Ground-based Optical Transmission Spectroscopy of the Nearby Terrestrial Exoplanet LTT 1445Ab

Abstract

Nearby M dwarf systems currently offer the most favorable opportunities for spectroscopic investigations of terrestrial exoplanet atmospheres. The LTT~1445 system is a hierarchical triple of M dwarfs with two known planets orbiting the primary star, LTT~1445A. We observe four transits of the terrestrial world LTT~1445Ab ($R=1.3$ R${}_{\oplus }$, $M=2.9$ M${}_{\oplus }$) at low resolution with Magellan II/LDSS3C. We use the combined flux of the LTT~1445BC pair as a comparison star, marking the first time that an M dwarf is used to remove telluric variability from time-series observations of another M dwarf. We find H$\alpha$ in emission from both LTT~1445B and C, as well as a flare in one of the data sets from LTT~1445C. These contaminated data are removed from the analysis. We construct a broadband transit light curve of LTT~1445Ab from 620--1020 nm. Binned to 3-minute time bins we achieve an rms of 49 ppm for the combined broadband light curve. We construct a transmission spectrum with 20 spectrophotometric bins each spanning 20 nm and compare it to models of clear, 1$\times$ solar composition atmospheres. We rule out this atmospheric case with a surface pressure of 10 bars to $3.2\sigma$ confidence, and with a surface pressure of 1 bar to $3.1\sigma$ confidence. Upcoming secondary eclipse observations of LTT~1445Ab with JWST will further probe the cases of a high mean molecular weight atmosphere, a hazy or cloudy atmosphere, or no atmosphere at all on this terrestrial world.

arXiv commentAccepted for publication in AJ

References in corpus (60)

• Astropy: A Community Python Package for Astronomy
• The Transiting Exoplanet Survey Satellite
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• The false positive rate of Kepler and the occurrence of planets
• batman: BAsic Transit Model cAlculatioN in Python
• Kepler planets: a tale of evaporation
• Most 1.6 Earth-Radius Planets are not Rocky
• A high accuracy computed water line list
• The Occurrence Rate of Small Planets around Small Stars
• An asteroseismic view of the radius valley: stripped cores, not born rocky
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9m Program -- Twenty New Members of the RECONS 10 Parsec Sample
• ExoMol line lists IV: The rotation-vibration spectrum of methane up to 1500 K
• Design Considerations for a Ground-based Transit Search for Habitable Planets Orbiting M dwarfs
• A variationally computed line list for hot NH3
• Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• Absence of a thick atmosphere on the terrestrial exoplanet LHS 3844b
• The Near-Infrared and Optical Spectra of Methane Dwarfs and Brown Dwarfs
• Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1
• Improved HCN/HNC linelist, model atmospheres and synthetic spectra for WZ Cas
• ExoMol molecular line lists - XVI: The rotation-vibration spectrum of hot H${}_2$S
• LDTk: Limb Darkening Toolkit
• The Mass of Kepler-93b and The Composition of Terrestrial Planets
• A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c
• Doppler Signatures of the Atmospheric Circulation on Hot Jupiters
• Calculations of the Far-Wing Line Profiles of Sodium and Potassium in the Atmospheres of Substellar-Mass Objects
• HELIOS: An Open-source, GPU-accelerated Radiative Transfer Code For Self-consistent Exoplanetary Atmospheres
• ExoMol line lists VII: The rotation-vibration spectrum of phosphine up to 1500 K
• The Atmospheric Chemistry of GJ 1214b: Photochemistry and Clouds
• ACCESS I: An Optical Transmission Spectrum of GJ 1214b Reveals a Heterogeneous Stellar Photosphere
• FastChem: A computer program for efficient complex chemical equilibrium calculations in the neutral/ionized gas phase with applications to stellar and planetary atmospheres
• HELIOS-K 2.0 Opacity Calculator and Open-source Opacity Database for Exoplanetary Atmospheres
• Self-luminous and irradiated exoplanetary atmospheres explored with HELIOS
• Exo-Transmit: An Open-Source Code for Calculating Transmission Spectra for Exoplanet Atmospheres of Varied Composition
• New rotation period measurements for M dwarfs in the southern hemisphere: an abundance of slowly rotating, fully convective stars
• Limb-darkening and exoplanets II: Choosing the Best Law for Optimal Retrieval of Transit Parameters
• Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs
• Revisiting the Phase Curves of WASP-43b: Confronting Reanalyzed Spitzer Data with Cloudy Atmospheres
• A Search for Water in the Atmosphere of HAT-P-26b Using LDSS-3C
• Flare Rates, Rotation Periods. and Spectroscopic Activity Indicators of a Volume-Complete Sample of Mid-to-Late M dwarfs within 15 Parsecs
• Ground-based optical transmission spectroscopy of the small, rocky exoplanet GJ 1132b
• Identifying Candidate Atmospheres on Rocky M dwarf Planets via Eclipse Photometry
• Hydrogen dominated atmospheres on terrestrial mass planets: evidence, origin and evolution
• On the Method to Infer an Atmosphere on a Tidally-Locked Super Earth Exoplanet and Upper limits to GJ 876d
• ARES V: No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b
• Analyzing Atmospheric Temperature Profiles and Spectra of M dwarf Rocky Planets
• Short-Term H-alpha Variability in M Dwarfs
• A Second Planet Transiting LTT 1445A and a Determination of the Masses of Both Worlds
• Proxima Centauri as a Benchmark for Stellar Activity Indicators in the Near Infrared
• Optical Transmission Spectroscopy of the Terrestrial Exoplanet LHS 3844b from 13 Ground-Based Transit Observations
• Simultaneous Optical Transmission Spectroscopy of a Terrestrial, Habitable-Zone Exoplanet with Two Ground-Based Multi-Object Spectrographs
• Rayleigh Scattering Cross Section Redward of Ly$\alpha$ by Atomic Hydrogen
• A transmission spectrum of the sub-Earth planet L98-59~b in 1.1-1.7 $\mu$m
• Hubble WFC3 Spectroscopy of the Terrestrial Planets L~98-59~c \& d: No Evidence for a Clear Hydrogen Dominated Primary Atmosphere
• Hubble WFC3 Spectroscopy of the Rocky Planet L 98-59 b: No Evidence for a Cloud-Free Primordial Atmosphere
• Variability Timescales of H$\alpha$ on Active Mid-to-Late M dwarfs
• Modelling the 3D Climate of Venus with OASIS
• X-ray Emission from the Exoplanet Hosting LTT 1445 Triple Star System

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