M Dwarf Stellar Companions to the Exoplanet Host Stars HD 2638 and HD 164509

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

Authors:

Wittrock et al

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 nm 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 $0.512 \pm 0.002\arcsec$ and for HD 164509 is $0.697 \pm 0.002\arcsec$. 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 $M_\sun$ and 0.416±0.007 $M_\sun$, 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.

Are Hot Jupiters Linked to Multi Stellar Systems?

KNOW THE STAR, KNOW THE PLANET. III. DISCOVERY OF LATE-TYPE COMPANIONS TO TWO EXOPLANET HOST STARS

Authors:

Roberts et al

Abstract:

We discuss two multiple star systems that host known exoplanets: HD 2638 and 30 Ari B. Adaptive optics imagery revealed an additional stellar companion to both stars. We collected multi-epoch images of the systems with Robo-AO and the PALM-3000 adaptive optics systems at Palomar Observatory and provide relative photometry and astrometry. The astrometry indicates that the companions share common proper motion with their respective primaries. Both of the new companions have projected separations less than 30 AU from the exoplanet host star. Using the projected separations to compute orbital periods of the new stellar companions, HD 2638 has a period of 130 yr and 30 Ari B has a period of 80 yr. Previous studies have shown that the true period is most likely within a factor of three of these estimated values. The additional component to 30 Ari makes it the second confirmed quadruple system known to host an exoplanet. HD 2638 hosts a hot Jupiter and the discovery of a new companion strengthens the connection between hot Jupiters and binary stars. We place the systems on a color–magnitude diagram and derive masses for the companions which turn out to be roughly 0.5 solar mass stars.