BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Alexander Ji\, Carnegie Observatories\n\n
The heaviest element s in the periodic table are synthesized through the rapid neutron-capture process (r-process)\, but the astrophysical site producing these elements has been a long-standing conundrum. Ultra-faint dwarf galaxies contain a s imple fossil record of early chemical enrichment that provide an ideal lab oratory to investigate the origin of r-process elements. Previous measurem ents found very low levels of neutron-capture elements in ultra-faint dwar fs\, preferring supernovae as the r-process site. I present high-resolutio n chemical abundances of nine stars in the recently discovered ultra-faint dwarf Reticulum II\, which display extremely enhanced r-process abundance s 2-3 orders of magnitude higher than the other ultra-faint dwarfs. Stars with such extreme r-process enhancements are only rarely found in the Milk y Way halo. The r-process abundances imply that the neutron-capture materi al in Reticulum II was synthesized in a single prolific event that is inco mpatible with r-process yields from ordinary core-collapse supernovae but consistent with a neutron star merger. Together with the recent gravitatio nal wave observations of a neutron star merger and its electromagnetic aft erglow\, it is now clear that neutron star mergers dominate cosmic product ion of r-process elements.
\n DTSTART:20180209T203000Z LOCATION:Physics Building\, Room 203 SUMMARY:A Rare and Prolific r-process Event Preserved in an Ultra-Faint Dwa rf Galaxy END:VEVENT END:VCALENDAR