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The search for planets orbiting other stars has recently expanded to includestars from galaxies outside the Milky Way. With the TESS and Gaia surveys,photometric and kinematic information can be combined to identify transitingplanet candidates of extragalactic origin. Here, 1,080 low-luminosity red giantbranch stars observed by Gaia and TESS with kinematics suggesting a highlikelihood of extragalactic origin were searched for planet transits. Transitinjection-recovery tests were performed to measure the sensitivity of the TESSdata and completeness of the transit search. Injected signals of planets largerthan Jupiter with orbital periods of 10 days or less were recovered in$\approx$44% of cases. Although no planet transits were detected in thissample, we find an upper limit on planet occurrence of 0.52% for hot Jupiters,consistent with previous studies of planet occurrence around similar hoststars. As stars in the halo tend to be lower metallicity, and short periodgiant planet occurrence tends to be strongly correlated with stellarmetallicity, we predict that relative to the Galactic disk population, asmaller fraction of halo stars will host planets detectable by transit surveys.Thus, applying the known planet occurrence trends to potential planet detectionaround halo stars, we predict $\gtrsim$7,000 stars must be searched withsimilar cadence and precision as the stars studied here before a detection of aplanet of extragalactic origin is likely. This may be possible with future datareleases from the TESS and Gaia missions.

Constraining the Planet Occurrence Rate around Halo Stars of Potentially Extragalactic Origin