TRAPPIST-1: Global Results of the Spitzer Exploration Science Program {\it Red Worlds}

Abstract

With more than 1000 hours of observation from Feb 2016 to Oct 2019, the Spitzer Exploration Program Red Worlds (ID: 13067, 13175 and 14223) exclusively targeted TRAPPIST-1, a nearby (12pc) ultracool dwarf star orbited by seven transiting Earth-sized planets, all well-suited for a detailed atmospheric characterization with the upcoming JWST. In this paper, we present the global results of the project. We analyzed 88 new transits and combined them with 100 previously analyzed transits, for a total of 188 transits observed at 3.6 or 4.5 $\mu$m. We also analyzed 29 occultations (secondary eclipses) of planet b and eight occultations of planet c observed at 4.5 $\mu$m to constrain the brightness temperatures of their daysides. We identify several orphan transit-like structures in our Spitzer photometry, but all of them are of low significance. We do not confirm any new transiting planets. We estimate for TRAPPIST-1 transit depth measurements mean noise floors of $\sim$35 and 25 ppm in channels 1 and 2 of Spitzer/IRAC, respectively. most of this noise floor is of instrumental origins and due to the large inter-pixel inhomogeneity of IRAC InSb arrays, and that the much better interpixel homogeneity of JWST instruments should result in noise floors as low as 10ppm, which is low enough to enable the atmospheric characterization of the planets by transit transmission spectroscopy. We construct updated broadband transmission spectra for all seven planets which show consistent transit depths between the two Spitzer channels. We identify and model five distinct high energy flares in the whole dataset, and discuss our results in the context of habitability. Finally, we fail to detect occultation signals of planets b and c at 4.5 $\mu$m, and can only set 3$\sigma$ upper limits on their dayside brightness temperatures (611K for b 586K for c).

50 pages, 21 figures. Accepted for publication in Astronomy and Astrophysics

References in corpus (32)

• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• Detection of Thermal Emission from an Extrasolar Planet
• Extreme Water Loss and Abiotic O${}_2$ Buildup On Planets Throughout the Habitable Zones of M Dwarfs
• The effect of red noise on planetary transit detection
• Transit Least Squares: Optimized transit detection algorithm to search for periodic transits of small planets
• Observing the Atmospheres of Known Temperate Earth-sized Planets with JWST
• The Detectability and Characterization of the TRAPPIST-1 Exoplanet Atmospheres with JWST
• ACCESS I: An Optical Transmission Spectrum of GJ 1214b Reveals a Heterogeneous Stellar Photosphere
• Habitable Evaporated Cores: Transforming Mini-Neptunes into Super-Earths in the Habitable Zones of M Dwarfs
• Placing the spotted T Tauri star LkCa 4 on an HR diagram
• Impact of Clouds and Hazes on the Simulated JWST Transmission Spectra of Habitable Zone Planets in the TRAPPIST-1 System
• Detectability of atmospheric features of Earth-like planets in the habitable zone around M dwarfs
• On the Age of the TRAPPIST-1 System
• Temporal evolution of the high-energy irradiation and water content of TRAPPIST-1 exoplanets
• The Threatening Environment of the TRAPPIST-1 Planets
• Early 2017 observations of TRAPPIST-1 with $\text{Spitzer}$
• Rocky super-Earths or waterworlds: the interplay of planet migration, pebble accretion and disc evolution
• A review of possible planetary atmospheres in the TRAPPIST-1 system
• Pebble-driven planet formation for TRAPPIST-1 and other compact systems
• The Stellar Activity of TRAPPIST-1 and Consequences for the Planetary Atmospheres
• Surprisingly different starspot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB
• Planet-Planet Occultations in TRAPPIST-1 and Other Exoplanet Systems
• Tidal Heating and the Habitability of the TRAPPIST-1 Exoplanets
• Observing Isotopologue Bands in Terrestrial Exoplanet Atmospheres with the James Webb Space Telescope---Implications for Identifying Past Atmospheric and Ocean Loss
• Tidal dissipation in rotating low-mass stars and implications for the orbital evolution of close-in massive planets. II. Effect of stellar metallicity
• K2 Ultracool Dwarfs Survey. V. High superflare rates on rapidly rotating late-M dwarfs
• Do the TRAPPIST-1 Planets Have Hydrogen-rich Atmospheres?
• A Reanalysis of the Fundamental Parameters and Age of TRAPPIST-1
• Evolution and Spectral Response of a Steam Atmosphere for Early Earth with a coupled climate-interior model
• Ground-based follow-up observations of TRAPPIST-1 transits in the near-infrared
• Simulating Radial Velocity Observations of Trappist-1 with SPIRou

Cited by in corpus (37)

• Thermal emission from the Earth-sized exoplanet TRAPPIST-1 b using JWST
• No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c
• Atmospheric Reconnaissance of TRAPPIST-1 b with JWST/NIRISS: Evidence for Strong Stellar Contamination in the Transmission Spectra
• A review of possible planetary atmospheres in the TRAPPIST-1 system
• Characterisation of the hydrospheres of TRAPPIST-1 planets
• Constraining the Thickness of the Atmosphere of TRAPPIST-1 b from its JWST Secondary Eclipse Observation
• Combined analysis of the 12.8 and 15 $\mu m$ JWST/MIRI eclipse observations of TRAPPIST-1 b
• The Ariel Target List: The Impact of TESS and the Potential for Characterising Multiple Planets Within a System
• HST/WFC3 transmission spectroscopy of the cold rocky planet TRAPPIST-1h
• An upper limit on late accretion and water delivery in the Trappist-1 exoplanet system
• The dynamics of the TRAPPIST-1 system in the context of its formation
• Extending Optical Flare Models to the UV: Results from Comparing of TESS and GALEX Flare Observations For M Dwarfs
• Water Condensation Zones around Main Sequence Stars
• A roadmap for the atmospheric characterization of terrestrial exoplanets with JWST
• Differentiating Modern and Prebiotic Earth Scenarios for TRAPPIST-1e: High-resolution Transmission Spectra and Predictions for JWST
• Near-infrared transmission spectrum of TRAPPIST-1 h using Hubble WFC3 G141 observations
• Evaluating the Plausible Range of N2O Biosignatures on Exo-Earths: An Integrated Biogeochemical, Photochemical, and Spectral Modeling Approach
• Phase curve pollution of exoplanet transmission spectra
• A Study of Flares in the Ultra-Cool Regime from SPECULOOS-South
• JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e
• JWST-TST DREAMS: Secondary Atmosphere Constraints for the Habitable Zone Planet TRAPPIST-1 e
• TRAPPIST-1: Dynamical analysis of the transit-timing variations and origin of the resonant chain
• The Flaring TESS Objects of Interest: Flare Rates for all Two Minute Cadence TESS Planet Candidates
• Improved Constraints for the XUV Luminosity Evolution of Trappist-1
• Interior heating of rocky exoplanets from stellar flares with application to TRAPPIST-1
• Eta-Earth Revisited II: Deriving a Maximum Number of Earth-like Habitats in the Galactic Disk
• Cross-sections for heavy atmospheres: H${}_2$O self-broadening
• Refining the properties of the TOI-178 system with CHEOPS and TESS
• Long-term 4.6$\mu$m Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates
• The CARMENES search for exoplanets around M dwarfs. A sub-Neptunian mass planet in the habitable zone of HN Lib
• Uniform Reanalysis of JWST MIRI 15μm Exoplanet Eclipse Observations using Frame-Normalized Principal Component Analysis
• Estimation of the tidal heating in the TRAPPIST-1 planets. Influence of the internal structure
• No Robust Statistical Evidence for a Population of Water Worlds in a 2025 Sample of Planets Orbiting M Stars
• Interaction of Trappist-1 exoplanets with coronal mass ejections: Joule heating, Poynting fluxes and the role of magnetic fields
• Bioverse: Potentially Observable Exoplanet Biosignature Patterns Under the UV Threshold Hypothesis for the Origin of Life
• Non-detection of Helium in the upper atmospheres of TRAPPIST-1b, e and f
• L 98-59: a Benchmark System of Small Planets for Future Atmospheric Characterization