Observational manifestations of jet-ejecta interaction from 3D GRMHD simulations of binary neutron star merger aftermath. (arXiv:2205.01691v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Gottlieb_O/0/1/0/all/0/1">Ore Gottlieb</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moseley_S/0/1/0/all/0/1">Serena Moseley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ramirez_Aguilar_T/0/1/0/all/0/1">Teresita Ramirez-Aguilar</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Murguia_Berthier_A/0/1/0/all/0/1">Ariadna Murguia-Berthier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Liska_M/0/1/0/all/0/1">Matthew Liska</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tchekhovskoy_A/0/1/0/all/0/1">Alexander Tchekhovskoy</a>
Short $gamma$-ray burst (sGRB) jets form in the aftermath of a neutron star
merger, drill through disk winds and dynamical ejecta, and extend over 5 orders
of magnitude in distance before reaching the photosphere. We present the first
3D general-relativistic magnetohydrodynamic sGRB simulations to span this
enormous scale separation. They feature three possible outcomes: jet+cocoon,
cocoon, and neither. Typical sGRB jets break out of the dynamical ejecta if:
(i) the bound ejecta isotropic equivalent mass along the pole at the time of
the BH formation is $ lesssim10^{-4}~{rm M_{odot}} $, setting a limit on the
delay time between the merger and BH formation, otherwise the jets perish
inside the ejecta and leave the jet-inflated cocoon to power a low-luminosity
sGRB; and (ii) post-merger remnant disk contains strong large-scale vertical
magnetic field, $gtrsim10^{15}$ G; and (iii) if the jets are weak
($lesssim10^{50}$ erg), the ejecta isotropic equivalent mass along the pole
must be small ($lesssim10^{-2}~{rm M_{odot}}$). Generally, the jet structure
is shaped by the early interaction with disk winds rather than the dynamical
ejecta. As long as our jets break out of the ejecta, they reach the photosphere
at $sim10^{10.5}$ cm while retaining significant magnetization ($lesssim1$),
suggesting that magnetic reconnection is a fundamental property of sGRB
emission. The angular structure of the outflow isotropic equivalent energy
after breakout consistently features a flat core followed by a steep power-law
distribution (slope $gtrsim3$), similar to hydrodynamic jets. In the
cocoon-only outcome, the dynamical ejecta broadens the outflow angular
distribution and flattens it (slope $sim1.5$).
Short $gamma$-ray burst (sGRB) jets form in the aftermath of a neutron star
merger, drill through disk winds and dynamical ejecta, and extend over 5 orders
of magnitude in distance before reaching the photosphere. We present the first
3D general-relativistic magnetohydrodynamic sGRB simulations to span this
enormous scale separation. They feature three possible outcomes: jet+cocoon,
cocoon, and neither. Typical sGRB jets break out of the dynamical ejecta if:
(i) the bound ejecta isotropic equivalent mass along the pole at the time of
the BH formation is $ lesssim10^{-4}~{rm M_{odot}} $, setting a limit on the
delay time between the merger and BH formation, otherwise the jets perish
inside the ejecta and leave the jet-inflated cocoon to power a low-luminosity
sGRB; and (ii) post-merger remnant disk contains strong large-scale vertical
magnetic field, $gtrsim10^{15}$ G; and (iii) if the jets are weak
($lesssim10^{50}$ erg), the ejecta isotropic equivalent mass along the pole
must be small ($lesssim10^{-2}~{rm M_{odot}}$). Generally, the jet structure
is shaped by the early interaction with disk winds rather than the dynamical
ejecta. As long as our jets break out of the ejecta, they reach the photosphere
at $sim10^{10.5}$ cm while retaining significant magnetization ($lesssim1$),
suggesting that magnetic reconnection is a fundamental property of sGRB
emission. The angular structure of the outflow isotropic equivalent energy
after breakout consistently features a flat core followed by a steep power-law
distribution (slope $gtrsim3$), similar to hydrodynamic jets. In the
cocoon-only outcome, the dynamical ejecta broadens the outflow angular
distribution and flattens it (slope $sim1.5$).
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