Evolution of the integrated flux of HeII 4686 Å emission line of KT Eri compared to its V-band light curve (from Hounsell et al. 2010, AAVSO database, Munari & Dallaporta 2014, and unpublished recent data). To facilitate the comparison, the integrated line flux is transformed in magnitudes and offset by the quantity given in Eq. (1). The arrow marks the upper limit to HeII integrated flux on day +35 spectra. Top panel: the hardness ratio (defined as the ratio between the count rates in the 1–10 keV and 0.3–1 keV bands) of the Swift X-ray observations (adapted from public data available on the Swift web site).