We measured the optical phase curve of the transiting brown dwarf KELT-1b \citep [ TOI 1476 , ] [ ] siverd2012 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 ^ { +43 } _ { -44 } ppm and a secondary eclipse depth of 371 ^ { +47 } _ { -49 } ppm .
We also measured a marginal eastward offset in the dayside hotspot of 18.3 ^ { \circ } \pm 7.4 ^ { \circ } 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 \pm 19 ppm .
Our results are roughly consistent with the Spitzer phase curves of KELT-1b \citep beatty2019 , 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 \mathrm { A } _ { \mathrm { g } } \sim 0.5 in the TESS bandpass , which would agree with the tentative trend between equilibrium temperature and geometric albedo recently suggested by [ ] .
We posit that if KELT-1b has a high dayside albedo , it is likely due to silicate clouds \citep gao2020 that form on KELT-1b ’ s nightside \citep beatty2019 , keating2019 and are subsequently transported onto the western side of KELT-1b ’ s dayside hemisphere before breaking up .