Swift light curves in different bands. The vertical dotted line indicates 1 January 2017. The data have been averaged over two days. The last datapoint was taken on January 3, 2018. Top panel: UVOT flux; middle panel: soft (0.3–1.5 keV) and hard (1.5–10 keV) X-ray count rate; bottom panel: hardness ratio R = (H − S )/(H + S ) with S and H the soft and hard X-ray count rates. Dotted horizontal line: average hardness without obscuration as described in the text; the grey area corresponds, with its typical variations, to variations in the continuum. Dashed horizontal line: hardness above which there is strong obscuration (see text).