Moreover, we perform three sets of simulations to cover a wide range of model parameters.
#Camara photosphere full
This procedure is well tested 15, but to achieve full decoupling of photons from the jet we extend the calculation domain by a factor of ~20 in space and time compared to our previous study. To examine these issues, we perform large scale 3D relativistic hydrodynamical simulations of jets breaking out of a massive stellar envelope 27, followed by a post-process radiation transfer calculation in 3D. Moreover, the studies explored only a small part of the parameter space, so it was unclear how emission depends on the intrinsic properties of the jet. High latitude ( θ obs ≳ 4°) emission lacked accuracy since the calculation domains (≲10 13 cm) were not sufficient for the photons to decouple from the fluid in the jet. However, these studies were only able to evaluate the emission at small viewing angles θ obs. We have previously reported on such a calculation 15, which was followed by another group 16– 18 in 2D. To capture all the essential features, the calculation needs to cover a large range in time and space, and must be performed in three dimensions (3D). This requires both relativistic hydrodynamics and full radiation transfer. We do so, robustly, here.įor an accurate analysis of photospheric emission, the jet evolution and accompanying photons must be followed from their origin, deep within the star, to the point where photons fully decouple from the jet. More sophisticated study is necessary to firmly connect photospheric emission to the Yonetoku relation. However, these analyses adopted oversimplified jet dynamics (e.g., steady spherical flow) 11, 12 and/or crude assumptions for radiation processes 13, 14. Indeed, many studies have discussed the origin of the relation based on photospheric emission. This model predicts the emergence of quasi-thermal radiation and can reproduce those spectral shapes that are incompatible with synchrotron theory.Īnother strong advantage of the photospheric model is that it does not require a large number of uncertain parameters, since it is based on thermal processes. The above difficulties have led recent theoretical and observational studies to consider photospheric emission (photons released from a relativistic jet during the transition from optically thick to thin states) as a promising alternative scenario 8– 26. These problems arise from the fundamental physics of synchrotron emission and so cannot be explained within this framework. In addition, models that invoke optically thin synchrotron emission also face problems in reproducing the spectrum (hard spectral slopes 6 and sharp spectral peak 7) in a non-negligible fraction of GRBs.
However, it is not obvious why such self-regulation should occur across bursts. As a result, in order to reproduce the observed correlation, one needs to assume that there is self-regulation among the imposed parameters 5. Too many parameters (e.g., particle acceleration efficiency and magnetization) do not have a strong constraint but must be specified to evaluate the non-thermal emission. Both the well-studied internal shock model 3 and the more recent magnetic reconnection model 4 lack the ability to make firm predictions about the resulting emission properties, since they invoke non-thermal plasma physics with large uncertainties. So far, no theoretical work has provided a fully consistent explanation for the origin of the Yonetoku relation 1, 2. This result strongly suggests that photospheric emission is the dominant component in the prompt phase of GRBs. Although jet dynamics depend sensitively on luminosity, the correlation holds regardless. Our simulations reproduce the Yonetoku relation as a natural consequence of viewing angle. Here we present three-dimensional hydrodynamical simulations, and post-process radiation transfer calculations, of photospheric emission from a relativistic jet. This Yonetoku relation is the tightest correlation found in the properties of the prompt phase of GRB emission, providing the best diagnostic for the radiation mechanism. One unresolved question is the origin of the tight correlation between the spectral peak energy and peak luminosity discovered in observations.
Despite decades of study, there is still no consensus on their emission mechanism. Long duration gamma-ray bursts (GRBs), the brightest events since the Big Bang itself, are believed to originate in an ultra-relativistic jet breaking out from a massive stellar envelope.
0 kommentar(er)
