New brown dwarf candidates in the Pleiades

Abstract

We have performed deep, wide-field imaging on a ∼ 0.4 deg 2 field in the Pleiades (Melotte 22). The selected field was not yet target of a deep search for low mass stars and brown dwarfs. Our limiting magnitudes are R ∼ 22 mag and I ∼ 20 mag, sufficient to detect brown dwarf candidates down to 40 MJ . We found 197 objects, whose location in the (I,R − I) color magnitude diagram is consistent with the age and the distance of the Pleiades. Using CTK R and I as well as JHK photometry from our data and the 2MASS survey we were able to identify 7 new brown dwarf candidates. We present our data reduction technique, which enables us to resample, calibrate, and co-add many images by just two steps. We estimate the interstellar extinction and the spectral type from our optical and the NIR data using a 2-dimensional χ 2 fitting.

Spectral classification of Pleiades brown dwarf candidates

“…. 1 mag determined by Eisenbeiss et al (2009) introduces an error of up to 0.5 mag or even more in the case of background stars. This should be considered regarding the results.…”

“…This pipeline Table 1 The observations carried out with FORS and ISAAC, the latter one in the H and K band. The I-band magnitudes given in Col. 2 are taken from Eisenbeiss et al (2009). The number of images made with each instrument (# images) and the exposure time per image (DIT) are given in the respective columns.…”

“…The relative flux correction was performed regarding the shape of the spectrum, telluric features have not been corrected. Finally, all spectra have been corrected with an extinction of A V = 0.75 as an average extinction for this region of the sky (Eisenbeiss et al 2009) using the deredden-procedure of IRAF.…”

“…As a result of a deep imaging analysis, Eisenbeiss et al (2009) reported on the discovery of seven brown dwarf candidates and three objects close to the border to brown dwarfs being set to the spectral type M6. This border is set by the high-mass brown dwarf Teide 2 (Martín et al 1998).…”

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We report on the results of the spectroscopy of 10 objects previously classified as brown dwarf candidates via RIJHK colors by Eisenbeiss et al (2009), who performed deep imaging observations on a ∼0.4 sq.deg. field at the edge of the Pleiades.

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