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Spitzer: Accretion in Low-Mass Stars and Brown Dwarfs in the λ Orionis Cluster

Barrado y Navascués, David and Stauffer, John R. and Morales-Calderón, María and Bayo, Amelia and Fazzio, Giovanni and Megeath, Tom and Allen, Lori and Hartmann, Lee W. and Calvet, Nuria (2007) Spitzer: Accretion in Low-Mass Stars and Brown Dwarfs in the λ Orionis Cluster. Astrophysical Journal, 664 (1). pp. 481-500. ISSN 0004-637X.

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We present multiwavelength optical and IR photometry of 170 previously known low-mass stars and brown dwarfs of the 5 Myr Collinder 69 cluster (λ Orionis). The new photometry supports cluster membership for most of them, with less than 15% of the previous candidates identified as probable nonmembers. The near-IR photometry allows us to identify stars with IR excesses, and we find that the Class II population is very large, around 25% for stars (in the spectral range M0-M6.5) and 40% for brown dwarfs, down to 0.04 M_⊙, despite the fact that the Hα equivalent width is low for a significant fraction of them. In addition, there are a number of substellar objects, classified as Class III, that have optically thin disks. The Class II members are distributed in an inhomogeneous way, lying preferentially in a filament running toward the southeast. The IR excesses for the Collinder 69 members range from pure Class II (flat or nearly flat spectra longward of 1 μm), to transition disks with no near-IR excess but excesses beginning within the IRAC wavelength range, to two stars with excess only detected at 24 μm. Collinder 69 thus appears to be at an age where it provides a natural laboratory for the study of primordial disks and their dissipation.

Item Type:Article
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URLURL TypeDescription DOIArticle
Stauffer, John R.0000-0003-3595-7382
Megeath, Tom0000-0001-7629-3573
Hartmann, Lee W.0000-0003-1430-8519
Calvet, Nuria0000-0002-3950-5386
Additional Information:© 2007 The American Astronomical Society. Received 2006 October 3; accepted 2007 April 6. We thank Calar Alto Observatory for allocation of director’s discretionary time to this programme. This research has been funded by Spanish grants MEC/ESP2004-01049, MEC/Consolider- CSD2006-0070, and CAM/PRICIT-S-0505/ESP/0361.
Funding AgencyGrant Number
Ministerio de Educación y Ciencia (MEC)MEC/ESP2004-01049
Ministerio de Educación y Ciencia (MEC)MEC/Consolider-CSD2006-0070
Ministerio de Educación y Ciencia (MEC)CAM/PRICIT-S-0505/ESP/0361
Subject Keywords:open clusters and associations : individual (lambda Orionis); stars : low-mass, brown dwarfs; stars : pre-main-sequence
Issue or Number:1
Record Number:CaltechAUTHORS:20100222-100130488
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Official Citation:Spitzer: Accretion in Low-Mass Stars and Brown Dwarfs in the λ Orionis Cluster David Barrado y Navascués, John R. Stauffer, María Morales-Calderón, Amelia Bayo, Giovanni Fazzio, Tom Megeath, Lori Allen, Lee W. Hartmann, and Nuria Calvet 2007 ApJ 664 481-500 doi: 10.1086/518816
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17550
Deposited By: Tony Diaz
Deposited On:02 Mar 2010 17:26
Last Modified:03 Oct 2019 01:29

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