Gamma-Ray Burstsicc.ub.edu/congress/FAA60/presentacions/meszaros.pdf · • Long history:...

Peter Mészáros,Pennsylvania State University

Felix Aharonian Fest, Barcelona, 2012

Gamma-Ray Bursts

Recent results

2

Fermi

3

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Abdo, A. and Fermi coll., 09,Sci. 323:1688

GRB 080916c

Light-curveE!

Note :GeV photons!“lag”

behind MeV!

GBM

GBM

LAT

LAT

LAT

Mészáros

GRB 080916C

• “Band” (broken power-law) fits, joint GBM/LAT, in all time intervals

• “Soft-to-hard” spectral time evolution

• Long-lived (103 s) GeV afterglow

• No evidence for 2nd spectr. comp. (in some cases)

Spectrum : up to ~10 GeV (obs.)

Mészáros

Evidence of the “extra components”

Joint spectral fit (of binned data) :GBM100MeV

GRB 090902BAbdo et al. 2009,ApJ, 706L, 138A

GRB 090510Ackermann, et al. 2010, ApJ, 716, 1178

!Constrains main keV-MeV component!Spectral evolution during prompt phase!Additional PL component seen at high and low energies

12

But:

(in some cases)

in other bursts,

Mészáros pan05

Jets in GRBs → int. & ext. shocks

8

↙internal shocks

↙external shock

Int. & ext. shocks,

accelerate electrons

e,B !" (leptonic);

and

accel. protons too (?)

p"!#, " (hadronic)

Theoretical Issues:

• Are single-component spectrum at GeV due to internal or external shocks? - or other, such as photosphere, ..?

• Are photons of purely leptonic or hadronic origin, or mixed?

• Besides delay providing QG upper limits (based on zero intra-source GeV-MeV delay): what are the astrophysical causes of delay?

• Is 2nd component a " zone/rad.mech. than 1st? Do we need at least a two-zone model?

A “leptonic” model:

• Photosphere: prompt, variable MeV broken PL spectr.• IS occurs at r!1015 cm (high ") : Sy=XR, IC(UP)=GeV

Toma, Wu, Mészáros, 2011, MN 415:1663

! !

!"#$#%&"'(')*+,)-+$'(+*.)%"#/0)#1)$"')234)5'$

(,'/67879)/:

(-6787;

Photosphere + Internal Shock leptonic model, cont.

! !

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Mészáros

Hadronic model: 090902B– 5 –

based on a likelihood analysis of the combined GBM and LAT data under the assumption

of a Band function plus an additional power-law (Abdo et al. 2009c).

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Mészáros

Paradigm shift• OLD: internal + external shock (weak phot.)• Photosphere: low rad. effic., wrong spectrum • Internal sh.: good for variability, easy to model ; but

poor radiative efficiency

• External sh.: was, and is, favored for afterglow model• NEW: phot. + external shock (weak int.sh.)• Photosphere: if dissipative, good rad. efficiency• (Internal shock: if magnetic, may be absent)• External shock: most of GeV and soft afterglow

Mészáros

Evolving Fireball paradigm:

" 2005

!2005

p-n collisions below phot.

• Long history: Derishev-Kocharovsky 89, Bahcall-Meszaros 00, Rossi et al 04, etc

• Either p-n decoupling or internal colls. $ relative p-n streaming, inelastic colls.

• Highly effective dissipation (involves baryons directly)- can get >50% efficiency

• Sub-photospheric dissipation can give strong photospheric component

Beloborodov, ’10, MN 407:1033

A hadronic “thermal” photosphere PL spectrum?

p-n coll.$e±$ photosphere %-spectrum

• The result is a thermal peak at the ~MeV Band peak, plus

• a high energy tail due to the non-thermal e± , whose slope is comparable to that of the observed Fermi bursts with a “single Band” spectrum

• The “second” higher energy component (when observed) must be explained with something else

GeV#

&MeV

A leptonic magnetic photosphere + external shock model

MeV GeV

'Leptonic photosph. spectrum extend to "ph me ~50-100 MeV' Ext. shock upscattering spectrum extend to "es %e,KN me $TeV

Veres & Mészáros ‘12, ApJ 755:12

Magnetic-dominated GRB jets

• Dynamics of expansion " ~ r1/3 $ " ~ const• Dissipative (mag.) scattering photosphere $

results in broken PL MeV spectrum

• No internal shocks expected• Magnetiz. param. ( drops to ~ o(1) at rdecel• External shock present (forward; +reverse?) $both shocks up-scatter photospheric MeV $to GeV -TeV range

Veres & Mészáros, 2012, ApJ 755:12

Phot+ExtSh : Single (Band) PL Veres & Mészáros, ‘12, ApJ 755:12

Phot+ExtSh : Band + 2nd comp.Veres & Mészáros ‘12, ApJ 755:12

Magnetic Photosphere (Leptonic) Fit Results

• Good fits obtained: can reproduce either 1- or 2-component observed spectra with same model

• In some bursts (e.g. 080916C, where 2nd comp. is “absent” (or rather, possible evidence for it is

090510Amagphot

P. Veres, BB Zhang & Mészáros, 1210.7811

090510Abarphot


080916C magphot


χ2 =113.6/98

080916C barphot

χ2 =129.7/98


Or else: Internal Shocks Redux:

modified internal shocks

• Magnetic dissipation regions, R~ 1015 cm, allow GeV

photons - but hard to calculate quantitatively details of

reconnection, acceleration and spectrum, e.g. McKinney-

Uzdensky ‘12, MN 419:573, Zhang & Yan ’11, ApJ 726:90

• Baryonic internal shocks, protons are 1st order Fermi

accelerated, and secondaries are subsequently re-

accelerated by 2nd order Fermi (‘slow heating”), e.g.

Murase et al, 2012, ApJ 746:164 - more susceptible to

quantitative analysis, e.g. as follows

26

currently of two main types:

Hadronic int. shock: more detailed

↙ Afterglow FS: X-ray, etc.;RS: Opt. flash

Prompt#' Orig: Waxman & Bahcall ’97 for neutrino prod. in internal shocks

'↙ Asano & PM, 09-12 on, calculate second’y photons &second’y neutrinos

Numerical time dependence of

photon & neutrino secondaries

• Generic dissipation region at a radius R~1014-1016 cm (could be Int.Sh. or mag. diss. region, etc.)

• Numerical Monte Carlo one-zone rad. transfer model with all EM & # physics

• $Fermi/LAT param. E"iso~2.1054, Lp/Le=20, %=600, R~1016cm, z=4.5

28ε!"#$%

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314/

510/

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30. 308 304 309 303030:30

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30:4

(Asano & PM ’12, ApJ 757:115)

"

“Moderate” hadronic case

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ε!"#$%

ε&'ε(!"#)*+,-.%

/0)#12!3#45678,

9:;)678,

:?@A

BC. BCD BCE BCF BCBC BCB.BC>BC

BC>G

BC>F

“Typical” GRB params., E"iso~5.1050 erg, Lp/Le=10, %=800, R~1014cm

• Predict complying nu-flux, at >1016 eV - may be detectable in future

• Predict larger 2nd photon component than does leptonic model, in all bursts and

starting in the prompt phase - perhaps hard to detect if low photon stats.?

• UHECR flux from escaped neutrons: not sufficient, if Lp/Le=10 - need more work!

Asano & PM ’12, ApJ 757:115)

"

#

n

Fermi/LAT hadronic case

• For very bright, rare bursts (

Some observed photon energies and redshifts

Eobs(GeV) z

13.2 4.357.5 3.575.3 0.7431.3 0.9033.4 1.8219.6 2.102.8 0.8974.3 1.37

• Even z>4 bursts result in Eobs~10 GeV photons

•Some z~1 bursts produce Eobs)30 GeV photons

( 130 GeV in rest frame!)

•⇒ encouraging for low Eth CTs: HAWC, CTA...

What about UHE CR, NU?

• Shocks present in HE non-thermal %-ray sources (or else: magnetic reconnection).

• Electrons are definitely accelerated• %-rays usually attributable to leptonic

mechanisms (synchrotron, inv. Compton)

• But: UHECR must be accelerated somewhere. Likely (?) in same shocks as the e- in one of these HE %-ray sources- but which?

Mészáros pan05

Jets in GRBs → int. & ext. shocks

33

↙internal shocks

↙external shock

Int. & ext. shocks,

accelerate electrons

e,B !" (leptonic);

and if

accel protons too,

p"!# (hadronic)

Mészáros, NOW 04

!s from p! from int. & ext. shocks

• !-res.: E’p E’! ~0.3GeV2 in comoving frame, in lab:

" Ep # 3x106 $2

2 GeV

" E! # 1.5x102 $2

2 TeV

• Internal shock p!MeV "

~100 TeV νs• ( External shock p!UV " ~

0.1-1 EeV νs )• Diffuse flux: det. w. km3Waxman, Bahcall 97 & 99 PRL

Internal shock(prompt)

External shock

( NOTE: internal shock ! old paradigm )

35

currently instrumented

AMANDA

Deep CoreEiffel Tower

324 m

IceTopIceCube

Digital Optical Module (DOM)

5160 DOMs on 86 strings

160 tank ice-Cherenkov surface! air shower array (IceTop) –"! see talk by T. Gaisser

Includes DeepCore infill array! (sensitivity to lower energies)

79 strings deployed to date in 6 construction seasons

(2010)

( 79/86 complete)

36

Alexander Kappes, NUSKY, Trieste, 24.06.2011

c

GRBs with IceCube

• GCN-satellite triggered searches

very low background ! 1 event can be significant !

• Individual modeling of neutrino fluxes(fireball model)

• Measured parameters: ! spectrum, (redshift)

• Average parameters: "jet (316), tvar (10 (1) ms), Liso (1052 (51) erg), !B (0.1), !e (0.1), fe/p (0.1)

15

On-time (blind) Off-timeOff-time

T0prompt

precursor (~100 s)

wide window (several hours)

background

IC59: 98 bursts in northern sky

(Kappes et al, NUSKY, June 2011)

Being tested here : internal shock

prompt #-burst (WB97 simplified)

IC40+59 search for VHE nus

from 190 GRB (105 northern)

• Analyze 190 GRBs

localized w. "-rays

betw, Tstart & Tend

• Use the WB’97 and

Guetta’04 proton

acceleration model in

internal shocks, with

E-2 spectr, &p/&e=10,

and p"!'-res !#µ

• Nu-flux normalized

by obs. "-ray flux, get

F# for 190 (right axis),

and diffuse flux (all)

assuming 677 yr-1

37

Nature 484:351 (2012), the Icecube collab.; Abbasi and 242 others (incl. P.M.)

(A) Model dependent search

Model

0.27

Data is factor 0.27 below model F# at 90% CL

IC59 model-indep. search• Searched 190 GRB

@ "-trigger ± 't window up to 1 day, also using ( spectra & params

• Two candidate events seen at low signif., probably due to (other) CRs

• $ Results shown are for E-2 spectra as function of 't

• Right axis is data

deficit below F# model

38

Nature 484:351 (2012)

UL % CL is similar as for model dep. search

IC59 2-year conclusions (190 GRBs)

• The fireball (more accurately: internal shock) model overpredicts the TeV-PeV nu-flux by a factor 3.7 ,(asuming Lp/Le=10, '-res only, Lorentz %~300-600)

• In the same model, the 95% CL nu-flux allowed by the data falls below 2-3" of what expected if GRBs contribute most of GZK UHECR flux.

• In these models, either Lp/Le must be substantially below factor 3-10 assumed here, or the production efficiency of neutrinos is lower than was assumed.

39

Nature 484:351 (2012)

Conclusion on the conclusions:

• These are conservatively stated conclusions

• The first time VHE nus have put a significant constraint on a well-calculable astrophysical UHECR-UHENU model, at 90-95% CL

• This is very valuable

• Icecube is doing exciting astrophysics

• A significant first step towards GZK physics

40

Some model details ....

41

p"!' interaction of a Band-" spec. with an E-2 proton spec.

(WB 97)

"

p

#

However ...

• IC22-59 analysis used a simplified version of WB97 , which

results in overestimated model nu-fluxes

• Assumed F#IC /Fp = (1/8) f),b , where 1/8 because 1/2 p"

lead to )+ and each #µ carries 1/4 E), and f),b=f) (E=Eb)

• But f) (E) = f),b is OK only for Eb < E

Graphically....

• fC: energy of all photons approx. by break energy

• f* : 0.7 (rounding error in one eq.)

• f+ : 2/3(negelected width of '-res.)

• Cs : correct en. loss of second’s & E-dep of proton mfp43

Even using the (old paradigm) int. shock

model, the simplifications have an effect

• IC-FC: IceCube Fball. Calc.

• RFC: “Revised” Fball.Calc. #

• NFC: Numerical Fball.Calc.

(Hümmer et al ’11, PRL 108:231101)

In summary .... • Even when using old paradigm of internal shock, but more detailed physics (incl. multi-pion and Kaon production, ( cool’g. break for ), µ, and numerical as opposed to analytical calcul.)

• ⇒ F! predictions below IC40+59 !

44

(" Hümmer et al,

’11, PRL 108:231101)

(see also

Li, ’12, PRD 85:027301 ;

He, et al ’12, ApJ 752:29)

• Internal shock model use is expedient: best documented so

far, and easy to calculate # reason why its use is widespread

• But ... int. shocks known (past 10 years) to have difficulties

for gamma-ray phenomenology (efficiency, spectrum, etc)

• And, acceleration rate of protons vs. electrons is unknown;

are protons injected into accel. process at = or ( rate as

electrons? Only energy restriction on model is Lp/Le " 10.

• Alternatives to internal shock: being investigated - but so far,

are less easy to calculate. Progress, however, is being made.

• Even if GRB are not GZK sources, model indep. searches

leave possibility of lower, observable nu-fluxes from GRB

45

Note also that.....

#µ from mag.dis.phot. + ext.sh.

46

Gao, Asano, Mészáros ’12, JCAP i.p. (1210.1186)

Compare mag.phot, bar.phot, int.shock @ var. , (or %)

47

(tvar=1 ms)

Gao et al, arXiv 1210.1186

Diffuse nu from MPh, Bph, IS, ,=300 & IC3 lim.

48Gao et al, arXiv 1210.1186

Diffuse nu from MPh, Bph, IS, ,=1000 & IC3 lim.

49

Gao, Asano, Mészáros ’12, JCAP ..(1210.1186)

Models and IC3 next steps:

• Need 3-5 years data accumulation to test the current (Fermi & Swift "-ray tested) models

• Will have to redo the IC3 statistical model fit evaluation of upper limits for these newer (non-WB) models, whose neutrino spectra and model parameters are different

50

Outlook

• Observational prospects for ground-based multi-GeV astrophysics of GRB are encouraging - there are enough bursts that show photons there!

• If GRB spectra reaching TeV are detected, this would provide new constraints on hadronic vs. leptonic GRB models - but much further theoretical work is needed to specify models

• Of course, GeV-TeV neutrino observations could clinch this issue - further address GRB-GZK UHECR contrib.

• Will be able to constrain particle acceleration / shock parameters, compactness of emission region (dimension, mag.field,.), etc.

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