VIBES: Visual Binary Exoplanet survey with SPHERE

Abstract

Context. Recent surveys indicate that planets in binary systems are more abundant than previously thought, which is in agreement with theoretical work on disc dynamics and planet formation in binaries. So far, most observational surveys, however, have focused on short-period planets in binaries, thus little is known about the occurrence rates of planets on longer periods (≥10 au). Aims. In order to measure the abundance and physical characteristics of wide-orbit giant exoplanets in binary systems, we have designed the “VIsual Binary Exoplanet survey with Sphere” (VIBES) to search for planets in visual binaries. It uses the SPHERE instrument at VLT to search for planets in 23 visual binary and four visual triple systems with ages of <145 Myr and distances of <150 pc. Methods. We used the IRDIS dual-band imager on SPHERE to acquire high-contrast images of the sample targets. For each binary, the two components were observed at the same time with a coronagraph masking only the primary star. For the triple star, the tight components were treated as a single star for data reduction. This enabled us to effectively search for companions around 50 individual stars in binaries and four binaries in triples. Results. We derived upper limits of <13.7% for the frequency of sub-stellar companions around primaries in visual binaries, <26.5% for the fraction of sub-stellar companions around secondaries in visual binaries, and an occurrence rate of <9.0% for giant planets and brown dwarfs around either component of visual binaries. We have combined our observations with literature measurements to astrometrically confirm, for the first time, that 20 binaries and two triple systems, which were previously known, are indeed physically bound. Finally, we discovered a third component of the binary HD 121336. Conclusions. The upper limits we derived are compatible with planet formation through the core accretion and the gravitational instability processes in binaries. These limits are also in line with limits found for single star and circumbinary planet search surveys.

The Census of Exoplanets in Visual Binaries: Population Trends from a Volume-Limited Gaia DR2 and Literature Search

“…A number of campaigns have thus searched for planets in and around stellar binaries, including radial velocity programs (e.g., Konacki et al, 2009), transit discoveries (e.g., Doyle et al, 2011) and direct imaging surveys (e.g., Asensio-Torres et al, 2018;Hagelberg et al, 2020), leading to the detection of a number of circumstellar (orbiting one star) and circumbinary (orbiting two stars) planets. Despite these efforts, most exoplanet searches routinely exclude stars in binary or multiple systems to avoid systematic errors in planet detection, and the first systems of this type were identified serendipitously (see e.g., Patience et al, 2002;Mugrauer et al, 2006).…”

Companion mass limits for 17 binary systems obtained with binary differential imaging and MagAO/Clio

“…In addition to the surveys of Kasper et al 2007 andHeinze et al 2010 discussed in the introduction, several other recent surveys have looked for companions in binaries using other starlight subtraction techniques. Hagelberg et al (2020) tar-geted 26 visible binary and multiple star young moving group members with SPHERE on VLT (Beuzit et al 2008) in dual-H band filters, with a Lyot coronagraph masking the brighter star, and used ADI to subtract the starlight. The SPOTS survey (Thalmann et al 2014;Bonavita et al 2016;Asensio-Torres et al 2018) searched for wide circumbinary planets in the 30-300 AU range.…”

“…HD 104231 -HD 104231 is a 4.5 binary at 100 pc in Lower Centaurs Crux (Hoogerwerf 2000) with an age of 21 Myr (derived from isochrone model fitting, Pecaut et al 2012). HD 104231 A has spectral type F5V (Houk & Cowley 1975) and mass 1.33 M ; HD 104231 B has mass 0.30 M (Hagelberg et al 2020). HD 104231 AB have RUWE = 0.82 and 2.29, suggesting a possible unresolved companion around B, although there is no significant PMa in Kervella et al (2019).…”

GTC/CanariCam deep mid-infrared imaging survey of northern stars within 5 pc

“…Although early research on this front have been carried, e.g. by the SPOTS (Bonavita et al 2016;Asensio-Torres et al 2018) and the VIBES (Hagelberg et al 2020) surveys, a more detailed analysis of the effect multiplicity has on the occurrence of substellar companions in general requires a larger, dedicated sample that is complete to both single stars and binaries.…”