TESS unveils the optical phase curve of KELT-1b. Thermal emission and ellipsoidal variation from the brown dwarf companion, and activity from the star

Abstract

We present the detection and analysis of the phase curve of KELT-1b at optical wavelengths, analyzing data taken by the Transiting Exoplanet Survey Satellite (TESS). With a mass of ~27 M_J, KELT-1b is a low-mass brown dwarf. Due to the high mass and close proximity of its companion, the host star has a TESS light curve which shows clear ellipsoidal variations. We model the data with a six-component model: secondary eclipse, phase curve accounting for reflected light and thermal emission, Doppler beaming, ellipsoidal variations, stellar activity and the primary transit. We determine the secondary eclipse depth in the TESS bandpass to be 304 +/- 75 parts-per-million (ppm), the most accurate eclipse depth determined so far for KELT-1b. We measure the amplitude of the phase curve to be 128 +/- 27 ppm, with a corresponding eastward offset between the region of maximum brightness and the substellar point of 19.2 +/- 9.6 degrees, in good agreement with Spitzer measurements. We determine day and night brightness temperatures of 3201 +/- 147 K and 1484 +/- 110 K, respectively, slightly higher than those from Spitzer 3.6 and 4.5 micrometer data. A one-dimensional self-consistent atmospheric model can explain the TESS and Spitzer day side brightness temperatures with thermal emission alone and no reflected light. The night side data can be explained by a model with an internal temperature of ~1100 K, which may be related to the inflated radius. The difference between the TESS and Spitzer brightness temperatures can be explained by stronger molecular opacity in the Spitzer bands. On the night side, this opacity is due primarily to CH4 and CO while on the day side it is due to H2-H2 and H2-He collision-induced absorption.

arXiv comment18 pages, 12 figures

References in corpus (41)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• Gaia Data Release 2. Summary of the contents and survey properties
• Analytic Lightcurves for Planetary Transit Searches
• A Non-Gray Theory of Extrasolar Giant Planets and Brown Dwarfs
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
• Chemical Equilibrium Abundances in Brown Dwarf and Extrasolar Giant Planet Atmospheres
• A Possible Bifurcation in Atmospheres of Strongly Irradiated Stars and Planets
• ExoMol line lists IV: The rotation-vibration spectrum of methane up to 1500 K
• Unresolved stellar companions with Gaia DR2 astrometry
• The Statistics of Albedo and Heat Recirculation on Hot Exoplanets
• Evidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxes
• Parameter Estimation from Time-Series Data with Correlated Errors: A Wavelet-Based Method and its Application to Transit Light Curves
• ExoMol line lists III: An improved hot rotation-vibration line list for HCN and HNC
• Can TiO Explain Thermal Inversions in the Upper Atmospheres of Irradiated Giant Planets?
• H- Opacity and Water Dissociation in the Dayside Atmosphere of the Very Hot Gas Giant WASP-18 b
• KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a mid-F Star
• Theoretical Spectra and Light Curves of Close-in Extrasolar Giant Planets and Comparison with Data
• ExoMol Molecular linelists -- XXXIII. The spectrum of Titanium Oxide
• Periodic Flux Variability of Stars due to the Reflex Doppler Effect Induced by Planetary Companions
• Tidal Evolution of Close-in Planets
• Improved HCN/HNC linelist, model atmospheres and synthetic spectra for WZ Cas
• Detection of H2O and evidence for TiO/VO in an ultra hot exoplanet atmosphere
• ExoMol line lists XVIII. The high temperature spectrum of VO
• The Very Low Albedo of an Extrasolar Planet: MOST Spacebased Photometry of HD 209458
• TESS Discovery of a Transiting Super-Earth in the $\pi$ Mensae System
• Inverting Phase Functions to Map Exoplanets
• Carbon-rich Giant Planets: Atmospheric Chemistry, Thermal Inversions, Spectra, and Formation conditions
• The high albedo of the hot Jupiter Kepler-7b
• The Discovery of Ellipsoidal Variations in the Kepler Light Curve of HAT-P-7
• GENESIS: New Self-Consistent Models of Exoplanetary Spectra
• Variability in the Atmosphere of the Hot Giant Planet HAT-P-7 b
• Vibrational transition moments of CH${}_4$ from first principles
• Exploring the atmospheric dynamics of the extreme ultra-hot Jupiter KELT-9b using TESS photometry
• Mass Loss from the Exoplanet WASP-12b Inferred from $\text{Spitzer}$ Phase Curves
• TESS unveils the phase curve of WASP-33b. Characterization of the planetary atmosphere and the pulsations from the star
• Spitzer and z' Secondary Eclipse Observations of the Highly Irradiated Transiting Brown Dwarf KELT-1b
• Inflection point in the power spectrum of stellar brightness variations. I. The model
• Assessing Spectra and Thermal Inversions due to TiO in Hot Jupiter Atmospheres
• Detection of the phase curve and occultation of WASP-100b with TESS
• Testing connections between exo-atmospheres and their host stars. GEMINI-N/GMOS ground-based transmission spectrum of Qatar-1b