Light curves have been extracted, from the same data cubes as have the spectral data (see section 2.6); in the energy bands 2-6, 6-7, 7-17 and 2-17 keV. These bands cover the soft X-ray emission, the iron K line emission, the hard X-ray continuum and the full energy band. There are light curves and light curve images for both the top- and mid-layers (see figure 6). In addition, the intrinsic variability (total variance minus statistical noise) is given in the databases as
where xi is the count rate for bin i, is the mean count rate during the observation and is the variance for bin i).
The format of the light curve files follows OGIP FITS conventions (Angelini, Pence & Tennant 1994) and they can be used within the XRONOS timing analysis package (Stella & Angellini 1993), which is part of the XANADU suite of software.