BANYAN. VIII. NEW LOW-MASS STARS AND BROWN DWARFS WITH CANDIDATE CIRCUMSTELLAR DISKS

We present the results of a search for new circumstellar disks around low-mass stars and brown dwarfs with spectral types > K5 that are confirmed or candidate members of nearby young moving groups. Our search input sample was drawn from the BANYAN surveys of Malo et al. and Gagne et al. Two Micron All-Sky Survey and Wide-field Infrared Survey Explorer data were used to detect near-to mid-infrared excesses that would reveal the presence of circumstellar disks. A total of 13 targets with convincing excesses were identified: 4 are new and 9 were already known in the literature. The new candidates are 2MASS. J05010082-4337102 (M4.5), J08561384-1342242 (M8 gamma), J12474428-3816464 (M9 gamma), and J02265658-5327032 ( L0 delta); they are candidate members of the TW Hya (similar to 10 +/-. 3 Myr), Columba (similar to 42(-4)(+6) 4 6 Myr), and Tucana-Horologium (similar to 45 +/-. 4 Myr) associations, with masses of 120 and 13-18 M-Jup. The M8-L0 objects in Columba and Tucana-Horologium are potentially among the first substellar disk systems aged similar to 40 Myr. Estimates of the new candidates' mean disk temperatures and fractional luminosities are in the ranges similar to 135- 520 K and 0.021-0.15, respectively. New optical spectroscopy of J0501-4337 reveals strong Ha emission, possibly indicating ongoing accretion, provides a detection of lithium absorption, and shows a radial velocity measurement that is consistent with a membership to Columba. We also present a near-infrared spectrum of J0226-5327 that reveals Paschen beta emission and shows signs of low surface gravity, consistent with accretion from a disk and a young age.