摘要：Aims.In this paper we present the results of the SPHERE observation of theHD 284149system, aimed at a more detailed characterisation of both the primary and its brown dwarf companion.Methods.We observedHD 284149in the near-infrared with SPHERE, using the imaging mode (IRDIS+IFS) and the long-slit spectroscopy mode (IRDIS-LSS). The data were reduced using the dedicated SPHERE pipeline, and algorithms such as PCA and TLOCI were applied to reduce the speckle pattern.Results.The IFS images revealed a previously unknown low-mass (~0.16M⊙) stellar companion (HD 294149B) at~0.1′′, compatible with previously observed radial velocity differences, as well as proper motion differences betweenGaiaandTycho-2 measurements. The known brown dwarf companion (HD 284149b) is clearly visible in the IRDIS images. This allowed us to refine both its photometry and astrometry. The analysis of the medium resolution IRDIS long slit spectra also allowed a refinement of temperature and spectral type estimates. A full reassessment of the age and distance of the system was also performed, leading to more precise values of both mass and semi-major axis.Conclusions.As a result of this study,HD 284149ABb therefore becomes the latest addition to the (short) list of brown dwarfs on wide circumbinary orbits, providing new evidence to support recent claims that object in such configuration occur with a similar frequency to wide companions to single stars.
关键词：enstars: individual: HD 284149brown dwarfsbinaries: visualstars: rotationtechniques: high angular resolution
