Physics & Astronomy Faculty Publications and Presentations
Document Type
Article
Publication Date
8-19-2025
Abstract
We present a new instrumentation technique for high-precision, ground-based spectrophotometric measurements ideal for low-resolution (R ∼ 20–60) exoplanet transmission spectroscopy. This technique employs novel thin-film coating technology for wide-band, simultaneous multi-band imaging, enabling high-precision differential photometry through self-referencing and comparison stars. Theoretical calculations and on-sky results show that this method effectively reduces 96% of amplitude scintillation noise and other systematics that typically limit ground-based spectrophotometric precision for bright stars. On-sky results are demonstrated using the custom-built Exoplanet Transmission Spectroscopy Imager (ETSI), deployed at the McDonald Observatory 2.1 m telescope in 2022. For a V = 9.7 mag star, ETSI achieves a spectrophotometric precision of 50 ppm in a 40 nm band over 1.0 hr, below the atmospheric scintillation noise floor. Using ETSI, we present a measured transmission spectrum of the hot Saturn HAT-P-44Bb to demonstrate the technique’s application. We perform a basic spectral retrieval to verify the measurement’s consistency with the planet’s known or expected physical parameters. Future deployment of this technique in instruments on mid to large-class observatories could enable the ability to characterize hundreds of exoplanet atmospheres in the visible with low resolution transmission spectroscopy.
Recommended Citation
Limbach, Mary Anne, Luke M. Schmidt, Ryan J. Oelkers, and D. L. DePoy. "Development of a New Ground-based Instrumentation Technique for Low-resolution Exoplanet Transmission Spectroscopy." Publications of the Astronomical Society of the Pacific 137, no. 8 (2025): 084402. https://doi.org/10.1088/1538-3873/adf358
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Publication Title
Publications of the Astronomical Society of the Pacific
DOI
10.1088/1538-3873/adf358
Comments
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