  Transiting planet systems offer a unique opportunity to measure the masses
and radii of many planets and their host stars. Yet, relative photometry and
radial velocity measurements alone only constrain the density of the host star.
In remedy, the community uses theoretical and semi-empirical methods to break
this one-parameter degeneracy and measure the mass and radius of the host star
and its planet(s). We investigate the differences in the inferred system
parameters due to modeling a host star with the Torres mass-radius relations,
YY evolutionary tracks, MIST evolutionary tracks, and a stellar radius estimate
from the spectral energy distribution (SED). We consider the effects of
different priors on the stellar effective temperature, limb darkening, and
eccentricity of the planet. Using the publicly available software package
EXOFASTv2, we globally model TESS photometry and radial velocity observations
of KELT-15, which hosts a fairly representative hot Jupiter. In total, we
explore the impact of 28 different choices of priors on the inferred parameters
of KELT-15b. We find broad agreement in the inferred system parameters across
methodologies at the level of ~1.1 sigma between the MIST and SED constraints.
This gives some confidence that systematic errors are not ubiquitous in
transiting planets systems. We also find a ~2 sigma difference in the stellar
radius estimated by the MIST models when we adopt differing literature
spectroscopic effective temperature estimates. Similar studies of a large
number of systems are needed to definitely assess systematic uncertainties the
exoplanet population as a whole.
