Multi-object and long-slit spectroscopy of very low mass brown dwarfs in the Orion Nebular Cluster
Oct 30, 201310 pages
Published in:
- Publ.Astron.Soc.Jap. 66 (2014) 2, 33
- Published: Apr 1, 2014
e-Print:
- 1310.8087 [astro-ph.SR]
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Abstract: (Oxford University Press)
We present the results of an H- and K-band multi-object and long-slit spectroscopic survey of substellar mass candidates in the outer regions of the Orion Nebula Cluster. The spectra were obtained using MOIRCS on the 8.2 m Subaru telescope and ISLE on the 1.88 m telescope of Okayama Astrophysical Observatory. Eight out of twelve spectra show strong water absorption and we confirm that their effective temperatures are ≤ 3000 K (spectral type ≥ M6) from a chi-square fit to synthetic spectra. We plot our sources on an HR diagram overlaid with theoretical isochrones of low-mass objects and identify three new young brown dwarf candidates. One of the three new candidates is a cool object near the brown dwarf and planetary mass boundary. Based on our observations and those of previous studies, we determine the stellar (0.08 < M/M_⊙ < 1) to substellar (0.03 < M/M_⊙ < 0.08) mass number ratio in the outer regions of the Orion Nebular Cluster to be 3.5 ± 0.8. In combination with the number ratio reported for the central region (), this result suggests the number ratio does not simply change with the distance from the center of the Orion Nebular Cluster.Note:
- Accepted for publication in Publications of the Astronomical Society of Japan
- brown dwarfs
- open clusters and associations: individual: (Orion Nebular Cluster)
- stars: low-mass
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