Informal Pizza Seminar

r-process nucleosynthesis from compact stars

Prashanth Jaikumar

Argonne National Laboratory

Elements above the Iron peak are made in neutron capture processes that can occur in stellar environments. The r-process, or rapid neutron capture, is remarkable in that it has operated essentially unchanged since the earliest generation of stars. Abundance observations of r-process-rich halo stars show that the heaviest neutron-capture elements are consistent with a scaled solar system r-process abundance distribution, while the lighter elements do not conform to the solar pattern. The astrophysical site for the r-process remains a mystery (the two major candidates being Type II supernovae and neutron star mergers). We propose an alternate scenario based on a quark-hadron phase transition in a neutron star, followed by decompressing neutron matter, which may be promising for heavy-element nucleosynthesis.