Research

I am primarily interested in understanding stellar spectroscopic variability and its impact on radial velocity measurements, specifically the Rossiter-McLaughlin effect.

Shadowing the Sun: Testing Synthetic Granulation Spectra with Solar Eclipse Observations

Observations of the Rossiter-McLaughlin (RM) effect during a solar eclipse, with a peak-to-peak amplitude of ~1.4 km/s, are a rigorous test of granulation and convective blueshift in the solar spectrum. Using NEID and EXPRES 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 Å model show an RMS of 11.8 m/s over the RM signal (~0.8%), a level of accuracy well beyond the reach of current exoplanet transit observations. However, although a promising tool for modeling granulation variability during a solar eclipse, GRASS-E is potentially limited by sparse center-to-limb sampling. We find a simple model with an optimized convective blueshift polynomial for Fe I 5434 Å to outperform GRASS-E with an RMS of 6.7 m/s.

The GRASS-E software can be found as a Julia submodule on the GRASS GitHub. The NEID analysis can also be found on GitHub.