Shadowing the Sun I: Testing Synthetic Granulation Spectra with NEID Solar Eclipse Observations
Abstract
The subtle Doppler radial velocity (RV) signature of an Earth-mass exoplanet in the Habitable Zone around a nearby Sun-like star is difficult to detect due to stellar variability. While multiple techniques aim to mitigate rotationally-modulated stellar activity, granulation, introducing 0.1-1 m s−1 RV shifts, currently sets the floor for detecting Earth-mass RV signals for low-activity stars. Observations of the Rossiter-McLaughlin (RM) effect during a solar eclipse, with a peak-to-trough amplitude of ∼1.4 km s−1, are a rigorous test of granulation and convective blueshift in the solar spectrum. Using NEID solar feed data of the October 2023 solar eclipse and GRASS-E (a geometry-modified version of GRASS), we compare the observed RVs for 22 lines with the simulated RVs from the synthetic granulation-driven spectra. Residuals of the GRASS-E Fe I 5434 angstrom model show an RMS of 13.47 m s−1 over the RM signal. We find that a model with an optimized convective blueshift polynomial for Fe I 5434 significantly outperforms GRASS-E with an RMS of only 2.90 m s−1, suggesting that GRASS-E is currently limited by sparse center-to-limb observations. By combining a set of spectral lines, we achieve a weighted RMS of 5.2 m s−1 over the RM signal (∼0.37\%), a level of accuracy well beyond the reach of current exoplanet transit observations. In all, we demonstrate that solar eclipse observations allow us to recover the center-to-limb variation of the convective blueshift for individual spectral lines.
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BibTeX
@misc{gonzalez2026shadowing,
title = {{Shadowing the Sun I: Testing Synthetic Granulation Spectra with NEID Solar Eclipse Observations}},
author = {Elizabeth Gonzalez and Michael L. Palumbo III and Suvrath Mahadevan and Eric B. Ford and Sarah E. Logsdon and Chad F. Bender and Andrea S. J. Lin and Daniel M. Krolikowski and Ashutosh Joshi and Joe P. Ninan and Jason T. Wright and Ansgar Reiners and Samuel Halverson and Michael W. McElwain and Jayadev Rajagopal and Paul Robertson and Arpita Roy and Christian Schwab and Gudmundur Stefansson and Ryan C. Terrien},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.03898},
eprint = {2611.03898},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.03898},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Shadowing the Sun I: Testing Synthetic Granulation Spectra with NEID Solar Eclipse Observations
AU - Elizabeth Gonzalez
AU - Michael L. Palumbo III
AU - Suvrath Mahadevan
AU - Eric B. Ford
AU - Sarah E. Logsdon
AU - Chad F. Bender
AU - Andrea S. J. Lin
AU - Daniel M. Krolikowski
AU - Ashutosh Joshi
AU - Joe P. Ninan
AU - Jason T. Wright
AU - Ansgar Reiners
AU - Samuel Halverson
AU - Michael W. McElwain
AU - Jayadev Rajagopal
AU - Paul Robertson
AU - Arpita Roy
AU - Christian Schwab
AU - Gudmundur Stefansson
AU - Ryan C. Terrien
PY - 2026
DA - 2026/11/02
PB - arXiv
DO - 10.48550/arxiv.2611.03898
UR - https://arxiv.org/abs/2611.03898
AB - The subtle Doppler radial velocity (RV) signature of an Earth-mass exoplanet in the Habitable Zone around a nearby Sun-like star is difficult to detect due to stellar variability. While multiple techniques aim to mitigate rotationally-modulated stellar activity, granulation, introducing 0.1-1 m s^−1 RV shifts, currently sets the floor for detecting Earth-mass RV signals for low-activity stars. Observations of the Rossiter-McLaughlin (RM) effect during a solar eclipse, with a peak-to-trough amplitude of ∼1.4 km s^−1, are a rigorous test of granulation and convective blueshift in the solar spectrum. Using NEID solar feed data of the October 2023 solar eclipse and GRASS-E (a geometry-modified version of GRASS), we compare the observed RVs for 22 lines with the simulated RVs from the synthetic granulation-driven spectra. Residuals of the GRASS-E Fe I 5434 angstrom model show an RMS of 13.47 m s^−1 over the RM signal. We find that a model with an optimized convective blueshift polynomial for Fe I 5434 significantly outperforms GRASS-E with an RMS of only 2.90 m s^−1, suggesting that GRASS-E is currently limited by sparse center-to-limb observations. By combining a set of spectral lines, we achieve a weighted RMS of 5.2 m s^−1 over the RM signal (∼0.37\%), a level of accuracy well beyond the reach of current exoplanet transit observations. In all, we demonstrate that solar eclipse observations allow us to recover the center-to-limb variation of the convective blueshift for individual spectral lines.
ER -