We have studied the O and Ne absorption features in the X-ray spectrum of Cyg X-2 observed with the Chandra LETG .
The O absorption edge is represented by the sum of three absorption-edge components within the limit of the energy resolution and the photon counting statistics .
Two of them are due to the atomic O ; their energies correspond to two distinct spin states of photo-ionized O atoms .
The remaining edge component is considered to represent compound forms of oxide dust grains .
Since Cyg X-2 is about 1.4 kpc above the galactic disk , the H column densities can be determined by radio ( 21 cm and CO emission line ) and { H } _ { \alpha } observations with relatively small uncertainties .
Thus the O abundance relative to H can be determined from the absorption edges .
We found that the dust scattering can affect the apparent depth of the edge of the compound forms .
We determined the amplitude of the effect , which we consider is the largest possible correction factor .
The ratio of column densities of O in atomic to compound forms and the O total abundance were respectively determined to be in the range 1.7 ^ { +3.0 } _ { -0.9 } to 2.8 ^ { +5.1 } _ { -1.5 } ( ratio ) , and 0.63 \pm 0.12 solar to 0.74 \pm 0.14 solar ( total ) , taking into account the uncertainties in the dust-scattering correction and in the ionized H column density .
We also determined the Ne abundance from the absorption edge to be 0.75 \pm 0.20 solar .
These abundance values are smaller than the widely-used solar values but consistent with the latest estimates of solar abundance .