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CHEOPS finds KELT-1b darker than expected in visible light: Discrepancy between the CHEOPS and TESS eclipse depths

Parviainen, H. ; Davies, M.B. LU and Walton, N.A. (2022) In Astronomy and Astrophysics 668.
Abstract
Recent studies based on photometry from the Transiting Exoplanet Survey Satellite (TESS) 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 the infrared. We observed eight eclipses of KELT-1b with CHaracterising ExOPlanet Satellite (CHEOPS) to measure its dayside brightness temperature in the bluest passband observed so far, and we jointly modelled the CHEOPS photometry with the existing optical and near-infrared photometry from TESS, LBT, CFHT, and Spitzer. Our modelling has led to a self-consistent dayside spectrum for KELT-1b covering the CHEOPS, TESS, H, Ks, and Spitzer IRAC 3.6 and 4.5 μm bands, where our... (More)
Recent studies based on photometry from the Transiting Exoplanet Survey Satellite (TESS) 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 the infrared. We observed eight eclipses of KELT-1b with CHaracterising ExOPlanet Satellite (CHEOPS) to measure its dayside brightness temperature in the bluest passband observed so far, and we jointly modelled the CHEOPS photometry with the existing optical and near-infrared photometry from TESS, LBT, CFHT, and Spitzer. Our modelling has led to a self-consistent dayside spectrum for KELT-1b covering the CHEOPS, TESS, H, Ks, and Spitzer IRAC 3.6 and 4.5 μm bands, where our TESS, H, Ks, and Spitzer band estimates largely agree with the previous studies. However, we discovered a strong discrepancy between the CHEOPS and TESS bands. The CHEOPS observations yield a higher photometric precision than the TESS observations, but they do not show a significant eclipse signal, while a deep eclipse is detected in the TESS band. The derived TESS geometric albedo of 0.36-0.13+0.12 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. © 2022 EDP Sciences. All rights reserved. (Less)
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Contribution to journal
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published
subject
keywords
Brown dwarfs, Methods: observational, Planetary systems, Stars: atmospheres, Stars: individual: KELT-1, Extrasolar planets, Geometry, Photometry, Solar radiation, Stars, Exo-planets, Geometric albedos, Methods:observational, Planetary system, Spitzer, Star: individual: KELT-1, Stars: atmosphere, Stars: individual: proxima Centauri, Visible light, Infrared devices
in
Astronomy and Astrophysics
volume
668
article number
A93
publisher
EDP Sciences
external identifiers
  • scopus:85145260706
ISSN
0004-6361
DOI
10.1051/0004-6361/202244117
language
English
LU publication?
yes
id
4b1b1ac6-9373-49a5-92bf-01e4a9389ff8
date added to LUP
2023-01-16 13:37:42
date last changed
2023-05-10 15:12:19
@article{4b1b1ac6-9373-49a5-92bf-01e4a9389ff8,
  abstract     = {{Recent studies based on photometry from the Transiting Exoplanet Survey Satellite (TESS) 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 the infrared. We observed eight eclipses of KELT-1b with CHaracterising ExOPlanet Satellite (CHEOPS) to measure its dayside brightness temperature in the bluest passband observed so far, and we jointly modelled the CHEOPS photometry with the existing optical and near-infrared photometry from TESS, LBT, CFHT, and Spitzer. Our modelling has led to a self-consistent dayside spectrum for KELT-1b covering the CHEOPS, TESS, H, Ks, and Spitzer IRAC 3.6 and 4.5 μm bands, where our TESS, H, Ks, and Spitzer band estimates largely agree with the previous studies. However, we discovered a strong discrepancy between the CHEOPS and TESS bands. The CHEOPS observations yield a higher photometric precision than the TESS observations, but they do not show a significant eclipse signal, while a deep eclipse is detected in the TESS band. The derived TESS geometric albedo of 0.36-0.13+0.12 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. © 2022 EDP Sciences. All rights reserved.}},
  author       = {{Parviainen, H. and Davies, M.B. and Walton, N.A.}},
  issn         = {{0004-6361}},
  keywords     = {{Brown dwarfs; Methods: observational; Planetary systems; Stars: atmospheres; Stars: individual: KELT-1; Extrasolar planets; Geometry; Photometry; Solar radiation; Stars; Exo-planets; Geometric albedos; Methods:observational; Planetary system; Spitzer; Star: individual: KELT-1; Stars: atmosphere; Stars: individual: proxima Centauri; Visible light; Infrared devices}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{CHEOPS finds KELT-1b darker than expected in visible light: Discrepancy between the CHEOPS and TESS eclipse depths}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/202244117}},
  doi          = {{10.1051/0004-6361/202244117}},
  volume       = {{668}},
  year         = {{2022}},
}