New low-mass members of the Lupus 3 dark cloud: Further indications of pre-main-sequence evolution strongly affected by accretion

A spectroscopic survey of a small area at the center of the Lupus 3 star-forming core has revealed four new mid-to-late Mtype members, including a M7.5 brown dwarf. One of the new members, classified as M5, displays prominent forbidden lines and strong H (alpha)emission...), in addition to other permitted lines, and its luminosity is far below that of other members of the region with similar or later spectral types. We estimate a mass accretion rate rate of ~ ...for this object, although with uncertainties that do not exclude values as low as 10-10 .... Based on the ...ratio, the detection of HeI, and the CaII infrared triplet, we argue that most of the H (alpha)emission is produced near the surface of the object, probably in accretion columns or at the base of jets, rather than in a low-density extended region. The strong emission-line spectrum superimposed on an unusually faint photospheric continuum thus seems to be a real, intrinsic feature rather than a result of the viewing geometry caused by an edge-on disk blocking the light from the central object. Other Lupus 3 late-type members also display noticeable underluminosity, all of them having ...A as a result of the faint underlying continuum. We tentatively interpret these findings as evidence for the pre-main sequence evolution of objects with very low (possibly substellar) initial masses being significantly modified by accretion.