Physical parameters of the relativistic shells in the GRBs S. Simić 1, L. Grassitelli 2 and L. Č. Popović 3,4 1) Faculty of Science, Department of Physics, Radoja Domanovića 12, Kragujevac, Serbia 2) Argelander Institute fur Astronomie, Auf dem Hugel 71, D Bonn, Germany 3) Astronomical Observatory, Volgina 7, Belgrade, Serbia 4) Faculty of Mathematics, Department of Astronomy and Astrophysics, Studentrski trg 16, Belgrade, Serbia The biggest accelerators in space and on earth chaired by Michelangelo Mangano (CERN), Antxon Alberdi, Silke Britzen, Greg Landsberg (Brown University (US)), Boris Samuel Pioline (CERN), UlrikeWyputta from Monday, March 18, 2013 at 13:30 to Friday, March 22, 2013 at 18:30

Gamma-ray bursts: the most violent explosions in the universe!

GRBs in short – observational facts The biggest accelerators in the Universe? Observed as a short and very intensive emission of radiation Broad emission band, from high energy gamma’s down to low energy radio band Multi phase transition event ▫Initial phase – gamma emission (longest < 1-2min ) ▫Afterglow – X-ray optical and radio domain High temporal variability observed in the first phase Homogenous distribution over celestial sphere Afterglow with much less emitted energy Rate approx. 1 GRB/day Two sorties extracted T 90 2s (BATSE team definition)

GRBs in short – observational facts The biggest accelerators in the Universe? Observed as a short and very intensive emission of radiation Broad emission band, from high energy gamma’s down to low energy radio band Multi phase transition event ▫Initial phase – gamma emission ▫Afterglow – X-ray optical and radio domain High temporal variability observed in the first phase Homogenous distribution over celestial sphere Afterglow with much less emitted energy Rate approx. 1 GRB/day Two sorties extracted T 90 2s (BATSE team definition)

GRBs in short – observational facts The biggest accelerators in the Universe? Observed as a short and very intensive emission of radiation Broad emission band, from high energy gamma’s down to low energy radio band Multi phase transition event ▫Initial phase – gamma emission ▫Afterglow – X-ray optical and radio domain High temporal variability observed in the first phase Homogenous distribution over celestial sphere Afterglow with much less emitted energy Rate approx. 1 GRB/day Two sorties extracted T 90 2s (BATSE team definition)

GRBs in short – observational facts The biggest accelerators in the Universe? Observed as a short and very intensive emission of radiation Broad emission band, from high energy gamma’s down to low energy radio band Multi phase transition event ▫Initial phase – gamma emission ▫Afterglow – X-ray optical and radio domain High temporal variability observed in the first phase Homogenous distribution over celestial sphere Afterglow with much less emitted energy Rate approx. 1 GRB/day Two sorties extracted T 90 2s (BATSE team definition)

GRBs in short – what we conclude Homogenous distribution out of our galaxy galactic halo Detection of the afterglow measurement of redshift extragalactic High temporal variability constraints on the core size compact phenomena Two classes - progenitor type Long-soft bursts – collapsar model Short-hard bursts – NS-NS (NS-BH) merger model

GRBs in short – spectrum and energy Non thermal spectrum distribution two power law joined at the maximum energy max. energy change during the event constraints on the emission mechanism synchrotron, IC, synchrotron self Compton high and ultra high energy photons, MeVs and GeVs Total emitted energy enormous – even ergs constraints on form of ejected material – collimated or not?

GRBs in short – spectrum and energy Non thermal spectrum distribution two power law’s joined at the maximum energy max. energy change during the event constraints on the emission mechanism synchrotron, IC, synchrotron self Compton high and ultra high energy photons, MeVs and GeVs Total emitted energy enormous – even ergs constraints on form of ejected material – collimated or not? Band et al., 1993.

GRBs in short – spectrum and energy Non thermal spectrum distribution two power law joined at the maximum energy max. energy change during the event constraints on the emission mechanism synchrotron, IC, synchrotron self Compton high and ultra high energy photons, MeVs and GeVs Total emitted energy enormous – even ergs in isotropic models constraints on form of ejected material – collimated or not?

GRBs in short – spectrum and energy Non thermal spectrum distribution two power law joined at the maximum energy max. energy change during the event constraints on the emission mechanism synchrotron, IC, synchrotron self Compton high and ultra high energy photons, MeVs and GeVs Total emitted energy enormous – even ergs constraints on form of ejected material – collimated or not? Piran, T., 2005

GRBs in short – current theoretical view Structure of accelerated material – baryons, leptons in equipartition Because of large optical depth for pair production γ γ->e - e + high Lorentz factors > 100 are demanded Low baryon load Relativistic shells ~ M sun Afterglow shock wave ~ M sun Density of the surrounding material ~ c m -3 Distances for burst production ~ cm

GRB progenitors – long bursts Collapsar model: Death of massive star like supernova, but with creation of BH Material from star mantle swirl down toward the BH in a form of high density accretion disc.

GRB progenitors – long bursts Conditions: Massive star > 40 M sun – to create a BH Rapid rotation - to create accretion disc and pair of jets Low metallicity – to be stripped from the Hydrogen mantle Evidence: Long GRBs are found exclusively in star forming region For closer GRBs a supernova is detected immediately after GRB event (GRB060218, GRB030329, GRB980425). But not in all cases! Type I b/c have no hydrogen lines.

GRB progenitors – short bursts Hard for localization. Out of the star forming regions – in the outer regions or even the outer halo of large elliptical galaxies – not included in the star formation process Most of the hosts galaxies are at low redshift Merger model – NS-NS or NS-BH NS-NS (NS-BH) in a binary system will loose energy through gravitational waves The 2 objects will get closer until tidal forces rip the NS apart and matter falls into a BH. The process has ms timescale Evidence – events located in the old galaxies without star formation.

GRBs - shell interaction We propose following: Interactions are happen in the first phase of GRBs Produce the observed temporal variability of gamma emission Stochastic process Put the constraints on the central engine – relativistic flow of well defined collimated shells with random parameters (masses, velocities, …) Interaction decelerate the shells Effect of accumulation of ejected material and it’s shell interaction Main mechanism for observed variability

Relativistic shells - model We apply a phenomenological model Evaluate a three main variables: R,  and m Material barriers are embedded into surrounding media Mag. field in shell frame is the part of total energy of the shell Homogenous distribution of radiation over the shell Huang, et al, 2000 Simić, et al., 2007

Relativistic shells - model Evolution of Lorenz factor and mass of the shell Sharp change

Relativistic shells - interaction Fitting of variety of different pulses – longer or shorter FRED pulse shape – electron cooling

Relativistic shells - interaction Fit in different BATSE channels Combined pulses generate synthetic GRB light curve Parameters randomly chosen in a given domain

Constraints on GRB light curve selection: isolated pulses avoid small pulses – low temporal resolution different pulse shapes Selected pulses parameters FWHM, t peak, Int and  s GRBs – sample parameter distribution Simić - Popović, 2012.

Relativistic shells - parameters

param 00 Mej  [M s ] bb n 0 [cm -3 ]  m [rad] Rc  [cm]  Rc  [cm] n b  10 4 [cm -3 ] max min mean dev

Some weak correlation between used parameters can be extracted GRBs – sample parameter distribution

Stretch the model on the cases with two peaks combined Multiple interactions of shells with different velocities (Grassitelli at al) Expect even more constraints on the physical parameters of relativistic shells GRBs – sample parameter distribution Grassitelli, et al

Thank you References: Piran, T., RvMP, 76, (2005), Band, D. et al. (1993), ApJ 413, 281 Simić, S., A&SS, 309, (2007), 173 Simić, S, Popović, L. Č., (2012), 21, 3. Grassitelli, L., 2013 in preparation