  We present the discovery of 13 new widely separated T dwarf companions to M
dwarf primaries, identified using WISE/NEOWISE data by the CatWISE and Backyard
Worlds: Planet 9 projects. This sample represents a $\sim$60% increase in the
number of known M+T systems, and allows us to probe the most extreme products
of binary/planetary system formation, a discovery space made available by the
CatWISE2020 catalog and the Backyard Worlds: Planet 9 effort. Highlights among
the sample are WISEP J075108.79-763449.6, a previously known T9 thought to be
old due to its SED, which we now find is part of a common-proper-motion pair
with L 34-26 A, a well studied young M3 V star within 10 pc of the Sun; CWISE
J054129.32-745021.5 B and 2MASS J05581644-4501559 B, two T8 dwarfs possibly
associated with the very fast-rotating M4 V stars CWISE J054129.32-745021.5 A
and 2MASS J05581644-4501559 A; and UCAC3 52-1038 B, which is among the widest
late T companions to main sequence stars, with a projected separation of
$\sim$7100 au. The new benchmarks presented here are prime $JWST$ targets, and
can help us place strong constraints on formation and evolution theory of
substellar objects as well as on atmospheric models for these cold exoplanet
analogs.
