All Figures

Figure 1: The VLBI T Tau S field. All positions have been proper motion corrected to the epoch of the VLBI observation but no attempt has been made to correct for possible orbital motion of components. A compact radio source is clearly seen. The circle plotted around this shows the estimated position uncertainty of the VLBI observation at 3.6 cm. The positions of T Tau Sa and two positions for T Tau Sb, one from Köhler et al. (2000) and one from Duchêne et al. (2002), are marked with crosses. The size of the crosses show the position uncertainties. The 2 cm radio position measured by Johnston et al. (2003) at epoch 2001.0531 is shown as a small cross. Also marked (small circle) is the position expected for Sa if the radio source is taken to be Sb. The size of this small circle corresponds to the relative position uncertainty reported by Köhler et al. (2000).

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In the text

Figure 2: Contour maps of the T Tau field from the VLA only data. The map on the left has been cleaned using the fitted beam of 1.15  0.94'', whilst the map on the right has been cleaned using a restoring beam set to  to produce an artificial overresolution of the data. This allows T Tau N to be distinguished from T Tau S for the purposes of flux measurement. Positions are given as offsets from the position of the VLBI source, which is marked with a star. The position of T Tau N, T Tau Sa and T Tau Sb (from Duchêne et al. 2002, epoch 2000.2) are marked with crosses.

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In the text

Figure 3: Upper panels: the VLA lightcurves. In the left panel are shown Stokes I and V, and in the right Stokes RR and LL. Every group of points includes three on-source scans. Two sharp increases in flux are seen. Both show significant right-hand circular polarization, and the second appears to be almost 100% polarized. Lower panels: blow-ups of two sections of special interest, showing rapidly varying behaviour. These sections are indicated in the upper right-hand panel. Stokes RR and LL are plotted separately. The RR points are plotted as open circles, the LL points as filled triangles. The RR points in both figures have been shifted upwards by 4 mJy to prevent overlap. Successive points are approximately 10 s apart, which corresponds to the basic integration time and is therefore the highest time resolution available in our data.

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In the text

Figure 4: Correlated flux vs. uv distance. The panels show (top to bottom) the visibility amplitude for the time periods 0 to 6 h, 6 h to 10 h and 10 h to the end of the observation. These time segments correspond to the three stages of flaring behaviour seen in Fig. 3. The dotted straight lines mark the weighted data average. Dashed lines show the narrowest possible Gaussian fitting the data. See the discussion in the text for details of the fits.

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In the text

	Figure 5: Correlated polarized flux vs. uv distance for the periods of the two flares, separated in RR and LL. For the description of the plots see Fig. 4. The LL data for Mauna Kea after  h, which forms the longest baselines at this time, was flagged as unreliable and so the long baseline point is missing in the lower right-hand panel.
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In the text