The Evolution of a Structured Relativistic Jet and Gamma-Ray Burst Afterglow Light Curves
By Pawan Kumar, J. Granot. 2003
182 citations recorded by the source corpus.
We carry out a numerical hydrodynamical modeling for the evolution of a relativistic collimated outflow as it interacts with the surrounding medium and calculate the light curve resulting from synchrotron emission of the shocked fluid. The hydrodynamic equations are reduced to one-dimensional by assuming axial symmetry and integrating over the radial profile of the flow, thus considerably reducing the computation time. We present results for a number of different initial jet structures, including several different power laws and a Gaussian profile for the dependence of the energy per unit solid angle, ϵ, and the Lorentz factor, Γ, on the angle from the jet symmetry axis. Our choice of parameters for the various calculations is motivated by the current knowledge of relativistic outflows from gamma-ray bursts and the observed afterglow light curves. Comparison of the light curves for different jet profiles with gamma-ray burst afterglow observations provides constraints on the jet structure. One of the main results we find is that the transverse fluid velocity in the comoving frame (vt) and the speed of sideways expansion for smooth jet profiles is typically much smaller than the speed of sound (cs) throughout much of the evolution of the jet; vt approaches cs when Γ along the jet axis becomes of order a few (for a large angular gradient of ϵ, vt ~ cs while Γ is still large). This result suggests that the dynamics of relativistic structured jets may be reasonably described by a simple analytic model in which ϵ is independent of time, as long as Γ along the jet axis is larger than a few.
Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/23df187c6297617757b821301761005fe637b09a
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Citations in the corpus
- The physics of gamma-ray bursts & relativistic jets (2014, methodology): “Alternatively, this may be understood as a universal (Zhang and Mészáros, 2002b; Rossi et al., 2002) or quasi-universal (Zhang et al., 2004a) jet for all GRBs, with the measured jet break defined by observers’ viewing angle wrt the jet-axis.”
- Gamma-Ray Burst Afterglows in the Multimessenger Era: Numerical Models and Closure Relations (2019, background): “Detailed theoretical calculations of structured jet afterglow light curves concluded several facts: on-axis structured light curves resemble those from top-hat jets, offaxis structured light curves show an achromatic break at time qµtb obs 8 3 (where qobs is the viewing angle), and the pre-break slo”
- Short-hard gamma-ray bursts (2007, unknown): “Numerical simulations (Granot et al. , 2001; Cannizzo, Gehrels & Vishniac, 2004) and approximate analytical treatment (Kumar & Granot, 2003) suggest that the spreading velocity Fν ∝ ν2 t0 ν < νa ν1/3 t− 1 3 νa < ν < νm ν−(p−1)/2 t−p νm < ν < νc ν−p/2 t−p νc < ν .”
- Physical Processes Shaping Gamma-Ray Burst X-Ray Afterglow Light Curves: Theoretical Implications from the Swift X-Ray Telescope Observations (2005, background): “In principle, GRB jets could be structured (Zhang & Mészáros 2002b; Rossi et al. 2002; Zhang et al. 2004a; Kumar & Granot 2003).”
- Gamma-Ray Bursts in the Swift Era (2007, background): “…there are relativistically moving materials (though with a smaller energy) along the line of sight, the light curve in this model decays from the very beginning (Kumar & Granot 2003; Salmonson 2003), not inconsistent with the observational constraint from X-ray light curves (Mangano et al. 2007a).”
- A Decline in the X-Ray through Radio Emission from GW170817 Continues to Support an Off-axis Structured Jet (2018, background): “…jets consist of an initially highly relativistic collimated core surrounded by wings of mildly relativistic material at larger angles (e.g., Rossi et al. 2002; Kumar & Granot 2003); they are also sometimes called “successful jets with cocoons” in the literature (e.g., Nakar & Piran 2018).”
- Variabilities of Gamma-Ray Burst Afterglows: Long-acting Engine, Anisotropic Jet, or Many Fluctuating Regions? (2004, background): “[Notice that several numerical simulations imply a slow lateral expansion (Granot et al. 2001; Kumar & Granot 2003; Cannizzo, Gehrels, & Vishniac 2004).]”
- A complete reference of the analytical synchrotron external shock models of gamma-ray bursts (2013, background): “…observer (Rossi et al., 2002; Zhang and Mészáros, 2002a), the lightcurve may show a jet-break-like feature as the jet axis enters the field of view, but the exact shape of the break depends on the angular structure of the jet and the viewing angle (Kumar and Granot, 2003; Granot and Kumar, 2003).”
- Gamma-Ray Burst Energetics and the Gamma-Ray Burst Hubble Diagram: Promises and Limitations (2003, methodology): “We also assume a top-hat model for the structure of the jet but note the resulting energy determinations are identical under the universal jet model interpretation when the energy per unit solid angle drops as 2 (Zhang & Mészáros 2002; see also Kumar & Granot 2003 and references therein).”