and become progressively longer. This pattern repeats in a very regular way. In the CD, the quiet periods result in elongated clouds, the oscillations in small rings (not clearly visible in Fig. 2v) like those of classes $\rho$ and $\nu$, and the flare as a curved trail of soft (low HR$_2$) points (Fig. 2u).

$\bullet$ class $\beta$

:   This class shows complex behavior in the light curves, some of which can be seen within other classes. What identifies class $\beta$ however, is the presence in the CD of a characteristic straight elongated branch stretching diagonally.

The number of the classes presented above could be reduced, given the strong similarities between them, but our goal is not to have as few classes as possible, but to give as comprehensive a description of the source behavior as possible, in order to look for basic ‘states’ of the source. For this purpose, defining a relatively large number of classes means we are being conservative in order not to overlook important details in source behavior. All observation intervals in the sample considered for this work are covered by this classification, but it is quite possible that future observations would require yet other classes. Some 