Magnesium and silicon K-edges cross sections

We used the models to reproduce the dust absorption features observed in the spectrum of the bright low mass X-ray binary GX 3+1, which is used as a background source. With the simultaneous analysis of the two edges we test two different size distributions of dust: one corresponding to the standard Mathis-Rumpl-Nordsieck model and one considering larger grains (n(a){prop.to}a_i_^-3.5^ with 0.005{mu}m<a_1_<0.25{mu}m and 0.05{mu}m<a_2_<0.5{mu}m, respectively, with a the grain size).

These distributions may be representative of the complex Galactic region towards this source. We find that up to 70% of dust is constituted by amorphous olivine. We discuss the crystallinity of the cosmic dust found along this line of sight.

Both magnesium and silicon are highly depleted into dust ({delta}_Z_=0.89 and 0.94, respectively), while their total abundance does not depart from solar values.