Gravity-Darkened Seasons: Insolation Around Rapid Rotators

Abstract

I model the effect of rapid stellar rotation on a planet's insolation. Fast-rotating stars have induced pole-to-equator temperature gradients (known as gravity-darkening) of up to several thousand Kelvin that affect the star's luminosity and peak emission wavelength as a function of latitude. When orbiting such a star, a planet's annual insolation can strongly vary depending on its orbit inclination. Specifically, inclined orbits result in temporary exposure to the star's hotter poles. I find that gravity-darkening can drive changes in a planet's equilibrium temperature of up to $\sim 15\%$ due to increased irradiance near the stellar poles. This effect can also vary a planet's exposure to UV radiation by up to $\sim 80\%$ throughout its orbit as it is exposed to an irradiance spectrum corresponding to different stellar effective temperatures over time.

arXiv comment8 pages, 6 figures, accepted for publication in ApJ

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