CHEOPS finds KELT-1b darker than expected in visible light: Discrepancy between the CHEOPS and TESS eclipse depths
Abstract
Recent TESS-based studies have suggested that the dayside of KELT-1b, a strongly-irradiated brown dwarf, is significantly brighter in visible light than what would be expected based on Spitzer observations in infrared. We observe eight eclipses of KELT-1b with CHEOPS (CHaracterising ExOPlanet Satellite) to measure its dayside brightness temperature in the bluest passband observed so far, and model the CHEOPS photometry jointly with the existing optical and NIR photometry from TESS, LBT, CFHT, and Spitzer. Our modelling leads to a self-consistent dayside spectrum for KELT-1b covering the CHEOPS, TESS, H , Ks, and Spitzer IRAC 3.6 and 4.5 m bands, where our TESS, H , Ks, and Spitzer band estimates largely agree with the previous studies, but we discover a strong discrepancy between the CHEOPS and TESS bands. The CHEOPS observations yield a higher photometric precision than the TESS observations, but do not show a significant eclipse signal, while a deep eclipse is detected in the TESS band. The derived TESS geometric albedo of is difficult to reconcile with a CHEOPS geometric albedo that is consistent with zero because the two passbands have considerable overlap. Variability in cloud cover caused by the transport of transient nightside clouds to the dayside could provide an explanation for reconciling the TESS and CHEOPS geometric albedos, but this hypothesis needs to be tested by future observations.
Cite
@article{arxiv.2209.03890,
title = {CHEOPS finds KELT-1b darker than expected in visible light: Discrepancy between the CHEOPS and TESS eclipse depths},
author = {H. Parviainen and T. G. Wilson and M. Lendl and D. Kitzmann and E. Pallé and L. M. Serrano and E. Meier Valdes and W. Benz and A. Deline and D. Ehrenreich and P. Guterman and K. Heng and O. D. S. Demangeon and A. Bonfanti and S. Salmon and V. Singh and N. C. Santos and S. G. Sousa and Y. Alibert and R. Alonso and G. Anglada and T. Bárczy and D. Barrado y Navascues and S. C. C. Barros and W. Baumjohann and M. Beck and T. Beck and N. Billot and X. Bonfils and A. Brandeker and C. Broeg and J. Cabrera and S. Charnoz and A. Collier Cameron and C. Corral Van Damme and Sz. Csizmadia and M. B. Davies and M. Deleuil and L. Delrez and B. -O. Demory and A. Erikson and J. Farinato and A. Fortier and L. Fossati and M. Fridlund and D. Gandolfi and M. Gillon and M. Güdel and S. Hoyer and K. G. Isaak and L. L. Kiss and E. Kopp and J. Laskar and A. Lecavelier des Etangs and C. Lovis and D. Magrin and P. F. L. Maxted and M. Mecina and V. Nascimbeni and G. Olofsson and R. Ottensamer and I. Pagano and G. Peter and D. Piazza and G. Piotto and D. Pollacco and D. Queloz and R. Ragazzoi and N. Rando and H. Rauer and I. Ribas and G. Scandariato and D. Ségransan and A. E. Simon and A. M. S. Smith and M. Steller and Gy. M. Szabó and N. Thomas and S. Udry and V. VanGrootel and N. A. Walton},
journal= {arXiv preprint arXiv:2209.03890},
year = {2022}
}
Comments
Accepted to A&A