  We introduce the OATMEAL survey, an effort to measure the obliquities of
stars with transiting brown dwarf companions. We observed a transit of the
close-in ($P_{\rm orb} = 1.74 \,$ days) brown dwarf GPX-1 b using the Keck
Planet Finder (KPF) spectrograph to measure the sky-projected angle between its
orbital axis and the spin axis of its early F-type host star ($\lambda$). We
measured $\lambda = 6.88 \pm 1.72 ^\circ$ (with additional unquantified
systematic uncertainty), suggesting an orbit that is prograde and well aligned
with the stellar equator. Hot Jupiters around early F stars are frequently
found to have highly misaligned orbits, with polar and retrograde orbits being
commonplace. It has been theorized that these misalignments stem from dynamical
interactions, such as von Zeipel-Kozai-Lidov cycles, and are retained over long
timescales due to weak tidal dissipation in stars with radiative envelopes. By
comparing GPX-1 to similar systems under the frameworks of different tidal
evolution theories, we argued that the rate of tidal dissipation is too slow to
have re-aligned the system. This suggests that GPX-1 may have arrived at its
close-in orbit via coplanar high-eccentricity migration or migration through an
aligned protoplanetary disk. Our result for GPX-1 is the fifth measurement of
the obliquity of a star with a transiting brown dwarf. By enlarging the number
of such measurements and comparing them with hot Jupiter systems, we will more
clearly discern the differences between the mechanisms that dictate the
formation and evolution of both classes of objects.
