BROWN DWARFS IN YOUNG STELLAR CLUSTERS

The early evolution of brown dwarfs and very low mass stars are calculated and isochrones presented which span a mass range of 0.01-0.20 M. for ages between 10(6) and 3 x 10(8) yr. I find that the brown dwarfs remain sharply segregated in T(eff) from low-mass stars for ages less-than-or-similar-to 10(8) yr. Hence, for coeval populations of known age, as in young stellar clusters, a domain exists in the H-R diagram wherein only brown dwarfs lie; for T(eff) less-than-or-similar-to 2800 +/- 50 K. Because of this and the high temperatures and luminosities the young brown dwarfs maintain, the most promising means of discovering brown dwarfs is to search in young stellar clusters. The theoretical results are compared with recent observations of Pleiades brown dwarf candidates made by Jameson & Skillen and Stauffer et al. Both groups had previously used the Berriman & Reid temperature scale which contains erroneous R and I photometry that generates incorrect color-T(eff) relations, yielding temperatures which are too cool by several hundred degrees that led to the misidentification of brown dwarf candidates in the former group's case. Two new sets of color-T(eff) transformations (by Bessell & Stringfellow) are used to compare the observations with theory. Both sets yield consistent interpretations: the former group's candidates are not Pleiades members, while the majority of the latter group's candidates could be Pleiades members with seven possibly being brown dwarfs. However, in the latter case, the optical and IR photometry seem inconsistent with one another or with the color-T(eff) relations derived from old field stars, leaving doubts concerning the candidates' identification.