Stellar Companions to the Exoplanet Host Stars Hd 2638 and Hd 164509

Abstract

An important aspect of searching for exoplanets is understanding the binarity of the host stars. It is particularly important, because nearly half of the solar-like stars within our own Milky Way are part of binary or multiple systems. Moreover, the presence of two or more stars within a system can place further constraints on planetary formation, evolution, and orbital dynamics. As part of our survey of almost a hundred host stars, we obtained images at 692 and 880 nm bands using the Differential Speckle Survey Instrument (DSSI) at the Gemini-North Observatory. From our survey, we detect stellar companions to HD2638 and HD164509. The stellar companion to HD2638 has been previously detected, but the companion to HD164509 is a newly discovered companion. The angular separation for HD2638 is 0.512±0 002 and for HD164509 is   0.697 0. 002. This corresponds to a projected separation of 25.6±1.9 au and 36.5±1.9 au, respectively. By employing stellar isochrone models, we estimate the mass of the stellar companions of HD2638 and HD164509 to be 0.483±0.007M e and   M 0.416 0.007, respectively, and their effective temperatures to be 3570±8K and 3450±7K, respectively. These results are consistent with the detected companions being late-type M dwarfs.

Assessing the Effect of Stellar Companions from High-resolution Imaging of Kepler Objects of Interest

“…This technique has been employed in previous works by Everett et al (2015), Teske et al (2015), and Wittrock et al (2016). We provide sample figures to elucidate this process in Figures 5 and 6, choosing one unambiguously bound companion (KOI 1 B), and one unambiguously unbound companion (KOI 3444 F) to clarify the technique.…”

Exclusion of Stellar Companions to Exoplanet Host Stars

“…The stars were selected from the known RV exoplanet host star population where there was no known stellar companion. Two of the stars, HD 2638 and HD 164509, were found to have evidence for bound stellar companions contained in the data (Wittrock et al 2016). Tables 1 and 2 list the 69 targets from the survey for which no stellar companion was detected.…”

“…BD+48 738 and HD 13189 were excluded since their luminosity and/or age data are unavailable, and HD 240237 was excluded due to its extremely large distance of 5300 pc. As described by Wittrock et al (2016), this is a magnitude-limited survey that targets the brightest of known exoplanet host stars, and so the sample consists mostly of relatively nearby dwarf stars with a peak in the distance distribution of ∼50 pc. The large distances of the giant stars results in a small angular separation sensitivity for detecting stellar companions.…”

“…The details on the process undergone to obtain the final reconstructed images is provided in the previous paper (Wittrock et al 2016) and with greater depth in Horch et al (2012Horch et al ( , 2015 but will be summarized here. The DSSI obtains the raw speckle data and stores it as FITS data cubes containing 1000 single short-exposure frames, where each frame is a 256 × 256-pixel image centered on the target.…”

“…Consequently, it has become critical for us to establish the multiplicity of exoplanet host stars so that we can be absolutely confident with the resulting interpretation of exoplanet signals and be successful in fully characterizing the overall system properties. Wittrock et al (2016) described a survey for exoplanet host star multiplicity and presented the detection of stellar companions to 2 of 71 surveyed exoplanet host stars, HD 2638 and HD 164509. Here we present the results for the remaining 69 stars of the survey that place significant constraints on the presence of stellar companions to those stars.…”