A search for wide visual companions of exoplanet host stars: The Calar Alto Survey

Abstract

We have carried out a search for co-moving stellar and substellar companions around 18 exoplanet host stars with the infrared camera MAGIC at the 2.2 m Calar Alto telescope, by comparing our images with images from the all sky surveys 2MASS, POSS I and II. Four stars of the sample namely HD 80606, 55 Cnc, HD 46375 and BD−10• 3166, are listed as binaries in the Washington Visual Double Star Catalogue (WDS). The binary nature of HD 80606, 55 Cnc, and HD 46375 is confirmed with both astrometry as well as photometry, thereby the proper motion of the companion of HD 46375 was determined here for the first time. We derived the companion masses as well as the longterm stability regions for additional companions in these three binary systems. We can rule out further stellar companions around all stars in the sample with projected separations between 270 AU and 2500 AU, being sensitive to substellar companions with masses down to ∼ 60 M Jup (S/N = 3). Furthermore we present evidence that the two components of the WDS binary BD−10• 3166 are unrelated stars, i.e this system is a visual pair. The spectrophotometric distance of the primary (a K0 dwarf) is ∼ 67 pc, whereas the presumable secondary BD−10• 3166 B (a M4 to M5 dwarf) is located at a distance of 13 pc in the foreground.

Planetary Phase Variations of the 55 Cancri System

“…It should also be noted that there is an M dwarf binary companion, 55 Cnc B, with an angular separation of 84. 7 (1150 AU) (Mugrauer et al 2006), so it is unlikely to be inside a photometric aperture.…”

Binarity of transit host stars

“…Raghavan et al (2006) used the Sloan Digital Sky Survey (SDSS) to detect 30 exoplanet hosts with one or more stellar companions. Mugrauer et al (2004) carried out near infrared imaging with the UFTI/UKIRT and SofI/NTT instruments in order to detect wide stellar companions. These early surveys were limited to the seeing limit, confirming theorists' claims that planetary systems in wide binaries are not greatly affected in terms of frequency and parameter statistics (e.g.…”

On the potentially dramatic history of the super-Earth ρ 55 Cancri e

“…In addition to the classical equations to second order in eccentricity and inclination (Murray & Dermott 1999), we also include the effects of relativistic precession (Adams & Laughlin 2006). There is potentially also an additional precession due to the presence of a distant M dwarf companion, a 0.26M⊙ M dwarf located at 1260 AU (Mugrauer et al 2006). However, this is too small to affect the dynamics of the planetary configuration on small scales, although it can generate precession of the system as a unit (Innanen et al 1997;Kaib et al 2011;Boue' & Fabrycky 2014).…”

“…It has also been suggested (Kaib, Raymond & Duncan 2011) that the presence of a distant M-dwarf companion (Mugrauer et al 2006) can induce a coherent precession of the entire planetary system (Innanen et al 1997), potentially leading to a substantial obliquity offset between the stellar spin and the orbital plane of the planetary system. However, for the 55 Cancri system, spin-orbit coupling between the star and the planets likely quenches such an offset unless the companion is in a highly eccentric (e ∼ 0.95) orbit (Boue' & Fabrycky 2014).…”