Low-resolution spectroscopy and spectral energy distributions of selected sources towards σ Orionis
Abstract
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 V i J H Ks 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.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 2008
- DOI:
- 10.1051/0004-6361:200810616
- arXiv:
- arXiv:0809.0996
- Bibcode:
- 2008A&A...491..515C
- Keywords:
-
- stars: emission-line;
- Be;
- stars: low-mass;
- brown dwarfs;
- stars: pre-main sequence;
- Galaxy: open clusters and associations: individual: σ Orionis;
- galaxies: quasars: emission lines;
- Astrophysics
- E-Print:
- Accepted for publication in A&