Bibcode
Bouy, H.; Huélamo, N.; Martín, E. L.; Marchis, F.; Barrado Y Navascués, D.; Kolb, J.; Marchetti, E.; Petr-Gotzens, M. G.; Sterzik, M.; Ivanov, V. D.; Köhler, R.; Nürnberger, D.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 493, Issue 3, 2009, pp.931-946
Advertised on:
1
2009
Revista
Número de citas
41
Número de citas referidas
33
Descripción
Context: Nearby young clusters are privileged places to study the star
formation history. Over the last decade, the σ-Orionis cluster has
been a prime location for the study of young very low mass stars,
substellar and isolated planetary mass objects and the determination of
the initial mass function. Aims: To extend previous studies of
this association to its core, we searched for ultracool members and new
multiple systems within the 1.5 arcmin×1.5 arcmin central region
of the cluster. Methods: We obtained deep multi-conjugate
adaptive optics (MCAO) images of the core of the σ-Orionis cluster
with the prototype MCAO facility MAD at the VLT using the H and
Ks filters. These images allow us to detect companions
fainter by Δ H ≈ 5 mag as close as 0.2 arcsec on a typical
source with H=14.5 mag. These images were complemented by archival SofI
K_s-band images and Spitzer IRAC and MIPS mid-infrared images Results: We report the detection of 2 new visual multiple systems, one
being a candidate binary proplyd and the other one a low mass companion
to the massive star σ Ori E. Of the 36 sources detected in the
images, 25 have a H-band luminosity lower than the expected planetary
mass limit for members, and H-Ks color consistent with the
latest theoretical isochrones. Nine objects have additional Spitzer
photometry and spectral energy distribution consistent with them being
cluster members. One of them has a spectral energy distribution from H
to 3.6 μm consistent with that of a 5.5 M_Jup cluster member.
Complementary NTT/SofI and Spitzer photometry allow us to confirm the
nature and membership of two L-dwarf planetary mass candidates.
Based on observations made at the ESO La Silla and Paranal Observatory
under programmes 67.C-0042, 074.C-0084, and 074.C-0628.