Binary frequency of planet-host stars at wide separations

Abstract

Aims. The aim of the project is to improve our knowledge on the multiplicity of planet-host stars at wide physical separations. Methods. We cross-matched approximately 6200 square degree area of the southern sky imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for wide common proper motion companions to known planet-host stars. We complemented our astrometric search with photometric criteria. Results. We confirmed spectroscopically the co-moving nature of seven sources out of 16 companion candidates and discarded eight, while the remaining one stays as a candidate. Among these new wide companions to planet-host stars, we discovered a T4.5 dwarf companion at 6.3 arcmin (∼9000 au) from HIP 70849, a K7V star which hosts a 9 Jupiter mass planet with an eccentric orbit. We also report two new stellar M dwarf companions to one G and one metal-rich K star. We infer stellar and substellar binary frequencies for our complete sample of 37 targets of 5.4 ± 3.8% and 2.7 ± 2.7% (1σ confidence level), respectively, for projected physical separations larger than ∼60-160 au assuming the range of distances of planet-host stars (24-75 pc). These values are comparable to the frequencies of non planet-host stars. We find that the period-eccentricity trend holds with a lack of multiple systems with planets at large eccentricities (e > 0.2) for periods less than 40 days. However, the lack of planets more massive than 2.5 Jupiter masses and short periods (<40 days) orbiting single stars is not so obvious due to recent discoveries by ground-based transit surveys and space missions.

Searching for Spectroscopic Binaries Within Transition Disk Objects*

“…This is consistent with that of the non-TD, late-type stars in Ophiuchus (Prato 2007) Nguyen et al 2009). The result is also in agreement with Lodieu et al (2014), who report an SB fraction of 0.054±0.038 for wide binaries (50-150 au) in which one star is a planet-host. Their SB fraction for wide, planet-hosting substellar binaries is also within our range at 0.027±0.027.…”

A 3D view of the Hyades stellar and sub-stellar population

“…We selected the faintest Hyades members confirmed spectroscopically from three surveys. First, ten of the 12 ultracool dwarf candidates from Hogan et al (2008), confirmed spectroscopically as late-M and early-L dwarfs by Casewell et al (2014) and Lodieu et al (2014b). Second, the recent L5 dwarf discovered by Pérez-Garrido et al (2017) and confirmed as a sub-stellar member by Lodieu et al (2018).…”

2MASS 0213+3648 C: A wide T3 benchmark companion to an an active, old M dwarf binary

“…Reviews of this population are presented in Faherty et al (2010) and Deacon et al (2014). Currently, there are 22 known T dwarf companions with separations greater than 100 au, the 21 listed in the literature review of Deacon et al (2014) plus the recently discovered companion to the exoplanet host star HIP 70849 (Lodieu et al 2014). Of these, four (Gl 570 D, Burgasser et al 2000; Wolf 1130 B, Mace et al 2013; Ross 458 C, Goldman et al 2010, and ξ UMa E, Wright et al 2013) lie in systems with higher order stellar multiplicity.…”