Gamma-ray bursts

Tomasz Bulik CAMK, Warsaw

Outline

● Observations: prompt gamma emission, afterglows

● Theoretical modeling● Current challenges in the field● Future

The first GRB More than 30 years ago!

Klebesadel, Strong i Olson ApJ 182, L85 1973

Sky distribution

Spatial distribution

max 0.330 0.010V V

3 2N P P

Temporal properties

● Duration from 0.01 s to 1000s● Irregular lightcurves● Individual pulses: less than a ms, ● Asymmetric pulses, FRED type

310/ Tt

Lightcurves

Every burst is different!

Power density spectrawith a –5/3 slope

Spectra

Spectral break between 100keV do 1MeV

E (MeV)

Spectral properties

● Nonthermal continuum● Broken PL,● Break energy distribution, X-ray rich bursts● High energy tails: GeV, (up to 1.5 hours)● Even higher: TeV (GRB970417)● Spectral features?

2,1

Classes of bursts

Short (hard)

Long (soft)

2st 90

2st 90

Other classes of bursts• X-ray rich bursts

•Long lag-bursts – the first anisotropy found, posible connection with supergalactic plane

AfterglowsX-ray

Optical Radio

Afterglow lightcurve breaks

GRB host galaxies

GRB990123 GRB 990712

GRB redshifts

Most observed bursts at: z<2

GRBs and supernovae

1998bw GRB980425

GRB 980326Bloom et al 99

L=10 46 erg , z=0.008

Supernovae

Stanek et al 2003

GRB 030329

SN Ic

Afterglow properties

• Broad band phenomenon – from radio to X-rays

•Power law decay, but bumps and wiggles

•Achromatic brakes in the lightcurves

•Underlying host galaxies

•X-ray lines – probable

Characteristic GRB numbers

● Distance: z=1-2● Spectrum: nonthermal, peaks around 300keV ● Luminosity: isotropic● Duration: ● Collimation:● Rate - a few daily (observed)

erg=E 5451 1010

oΘ 5s3100.01

Theoretical models

Compactness problem

2

2-615

3cm erg1010

22)(

2

Gpc

DFf

mctc

FDTp

f

p

Pair creation optical depth:

Relativistic motion:

2

2-6 3cm erg1022

1510

Gpc

DFf p

100

Blastwave model

Internal shocks – gamma ray burst prompt emission

External shocks - afterglow

Afterglow lightcurve breaks

Θ=Γ /1

Achromatic breaks – beaming estimate

sn

Et

3/83/1

1

52

1.02.6

Energy reservoir

Collimation correction -

Standard energy reservoir

GRB progenitors

● Black hole accretion torus models– Collapsars– Binary coalescences

● Magnetar collapse

Collapsars● A massive rotating star collapses● Rotating BH is formed● Dense matter torus ● Accretion and jets

Zhang Woosley 2003.

Can a jet leave a star?

Host galaxies● Typical for their

redshifts● Traces of active star

formation● GRBs inside galaxies● Distribution around

galaxies:

Binary coalescences: in or out of galaxies?

Belczyński Bulik 2002

Magnetar model

● Quickly rotating magnetar B=10^17 Gauss● Differential rotation● Toroidal field● Magnetohydrodynamic jet formed● Delay after supernova

Caution…

Not knownlogN- logS =3/2????

Known

????

Current problems

Short bursts

● A different population? Distances?● Other progenitors?● Inside or outside of galaxies?● Afterglows or not?

GRB SN connection

Are all bursts accompanied by supernovae?

What types of stars are connected with GRB SN?

Are supernovae and bursts simultaneous?

Correlations

● Luminosity variability● Luminosity - lags

Reichart etal 2001

Norris etal 2001

Do we already see bursts atz=10-30 ???

Polarization in gamma rays

GRB 021206

RHESSI

2080±=Π %

Polarization - possibilities

● Ordered magnetic fields in a wide jet

● Narrow jet, inverse Compton emission

● Emission from Poynting flux jet

Future…

SWIFT

Arcminute accuracy 10sAfter trigger

XRT and UVOT observein 50 s

Launch – spring 2004

GLAST

GBM – sensitive to GRBs in 5keV – 25MeV

LAT – in the range 20MeV – 300GeV

Launch – 2006

Neutrino emission

● MeV – stellar collapse● GeV – pn collision in acceleration phase● TeV – when jet propagates through star● PeV – in internal shocks ● EeV – in external reverse shock

ppp

Razzaque, Meszaros, Waxman 2002

Neutrinos

● AMANDA● Icecube● NESTOR● ANTARES

Gravitational waves

● LIGO I● LIGO II● VIRGO● GEO 600● TAMA 300

•Binary coalescences

•Supernovae

•Newly formed black holes