  We present new observations of the XZ Tau system made at high angular
resolution (55 milliarcsec) with the Karl G. Jansky Very Large Array (VLA) at a
wavelength of 7 mm. Observations of XZ Tau made with the VLA in 2004 appeared
to show a triple system, with XZ Tau A resolved into two sources, XZ Tau A and
XZ Tau C. The angular separation of XZ Tau A and C (0.09 arcsec) suggested a
projected orbital separation of around 13 AU with a possible orbital period of
around 40 yr. Our observations were obtained approximately 8 yr later, a fifth
of this putative orbital period, and should therefore allow us to constrain the
orbit of XZ Tau C, and evaluate the possibility that a recent periastron
passage of C coincided with the launch of extended optical outflows from XZ Tau
A. Despite improved sensitivity and resolution compared with previous
observations, we find no evidence of XZ Tau C in our data. Components A and B
are detected with a signal-to-noise ratio greater than ten; their orbits are
consistent with previous studies, although the emission from XZ Tau A appears
to be weaker. Three possible interpretations are offered: either XZ Tau C is
transiting XZ Tau A, which is broadly consistent with the periastron passage
hypothesis, or the emission seen in 2004 was that of a transient, or XZ Tau C
does not exist. A fourth interpretation, that XZ Tau C was ejected from the
system, is dismissed due to the lack of angular momentum redistribution in the
orbits of XZ Tau A and XZ Tau B that would result from such an event. Our
observations are insufficient to distinguish between the remaining
possibilities, at least not until we obtain further VLA observations at a
sufficiently later time. A further non-detection would allow us to reject the
transit hypothesis, and the periastron passage of XZ Tau C as agent of XZ Tau
A's outflows.
