Describing the Stellar Activity of the Binary System HD 99491 & HD 99492

We investigate the stellar activity of HD 99491 and HD 99492, a wide binary pair of sunlike stars. HD 99492 hosts a Neptune-like exoplanet on a 17-day period and has been reported to have a long-term activity cycle of approximately 3700 days. HD 99491 exhibits the presence of a strong stellar activity cycle in its radial velocity (RV) and activity indicators time series with a period of ~2200 days. Using observations taken by the HIRES spectrograph at the Keck Observatory, we analyzed the RV and activity indicator time series published with two different pipelines, one by the Lick-Carnegie Exoplanet Survey and the other by the California Legacy Survey. We utilize magnitude-squared coherence to determine periods shared between RVs with the activity indicators in search of stellar activity signals and use Gaussian processes to subtract these signals from the time series. We complement these data sets by using photometric measurements from the All Sky Automated Survey (ASAS), with the goal of finding the rotation period for both stars. After analyzing the newest RVs from HD 99492, we discovered a statistically significant signal at approximately 95 days in both RV data sets. We look for possible origins of this periodicity by modeling the data with a two-planet model and a quasi-periodic model, which attribute the origin of this signal to a second companion or stellar activity, respectively. For the case of HD 99491 we use a joint quasi-periodic model with the RVs and the activity indicator $S_{HK}$ to subtract the long-term activity cycle and search for remaining signals in the data. This work aims to provide a thorough examination of both stars in order to identify new periodicities and explain their possible origins.