evolution of MXB 1659 − 29 after outbursts I and II (black and green points, respectively). We have modelled this observed evolution with the crust heating and cooling code NSCOOL. The modelled cooling curves after outbursts I and II are shown in blue and red, respectively. Model A (shown by the solid lines) indicates the fit when all the parameters were free to vary. Model B (shown by the dotted lines) assumes that y_light after both the outbursts is the same and, therefore, that the crust returns to the same observed base level. It should be noted that Models A and B have parameters that are consistent with one another within their error bands. This is shown in Fig. 3 and Table 2.