Short gamma-ray burst jet propagation in binary neutron star merger environments

Abstract

The multimessenger event GW170817/GRB 170817A confirmed that binary neutron star (BNS) mergers can produce short gamma-ray burst (SGRB) jets. This evidence promoted new investigations on the mechanisms through which a BNS merger remnant can launch such a powerful relativistic outflow and on the propagation of the latter across the surrounding post-merger environment. In particular, great strides have been made in jet propagation models, establishing connections between the initial jet launching conditions, including the incipient jet launching time (with respect to merger) and the injection parameters, and the observable SGRB prompt and afterglow emission. However, present semi-analytical models and numerical simulations (with one notable exception) adopt simple hand-made prescriptions to account for the post-merger environment, lacking a direct association with any specific merging BNS system. Here, we present the first three-dimensional relativistic hydrodynamics simulations of incipient SGRB jets propagating through a post-merger environment that is directly imported from the outcome of a previous general relativistic BNS merger simulation. Our results show that the evolution and final properties of the jet can be largely affected by the anisotropies and the deviations from axisymmetry and homologous expansion characterizing more realistic BNS merger environments. In addition, we find that the inclusion of the gravitational pull from the central compact object, often overlooked, can have a major impact. Finally, we consider different jet launching times referred to the same BNS merger model and discuss the consequences for the ultimate jet properties.

On the jet-ejecta interaction in 3D GRMHD simulations of binary neutron star merger aftermath

“…• We can constrain the ejecta mass and the time delay between the merger and the BH formation, based on the success of launching a relativistic jet. If bound mass along the poles still exists at the time of jet formation, the jet may fail to proceed if it cannot overcome the ram pressure of the infalling ejecta (see Pavan et al 2021). In contrast to previous studies in which the jet power was a free parameter chosen as part of the setup, we find that the accretion onto the BH becomes dominated by the unmagnetized ejecta after a short while.…”

“…The understanding of the jet-ejecta interaction has been considerably improved thanks to a wide range of numerical studies in the past years (Kasliwal et al 2017;Lazzati et al 2017;Duffell et al 2018;Gottlieb et al 2018aGottlieb et al ,b, 2020aKathirgamaraju et al 2018;Geng et al 2019;Lazzati & Perna 2019;Gottlieb & Loeb 2020;Klion et al 2021;Murguia-Berthier et al 2021;Pavan et al 2021;Urrutia et al 2021;Nativi et al 2022;Lamb et al 2022). However, these studies have been subject to two major limitations:…”

“…In nature the ejecta likely includes anisotropies which may alter the jet evolution(Pavan et al 2021). This will be addressed in a follow-up paper where the ejecta will be set self-consistently by remapping it from numerical relativity simulations.…”

On the Jet–Ejecta Interaction in 3D GRMHD Simulations of a Binary Neutron Star Merger Aftermath

“…The understanding of the jet-ejecta interaction has been considerably improved, thanks to a wide range of numerical studies in the past years (Kasliwal et al 2017;Lazzati et al 2017;Gottlieb et al 2018aGottlieb et al , 2018bDuffell et al 2018;Kathirgamaraju et al 2018;Geng et al 2019;Lazzati & Perna 2019;Gottlieb et al 2020a;Gottlieb & Loeb 2020;Klion et al 2021;Murguia-Berthier et al 2021;Pavan et al 2021;Urrutia et al 2021;Lamb et al 2022;Nativi et al 2022). However, these studies have been subject to two major limitations:…”

Inhomogeneous Jets from Neutron Star Mergers: One Jet to Rule them all

“…A jet launched following a compact stellar merger will propagate through the merger ejecta and winds (e.g., Aloy et al 2005;Nagakura et al 2014;Duffell et al 2015;Murguia-Berthier et al 2017;Geng et al 2019;Nathanail et al 2021;Nativi et al 2021Nativi et al , 2022Pavan et al 2021;Urrutia et al 2021), this results in the collimation of the jet before breakout (Bromberg et al 2011;Salafia et al 2020;Hamidani & Ioka 2021). As a consequence of the turbulent motions arising during the hydrodynamic interaction between the jet and the surrounding ejecta, the resultant jet will have an angular shape that is independent of the injected jet structure (Nativi et al 2022), unless the ejecta density is very low or the jet power very high (Urrutia et al 2021).…”