Face-on Surface Density at Disk Inner Boundary
σ
(m2 of grain cross-section per m2 of disk)
| if α = 0, σ = | 2 · f ln( r2 / r1 ) |
| if α ¹ 0, σ = | 2 · α
· f ( r2 / r1 )α - 1 |
α = disk surface density power
law exponent
r2 , r1 = disk outer and inner boundary radii
f = infrared excess LIR/Lstar