The TESS Phase Curve of KELT-1b Suggests a High Dayside Albedo

Abstract

We measured the optical phase curve of the transiting brown dwarf KELT-1b (TOI 1476) using data from the TESS spacecraft. We found that KELT-1b shows significant phase variation in the TESS bandpass, with a relatively large phase amplitude of -+ 234 44 43 ppm and a secondary eclipse depth of -+371 49 47 ppm. We also measured a marginal eastward offset in the dayside hot spot of 18°.3±7°. 4 relative to the substellar point. We detected a strong phase-curve signal attributed to ellipsoidal distortion of the host star with an amplitude of 399±19 ppm. Our results are roughly consistent with the Spitzer phase curves of KELT-1b, but the TESS eclipse depth is deeper than expected. Our cloud-free 1D models of KELT-1b's dayside emission are unable to fit the full combined eclipse spectrum. Instead, the large TESS eclipse depth suggests that KELT-1b may have a significant dayside geometric albedo of A g ∼0.5 in the TESS bandpass, which would agree with the tentative trend between equilibrium temperature and geometric albedo recently suggested by Wong et al. We posit that if KELT-1b has a high dayside albedo, it is likely due to silicate clouds that form on KELT-1b's nightside and are subsequently transported onto the western side of KELT-1b's dayside hemisphere before breaking up.

Aerosols in Exoplanet Atmospheres

“…Wong et al, , 2016Zellem et al, 2014). Meanwhile, complementary observations of reflected light in the optical probe the longitudinal distribution of aerosols and the dayside albedo, as controlled by the reflectivity of aerosols and molecular absorption (e.g., Beatty et al, 2020;Borucki et al, 2009;Bourrier et al, 2020;Esteves et al, 2013;Jansen & Kipping, 2020;Kipping & Spiegel, 2011;Rowe et al, 2008;Shporer et al, 2014Shporer et al, , 2019Snellen et al, 2009;von Essen et al, 2020;I. Wong et al, 2020b).…”

“…These differences have been revealed by observations of thermal emission from their permanent daysides (e.g., Arcangeli et al., 2018; Charbonneau et al., 2005, 2008; Deming et al., 2005, 2007; de Wit et al., 2012; Garhart et al., 2020; Knutson et al., 2008; Kreidberg et al., 2014b; Majeau et al., 2012; Mikal‐Evans et al., 2019; Stevenson et al., 2010; Wallack et al., 2019) and phase curves (e.g., Cowan et al., 2012; Demory et al., 2016; Knutson et al., 2007, 2012; Kreidberg et al., 2018a, 2019; N. K. Lewis et al., 2013; Stevenson et al., 2014; I. Wong et al., 2015a, 2016; Zellem et al., 2014). Meanwhile, complementary observations of reflected light in the optical probe the longitudinal distribution of aerosols and the dayside albedo, as controlled by the reflectivity of aerosols and molecular absorption (e.g., Beatty et al., 2020; Borucki et al., 2009; Bourrier et al., 2020; Esteves et al., 2013; Jansen & Kipping, 2020; Kipping & Spiegel, 2011; Rowe et al., 2008; Shporer et al., 2014, 2019; Snellen et al., 2009; von Essen et al., 2020; I. Wong et al., 2020b). We refer the reader to Parmentier and Crossfield (2018) and Alonso (2018) for comprehensive reviews.…”

New Candidate Extreme T Subdwarfs from the Backyard Worlds: Planet 9 Citizen Science Project

“…We use the ScCHIMERA 1D-radiative-convective-thermochemical equilibrium tool (Arcangeli et al 2018;Mansfield et al 2018;Piskorz et al 2018;Gharib-Nezhad & Line 2019;Zalesky et al 2019;Baxter et al 2020;Beatty et al 2020;Colón et al 2020) to compute our cloud-free model grid. Briefly, the grid solves for the net radiative fluxes using the Toon et al (1989) two-stream source function technique.…”

Exploring deep and hot adiabats as a potential solution to the radius inflation problem in brown dwarfs: Long-timescale models of the deep atmospheres of KELT-1b, Kepler-13Ab, and SDSS1411B

“…Its orbital period is 1.21 days (Siverd et al 2012), slightly shorter than that of Kepler-13Ab. The day-side of KELT-1b has a blackbody (brightness) temperature of 3340 ± 110K, while the night-side has a more poorly constrained (brightness) temperature of 1820 +640 −1150 K (Beatty et al 2020). Due to the uncertainty in these values, our models use a day-night temperature difference of 1200K at 0.01bar (with additional tests run with a 1600K tem-perature difference -tests which reveal similar dynamics with just a slight increase in jet speed and deep heating rate).…”