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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 358525.0, MPI für Astronomie / Publikationen_mpia
Discs of planetary-mass objects in s Orionis
Authors:Zapatero Osorio, M. R.; Caballero, J. A.; Béjar, V. J. S.; Rebolo, R.; Barrado Y Navascués, D.; Bihain, G.; Eislöffel, J.; Martín, E. L.; Bailer-Jones, C. A. L.; Mundt, R.; Forveille, T.; Bouy, H.
Date of Publication (YYYY-MM-DD):2007
Title of Journal:Astronomy and Astrophysics
Start Page:L9
End Page:L12
Audience:Not Specified
Abstract / Description:Aims.We searched for infrared flux excesses of planetary-mass candidates in the sigma Orionis cluster (~3 Myr, ~350 pc). Methods: Using IJHKs data from the literature and the [3.6], [4.5], [5.8], and [8.0] IRAC images of the sigma Orionis cluster from the Spitzer Space Telescope public archives, we constructed colour-colour diagrams and spectral energy distributions from 0.8 to 8.0 mum of cluster candidates fainter than J = 18.0 mag, i.e. the planetary-mass borderline for sigma Orionis. Results: Infrared flux excesses are detected longward of 5 mum in seven objects (S Ori 54, 55, 56, 58, 60, S Ori J053956.8-025315 and S Ori J053858.6-025228) with masses estimated in the range 7-14 M_Jup. Emission at shorter wavelengths (4.5 mum) in excess of the photosphere is probably observed in S Ori 56 and S Ori J053858.6-025228. The faintest and least massive object, S Ori 60, exhibits flux excess only at 8 mum. We ascribe these infrared excesses to the presence of circumsubstellar warm discs, providing additional confirmation for the objects' membership of sigma Orionis. The observed incidence of inner discs around planetary-mass objects is >=50%, which is consistent with the measured inner disc frequency among cluster brown dwarfs and low-mass stars, suggesting that these objects share a common origin. However, there is a trend for the inner disc rate to increase with decreasing mass (from 10 Mo through the substellar domain), which may be due to a mass-dependent timescale for the dissipation of the interior discs.
Free Keywords:Galaxy: open clusters and associations: individual: σ Orionis; stars: planetary systems: protoplanetary disks; stars: low mass; brown dwarfs
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie

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