Orbital Refinement and Stellar Properties for the HD 9446, HD 43691, and HD 179079 Planetary Systems

Abstract

The Transit Ephemeris Refinement and Monitoring Survey (TERMS) is a project which aims to detect transits of intermediate-long period planets by refining orbital parameters of the known radial velocity planets using additional data from ground based telescopes, calculating a revised transit ephemeris for the planet, then monitoring the planet host star during the predicted transit window. Here we present the results from three systems that had high probabilities of transiting planets: HD 9446 b & c, HD 43691 b, & HD 179079 b. We provide new radial velocity (RV) measurements that are then used to improve the orbital solution for the known planets. We search the RV data for indications of additional planets in orbit and find that HD 9446 shows a strong linear trend of 4.8σ. Using the newly refined planet orbital solutions, which include a new best-fit solution for the orbital period of HD 9446 c, and an improved transit ephemerides, we found no evidence of transiting planets in the photometry for each system. Transits of HD 9446 b can be ruled out completely and transits HD 9446 c & HD 43691 b can be ruled out for impact parameters up to b = 0.5778 and b = 0.898 respectively due to gaps in the photometry. A transit of HD 179079 b cannot be ruled out however due to the relatively small size of this planet compared to the large star and thus low signal to noise. We determine properties of the three host stars through spectroscopic analysis and find through photometric analysis that HD 9446 exhibits periodic variability.

Science Extraction from TESS Observations of Known Exoplanet Hosts

“…Since these host stars are relatively bright, they provide numerous opportunities for detailed characterization of the systems, such as transmission spectroscopy, orbital dynamics, and potential targets for future imaging missions (Winn & Fabrycky 2015;Kane et al 2018;Batalha et al 2019). The detection of transits for known planets has been discussed in detail (Kane 2007;Hill et al 2020), including the transit probabilities of such planets (Kane & von Braun 2008;Stevens & Gaudi 2013). A study of anticipated TESS observations of known exoplanet hosts was carried out by Dalba et al (2019).…”