Fundamental stellar parameters for selected T-Tauri stars in the
  Chamaeleon and Rho Ophiuchus star-forming regions
  We present the results of an optical photometry and high-resolution
spectroscopy campaign for a modest sample of X-ray selected stars in the
Chamaeleon and Rho Ophiuchus star forming regions. With R~50000 optical
spectra, we establish kinematic membership of the parent association and
confirm stellar youth for each star in our sample. With the acquisition of new
standardized BVIc photometry, in concert with near-infrared data from the
literature, we derive age and mass from stellar positions in model-dependent
Hertzsprung-Russell diagrams. We compare isochronal ages derived using
colour-dependent extinction values finding that, within error bars, ages are
the same irrespective of whether E(B-V), E(V-Ic), E(J-H) or E(H-K) is used to
establish extinction, although model ages tend to be marginally younger for
redder Ecolour values. For Cham I and Eta Cham members we derive ages of ~< 5-6
Myr, whereas our three Eta Cha candidates are more consistent with a ~> 25 Myr
post-T Tauri star population. In Rho Ophiuchus, most stars in our sample have
isochronal ages <10 Myr. Five objects show evidence of strong infrared excess
(Av>5) in the 2MASS colour colour diagram, however in terms of Halpha emission,
all stars except RXJ1625.6-2613 are consistent with being weak-lined T-Tauri
stars. Spectral energy distributions (SEDs) over the range ~ 4000A < wavelength
< 1000 microns, show that only one Chamaeleon star (RXJ1112.7-7637) and three
Rho Ophiuchus stars (ROXR1 13, RXJ1625.6-2613 & RXJ1627.1-2419) reveal
substantial departures from a bare photosphere.
