We present new observations of the isolated young stars HD 98800 and
  CD -33 7795.  Pointed ROSAT observations show that
  their X-ray properties, including X-ray luminosity and variability,
  are consistent with those of pre--main-sequence (PMS) stars.  These
  observations do not reveal any additional PMS candidates in 40'
  fields centered on HD 98800 and CD -33 7795.  Hipparcos
  observations of TW Hya (Wichmann et al. 1998) and HD 98800
  (Soderblom et al. 1998) show that both stars are roughly 50 pc away
  and are PMS with ages of ~ 10^7 yr.  We searched the Hipparcos
  catalog (complete down to ~ 2--3 L_sun at this distance)
  for other PMS stars in the same area.  In a 10-pc radius volume of
  space centered on the previously known PMS stars, we find one
  additional candidate PMS star (CD -36 7429) with a low
  space velocity, X-ray emission comparable to that of HD 98800, and
  Li absorption.  There are eight other stars in this area that have
  dwarf spectral types and lie above the main sequence, but based on
  their weak X-ray emission, high space velocities, and lack of Li in
  low-resolution spectra (i.e. EW(Li) < 0.1 Angstroms), these are
  probably mis-classified subgiants or giants.  The current positions
  and proper motions of TW Hya, HD 98800, and CD -36 7429 are
  inconsistent with them having formed as a group.