The SPHERE infrared survey for exoplanets (SHINE)

Abstract

The SpHere INfrared Exoplanet (SHINE) project is a 500-star survey performed with SPHERE on the Very Large Telescope for the purpose of directly detecting new substellar companions and understanding their formation and early evolution. Here we present an initial statistical analysis for a subsample of 150 stars spanning spectral types from B to M that are representative of the full SHINE sample. Our goal is to constrain the frequency of substellar companions with masses between 1 and 75 M Jup and semimajor axes between 5 and 300 au. For this purpose, we adopt detection limits as a function of angular separation from the survey data for all stars converted into mass and projected orbital separation using the BEX-COND-hot evolutionary tracks and known distance to each system. Based on the results obtained for each star and on the 13 detections in the sample, we use a Markov chain Monte Carlo tool to compare our observations to two different types of models. The first is a parametric model based on observational constraints, and the second type are numerical models that combine advanced core accretion and gravitational instability planet population synthesis. Using the parametric model, we show that the frequencies of systems with at least one substellar companion are 23.0 +13.5 −9.7 %, 5.8 +4.7 −2.8 %, and 12.6 +12.9 −7.1 % for BA, FGK, and M stars, respectively. We also demonstrate that a planet-like formation pathway probably dominates the mass range from 1-75 M Jup for companions around BA stars, while for M dwarfs, brown dwarf binaries dominate detections. In contrast, a combination of binary star-like and planet-like formation is required to best fit the observations for FGK stars. Using our population model and restricting our sample to FGK stars, we derive a frequency of 5.7 +3.8 −2.8 %, consistent with predictions from the parametric model. More generally, the frequency values that we derive are in excellent agreement with values obtained in previous studies.

Discovery of a directly imaged planet to the young solar analog YSES 2

“…The preliminary statistical analysis of the first 300 stars from the Gemini PLanet Imager Exoplanet Survey (GPIES; Nielsen et al 2019) concludes that giant planets between 10 au and 100 au that have masses smaller than 13 M Jup favorably form via core accretion mechanisms, whereas brown dwarf companions in the same separation range but with masses from 13 M Jup to 80 M Jup seem to be predominantly created by disk instabilities. This finding is supported by the analysis of the first 150 stars observed within the scope of the SpHere INfrared survey for Exoplanets (SHINE; Vigan et al 2021), which additionally hypothesizes that companions with masses between 1 M Jup and 75 M Jup are likely to originate from bottom-up formation scenarios around B and A type stars, whilst objects of the same mass around M-type stars are consistent with simulated populations from top-down mechanisms. For the intermediate masses of F-, G-, and K-type stars, the observed detections can be explained by a combination of both formalisms.…”

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

“…The feature is partly due to a selection effect, as lower-mass stars are often too faint to be included in target samples for exoplanet campaigns (Eggenberger, 2010). Nonetheless, although Earth to Neptune-sized planets are more abundant around M dwarfs (Mulders et al, 2015), giant planet formation is thought to be more efficient around more massive stars (Mordasini, 2018), and giant planets are indeed observed to be more frequent around higher-mass stars (Bonfils et al, 2013;Vigan et al, 2020). Given that binary systems seem to preferentially host giant planets based on our results, it is not surprising that most planet hosts in multiple systems would be the most massive stellar component in these hierarchical systems.…”

Planet formation around M dwarfs via disc instability

“…Stamatellos et al 2007aStamatellos et al , 2011Stamatellos & Whitworth 2009b). Observational surveys indicate that only a small fraction of M dwarfs (less than ∼10%) host wide orbit planets and this also holds for higher-mass stars (Brandt et al 2014;Bowler et al 2015;Lannier et al 2016;Reggiani et al 2016;Galicher et al 2016;Bowler 2016;Vigan et al 2017;Baron et al 2018;Stone et al 2018;Wagner et al 2019;Nielsen et al 2019) (see review by Bowler & Nielsen 2018). These surveys typically explore a region out to a few hundred AU from the central star (or even a few thousand AU, Durkan et al 2016;Naud et al 2017) and they are sensitive down to Jupiter-mass planets.…”