Download - Gamma-ray bursts
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