High energy High energy emission in emission in Gamma Ray Gamma Ray

BurstsBurstsGabriele GhiselliniGabriele Ghisellini

INAF – Osservatorio Astronomico di INAF – Osservatorio Astronomico di BreraBrera

“Pillars” of knowledge

Criterion:Criterion: the most important and not controversial facts constructing the basics of our understanding

1st Pillar: GRBs are cosmological(therefore large energetics, but how large? Depends on collimation…). Thanks to BeppoSAX and its team, led by Luigi Piro, and to Paczynski)

Cost

a+

20

07

Metz

eger+

20

07970508; z=0.835970508; z=0.835

970228970228

Attention: not bolometric for Swift

2nd Pillar: GRBs have large (From GeV; msec variability; radio scintillation; theory)

Frail+ 1997: ~4 two weeks after

970508970508

Abdo+ 2009; Ghirlanda+ 2010; GG+2010; Ackermann+ 2010: >1000

090510090510

3rd Pillar: Prompt+Afterglow(but X-rays may be late prompt). Energy is NOT released ENTIRELY during the prompt.

Pir

o

Pir

o

astr

o-p

h/0

00

14

36

astr

o-p

h/0

00

14

36

SAX X-ray SAX X-ray afterglow afterglow light curvelight curve

PrompPromptt

Willin

gale

et

al.

W

illin

gale

et

al.

2007

2007

Before Swift After Swift

4th Pillar: Long & ShortBut there are exceptions + extended emission

SHORT LONG

Short – HardShort – Hard Long - SoftLong - Soft

5th Pillar: Same t of spikes during the prompt

Spikes have Spikes have same same durationduration

A process A process that repeats that repeats itselfitself

6th Pillar: Supernova connection i.e. progenitors. But there are exceptions. Evidence can be gathered only from nearby, under-luminous GRBs.

No SN060614

Della Valle+ 2006

Woosley Bloom 2006

Campana+ 2006

060218

7th Pillar: Phenomenology of the prompt & “afterglow” Diversity, but some common behavior exists. 2 examples:

Eiso erg

Ep

eak

k

eV

1000

100

10

Short

Short

Long

??

steep

steep

flat

flares

Log time

Log X

-ray fl

ux

The total energy of the prompt correlates with peak of the spectrum

The early X-ray afterglow is “typical”

Ideas (and enigmas)

Central EngineCentral EngineBlack hole or magnetar, or more exotic? (quark star?)

GRBs from quark stars: one-way membrane for baryons, only e+-, photons, B-fields escape… Paczynski & Haensel 2005 MNRAS 362, L4

Magnetars:Giant flares to explain SGRBs + some short (but numbers are not ok)

During the magnetar phase: flat X-ray plateaux

Magnetar BH transition (re-edition of SupraNova).

Magnetic or matter dominated?

~100

Internal pressure: Random bulk randomDisorder order disorder“Heavy FB” optical flash

Blandford: bulk randomorder disorderLight “FB” no opt. flash, no inertia, very

large

Dissipation at large R. Variability through mini-jets or small scale instabilities? (Lyutikov)

R~109

cm

=?

Annihilation

In any case:~Everybody:At the start: B0~1015 G for BZConversion of Poynting to kineticCyclo >mec2

Smaller scattering cross section

Different E different B0?Is the funnel useful to collimate? No, it is a myth, short can do without, as well as blazars

R~106

cm

=?

L ~ B02R0

2c/8~ 1051B15

2R62

erg/s

Efficiency is small.

Big prompt/afterglow ratioEven bigger if X-rays are late prompt. GeV relax, but not enough.

Internal shocks: collisions within the flow. Dissipate RELATIVE kinetic energy

5%5%

22//11

Lazzati+ 1999

Willingale+ 2007

Log E

aft

erg

low

Log Eprompt

EEaft aft ~ E~ Epromptprompt/10/10

Efficiency is small.

Big prompt/afterglow ratioEven bigger if X-rays are late prompt. GeV relax, but not enough.

Internal shocks: collisions within the flow. Dissipate RELATIVE kinetic energy

Deep impacts? Lazzati+ 2009

What makes the light we see?

For the prompt: we don’t know. we don’t know. Must be efficient: short cooling time. If synchro, or IC: F(E) = k E-1/2. SSC even steeper: kE-3/4

Kaneko+ Kaneko+ 20062006

Nava PhD thesis Nava PhD thesis 20092009

Lin

e o

f d

eath

Lin

e o

f d

eath

fo

r c

oolin

g e

-fo

r c

oolin

g e

-

Lin

e o

f d

eath

Lin

e o

f d

eath

fo

r n

on

coolin

g

for

non

coolin

g

e-

e-

“Afterglows”: X-rays and the optical have often different behaviors.

opticaloptical

X-ray

TTAAIs this “real” afte

rglow? i.e. e

xternal

Is this “real” afte

rglow? i.e. e

xternal

shock?

shock?

2 components? Late prompt+forward shock light curves resemble t-5/3, like rate of fallback material

~5/3~5/3

latelate promptprompt

LogLog

Log

Log

FF

GBMGBM

EEpeakpeak

Spectral-energy Spectral-energy correlationscorrelations

Amati, Ghirlanda, Firmani, Yonetoku…Under attack from the start (selection effects). Fiery replies.

Ghirlanda 2009

Ep-Eiso0.5

97 GRBs

““Amati”

Amati”

Amati, Ghirlanda, Firmani, Yonetoku…Under attack from the start (selection effects). Fiery replies.

Ghirlanda 2009

Ep-Eiso0.5

97 GRBs

““Amati”

Amati”

Amati, Ghirlanda, Firmani, Yonetoku…Under attack from the start (selection effects). Fiery replies.

Ghirlanda 2009

Ep-Eγ1.03

Ep-Eiso0.5

97 GRBs

29 GRBs

““Amati”

Amati”

““Ghi

rland

a

Ghi

rland

a

””

Yet we see the “Epeak-L” correlation in single GRBs

Luminosity [erg/s]Luminosity [erg/s]

EEp

eak

peak [keV

][k

eV

]R

ate

Rate

Gh

irla

nd

a+

20

09

EEpeak peak =k L=k L1/21/2

FERMI-FERMI-GBMGBM

This is not d

ue to selecti

on

This is not d

ue to selecti

on

effects.!!

effects.!!

High energy

Hurley et al. 1994

EGRET: 100 MeV-10 GeV

18 GeV

GG

+ 2

010

GG

+ 2

010

Fermi: 100 MeV - 100 GeV

short

LogLog

Log

Log

FF

GBMGBM

LAT

vs vs

vs vs

LogLog

Log

Log

FF

GBMGBM LAT

tt--10/710/7 Spectrum and Spectrum and decay: afterglow decay: afterglow = forward shock = forward shock in the circum-in the circum-burst mediumburst medium

The 4 brightest LAT GRBsThe 4 brightest LAT GRBs

This is This is puzzlingpuzzling

Adiabatic fireballs:Adiabatic fireballs:

LLbolombolom = a t = a t-1-1

Radiative fireballs:Radiative fireballs:

LLbolombolom = b t = b t-10/7-10/7

tt--10/710/7

Rad

iative!

Rad

iative!

The 4 brightest LAT GRBsThe 4 brightest LAT GRBs

tt--10/710/7

Rad

iative?

Rad

iative?

The 4 brightest LAT GRBsThe 4 brightest LAT GRBs

e

e

e+

e-

e

e+

e-

e

p

Time TimeTime Time

GRB 090510GRB 090510

ShortShort Very hardVery hard z=0.903z=0.903 Detected by the LAT up to 31 GeV!!Detected by the LAT up to 31 GeV!! Well defined timingWell defined timing Delay: ~GeV arrive after ~MeV Delay: ~GeV arrive after ~MeV

(fraction of seconds)(fraction of seconds) Quantum Gravity? Violation of Lorentz Quantum Gravity? Violation of Lorentz

invariance?invariance?

Fermi-L

AT

Fermi-L

AT

0.6s0.5

s

Time since trigger (precursor)Time since trigger (precursor)

precursorprecursor 8-260 keV8-260 keV

0.26-5 0.26-5 MeVMeV

LAT all LAT all

>>100 MeV100 MeV

>>1 GeV1 GeV31 31 GeVGeV

Ab

do e

t al 2009

Ab

do e

t al 2009

Delay between GBM and Delay between GBM and LATLATDue to Lorentz Due to Lorentz invariance violation?invariance violation?

Different Different componentcomponent

30 GeV0.1 GeV

1

2

3

3

4

AveragAveragee

Time Time resolveresolvedd

0.5-1s0.5-1s

F

(F(

) ) [e

rg/c

m[e

rg/c

m22/s

]

/s]

Energy [keV]Energy [keV]

Ab

do e

t al 2009

Ab

do e

t al 2009

If LAT and GBM radiation are If LAT and GBM radiation are cospatial: cospatial: >1000 to avoid photon->1000 to avoid photon-photon absorption photon absorption If If >1000: deceleration of the fireball >1000: deceleration of the fireball occurs early occurs early early afterglow! early afterglow!

If If >1000: large electron energies >1000: large electron energies synchrotron afterglow!synchrotron afterglow!

Ghirlanda+ Ghirlanda+ 20102010

tt22 tt-1.5-1.5

Fermi-

Fermi-

LATLAT

0.1-1 GeV0.1-1 GeV

>1 GeV>1 GeV

T-T* [s]T-T* [s]

Gh

irla

nd

a+

2010

Gh

irla

nd

a+

2010

T-T* [s]T-T* [s]

Gh

irla

nd

a+

2010

Gh

irla

nd

a+

2010~MeV and ~GeV emission are NOT ~MeV and ~GeV emission are NOT

cospatial. cospatial. But the ~GeV emission is…But the ~GeV emission is… No measurable delay in arrival time of No measurable delay in arrival time of high energy photons: thigh energy photons: tdelaydelay<0.2 s <0.2 s

Strong limit to quantum gravity Strong limit to quantum gravity

MMQGQG > 4.7 M > 4.7 MPlanckPlanck

ConclusionsConclusions

““Paradigm”: internal+external Paradigm”: internal+external shocks, synchrotron for both: shocks, synchrotron for both: it it does not workdoes not work

Fermi/LAT detection Fermi/LAT detection large large Early high energy (and powerful) Early high energy (and powerful) afterglowafterglow

Decay suggests Decay suggests radiativeradiative afterglowsafterglows

GRB 090510:GRB 090510: Violation of the Violation of the Lorentz invariance?Lorentz invariance? No (not yet) No (not yet)

4th Pillar: Long & Short (8)Similar spectra, especially for the first second of long

Fluence Fluence Peak FluxPeak Flux

Nava+

N

ava+

201

0201

0

Amati corr.

Ghirlanda et al. 2009

Yonetoku corr. EnergeticEnergeticss

LuminositieLuminositiess

LONG GRBsLONG GRBs

A2:Short vs Long: A2:Short vs Long: < < Energetics ; Energetics ; == Luminosities Luminosities

Ghirlanda et al. 2009

FERMI GRBs & TIME INTEGRATED correlations

For the prompt: we don’t know. Must be efficient: short cooling time. If synchro, or IC F(E) = k E-1/2. SSC even steeper: kE-3/4

1057 photons: large entropy (# of photons per particle), >1

For the afterglow: when it is forward shock it is synchrotron, but when it is late prompt… we don’t know.

Isotropic or collimated?Attention: not bolometric for Swift

Isotropic or collimated?

Strongest argument: Ghirlanda relation

<100

Nava+ 2006; Ghirlanda+ Nava+ 2006; Ghirlanda+ 22000077

“Am

at

i”

“Ghir

landa” 1- cos 1- cos jetjet

For long GRBs: Wolf-Rayet? Isolated or binary? (to give angular momentum). What triggers the SN, if a BH forms? The jet? In all SN Ic?

For short: merging NS-NS?

Isotropic or collimated?

But this? No jet breaks

<100

EEp

eak

peak(1

+z

(1+

z))

Gh

irla

nd

a,

Gh

isellin

i &

Lazz

ati

G

hir

lan

da,

Gh

isellin

i &

Lazz

ati

2004

2004

rr

EEp

eak

peak(1

+z

(1+

z))

Peak energy vs. True energyPeak energy vs. True energy

EE peak

peak

E E

true

true

0.70.7

HomogeneouHomogeneouss densitydensity

Nava e

t al.

2006

Nava e

t al.

2006

Wind-like Wind-like densitydensity

Nava e

t al.

2006

Nava e

t al.

2006

““Lor

entz

Lore

ntz

iinn

vvaa

rrii

aann

tt””

NN~

cons

t~10

~co

nst~

105757