Exoplanet research has become a major focus due to advancements like the transit method, which allows us to observe the features of exoplanet atmospheres. Shared features between exoplanetary atmospheres and their host stars limits confidence on any atmospheric interpretation. Our ability to characterize the variability of these shared stellar features is critical in accurately characterizing planetary atmospheres. The Helium I 1083 nm line is one such shared feature and is an ideal absorption line to study when probing the upper atmosphere of certain exoplanets for atmospheric escape. By investigating the variability of the He I 1083nm absorption line in the Sun we can begin to understand how the feature behaves in other sunlike stars. I analyzed publicly available SOLIS/ISS spectra of the Sun as a star to document how the He I 1083nm line strength changed as a function of time. Using the Sherpa model-fitting python package, I was able to calculate the equivalent widths for nearly 3,000 observations between 2007 and 2017. Tracking these fluctuations through both low and high stellar activity, which can be approximated by the S-index, can reveal more precise constraints on how we expect the line to vary during specific points in a star’s cycle. This analysis will allow us to better disentangle the stellar component of the He I 1083nm signal from exoplanetary atmospheres.

This work was supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313.