Related papers: On the Composition of GRBs' Collapsar Jets
Two-dimensional hydrodynamic simulations are performed to investigate explosive nucleosynthesis in a collapsar using the model of MacFadyen and Woosley (1999). It is shown that 56Ni is not produced in the jet of the collapsar sufficiently…
The joint detection of GW~170817/GRB 170817 confirmed the long-standing theory that binary neutron star mergers produce short gamma-ray burst (sGRB) jets that can successfully break out of the surrounding ejecta. At the same time, the…
We explore the photospheric emission from a relativistic jet breaking out from a massive stellar envelope based on relativistic hydrodynamical simulations and post-process radiation transfer calculations in three dimensions. To investigate…
Short gamma-ray bursts (sGRBs) are thought to be produced by binary NS mergers. While a sGRB requires a relativistic jet to break out of ejecta, the jet may be choked and fails to produce a successful sGRB. We propose a "delayed breakout"…
We present our numerical results of two-dimensional magnetohydrodynamic (MHD) simulations of the collapse of rotating massive stars in light of the collapsar model of gamma-ray bursts (GRBs). Pushed by recent evolution calculations of GRB…
Gamma-Ray Bursts (GRBs) are traditionally divided to long and short according to their durations (>/< 2 sec). It was generally believed that this reflects a different physical origin: Collapsars (long) and non-Collapsars (short). We have…
Using a collapsar progenitor model of MacFadyen & Woosley we have simulated the propagation of an axisymmetric jet through a collapsing rotating massive star with the GENESIS multi-dimensional relativistic hydrodynamic code. The jet forms…
As the brightest Gamma-Ray burst (GRB) ever detected, GRB 221009A may offer a chance that reveals some interesting features which are hidden in those bursts that are not so bright. There seems a very weak emission with a flux of…
The precession phenomenon of the jet in a gamma-ray burst (GRB) is a key probe of the physics of the central engine. Previous studies generally assumed a fixed precession period when analysing the temporal profiles in GRBs; however, the…
There are several lines of evidence indicating that the ultra-relativistic outflows powering gamma-ray bursts (GRBs) are collimated into narrow jets. However, these are indirect, and the jet structure is rather poorly constrained. What is…
The collapsar model is the most promising scenario to explain the huge release of energy associated with long duration gamma-ray-bursts (GRBs). Within this scenario GRBs are believed to be powered by accretion through a rotationally support…
For the collapsar scenario to be effective in the production of Gamma Ray Bursts, the infalling star's angular momentum $J(r)$ must be larger than the critical angular momentum needed to form an accretion disk around a blackhole (BH),…
Recently, a short-duration GRB with supernova association (GRB 200826A) and two long-duration GRBs with kilonova associations (GRB 211211A and GRB 230307A) have been detected, which demolished the hope for a tidy connection between GRB…
We consider a jet-disk symbiosis model to explain Gamma Ray Bursts and their afterglows. It is proposed that GRBs are created inside a pre-existing jet from a neutron star in a binary system which collapses to a black hole due to accretion.…
Motivated by GW170817 we examine constraints that observations put on the angular structure of long gamma-ray burst (GRB) jets. First, the relatively narrow observed distribution of $E_{X}/E_{\gamma}$ (the isotropic equivalent early X-ray…
I constrain a possible supernova origin for gamma-ray bursts by modeling the dynamical interaction between a relativistic jet and a stellar envelope surrounding it. The delay in observer's time introduced by the jet traversing the envelope…
The central engine in long gamma-ray bursts (GRBs) is thought to be a compact object produced by the core collapse of massive stars, but its exact nature (black hole or millisecond magnetar) is still debatable. Although the central engine…
Using a two-dimensional hydrodynamics code (PROMETHEUS), we study the continued evolution of rotating massive helium stars whose iron core collapse does not produce a successful outgoing shock, but instead forms a black hole. We study the…
We consider the explosion of supernovae and the possible production of a variety of high energy transients by delayed black hole formation in massive stars endowed with rotation. Following the launch of a ``successful'' shock by the usual…
We consider models for gamma-ray bursts in which a collimated jet expands either into a homogeneous medium or into a stellar wind environment, and calculate the expected afterglow temporal behavior. We show that (i) following a break and a…