Ground-based follow-up observations of TRAPPIST-1 transits in the near-infrared

Abstract

The TRAPPIST-1 planetary system is a favorable target for the atmospheric characterization of temperate earth-sized exoplanets by means of transmission spectroscopy with the forthcoming James Webb Space Telescope (JWST). A possible obstacle to this technique could come from the photospheric heterogeneity of the host star that could affect planetary signatures in the transit transmission spectra. To constrain further this possibility, we gathered an extensive photometric data set of 25 TRAPPIST-1 transits observed in the near-IR J band (1.2 $\mu$m) with the UKIRT and the AAT, and in the NB2090 band (2.1 $\mu$m) with the VLT during the period 2015-2018. In our analysis of these data, we used a special strategy aiming to ensure uniformity in our measurements and robustness in our conclusions. We reach a photometric precision of $\sim 0.003$ (RMS of the residuals), and we detect no significant temporal variations of transit depths of TRAPPIST-1 b, c, e, and g over the period of three years. The few transit depths measured for planets d and f hint towards some level of variability, but more measurements will be required for confirmation. Our depth measurements for planets b and c disagree with the stellar contamination spectra originating from the possible existence of bright spots of temperature 4500 K. We report updated transmission spectra for the six inner planets of the system which are globally flat for planets b and g and some structures are seen for planets c, d, e, and f.

accepted for publication in MNRAS

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Cited by in corpus (13)

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• Distinguishing between wet and dry atmospheres of TRAPPIST-1 e and f
• The dynamics of the TRAPPIST-1 system in the context of its formation
• Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?
• Near-infrared transmission spectrum of TRAPPIST-1 h using Hubble WFC3 G141 observations
• GJ357: A low-mass planetary system uncovered by precision radial-velocities and dynamical simulations
• The TRAPPIST-1 JWST Community Initiative
• Gliese 12 b: A temperate Earth-sized planet at 12 pc ideal for atmospheric transmission spectroscopy
• Searching for a cometary belt around Trappist-1 with ALMA
• L 98-59: a Benchmark System of Small Planets for Future Atmospheric Characterization