Know the Star, Know the Planet. V. Characterization of the Stellar Companion to the Exoplanet Host HD 177830

TL;DR

This study characterizes the stellar companion to the exoplanet host HD 177830, determining its spectral type and orbital parameters, and assesses its influence on the planetary system.

Contribution

It provides the first spectral classification of the stellar companion and estimates its orbital period, enhancing understanding of the system's dynamics.

Findings

Stellar companion is an M4V star.

Orbital period is approximately 800 years.

Companion likely has minimal impact on exoplanets.

Abstract

HD 177830 is an evolved K0IV star with two known exoplanets. In addition to the planetary companions it has a late-type stellar companion discovered with adaptive optics imagery. We observed the binary star system with the PHARO near-IR camera and the Project 1640 coronagraph. Using the Project 1640 coronagraph and integral field spectrograph we extracted a spectrum of the stellar companion. This allowed us to determine that the spectral type of the stellar companion is a M4$\pm$1V. We used both instruments to measure the astrometry of the binary system. Combining these data with published data, we determined that the binary star has a likely period of approximately 800 years with a semi-major axis of 100-200 AU. This implies that the stellar companion has had little or no impact on the dynamics of the exoplanets. The astrometry of the system should continue to be monitored, but due to the slow nature of the system, observations can be made once every 5-10 years.