signals for a ms magnetar post-merger (NS-NS) product Photosphere emission Optical and soft X-ray transient ~ days, weeks Yu, Gao &Zhang, 2013

GRB research with infrared CCD

Dust Extinction

Origin of dark GRBs Dust extinction ? High-redshift GRBs? Intrinsically dark?

high-z or high extinction? photometric z~9.4 ， the most distant stellar object ever detected ？

Thank You!