During the reporting period, REVEAL carried out a coordinated program of numerical modeling, spectral synthesis, data analysis, and interpretation of high-precision observations to address the impact of stellar variability on exoplanet detection and characterization.
A major effort focused on first-principles modeling of stellar surface variability. Using the 3D radiative magnetohydrodynamics code MURaM, the consortium simulated stellar photospheres across a wide range of spectral types, from Sun-like stars to late M dwarfs. These simulations enabled the calculation of emergent spectra from realistic 3D atmospheres and delivered the first starspot spectra based directly on magnetoconvective simulations (Smitha et al. 2025), providing essential inputs for modeling stellar contamination in transmission spectroscopy and radial-velocity measurements.
Within REVEAL, a novel approach was developed to quantify the sensitivity of spectral lines to granulation based on the ergodic nature of stellar convection, enabling efficient mitigation of granulation-induced radial-velocity variability (Sowmya et al., submitted).
On the observational side, the project analyzed ultra-precise data from facilities such as JWST. REVEAL demonstrated how stellar magnetic activity can interfere with measurements of exoplanet atmospheric properties, including morning–evening temperature contrasts inferred from transit light curves (Kostogryz et al. 2025), and identified diagnostics to separate stellar and planetary signals. In parallel, the consortium addressed methodological systematics in transit spectroscopy, quantifying biases from commonly used limb-darkening prescriptions and providing a robust recipe for reliable transmission-spectrum extraction (Keers et al. 2024). Additional work reassessed assumptions in stellar atmosphere modeling, showing that pressure broadening has been systematically overestimated in cool stars (Glidden et al., submitted).
REVEAL also contributed to a broader assessment of model-dependent biases in interpreting stellar and planetary spectra. This includes work extending stellar contamination concepts to emission spectroscopy (Fauchez et al. 2025) and studies showing how gravity and metallicity bias spectral diagnostics in ultracool dwarfs (Davoudi et al. 2025). Supporting results further strengthened the project’s foundations, including models of solar/stellar UV variability (Sowmya et al. 2025) and empirical constraints on magnetic surface features in ultracool dwarfs derived from JWST flare observations (Vasilyev et al. 2025).