2001AN....322....9K

I propose that the properties of the two outbursts observed in the X-ray transi ent XTEJ1118+480 in 2000 are akin to superoutbursts of SUUMa stars. In these systems a `normal' outburst immediately precedes a 5–10 times longer (`super')outburst. The optical light curve of the outbursts of XTEJ1118+480 is remarkably simila r to that seen in some SUUMa stars, such as UVPer and TLeo, where the precursor out burst is distinct from the superoutburst, but the time scales are a factor of ∼15 different. The first outburst of XTEJ1118+480 was relatively short (∼1 month) while the second outburst was ∼5 times longer. During the second outburst superhumps were seen, a fe ature characteristic for superoutbursts. The gap of about a month between the two outbursts is longe r in X-rays with respect to the optical, a feature not previously recognized for X-ray transient s. Also in SUUMa stars the precursor outburst becomes more distinct at shorter wavelengths. Finally, I show that the time of appearance of the superhumps in XTEJ1118+480 is consistent with the expected superhump growth time, if the superhump mechanism was triggered du ring the first outburst. I conclude that the similarity in outburst behaviour in the two types of system s provides further support that a common mechanism is at work to start the long ( `super')outbursts.