Title: Modeling Stellar Surface Features Using High-Precision Photometry
Abstract: Starspots are a major source of stellar contamination in transmission spectroscopy of exoplanet atmospheres, and the correction for exoplanet analyses depends on the temperature of the starspots and the covering fraction. Using high-precision data from both space-based and ground-based observatories, we use the starspot modeling program STSP to measure the position and size of stellar surface features on KOI-340, an eclipsing binary consisting of G-type subgiant with an M-dwarf companion and TOI-3884, an M dwarf with a planetary companion. STSP uses a novel technique to measure the spot positions and radii by using the transiting secondary as a magnifying glass to probe down to less than 1% changes in the surface brightness of the star for high-precision photometry. Our published results on the starspot properties of KOI-340, and our preliminary starspot modeling results for TOI-3884 are presented here. One necessary component to all of our analyses is the contrast of the spot which is related to the spot temperature, photosphere temperature, and the filter of the observed transit. With known spot position and radius, simultaneous multi-filter transits will show different spot signatures that can only be attributed to differences in the contrast (or temperature) of the spot. We have developed a technique to compare the contrast found using simultaneous multi-filter transits to theoretically determined contrast curves, which are determined by interpolating synthetic spectra over a given filter for both the stellar photosphere and a range of spot temperatures. We introduce this technique for HAT-P-11, a K-dwarf with known spot properties and a high-precision (diffuser-aided) simultaneous multi-filter transit obtained using the MuSCAT3 instrument on LCOGT’s 2-m telescope at Haleakala Observatory.
Seminar held in 538 Davey or please email CEHW-SEMINAR-QUESTIONS@lists.psu.edu to attend virtually.