The explosion of ultra-stripped stars in close binaries may explain new
discoveries of weak and fast optical transients. We have demonstrated that
helium star companions to neutron stars (NSs) may evolve into naked metal cores
as low as ~1.5 Msun, barely above the Chandrasekhar mass limit, by the time
they explode. Here we present a new systematic investigation of the progenitor
evolution leading to such ultra-stripped supernovae (SNe), in some cases
yielding pre-SN envelopes of less than 0.01 Msun. We discuss the nature of
these SNe (electron-capture vs iron core-collapse) and their observational
light-curve properties. Ultra-stripped SNe are highly relevant for binary
pulsars, as well as gravitational wave detection of merging NSs by LIGO/VIRGO,
since these events are expected to produce mainly low-kick NSs in the mass
range 1.10-1.80 Msun.Comment: 7 pages, 5 figures, NS4 talk presented at the Marcel Grossmann
Meeting (MG14), Rome, July 201