  The observed light curves and other properties of the two extragalactic fast
x-ray transients, CDF-S XT1 and CDF-S XT2, which were discovered recently in
archival data of the Chandra Deep Field-South (CDF-S) observations, indicate
that they belong to two different populations of X-ray transients. XT1 seems to
be an x-ray flash (XRF), i.e., a narrowly beamed long duration gamma ray burst
viewed from far off-axis while XT2 seems to be a nebular emission powered by a
newly born millisecond pulsar in a neutron stars binary merger.
