Possible Implications of. GeV - TeV. observations of GRB. Peter Mészáros. Pennsylvania State University. Mészáros, Gla04

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1 Possible Implications of GeV - TeV observations of GRB Peter Mészáros Pennsylvania State University

2 GeV g emission from GRB and other extragalactic, galactic & un-id d sources GeV: space obs. (SAS-2, HEAO-A4, Kvant.) EGRET spark chamber: 5 GRB, 6 PSR & 60 + ~25 other Unidentified EGRET g-ray sources

3 GRB: (current paradigm) Short (t g d 2 s) Long (t g t 2 s)

4 GRB: internal & external shocks in baryonic jet outflows XR, O, R g s (Forward shock)

5 GRB: from Poynting outflows Prompt g- rays: from mag. shell instab., reconnect,..) External forward shock: similar, but internal, reverse shock absent. Lorentz factor temporal & spatial evolution may be different, dep. on dissipative energy input Short time variability: dissipation hotspots with local g on top of bulk Γ Lyutikov & Blandford astroph/

6 Two EGRET spark chamber GeV Bursts GRB GRB >10 GeV photon flux can last for t 1 hr, start with MeV trigger Energy Fluence F GeV ~ F MeV

7 Simplest delayed GeV g mech. in baryonic jets, purely leptonic emission: GeV emission starts ~ same time as MeV trigger, but lasts 1 hr: could be due to: a) internal shock synchrotron normal duration MeV to dgev, plus b) external shock (moderate G, low n ext ) IC t GeV to TeV, lasts ~mins-hr (Meszaros & Rees 1994 MNRAS 269, L41) NOTE: if Poynting-jet, seed photons may be due to variable hotspots in mag. shell/external shock, or internal dissipation/reconnection, followed by IC (Other possib (Katz 94) : proton impact on bin. comp.* pp g )

8 High energy p-sy, e-ic & e-sy regimes in afterglows: ext. shock p-sy e-sy e-ic e B, e e parameter space div. in regions where emission at high energies dominated by (I) p-sy (+pg), (II) e-ic (III) e-sy use p=2.2 ; U p ~U e, gg abs. Largest region of param space taken up by (II) e-ic, using typical AG fit params Long-dash: e-sy, shortdash:p-sy, dots:ic

9 p-sy Spectral time evolution (I) Long-dash: e-sy, short-dash:p-sy, dots:ic Times: trigger, 1 min, 1 hr, 1 dy, 1 mo (from top to bottom). z=1 flat, E 0 =10 53 is.eq (I) p-sy : e e =10-3, e B =0.5, n=100; (II) e-ic: e e =0.5, e B =0.01, n=1; (III)e-sy: e e =10-2, e B =0.1, n=1 (Zhang & Mészáros 01 ApJ 559, 110) e-ic e-sy (II) (III)

10 XR & GeV XR (Chandra) light-curves IC GeV (GLAST, >100 MeV) p p IC Lightcurves start at t dec,, until reach G~2. I: p-sy, II: IC, III: e-sy Full lines: z=1, flat U Dotted: z=0.1 Model II (IC): recognize from late GeV peak min after MeV), and from late XR hump (day) Long-dash : e-sy radn component short-dash : p-sy(pg), radn dotted : e-ic radn Zhang & Mészáros 01 ApJ 559, 110

11 Vital information about GRB from GeV-TeV photons Baring 1999 Internal shocks: gg e, t gg E g G GeV pair cutoff in spectr ï get info about compactness, r sh, Γ External shock: gg cutoff at TeV (dep on Γ) test if shock is int. or ext; test bulk Lorentz factor, shock accel efficiency, mag field in shock, index (max. e energy? size of accel region)

12 G max upper limits in sel. GRB Lithwick & Sari 01 ApJ 555,540 : Use G-dependence of comoving photon density which determines max. escaping photon energy E m /m e c 2 z G m1 G m * * *

13 GeV-TeV (PeV?) g s from internal shocks in GRB Take obs MeV spectra, luminosities and variab. gg absorption sets in at tens of GeV (dep on Γ) Include synchrotron self-absorption ïggabsorption thins out again at ~ PeV Large Γ (~ 800): ï thin at all energies Razzaque et al, astroph/

14 Internal shock primary & sec ry GeV-TeV spectra Primary spectra of internal shocks are softer (cutoffs GeV) than external shock Primary spectra are further reprocessed by interaction with IGM diffuse IR bkg and CMB Secondary reprocessed rad n easier to detect since softer than primary (HESS, GLAST range) and longer duration. Delay of secondary rad n depends on IGM magnetic field (best prospects:bd10-17 G) (Razzaque, Meszaros, Zhang aph/ , apj in press)

15 Internal shock self-consistent pair form + compton Numerical calc, incl. pair form+annih, cyclo-synchr, inverse + direct Compton. L 52 =1,ε B =ε e =10-0.5, p=3 Neglect intergal. absorption Top: high compactness: solid: t=10-4 s, Γ=300,l =250; dash: t=10-5 s, Γ=300,l =2500 Bottom: med. compact s: solid: t=10-3 s, Γ=300,l =25 dash: t=10-3 s, Γ=400,l =6 dash-dot: t=10-4 s, Γ=600,l =8 Pe er & Waxman aph/

16 Delayed Secondary GeV g-rays also from external shock TeV External shock gg-(self)thin to TeV g-rays In IGM, TeV g from GRB shocks pair-produce on IR bkg g s, and e ± IC upscatter CMB g s, MeV secondary g Dt~10 3 s delayed (max[t gg, t IC ] obs frame), N sc /N n ~5, E GeV ~E MeV, N n sc ~n -(p+6)/4 (N n ~n -(p+2)/2 ) (Dai, Lu 02, ApJL, a-ph/ )

17 Hadronic processes TeV? basic p,g UHE n,g If protons present in jet they are also Fermi accelerated (as are e - ) p,g π ± µ ±,n µ e ±,,n e,n µ ( -res.: E p E g ~ 0.3 GeV 2 ) p 0 2g gg cascade GLAST, ACTs n E n,br ~ ev for MeV gs (int. shock) n E n,br ~ ev for 100 ev gs (ext. rev. sh.) ICECUBE (Waxman-Bahcall 1997;99; Boettcher-Dermer 1998; 00; ) Test hadronic content of jets (are they pure MHD/e?) Test acceleration physics (injection effic., e e, e B..)

18 GRB pg EM cascades (in external forward shocks) Low energy: normalize to GRB (z=.83) Ext. forw. shock MeV gs Proton index -2, U p ~U e, p-sy & pg cascades, e + sync, p 0 dec. Time decay of cascade rad, slower than leptonic a glow decay (p s have less rad. losses) Boettcher & Dermer 98 ApJ 499, L131

19 External shocks w. e - & p + Pe er & Waxman aph/ Numerical calc, incl. reverse+ forw shock, pair form, e - sync+ic, p + sync + cascade negl. intergal. absor. E 53.5 =1, Γ=10 2.5, T=10s, p=2, ε B =10-2, ε e =10-1 solid: unif ISM n=1/cc dash: wind, A=1 g/cc dots: wind, A=1, no p +

20 TeV secondary g from UHE p Fluence of > 1 TeV g from E=1051 erg GRB at 100 Mpc In patchy IGM (80% voids w. Bd10-15 G, 20% B~10-11 G; TeV Fluence ~2% of energy in GZK protons GRB can accelerate p to E p d10 20 ev Cascades on bkg CMB & IR g e ± e ±,g cmb,ir e ±,g TeV Delay: p, e ± in B igm TeV g from dd100 Mpc in Dtddy (Waxman & Coppi 96, ApJL (/ ) More detailed calculation: Dermer, 02 ApJ,

21 Longer delayed GeV-TeV g signatures of UHECR? (from neutron decay) Ioka, Kobayashi, Mészáros, 04, ApJ 613, L17 W49 SNR proposed as a GRB remnant (age ~3000 yr) (asymmetry, hyper-energetic) Assume GRB are sources of UHECR (w. or w/o. remnant) Even E p << ev can give rise to GeV, TeV g s Large fraction of UHECR may escape as energetic neutrons Neutrons decay at r~ct dec g n,8 (or ct age )~ kpc >> remnant n p + e - +n e IC: e -,g CMB hn IC ~ 50 TeV

22 If W49 is a GRB remnant, is it detectable at TeV? Marginally detectable from ground:veritas, MAGIC; possibly HEGRA (below GLAST range)

23 GRB : pg signature? t<14 s t <47 s t < 80 s t < 113 s t < 211 s Hard ( MeV) comp. in EGRET TASC calorimeter not compatible w. BATSE MeV fit (but in 26 other bursts a single BATSE/TASC fit works well) Hard comp. more prominent in time pg signature? might explain delay, hardness Alternative: could be leptonic IC, from reverse shock electrons, in regime where IC sp is harder than sync PL ; e.g. scatt. of lower energy synch. asymptote; or observe IC region where electrons with a range of energies scatter off a range of photon energies (Granot,Guetta, astroph/ ) Gonzalez, Dingus et al, 03, Nature 424, 749

24 Or: other alternative Leptonic IC for sub-gev in GRB IC by forward shock electrons of sync. self-abs seed photons emitted by reverse shock (steep IC slope provided by steep self-abs slope) Pe er & Waxman, astroph/

25 Number of GRBs GRB a Log10(prob) TeV g Detection Status Milagrito :Tentative ò (3s) TeV detection ; F TeV ~10 F MeV ; but, no z (abs? dd100 Mpc?) Atkins etal, 00, ApJL.. Tibet array: superpose bursts in timecoincid. w. MeV: joint TeV det. significance 6s? (Amenomori et al AA 96) GRAND: GRB ò TeV reported at 2.7s (Poirier et al PRD 03, aph/ )

26 Primary limitation : gg Opacity of the Universe g Coppi & Aharonian 97 In all but the densest (veiled) AGN sources (e.g. gal.nuc?), t gg 1 for >TeV on local target photons, but.. In IGM, t gg 1 for >TeV on IR bkg g (Dd100Mpc) test IR bkg spectral density, Bad for GRB physics (only D Mpc) But, constrain IR bkg, z-distr of SFR, LSS, cosmology

27 UHE n & g in GRB 4 possible sites in collapsar-jets 1 GW p,n 0) ôat collapse, make GW + thermal ns 1) ô If jet outflow is baryonic, have p,n p,n relative drift, pp/pn collisions inelastic nuclear collisions VHEn (GeV) 2 pg, pp 2) ôshocks while jet is inside ø can accel. protons pg, pp/pn collisions UHEn (TeV) 3 pg 3) ôshocks outside ø accel. protons pg collisions (+pp/pn - if supranova ) UHECR, UHEn, UHEg (d10 20, , t10 9 ev) 4) If supranova (SN >2 days before GRB) pg, pp of jet protons on shell targets UHEn (> TeV)

28 E ν Φ ν ε op (GeV cm s sr ) pp (stellar) H WB Limit 7.5 pγ (head) pp (shocks) pγ (head) 8.5 ICECUBE 9 9 pγ (shocks) 10 Burst 9.5 WR 10 He Afterglow H E ν (GeV) Atmospheric Razzaque, PM, EW 03 PRD 68, 3OO1) Meszaros, Waxman 01 PRL bursts/yr Jet inside & outside star: GRB n Precursor + n,g Simultaneous Jet propagating through progenitor, BEFORE emerging from stellar envelope, can have int. shocks which accel. p + pg on unobserved X-rays, p ±, n pp, pn on stellar envelope p ±, n ~ few TeV neutrino precursor If progenitor has R ø ~10 12 cm (BSG) Rate( n m, TeV )prec > Rate( n m, 100 TeV )int.shock ( easier to detect in ICECUBE ) but, if WR, R ø ~10 11 cm Rate( n m, TeV ) prec < Rate( n m, 100 TeV ) int.shock test progen. size high z : popiii?) At jet break-out: photon flashes (Ramirez-Ruiz, McFadyen, Lazzati 02; Waxman, Mészáros 02) i ) thermal kev g flash ii) non-therm MeV g ( IC upscatt of XR) precursors (d few sec.) of usual MeV g (3) ò Blue n- spectrum: t100 TeV p,g n from shocks outside star

29 ICECUBE: km 3 Extension of Amanda 0.05 km 3 km 3 =1Gton Funding approved, started 80 strings, 4800 PMTs (ice) + air shower surface array Design for det.all flavor n s, from 10 7 ev (SN) to ev

30 ôantares French/Italian/UK. collaboration Site off Toulon Also: NESTOR x Greek/German/Russian NEMO: extend to Km 3 water Cherenkov detector Deployment approx Complement ICECUBE: l sc,abs ~(100,10) H 2 0, l sc,abs ~(20,100) Ice Northern site: at lower E complementary sky coverage

31 Conclusions Will learn much about GRB in GeV range; many obs. with good photon stats. to TeV Will constrain electron acceleration / shock parameters, compactness of emission region (dimension, mag.field,.) UHE g,n will test proton/mhd content of jets Possibly probe hadron/em interactions at t TeV- PeV energies TeV g detection: mainly from few/nearby GRB TeV nu signals: provide complementary info on hadronic cascade components

32 GeV-TeV g experiments underway Cherenkov Telescopes MILAGRO Water Air HESS MAGIC & HEGRA Veritas VERITAS

33 Point Source Sensitivities HESS MAGIC: La Palma (Munich) Monoc. 1x17m, >30 GeV, 01 HESS: Namibia (Heidelberg) Stereo 4x12m, > 50 GeV, 02 CANGAROO-III: Austral(Tokyo) Stereo 4x10m, >50 GeV, 03 VERITAS: Arizona (SAO) Stereo 7x10m, >50 GeV, 05 STACEE: Sandia (UCLA/Chic) solar tower, GeV, 01 MILAGR(ITO)O, LANL, NM water, > 20 GeV, A~ cm 2 GLAST (LAT): space (Stanford) Silicon, 20 MeV-300 GeV, 06

34 Diffuse UHE n : CR bound and sensitivity, bckg