scholarly journals Can jets make the radioactively powered emission from neutron star mergers bluer?

2020 ◽  
Vol 500 (2) ◽  
pp. 1772-1783
Author(s):  
L Nativi ◽  
M Bulla ◽  
S Rosswog ◽  
C Lundman ◽  
G Kowal ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Neutron Star ◽  
Radiative Transfer ◽  
Initial Conditions ◽  
Heavy Elements ◽  
Electromagnetic Transients ◽  
Relativistic Hydrodynamic ◽  
Hydrodynamic Simulations ◽  
Relativistic Jet ◽  
Nuclear Composition

ABSTRACT Neutron star mergers eject neutron-rich matter in which heavy elements are synthesized. The decay of these freshly synthesized elements powers electromagnetic transients (‘macronovae’ or ‘kilonovae’) whose luminosity and colour strongly depend on their nuclear composition. If the ejecta are very neutron-rich (electron fraction Ye < 0.25), they contain fair amounts of lanthanides and actinides that have large opacities and therefore efficiently trap the radiation inside the ejecta so that the emission peaks in the red part of the spectrum. Even small amounts of this high-opacity material can obscure emission from lower lying material and therefore act as a ‘lanthanide curtain’. Here, we investigate how a relativistic jet that punches through the ejecta can potentially push away a significant fraction of the high opacity material before the macronova begins to shine. We use the results of detailed neutrino-driven wind studies as initial conditions and explore with 3D special relativistic hydrodynamic simulations how jets are propagating through these winds. Subsequently, we perform Monte Carlo radiative transfer calculations to explore the resulting macronova emission. We find that the hole punched by the jet makes the macronova brighter and bluer for on-axis observers during the first few days of emission, and that more powerful jets have larger impacts on the macronova.

Simulations of the W50-SS433 system

2018 ◽  
Vol 14 (S342) ◽  
pp. 257-259
Author(s):  
Dimitrios Millas ◽  
Oliver Porth ◽  
Rony Keppens
Keyword(s):  
Radiative Transfer ◽  
Supernova Remnant ◽  
Relativistic Hydrodynamic ◽  
Astrophysical Jets ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
System A ◽  
The Universe

AbstractSupernovae and astrophysical jets are two of the most energetic and intriguing objects in the universe. We examine an interesting scenario that involves the interaction of these two extreme phenomena, motivated by observations of the W50-SS433 system: a jet launched from the microquasar SS433 (an X-ray binary) located inside a supernova remnant, W50. These observations revealed a unique morphology of the remnant, attributed to the presence of the jet. We performed full 3D relativistic hydrodynamic simulations to better capture the interaction between the remnant and the jet and post-processed the data with a radiative transfer code to create emission maps.

scholarly journals The First Steps in the Life of a GRB

2005 ◽  
Vol 192 ◽  
pp. 483-489
Author(s):  
Miguel A. Aloy
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Relativistic Hydrodynamic ◽  
Gamma Ray Burst ◽  
Hydrodynamic Simulations ◽  
Preliminary Results

SummaryWe present some preliminary results of relativistic hydrodynamic simulations of post-neutron star merger disks as potential candidates for progenitors of short-lasting gamma-ray bursts. We discuss some of the generic conditions under which a gamma-ray burst can be initiated in this kind of progenitor and the main characteristics of the resulting outflow.

scholarly journals Automated Search-Based Robustness Testing for Autonomous Vehicle Software

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Kevin M. Betts ◽  
Mikel D. Petty
Keyword(s):  
Monte Carlo ◽  
Performance Metrics ◽  
Initial Conditions ◽  
Autonomous Vehicle ◽  
Vehicle Control ◽  
Test Case ◽  
Test Cases ◽  
Control Software ◽  
Robustness Testing ◽  
Testing Techniques

Autonomous systems must successfully operate in complex time-varying spatial environments even when dealing with system faults that may occur during a mission. Consequently, evaluating the robustness, or ability to operate correctly under unexpected conditions, of autonomous vehicle control software is an increasingly important issue in software testing. New methods to automatically generate test cases for robustness testing of autonomous vehicle control software in closed-loop simulation are needed. Search-based testing techniques were used to automatically generate test cases, consisting of initial conditions and fault sequences, intended to challenge the control software more than test cases generated using current methods. Two different search-based testing methods, genetic algorithms and surrogate-based optimization, were used to generate test cases for a simulated unmanned aerial vehicle attempting to fly through an entryway. The effectiveness of the search-based methods in generating challenging test cases was compared to both a truth reference (full combinatorial testing) and the method most commonly used today (Monte Carlo testing). The search-based testing techniques demonstrated better performance than Monte Carlo testing for both of the test case generation performance metrics: (1) finding the single most challenging test case and (2) finding the set of fifty test cases with the highest mean degree of challenge.

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