Radiation from dwarf nova discs

We use the Shaviv and Wehrse (1991) code to model the vertical structure an d the emission properties of quiescent dwarf nova disc. We find that in the case of HT Cas the quiescent disc must be optically thin, in contradiction with the requirements of the standard disc instability model. We find a vi scosity parameter alpha greater than or similar to 1. Although this is much less than values (similar to 10(2)) obtained in isothermal slab models it is not consistent with the accretion disc model assumptions. (C) 1999 Elsev ier Science B.V. All rights reserved.