  MeV neutrinos are produced in many astrophysical transients, such as stellar
collapses and high-energy jets, where they play a role in sustaining and
cooling energetic explosions. Detecting these neutrinos from sources outside
the Milky Way is very difficult due to the small neutrino-nucleon cross section
at MeV. Nevertheless, the non-observation of MeV neutrinos from high-energy
transients may provide useful constraints on related neutrino production
mechanisms where significant MeV production is expected. The IceCube Neutrino
Observatory, a cubic kilometer neutrino detector operating with nearly 100%
uptime at the South Pole, is sensitive to bursts of MeV neutrinos from
astrophysical sources in and beyond the Milky Way. In this work, we describe
the MeV neutrino detection system of IceCube and show results from several
categories of astrophysical transients.
