Kavli Affiliate: Li Xin Li
|Summary:The observation of a radioactively powered kilonova AT~2017gfo associated with the gravitational wave-event GW170817 from binary neutron star merger proves that these events are ideal sites for the production of heavy $r$-process elements. The gamma-ray photons produced by the radioactive decay of heavy elements are unique probes for the detailed nuclide compositions. Basing on the detailed $r$-process nucleosynthesis calculations and considering radiative transport calculations for the gamma-rays in different shells, we study the gamma-ray emission in a merger ejecta on a timescale of a few days. It is found that the total gamma-ray energy generation rate evolution is roughly depicted as $dotEpropto t^-1.3$. For the dynamical ejecta with a low electron fraction ($Y_rm elesssim0.20$), the dominant contributors of gamma-ray energy are the nuclides around the second $r$-process peak ($Asim130$), and the decay chain of $^132$Te ($t_1/2=3.21$~days) $rightarrow$ $^132$I ($t_1/2=0.10$~days) $rightarrow$ $^132$Xe produces gamma-ray lines at $228$ keV, $668$ keV, and $773$ keV. For the case of a wind ejecta with $Y_rm egtrsim0.30$, the dominant contributors of gamma-ray energy are the nuclides around the first $r$-process peak ($Asim80$), and the decay chain of $^72$Zn ($t_1/2=1.93$~days) $rightarrow$ $^72$Ga ($t_1/2=0.59$~days) $rightarrow$ $^72$Ge produces gamma-ray lines at $145$ keV, $834$ keV, $2202$ keV, and $2508$ keV. The peak fluxes of these lines are $10^-9sim 10^-7$~ph~cm$^-2$ s$^-1$, which are marginally detectable with the next-generation MeV gamma-ray detector emphETCC if the source is at a distance of $40$~Mpc.| Search Query: arXiv Query: search_query=au:”Li Li-Xin”&id_list=&start=0&max_results=10Read More