Furthermore, a sample of benchmark objects should ideally span a wide range of properties (e.g. An independent determination of masses from dynamical arguments is therefore crucial to overcome the large uncertainties introduced by evolutionary models, and in turn refine the theories. ![]() Mass estimates for imaged planets and BDs therefore rely entirely on evolutionary models, which currently carry high uncertainties, particularly at young to intermediate ages. ![]() However, even when a comprehensive view and an extensive spectrophotometric characterisation is possible, imaging surveys still only provide measurements of an object’s luminosity. In order to empirically constrain the formation, evolution, and atmospheric properties of both isolated and bound sub-stellar companions, we need to uncover a substantial population of these objects, and measure their fundamental properties, such as the effective temperature and mass. DI is also necessary to study the outer regions of planetary systems, that cannot be probed by other detection methods.ĭespite the remarkable efforts that have been invested in the development of new observing technologies and image processing techniques, and a steady increase in the census of wide-orbit companions, only a handful of systems below the deuterium-burning limit have been uncovered around stars in DI programs, and the occurrences of wide companions appear to be intrinsically low (Biller et al. With the unique opportunity to obtain photometric and spectroscopic observations of substellar objects, this detection method allows for a direct probe of cold companions atmospheres. Instrumentation: adaptive optics, astrometry, binaries: visual, brown dwarfs, stars: low-mass 1 INTRODUCTIONĭirect imaging (DI) is the only detection method that provides observations of an exoplanet or brown dwarf (BD) itself, as it captures the thermal emission of self-luminous companions. Given the agreement between the values of the masses of the new sub-stellar companions from the photometry with the model-independent ones obtained with FORECAST, the results of COPAINS represent a significant increase in the number of potential benchmarks for BD and planet formation and evolution theories. We also introduce FORECAST (Finely Optimised REtrieval of Companions of Accelerating STars), a tool which allows to check the agreement between position and mass of the detected companions with the measured Δμ. Our results clearly demonstrate how astrometric signatures, in the past only giving access to stellar companions, can now thanks to Gaia reveal companions well in the sub-stellar regime. ![]() We observed 25 stars and detected ten companions, including four new BDs: HIP 21152 B, HIP 29724 B, HD 60584 B, and HIP 63734 B. We present the results of the COPAINS Survey conducted with SPHERE/VLT, searching for sub-stellar companions to stars showing significant proper motion differences (Δμ) between different astrometric catalogues. It is therefore becoming clear that efficient target selection methods are essential to ensure a larger number of detections. These results clearly show how blind surveys, crucial to constrain the underlying planet and sub-stellar companion population, are not an efficient way to increase the sample of DI companions. The last decade of direct imaging (DI) searches for sub-stellar companions has uncovered a widely diverse sample that challenges the current formation models, while highlighting the intrinsically low occurrence rate of wide companions, especially at the lower end of the mass distribution.
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