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XMM-Newton investigations of the Lambda Orionis star-forming region (XILO). I. The young cluster Collinder 69

Barrado, D. and Stelzer, B. and Morales-Calderón, M. and Bayo, A. and Huélamo, N. and Stauffer, J. R. and Hodgkin, S. and Galindo, F. and Verdugo, E. (2011) XMM-Newton investigations of the Lambda Orionis star-forming region (XILO). I. The young cluster Collinder 69. Astronomy and Astrophysics, 526 . Art. No. A21. ISSN 0004-6361.

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Context. This is the first paper of a series devoted to the Lambda Orionis star-forming region, Orion’s Head, from the X-ray perspective. Our final aim is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. Aims. We aim to uncover the population of the central, young star cluster Collinder 69, and in particular those diskless Class III objects not identified by previous surveys based on near- and mid-infrared searches, and to establish the X-ray luminosity function for the association. Methods. We have combined two exposures taken with the XMM-Newton satellite with an exhaustive data set of optical, near- and mid-infrared photometry to assess the membership of the X-ray sources based on different color–color and color–magnitude diagrams, as well as other properties, such as effective temperatures, masses and bolometric luminosities derived from spectral energy distribution fitting and comparison with theoretical isochrones. The presence of circumstellar disks is discussed using mid-infrared photometry from the Spitzer Space Telescope. Results. With an X-ray flux limit of ~5 × 10^(−15) erg/cm^2/s we detected a total of 164 X-ray sources, of which 66 are probable and possible cluster members. A total of 16 are newly identified probable members plus another three possible new members. The two XMM-Newton pointings east and west of the cluster center have allowed us to verify the heterogeneous spatial distribution of young stars, which is probably related to the large scale structure of the region. The disk fraction of the X-ray detected cluster sample (complete down to ~0.3 M_☉) is very low, close to 10%, in remarkable contrast to the low-mass stellar and substellar population (mostly undetected in X-rays) where the disk fraction reaches about 50%. The X-ray luminosity function of Collinder 69 in different mass bins provides support for an age of several Myr when compared with other well known young associations. Conclusions. The X-ray properties of the young stars in Collinder 69 resemble those found in other young stellar associations, with saturation at log (L_x/L_(bol)) ~ −3 and low fractional X-ray luminosities for stars with M ≥ 2 M_☉. With our improved cluster census we confirm previous reports on the untypically low disk fraction compared to other clusters of several Myr age. The different disk fractions of X-ray detected (essentially solar-like) and undetected (mostly low-mass stars and brown dwarfs) members can be understood as a consequence of a mass-dependence of the time-scale for disk evolution.

Item Type:Article
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Huélamo, N.0000-0002-2711-8143
Stauffer, J. R.0000-0003-3595-7382
Additional Information:© 2010 ESO. Received 4 April 2010. Accepted 25 September 2010. Published online 15 December 2010. We thank the Calar Alto Observatory, specially J. Alves, for the allocation of director’s discretionary time to this program. B.S. wishes to thank E. Flaccomio for stimulating discussions. Discussions about the properties of extragalactic sources with Almudena Alonso Herrero were also very revealing. The careful reading by the referee, Manuel Guedel, and his suggestions, have been very helpful. This research has been funded by Spanish grants ESP2007-65475-C02-02, CSD2006-00070 and PRICIT-S2009/ESP-1496. B.S. has been supported by ASI/INAF contract I/088/06/0. The support of the ESAC faculty is also recognized. It makes use of VOSA, developed under the Spanish Virtual Observatory project supported from the Spanish MICINN through grant AyA2008-02156, and of the SIMBAD database, operated at CDS, Strasbourg, France.
Funding AgencyGrant Number
Ministerio de Ciencia e Innovación (MCINN)ESP2007-65475-C02-02
Ministerio de Economía y Competitividad (MINECO)CSD2006-00070
Ministerio de Economía y Competitividad (MINECO)PRICIT-S2009/ESP-1496
Agenzia Spaziale Italiana (ASI)I/088/06/0
Ministerio de Ciencia e Innovación (MCINN)AYA2008-02156
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Subject Keywords:stars: coronae; stars: late-type; stars: solar-type; X-rays: stars; open clusters and associations: individual: Collinder 69; stars: pre-main sequence
Record Number:CaltechAUTHORS:20110222-113008703
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Official Citation:XMM-Newton investigations of the Lambda Orionis star-forming region (XILO) - I. The young cluster Collinder 69 D. Barrado, B. Stelzer, M. Morales-Calderón, A. Bayo, N. Huélamo, J. R. Stauffer, S. Hodgkin, F. Galindo and E. Verdugo A&A 526 A21 (2011) DOI: 10.1051/0004-6361/201014732
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22422
Deposited By: Ruth Sustaita
Deposited On:22 Feb 2011 21:16
Last Modified:01 Nov 2019 23:39

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