Gamma-Ray Bursts Xue-Feng Wu 2014, June 6, Nanjing 3rd International Collaboration Meeting on Antarctic Survey Telescopes Gamma-Ray Bursts Xue-Feng Wu Chinese Center for Antarctic Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences 2014, June 6, Nanjing

What are gamma-ray bursts (GRBs)

isotropic distribution in the sky cosmological origin?

compact stellar objects: black hole, neutron star? GRB light curves morphology complicated & irregular duration ～ ms - 1000 s, or even longer variability timescale δt ～ 1ms, even ～ 0.1ms size of the emission region R < c δt ~ 300km compact stellar objects: black hole, neutron star?

GRB prompt emission spectra non-thermal: synchrotron or inverse Compton?

GRB prompt emission spectra -continued Thermal Component Extra High Energy Component GRB090902B GRB090926A broadened Planck function Abdo et al. 2009, ApJ, 706, L138 Ackermann et al. 2011, ApJ, 729, 114 If this spectral break is due to γγ annihilation (optical depth ~1) , then the Lorentz factor can be estimated as ! fastest bulk motion in the universe!

classification: long soft vs short hard short GRBs long GRBs 2 s Kulkarni et al. 2000

discovery of afterglows from long GRBs one of the breakthroughs of the year 1997, Science magazine the first afterglow (from GRB970228) t -1.3 BeppoSAX Costa et al., 1997, Nature, 387, 783

first redshift measurement for long GRBs absorption lines in afterglow spectrum host galaxy emission lines GRB 970508 z=0.835 (t~2.3day) (t~6-11months) Bloom et al., 2001, ApJ, 554, 678 Metzger et al., 1997, Nature, 387, 878

first optical flash one of the breakthroughs of the year 1999, Science magazine GRB 990123 GRB 990123 ROTSE Akerlof et al., 1999, Nature, 398, 400

brightest GRB optical afterglows Bloom et al., 2009, ApJ GRB Peak Magnitude redshift Peak Absolute Magnitude Luminosity in unit of the brightest SN 080319B 5.3 0.937 -38 1.6e6 130427A 7.03 0.34 -34 2.5e4 990123 8.9 1.6 -36.38 2.25e5 061007 10.3 1.261 -34.44 3.7e4 Vestrand et al., 2013, Science

GRB 140311A: early optical afterglow by Zadko telescope Why early optical afterglow observations are important: To determine the initial Lorentz factor; To estimate the type and density of circum-burst environment (ISM, or stellar wind) Courtesy of David Coward, UWA

first possible association between long GRB 980425 and the supernova SN 1998bw Galama et al，1998, Nature

possible association between long GRBs and Type Ic supernovae (indirect / late rebrightening or bump) Bloom J. S. et al.,1999, Nature, 401, 453

first confirmed association between long GRB 030329 and the supernova SN 2003dh (direct / spectroscopy) one of the breakthroughs of the year 2003, Science magazine Hjorth et al., 2003, Nature, 423, 847

GRB-SNe associations：Sample A strong spectroscopic evidence, spectroscopic SNe association redshift 980425/1998bw 0.0085 030329/2003dh 0.1685 031203/2003lw 0.1055 060218/2006aj 0.0334 091127/2009nz 0.490 100316D/2010bh 0.0591 120422A/2012bz 0.283 120714B/2012eb 0.398 130215A/2013ez 0.597 130427A/2013cq 0.3399 130702A/2013dx 0.145 130831A/2013fu 0.479 redshift distribution：0.0085～0. 597，mean z = 0.2589； SN 2008D / XRF 080109 not listed, because this association is under debate，(Hjorth & Bloom 2012) Credit: Shanqin Wang

GRB-SNe associations：Sample B a clear lightcurve bump as well as some spectroscopic evidence resembling a GRB-SN. association redshift 011121/2001ke 0.362 020903 0.251 021211/2002lt 1.006 050525A/2005nc 0.606 081007/2008hw 0.530 101219B/2010ma 0.552 111211A 0.478 120714B/2012eb 0.398 redshift distribution：0.251 ～1.006 ，mean z = 0.55 Credit: Shanqin Wang

GRB-SNe associations：Sample C a clear bump consistent with other GRB-SNe putting at the spectroscopic redshift of the GRB. association redshift 970228 0.695 990712 0.433 020405 0.691 040924 0.859 041006 0.716 080319B 0.938 090618 0.54 120729A 0.80 redshift distribution：0.433 ～0.938 ，mean z = 0.709 Credit: Shanqin Wang

GRB-SNe associations：Sample D a bump，but the inferred SN properties are not fully consistent with other GRB-SNe, or the bump was not well sampled, or there is no spectroscopic redshift for the GRB. association redshift caveat 980326 red bump 020410 discovered via bump 030723 red bump，X-ray excess 050416A 0.654 poor sampling 070419A 0.971 poor sampling 100418A 0.624 101225A 0.847 redshift distribution：0.654～ 0.971，mean z = 0.774 Credit: Shanqin Wang

GRB-SNe associations：Sample E a bump，either of low significance or inconsistent with other GRB-SNe. association redshift caveat 991208 0.706 low significance 000911 1.058 low significance 020305 not fitted by GRB-SNe 050824 0.828 low significance 060729 0.543 afterglow dominated 111209A 0.677 redshift distribution：0.543～1.058，mean z = 0.762 Credit: Shanqin Wang

GRB-SNe associations: why most long GRBs are not detected with Ic SNe? External reasons: (1) Pre-Swift era, lack of quick precise positioning pretend the follow-up of large optical facilities; (2) Some GRBs are close to Sun or full moon; (3) Dust extinction; (4) SN brightness decreases with increase redshift, especially for z>0.5. For z>1.2, it is extremely difficult to identify the SN component from GRB afterglow; (5) Host galaxy contamination (host can be as bright as SN, i.e., M=-19). Internal reasons: (1) Associated SN is intrinsically dim; (2) Some GRB late afterglows are relatively bright.

jet signature in GRB afterglows Greiner et al., 2003, ApJ, 599, 1223

Origin of Long GRBs Long Bursts: collapsars Young (few million yrs) Star-forming regions

GRB 050509B: first discovered X-ray afterglow from short GRBs one of the breakthroughs of the year 2005, Science magazine BAT error circle XRT error circle possibility of the chance superposition of GRB 050509B with the elliptical galaxy: P<0.2% (Pedersen et al., 2005, ApJ 634, L17) Gehrels et al., Nature 437, 851

GRB 050509B: optical up limits Hjorth et al., 2005, ApJ 630, L117

GRB 050709: host galaxy host galaxy: z=0.160 GRB located in the outskirt of the host galaxy with irregular morphology host galaxy: z=0.160 Fox et al., Nature 437, 845

Properties of short GRBs compared with long GRBs 1. usually happened at low redshifts (z<1)； 2. typical isotropic energy of1048 – 1050 erg, smaller than that of long GRBs by 2-3 orders of magnitude； 3. unassociated with supernovae; 4. diversity of host galaxies, from early ellipticals to irregulars; usually take place at the ourskirt of the host galaxy  support the NS-NS/NS-BH merger model !

Gehrels, Piro & Leonard 2002, Scientific American

Gehrels, Piro & Leonard 2002, Scientific American

Gehrels, Piro & Leonard 2002, Scientific American

Radio-selected GRB afterglow sample （1997-2011, Chandra & Frail 2012） Crazy day of 5 bursts in 24 hours Optical viewing before burst 5.3 visible to naked eye for ~40 s 31

Radio-selected GRB afterglow sample （1997-2011, Chandra & Frail 2012） (216GRBs) (53GRBs) (163GRBs) Crazy day of 5 bursts in 24 hours Optical viewing before burst 5.3 visible to naked eye for ~40 s 32

GRB research with AST3 Regular GRB optical observation GRB orphan afterglow survey Merger-nova optical observation

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

Long GRB optical afterglow lightcurves MW dust extinction corrected AST3极限星等？ Kann, et al., 2010, ApJ, 720, 1513

Peak Mag vs. Peak Time

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

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

Merger-nova optical observation: EM signals for a ms magnetar post-merger (NS-NS) product SGRB EP detectable X-ray counterpart! Jet-ISM shock (Afterglow) Shocked ISM Ejecta SGRB Radio Optical X-ray Poynting flux MNS Late central engine activity ~Plateau & X-ray flare Magnetic Dissipation X-ray Afterglow 1000 ~10000 s Zhang, 2013 Photosphere emission Optical and soft X-ray transient ~ days, weeks Yu, Gao &Zhang, 2013 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

GRB research with optical polarimeter (e.g., installed in >30cm antarctic telescope )

GRB optical polarization GRB090102: first poln detection of reverse shock emission F~ t -a, a1~1.50, tb ~ 103 s, a2~0.97 偏振曝光时间: t0+160.8s to t0+220.8s 线偏振度: (10.1+/-1.3)% RINGO: 2-m Liverpool Telescope in La Palma Steele et al., 2009, Nature, 462, 767

GRB optical polarization GRB060418: first poln observation (upper limit) of the early emission from the forward shock F~ t -a, a1~-2.7, tb ~ 130s, a2~1.2 偏振曝光时间: t0+203s to t0+233s 线偏振度: <8% RINGO: 2-m Liverpool Telescope in La Palma Mundell et al., 2007, Science, 315, 1822

GRB optical polarization GRB091208: first poln detection of the early emission from the forward shock F~ t -a, a1~0.75； 偏振曝光时间: t0+149s to t0+706s 线偏振度: 10.4+/-2.5 % Kanata 1.5-m Telescope Uehara et al., 2012, ApJL, 752, L6

GRB optical polarization GRB120308A: first poln evolution from reverse shock to forward shock emission r’ RINGO: 2-m Liverpool Telescope in La Palma Mundell et al., 2013, Nature, 504, 119

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？

GRB research with KDUST

redshift record GRBs Quasars Galaxies Zhang, B., 2009, Nature

High-z GRBs (Pop II, Pop III stars) 4+1 GRBs with z > 6： GRB 050904 (z=6.3), GRB 080913 (z=6.7), GRB 090423 (z=8.2) GRB 090429B (z=9.4?), GRB 140515A (z=6.33)

detectability of high-z GRB afterglows at infrared band 1216A*(1+20) = 2.4 micron Lamb, & Reichart, 2000, ApJ

GRBs as probe of cosmic star forming history Wei, Wu, Melia, Wei, Feng, 2014, MNRAS

Thank You!