Refined masses and distance of the young binary Haro 1-14 C

We aim to refine the dynamical masses of the individual component of the low-mass pre-main sequence binary Haro 1-14 C. We combine the data of the preliminary orbit presented previously with new interferometric observations obtained with the four 8m telescopes of the Very Large Telescope Interferometer. The derived masses are $M_a=0.905pm0.043,Msun$ and $M_b=0.308pm0.011,Msun$ for the primary and secondary components, respectively. This is about five times better than the uncertainties of the preliminary orbit. Moreover, the possibility of larger masses is now securely discarded. The new dynamical distance, $d=96pm,9,$pc, is smaller than the distance to the Ophiuchus core with a significance of $2.6,sigma$. Fitting the spectral energy distribution yields apparent diameters of $phi_a=0.13pm0.01mas$ and $phi_b=0.10pm0.01mas$ (corresponding to $Ra=1.50,Rsun$ and $Rb=1.13,Rsun$) and a visual extinction of $A_vapprox1.75$. Although the revised orbit has a nearly edge-on geometry, the system is unlikely to be a long-period eclipsing binary. The secondary in Haro~1-14C is one of the few low-mass, pre-main sequence stars with an accurately determined dynamical mass and distance.

The large-scale disk fraction of brown dwarfs in the Taurus cloud as measured with Spitzer

Aims. The brown dwarf (BD) formation process has not yet been completely understood. To shed more light on the differences and similarities between star and BD formation processes, we study and compare the disk fraction among both kinds of objects over a large angular region in the Taurus cloud. In addition, we examine the spatial distribution of stars and BD relative to the underlying molecular gas Methods. In this paper, we present new and updated photometry data from the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope on 43 BDs in the Taurus cloud, and recalculate of the BD disk fraction in this region. We also useed recently available CO mm data to study the spatial distribution of stars and BDs relative to the clouds molecular gas. Results. We find that the disk fraction among BDs in the Taurus cloud is 41 pm 12%, a value statistically consistent with the one among TTS (58 pm 9%). We find that BDs in transition from a state where they have a disk to a diskless state are rare, and we study one isolated example of a transitional disk with an inner radius of approx 0.1 AU (CFHT BD Tau 12, found via its relatively small mid-IR excess compared to most members of Taurus that have disks. We find that BDs are statistically found in regions of similar molecular gas surface density to those associated with stars. Furthermore, we find that the gas column density distribution is almost identical for stellar and substellar objects with and without disks.