  The use of Type Ia Supernovae (SNe Ia) to measure cosmological parameters has
grown significantly over the past two decades. However, there exists a
significant diversity in the SN Ia population that is not well understood.
Over-luminous SN 1991T-like and sub-luminous SN 1991bg-like objects are two
characteristic examples of peculiar SNe. The identification and classification
of such objects is an important step in studying what makes them unique from
the remaining SN population. With the upcoming Vera C. Rubin Observatory
promising on the order of a million new SNe over a ten-year survey,
spectroscopic classifications will be possible for only a small subset of
observed targets. As such, photometric classification has become an
increasingly important concern in preparing for the next generation of
astronomical surveys. Using observations from the Sloan Digital Sky Survey II
(SDSS-II) SN Survey, we apply here an empirically based classification
technique targeted at the identification of SN 1991bg-like SNe in photometric
data sets. By performing dedicated fits to photometric data in the rest-frame
redder and bluer bandpasses, we classify 16 previously unidentified 91bg-like
SNe. Using SDSS-II host-galaxy measurements, we find that these SNe are
preferentially found in host galaxies having an older average stellar age than
the hosts of normal SNe Ia. We also find that these SNe are found at a further
physical distance from the center of their host galaxies. We find no
statistically significant bias in host galaxy mass or specific star formation
rate for these targets.
