  We search for mass segregation in the intermediate-aged open cluster NGC 6819
within a carefully identified sample of probable cluster members. Using
photometry from the Gaia, 2MASS, and Pan-STARRS surveys as inputs for a
Bayesian statistics software suite, BASE-9, we identify a rich population of
(photometric) binaries and derive posterior distributions for the cluster age,
distance, metallicity and reddening as well as star-by-star photometric
membership probabilities, masses and mass ratios (for binaries). Within our
entire sample, we find 2632 cluster members and 777 binaries. We then select a
main-sequence 'primary sample' with 14.85 < G < 19.5 containing 1342 cluster
members and 250 binaries with mass ratios q > 0.5, to investigate for mass
segregation. Within this primary sample, we find the binary radial distribution
is significantly shifted toward the cluster center as compared to the single
stars, resulting in a binary fraction that increases significantly toward the
cluster core. Furthermore, we find that within the binary sample, more massive
binaries have more centrally concentrated radial distributions than less
massive binaries. The same is true for the single stars. We verify the
expectation of mass segregation for this stellar sample in NGC 6819 through
both relaxation time arguments and by investigating a sophisticated N-body
model of the cluster. Importantly, this is the first study to investigate mass
segregation of the binaries in the open cluster NGC 6819.
