The effect of irradiation on outbursts in x‐ray novae

Abstract

We study the disk‐instability and the effect of irradiation on accretion disks around black holes in x‐ray novae outbursts. The disk instability theory is proposed as the mechanism for the cause of outbursts in x‐ray novae. The mass flow rate into the black hole predicted by the disk instability theory is consistent with observations in both outburst and quiescence. Furthermore, a strong correlation between the optical and soft x‐rays in outburst can be naturally explained by the disk instability theory. We adopt a simple model for the direct irradiation of the whole disk by x‐rays from the innermost disk and examine its effects on the outburst in the context of the disk instability model. The effect of radiation influences both optical and soft x‐ray light curves and the disk evolution. In outburst, the disk becomes brighter and hotter in both optical and soft x‐ray bands, and both the duration of the outburst and the recurrence time are lengthened.