67 research outputs found
Multi-object and long-slit spectroscopy of very low mass brown dwarfs in the Orion Nebular Cluster
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 8.2m Subaru telescope and ISLE on the 1.88m telescope of Okayama Astrophysical Observatory. Eight out of twelve spectra show strong water absorption and we confirm that their effective temperatures are ≤3000K (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 (0.08Peer reviewe
H and K Band Methane Features in an L Dwarf, 2MASS 0920+35
We have obtained near-infrared spectra of three L dwarfs discovered by 2MASS,
1506+13 (L3), 1507-16 (L5), and 0920+35 (L6.5). From the comparison of the H
and K band spectra of these L dwarfs, we have found the presence of methane
absorption in 0920+35. This implies that detectable methane absorption in the H
and K bands, usually considered the signature of a T dwarf, can be present in
objects classified optically as late L. Methane detection in L dwarfs is
consistent with the presence of a dust layer deep in the atmosphere as the
unified model of Tsuji suggests.Comment: Accepted for publication in ApJ Letters; 8 pages, 4 figure
Spectral Classification and Effective Temperatures of L and T Dwarfs Based of Near-Infrared Spectra
We have obtained near-infrared spectra of L dwarfs, L/T transition objects
and T dwarfs using Subaru. Resulting spectra are examined in detail to see
their dependence on the spectral types. We have obtained bolometric
luminosities of the objects with known parallaxes in our sample, first by
integrating the spectra and second by K band bolometric correction. We derive
the relation between effective temperature and spectral type.Comment: To appear in May 20, 2004 issue of ApJ There is a companion paper by
Tsuji, Nakajima and Yanagisaw
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