Type Ib/c Supernovae with and without Gamma-Ray Bursts
  While the connection between Long Gamma-Ray Bursts (GRBs) and Type Ib/c
Supernovae (SNe Ib/c) from stripped stars has been well-established, one key
outstanding question is what conditions and factors lead to each kind of
explosion in massive stripped stars. One promising line of attack is to
investigate what sets apart SNe Ib/c with GRBs from those without GRBs. Here, I
briefly present two observational studies that probe the SN properties and the
environmental metallicities of SNe Ib/c (specifically broad-lined SNe Ic) with
and without GRBs. I present an analysis of expansion velocities based on
published spectra and on the homogeneous spectroscopic CfA data set of over 70
SNe of Types IIb, Ib, Ic and Ic-bl, which triples the world supply of
well-observed Stripped SNe. Moreover, I demonstrate that a meta-analysis of the
three published SN Ib/c metallicity data sets, when including only values at
the SN positions to probe natal oxygen abundances, indicates at very high
significance that indeed SNe Ic erupt from more metal-rich environments than
SNe Ib, while SNe Ic-bl with GRBs still prefer, on average, more metal-poor
sites than those without GRBs.
