K-band spectra and narrowband photometry of DENIS field brown dwarfs

Infrared spectra at 1.9-2.5 mu m and narrowband photometry of three low-mass objects, DENIS-P J0205.4-1159, J1058.7-1548, and J1228.2-1547, are presented. As shown previously by Delfosse et al., DENIS-P 50205.4-1159 shows an absorption feature at 2.2 mu m. We attribute this absorption to H-2. A simple two-parameter analysis of the K-band spectrum of low-mass objects is presented in which the relative strength of the H2O and H-2 absorption bands is found to be correlated with the effective temperature of the objects. The analysis confirms that DENIS-P J0205.4-1159 is the lowest temperature object of the three. We present narrowband photometry of these objects that provides the continuum flux level in between the deep H2O absorption bands. These data show the continuum level accurately for the first time, and they will provide tight constraints for spectral models of these interesting objects.