SELF-SIMILAR SOLUTIONS OF ADVECTION-DOMINATED ACCRETION FLOWS REVISITED

A model of advection-dominated accretion flows has been highlighted in the last decade. Most of calculations are based on self-similar solutions of equations governing the accreting flows. We revisit self-similar solutions of the simplest form of advection-dominated accretion flows. We explore the parameter space thoroughly and seek another category of self-similar solutions. In this study we allow the parameter f less than zero, which denotes the fraction of energy transported through advection. We have found followings: 1. For f>0, in real ADAF solutions the ratio of specific heats γ satisfies 1<γ<5/3 for 0≤ f ≤ 1. On the other hands, in wind solutions a rotating disk does not exist. 2. For f<0, in real ADAF solutions with ɛ greater than zero γ requires rather exotic range, that is, γ<1 or γ>5/3. When -5/2<ɛ'<0, however, allowable γ can be found in γ<5/3, in which case Ω0,- is imaginary. 3. For a negative u0,+ with f>0, solutions are only allowed with exotic γ, that is, 1<γ or γ>(5f/2-5/3)/(5f/2-1) when 02/5. Since ɛ' is negative, Ω0,+ is again an imaginary quantity. For a negative u0,+ with f<0, γ is allowed in 1<γ < (5|f|/2+5/3)/(5|f|/2+1). We briefly discuss physical implications of what we have found