Nucleosynthesis in the Outflow from Gamma‐Ray Burst Accretion Disks

We examine the nucleosynthesis products that are produced in the outflow fromrapidly accreting disks. We find that the type of element synthesis variesdramatically with the degree of neutrino trapping in the disk and therefore theaccretion rate of the disk. Disks with relatively high accretion rates such as10 M_solar/s can produce very neutron rich nuclei that are found in the rprocess. Disks with more moderate accretion rates can produce copious amountsof Nickel as well as the light elements such as Lithium and Boron. Disks withlower accretion rates such as 0.1 M_solar/s produce large amounts of Nickel aswell as some unusual nuclei such as Ti-49, Sc-45, Zn-64, and Mo-92. This widearray of potential nucleosynthesis products is due to the varying influence ofelectron neutrinos and antineutrinos emitted from the disk on theneutron-to-proton ratio in the outflow. We use a parameterization for theoutflow and discuss our results in terms of entropy and outflow acceleration.Comment: 12 pages, 12 figures; submitted to Ap