Gravity-darkening Analysis of the Misaligned Hot Jupiter MASCARA-4 b

Ahlers, John P.; Kruse, Ethan; Colón, Knicole D.; Dorval, Patrick; Talens, Geert Jan; Snellen, Ignas; Albrecht, Simon; Otten, Gilles; Ricker, George; Vanderspek, Roland; Latham, David; Seager, Sara; Winn, Joshua; Jenkins, Jon M.; Haworth, Kari; Cartwright, Scott; Morris, Robert; Rowden, Pam; Tenenbaum, Peter and Ting, Eric B. (2020). Gravity-darkening Analysis of the Misaligned Hot Jupiter MASCARA-4 b. The Astrophysical Journal, 888(63)



MASCARA-4 b is a hot Jupiter in a highly misaligned orbit around a rapidly rotating A3V star that was observed for 54 days by the Transiting Exoplanet Survey Satellite (TESS). We perform two analyses of MASCARA-4 b using a stellar gravity-darkened model. First, we measure MASCARA-4 b's misaligned orbital configuration by modeling its TESS photometric light curve. We take advantage of the asymmetry in MASCARA-4 b's transit due to its host star's gravity-darkened surface to measure MASCARA-4 b's true spin–orbit angle to be 104°+7°-13°. We also detect a ~4σ secondary eclipse at 0.491 ± 0.007 orbital phase, proving that the orbit is slightly eccentric. Second, we model MASCARA-4 b's insolation including gravity darkening and find that the planet's received X-ray and ultraviolet flux varies by 4% throughout its orbit. MASCARA-4 b's short-period, polar orbit suggests that the planet likely underwent dramatic orbital evolution to end up in its present-day configuration and that it receives a varying stellar irradiance that perpetually forces the planet out of thermal equilibrium. These findings make MASCARA-4 b an excellent target for follow-up characterization to better understand the orbital evolution and present-day environment of planets around high-mass stars.

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