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Abstract: Over the past years, the lambda-Orionis cluster has been a prime location forthe study of young very low mass stars, substellar and isolated planetary massobjects and the determination of the initial mass function and other propertiesof low mass cluster members. In the continuity of our previous studies of youngassociations cores, we search for ultracool members and new multiple systemswithin the central 5.3- ~0.6pc of the cluster. We obtained deep seeinglimited J, Ks-band images of the 5.3- central part of the cluster with NTT-SofIand H-band images with CAHA-Omega2000. These images were complemented bymulti-conjugate adaptive optics MCAO H and Ks images of the 1.5- centralregion of the lambda-Orionis cluster obtained with the prototype MCAO facilityMAD at the VLT. The direct vicinity of the massive lambda-Ori O8III-star wasprobed using NACO-SDI at the VLT. Finally, we also retrieved Spitzer IRACimages of the same area and used archival Subaru Suprime-Cam and CFHT CFHT12Ki-band images. We report the detection of 9 new member candidates selected fromoptical and near-IR color-color and color-magnitude diagrams and 7 previouslyknown members. The high spatial resolution images resolve 3 new visual multiplesystems. Two of them are most likely not members of the association. The thirdone is made of a brown dwarf candidate companion to the F8V star HD36861C. Thesimultaneous differential images allow us to rule out the presence of visualcompanions more massive than M>0.07Msun in the range 1-2.5-, and M>0.25Msun inthe range 0.5-2.5-

Autor: H. Bouy, N. Huelamo, D. Barrado y Navascues, E. L. Martin, M.G. Petr-Gotzens, J. Kolb, E. Marchetti, M. Morales-Calderon, A. Bayo

Fuente: https://arxiv.org/

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