Preliminary observational findings suggest a deficiency of short-period hot Jupiters around post-main-sequence (G giant and subgiant) stars, although the total fraction of them with known planets appears to increase with stellar masses. Here we consider the possibility that some very close-in gas giants or a population of rocky planets may have either undergone orbital decay or been engulfed by the expanding envelope of their intermediate-mass host stars. If such events occur during or shortly after those stars' main-sequence evolution when their convection zone remains relatively shallow, their surface metallicity would be significantly enhanced by the consumption of one or more gas giants. During the evolution of a star with a given mass and internal metallicity, a surface temperature-luminosity relation maps its evolutionary track. Therefore, we can infer the internal metallicity with the observables including the star's brightness, color, parallax, and the planet's transit light curve. Whether a star is polluted is then determined by the comparison between the inferred internal metallicity and the observed surface metallicity. As an example, we consider HD 149026, possibly a post-main-sequence star, and suggest its observed high (nearly twice solar) metallicity may be confined to its surface layer as a consequence of pollution by the accretion of a gas giant or a population of smaller-mass rocky planets. We show that the extent of pollution can be inferred directly from high-precision distance determinations, radial velocity, and transit light curves.
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