Unstable Grb Photospheres and E ± Annihilation Lines
نویسنده
چکیده
We propose an emission mechanism of prompt gamma-ray bursts (GRBs) that can reproduce the observed non-thermal spectra with high radiative efficiencies, > 50%. Internal dissipation below a photosphere can create a radiation-dominated thermal fireball. If e pairs outnumber protons, radiative acceleration of e pairs drives the two-stream instabilities between pairs and protons, leading to the “proton sedimentation” in the accelerating pair frame. Pairs are continuously shock heated by proton clumps, scattering the thermal photons into the broken power-law shape, with the non-thermal energy that is comparable to the proton kinetic energy, consistent with observations. Pair photospheres become unstable around the radius of the progenitor star where strong thermalization occurs, if parameters satisfy the observed spectral (Yonetoku) relation. Pair annihilation lines are predicted above continua, which could be verified by GLAST. Subject headings: gamma rays: bursts — gamma rays: theory — radiation mechanism: non-thermal
منابع مشابه
Photospheres, Comptonization and X-ray Lines in Gamma Ray Bursts
Steep X-ray spectral slopes, X-ray excesses and preferred spectral energy breaks in the 01-0.3 MeV range are discussed as the possible consequences of the photospheric component of the GRB relativistic outflow, and of pair breakdown in internal shocks leading to comptonization on semirelativistic electrons or MHD waves. We also discuss the X-ray and UV spectra of GRB afterglows occuring in a de...
متن کاملIdentifying Gamma-ray Burst Remnants through Positron Annihilation Radiation
We model the annihilation of relic positrons produced in a gamma-ray burst (GRB) after its afterglow has faded. We find that the annihilation signal from at least one GRB remnant in the Milky Way galaxy should be observable with future space missions such as INTEGRAL and EXIST, provided that the gas surrounding the GRB source has the typical density of the interstellar medium, ∼< 1 cm . Three f...
متن کاملEfficiency of Neutrino Annihilation around Spinning Black Holes
A fraction of neutrino emission from GRB accretion disks annihilates above the disk, creating e+plasma that can drive GRB explosions. We calculate the efficiency of this annihilation using the recent detailed model of hyper-accretion disks around Kerr black holes. Our calculation is fully relativistic and based on a geodesic-tracing method. We find that the efficiency is a well-defined function...
متن کاملThe influence of free neutrons on dynamics and radiation of astrophysical plasmas
We present arguments in favor of the presence of free neutrons in plasmas generated by compact astrophysical objects and find conditions necessary for the formation of the neutron component. The broad range of phenomena caused by neutrons includes both dynamical (sources’ variability, transition of fireballs to the two-flow regime) and kinetic (fission of helium nuclei by neutrons, electromagne...
متن کاملar X iv : a st ro - p h / 02 05 14 4 v 2 1 9 Ju n 20 02 X - ray Rich GRB , Photospheres and Variability
We investigate the relationship between the quasi-thermal baryon-related photosphere in relativistic outflows, and the internal shocks arising outside them, which out to a limiting radius may be able to create enough pairs to extend the optically thick region. Variable gamma-ray light curves are likely to arise outside this limiting pair-forming shock radius, while X-ray excess bursts may arise...
متن کامل