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Orbiting a binary: SPHERE characterisation of the HD 284149 system

M. Bonavita 1, 2 V. d'Orazi 1, 3 D. Mesa 1 C. Fontanive 4 S. Desidera 1 S. Messina 1, 5 S. Daemgen 6 R. Gratton 1 Arthur Vigan 7 M. Bonnefoy 8 A. Zurlo 1, 9 J. Antichi 10 H. Avenhaus 11 A. Baruffolo 1 J. L. Baudino 12 J. L. Beuzit 8 A. Boccaletti 13 P. Bruno 1 T. Buey 13 M. Carbillet 14 E. Cascone 15 G. Chauvin 8 R. U. Claudi 1 V. de Caprio 15 D. Fantinel 1 G. Farisato 1 M. Feldt 16 R. Galicher 13 E. Giro 1 C. Gry 7 J. Hagelberg 8 S. Incorvaia 17 M. Janson 18 M. Jaquet 7 A. M. Lagrange 8 M. Langlois 7 J. Lannier 8 H. Le Coroller 7 L. Lessio 1 R. Ligi 7 A. L. Maire 19 M. Meyer 20 F. Menard 21, 8 C. Perrot 13 S. Peretti 22 C. Petit 23 J. Ramos 16 A. Roux 8 B. Salasnich 1 G. Salter 7 M. Samland 16 S. Scuderi 5 J. Schlieder 16, 24 M. Surez 23 M. Turatto 1 L. Weber 25
Abstract : Aims. In this paper we present the results of the SPHERE observation of the HD 284149 system, aimed at a more detailed characterisation of both the primary and its brown dwarf companion.Methods. We observed HD 284149 in 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 (~0.16 M⊙) stellar companion (HD 294149 B) at ~0.1′′, compatible with previously observed radial velocity differences, as well as proper motion differences between Gaia and Tycho-2 measurements. The known brown dwarf companion (HD 284149 b) 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 284149 ABb 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.
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M. Bonavita, V. d'Orazi, D. Mesa, C. Fontanive, S. Desidera, et al.. Orbiting a binary: SPHERE characterisation of the HD 284149 system. Astronomy and Astrophysics - A&A, EDP Sciences, 2017, 608, pp.A106. ⟨10.1051/0004-6361/201731003⟩. ⟨hal-01764685⟩



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