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

Thomas G. Beatty, Ian Wong, Tara Fetherolf, Michael R. Line, Avi Shporer, Keivan G. Stassun, George R. Ricker, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Dana R. Louie, Joshua E. Schlieder, Lizhou Sha, Peter Tenenbaum, Daniel A. Yahalomi

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16 Scopus citations


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.

Original languageEnglish (US)
Article number211
JournalAstronomical Journal
Issue number5
StatePublished - Nov 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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