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Low-resolution spectroscopy and spectral energy distributions of selected sources towards σ Orionis



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Caballero, J. A. and Valdivielso, L. and Martín, E. L. and Montes Gutiérrez, David and Pascual, S. and Pérez González, Pablo Guillermo (2008) Low-resolution spectroscopy and spectral energy distributions of selected sources towards σ Orionis. Astronomy & Astrophysics, 491 (2). pp. 515-523. ISSN 0004-6361

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Official URL: http://dx.doi.org/10.1051/0004-6361:200810616


Aims. We study in detail nine sources in the direction of the young σ Orionis cluster, which is considered to be a unique site for studying stellar and substellar formation. The nine sources were selected because of their peculiar properties, such as extremely-red infrared colours or excessively strong Hα emission for their blue optical colours. Methods. We acquired high-quality, low-resolution spectroscopy (R ∼ 500) of the nine targets with ALFOSC at the Nordic Optical Telescope. We also re-analysed [24]-band photometry from MIPS/Spitzer and compiled the highest quality photometric dataset available at the ViJHK_s passbands and the four IRAC/Spitzer channels, for constructing accurate spectral energy distributions between 0.55 and 24 μm. Results.
The nine targets were classified into: one Herbig Ae/Be star with a scattering edge-on disc; two G-type stars; one X-ray flaring, early-M, young star with chromospheric Hα emission; one very low-mass, accreting, young spectroscopic binary; two young objects at the brown-dwarf boundary with the characteristics of classical T Tauri stars; and two emission-line galaxies, one undergoing star formation, and another whose spectral energy distribution is dominated by an active galactic nucleus. We also discovered three infrared sources associated with overdensities in a cold cloud of the cluster centre. Conclusions. Low-resolution spectroscopy and spectral energy distributions are a vital tool for measuring the physical properties and evolution of young stars and candidates in the σ Orionis cluster.

Item Type:Article
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© ESO 2008.
We thank the anonymous referee, G. Barro Calvo, M. Rego, V. Villar, and J. Zamorano for helpful comments. The data presented here have been taken using ALFOSC, which is owned by the Instituto de Astrofísica de Andalucía (IAA) and operated at the Nordic Optical Telescope under agreement between IAA and the NBIfAFG of the Astronomical Observatory of Copenhagen. Partial financial support was provided by the Universidad Complutense de Madrid, the Spanish Virtual Observatory, the Spanish Ministerio Educación y Ciencia, and the European Social Fund under grants AyA2005-02750, AyA2005-04286, AyA2005-24102-E, and AyA2007-67458 of the Programa Nacional de Astronomía y Astrofísica and by the Comunidad Autónoma de Madrid under PRICIT project S-0505/ESP-0237 (AstroCAM).

Uncontrolled Keywords:Low-mass stars; Alpha emission stars; XMM-Newton observations; Young brown dwarfs; T-Tauri stars; H-alpha; Main-sequence; Ori cluster; Optical spectroscopy; Candidate members
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:37844
Deposited On:25 May 2016 13:39
Last Modified:10 Dec 2018 15:05

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