Be It Unresolved: Measuring Time Delays from Lensed Supernovae
  Gravitationally lensed Type Ia supernovae may be the next frontier in cosmic
probes, able to deliver independent constraints on dark energy, spatial
curvature, and the Hubble constant. Measurements of time delays between the
multiple images become more incisive due to the standardized candle nature of
the source, monitoring for months rather than years, and partial immunity to
microlensing. While currently extremely rare, hundreds of such systems should
be detected by upcoming time domain surveys. Even more will have the images
spatially unresolved, with the observed lightcurve a superposition of time
delayed image fluxes. We investigate whether unresolved images can be
recognized as lensed sources given only lightcurve information, and whether
time delays can be extracted robustly. We develop a method that successfully
identifies such systems, with a false positive rate of $\lesssim 5\%$, and
measures the time delays with a completeness of $\gtrsim 93\%$ and with a bias
of $\lesssim 0.5\%$ for $\Delta t_{\rm fit} \gtrsim 10$ days.
