The Thermal Emission Spectrum of the Nearby Rocky Exoplanet LTT 1445A b from JWST MIRI/LRS
Patcharapol Wachiraphan, Zachory K. Berta-Thompson, Hannah Diamond-Lowe, Jennifer G. Winters, Catriona Murray, Michael Zhang, Qiao Xue, Caroline V. Morley, Marialis Rosario-Franco, Girish M. Duvvuri

TL;DR
This study uses JWST MIRI/LRS secondary eclipse data to analyze the atmosphere of the rocky exoplanet LTT 1445A b, finding evidence against very thick atmospheres and suggesting it likely lacks a substantial CO2-rich atmosphere.
Contribution
First detailed emission spectrum of LTT 1445A b from JWST, constraining its atmospheric composition and ruling out thick CO2 atmospheres with high confidence.
Findings
Detected a 41 ppm secondary eclipse depth.
Measured dayside temperature of 525 ± 15 K.
Disfavored thick CO2 atmospheres at high confidence.
Abstract
The nearby transiting rocky exoplanet LTT 1445A b presents an ideal target for studying atmospheric retention in terrestrial planets orbiting M dwarfs. It is cooler than many rocky exoplanets yet tested for atmospheres, receiving a bolometric instellation similar to Mercury's. Previous transmission spectroscopy ruled out a light H/He-dominated atmosphere but could not distinguish between a bare-rock, a high-MMW, or a cloudy atmosphere. We present new secondary eclipse observations using JWST's MIRI/LRS, covering the 5-12 m range. From these observations, we detect a broadband secondary eclipse depth of 41 9 ppm and measure a mid-eclipse timing consistent with a circular orbit (at 1.7). From its emission spectrum, the planet's dayside brightness temperature is constrained to 525 15 K, yielding a temperature ratio relative to the maximum average dayside…
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Taxonomy
TopicsCalibration and Measurement Techniques · Astronomy and Astrophysical Research · Stellar, planetary, and galactic studies
