ﻻ يوجد ملخص باللغة العربية
The I-Z colour has been recently shown to be a good temperature indicator for M dwarfs. We present the first IZ photometry of a small sample of L dwarfs ranging in spectral type from L0.5V to L6.0V. We find that the I-Z colour is not a good temperature indicator for objects between L1V and L5V, such objects having colours that overlap with mid M dwarfs. We attribute this to the reduction in the strength of the TiO and VO bands in the L dwarfs which are the dominant opacity source in the I band for late M dwarfs. Beyond L5V, I-Z appears to be a reasonable indicator. This has important implications for the planning of optical surveys for cool objects in clusters and the field. For example I-Z will cease to be a good method of discriminating brown dwarfs in the Pleiades below around 0.04 Msolar, and at around 0.075 Msolar in the Hyades and Praesepe.
Using a large sample of optical spectra of late-type dwarfs, we identify a subset of late-M through L field dwarfs that, because of the presence of low-gravity features in their spectra, are believed to be unusually young. From a combined sample of 3
Trigonometric parallax determinations are presented for 28 late type dwarfs and brown dwarfs, including eight M dwarfs with spectral types between M7 and M9.5, 17 L dwarfs with spectral types between L0 and L8, and three T dwarfs. Broadband photometr
We have compiled L and M photometry of 63 single and binary M, L,and T dwarfs obtained at UKIRT using the MKO filter set. This compilation includes new L data for 8 L dwarfs and 13 T dwarfs and new M data for 7 L dwarfs, 5 T dwarfs, and Gl 229A. We c
We combine 131 new medium-resolution (R~2000) J-band spectra of M, L, and T dwarfs from the Keck NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) with 97 previously published BDSS spectra to study surface-gravity-sensitive indices for 228 low-mass sta
WD0137-349 is a white dwarf-brown dwarf binary system in a 116 minute orbit. We present radial velocity observations and multiwaveband photometry from V, R and I in the optical, to J, H and Ks in the near-IR and [3.6], [4.5], [5.8] and [8.0] microns