Gammaray bursts Tomasz Bulik CAMK Warsaw Outline Observations

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 Ap. J 182, L 85 1973

Sky distribution

Spatial distribution

Temporal properties ● Duration from 0. 01 s to 1000 s ● Irregular lightcurves ● Individual pulses: less than a ms, ● Asymmetric pulses, FRED type

Lightcurves Every burst is different! Power density spectra with a – 5/3 slope

Spectral break between 100 ke. V do 1 Me. V E (Me. V)

Spectral properties ● Nonthermal continuum ● Broken PL, ● Break energy distribution, X-ray rich bursts ● High energy tails: Ge. V, (up to 1. 5 hours) ● Even higher: Te. V (GRB 970417) ● Spectral features?

Classes of bursts Short (hard) Long (soft)

Other classes of bursts • X-ray rich bursts • Long lag-bursts – the first anisotropy found, posible connection with supergalactic plane

Afterglows X-ray Optical Radio

Afterglow lightcurve breaks

GRB host galaxies GRB 990123 GRB 990712

GRB redshifts Most observed bursts at: z<2

GRBs and supernovae 1998 bw GRB 980425 GRB 980326 Bloom et al 99

Supernovae GRB 030329 SN Ic Stanek et al 2003

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 300 ke. V ● Luminosity: ● Duration: ● Collimation: ● Rate - a few daily (observed) isotropic

Theoretical models

Compactness problem Pair creation optical depth: Relativistic motion:

Blastwave model Internal shocks – gamma ray burst prompt emission External shocks - afterglow

Afterglow lightcurve breaks Achromatic breaks – beaming estimate

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

Can a jet leave a star? Zhang Woosley 2003.

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 known log. N- log. S =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 Reichart etal 2001 Do we already see bursts at z=10 -30 ? ? ? Norris etal 2001 ● Luminosity variability ● Luminosity - lags

Polarization in gamma rays % GRB 021206 RHESSI

Polarization - possibilities ● ● ● Ordered magnetic fields in a wide jet Narrow jet, inverse Compton emission Emission from Poynting flux jet

Future…

SWIFT Arcminute accuracy 10 s After trigger XRT and UVOT observe in 50 s Launch – spring 2004

GLAST GBM – sensitive to GRBs in 5 ke. V – 25 Me. V LAT – in the range 20 Me. V – 300 Ge. V Launch – 2006

Neutrino emission ● Me. V – stellar collapse ● Ge. V – pn collision in acceleration phase ● Te. V – when jet propagates through star ● Pe. V – in internal shocks ● Ee. V – in external reverse shock

Neutrinos ● AMANDA ● Icecube ● NESTOR ● ANTARES

Gravitational waves • Binary coalescences • Supernovae • Newly formed black holes ● LIGO II ● VIRGO ● GEO 600 ● TAMA 300