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https://stockholmuniversity.zoom.us/j/61161537684
Abstract:
Besides being sources of gravitational waves, neutron star mergers eject neutron-rich material suitable for the production of heavy r-process nuclei. The radioactive decay of these freshly synthesised elements powers a rapidly evolving thermal transient (named "macronova" or "kilonova"), whose spectral properties strongly depend on the ejecta composition. In particular, the high opacities associated to the heaviest nuclei powers a transient peaking in the red-infrared bands over time scales of weeks.
The first detection of a binary neutron star merger was also accompanied by the detection of a relativistic jet. Despite being ascertained the presence of two dynamical components, mildly-relativistic ejecta and ultra-relativistic outflow, the observational consequences of the interplay between the two is still unclear.
In this talk I will discuss the consequences of jet propagation on the radioactively powered transient, by simulating the interaction with dedicated special-relativistic hydrodynamics simulations. Firstly, I will present the observational evidence of the two dynamical components. Second, I will discuss the simulations setup focusing on the initial ejecta distribution as obtained from previous dedicated works. Lastly, I will show how a relativistic jet can "punch-away" a fraction of high-opacity material before the brightening of the macronova, resulting in the transient getting brighter and bluer for on-axis observers in the first few days.