X-ray irradiation in low-mass binary systems

We calculate self-consistent models of X-ray-irradiated accretion discs in close binary systems, We show that a point X-ray source powered by accretio n and located in the disc plane cannot modify the disc structure, mainly be cause of the self-screening by the disc of its outer regions, As observatio ns show that the emission of the outer disc regions in low-mass X-ray binar ies is dominated by the reprocessed X-ray flux, accretion discs in these sy stems must be either warped or irradiated by a source above the disc plane, or both. We analyse the thermal-viscous stability of irradiated accretion discs and derive the stability criteria of such systems. We find that, cont rary to the usual assumptions, the critical accretion rate below which a di sc is unstable is rather uncertain because the correct formula describing i rradiation is not well known.