A new version of the spot oscillation and planet code, known as SOAPv4, has been introduced to enhance the modeling of stellar activity in the context of radial velocity (RV) measurements and their influence on transmission spectra.
The development team utilized solar observations in conjunction with synthetic spectra to validate the code”s capabilities. The SOAPv4 code was employed to simulate photospheric active regions and planetary transits for a Sun-like star that hosts a hot Jupiter.
By adjusting the input spectra, the researchers analyzed how these changes affected the resulting absorption spectra, leading to a comparison of the simulations. They examined the ways in which stellar activity alters these absorption profiles.
Additionally, the study focused on the chromatic signatures of stellar activity across various wavelength ranges. The authors discussed how these effects have been recognized in existing literature to substantiate planet detections in radial velocity measurements.
Recent updates to the SOAP code enable the simulation of active regions on the stellar disk while accounting for wavelength-dependent contrast. This advancement allows for a more comprehensive investigation of chromatic influences on radial velocity measurements.
SOAPv4 also incorporates models for planet-occulted line distortions, assessing the impact of active regions on absorption spectra. The simulations revealed that granulation could create line distortions that resemble planetary absorption features, which may lead to incorrect interpretations of atmospheric dynamics.
Furthermore, comparisons with observations from the ESPRESSO spectrograph indicated that models accounting for non-local thermodynamic equilibrium effects yield a better alignment with the absorption spectra of HD 209458 b, though they do not fully replicate all observed distortions.
