High‐ResolutionChandraHETGS andRossi X‐Ray Timing ExplorerObservations of GRS 1915+105: A Hot Disk Atmosphere and Cold Gas Enriched in Iron and Silicon

The Chandra AO1 HETGS observation of the micro-quasar GRS 1915+105 in the lowhard state reveals (1) neutral K absorption edges from Fe, Si, Mg, and S incold gas, and (2) highly ionized (Fe XXV and Fe XXVI) absorption attributed toa hot disk, disk wind, or corona. The neutral edges reveal anomalous Si and Feabundances which we attribute to surrounding cold material in/near theenvironment of GRS 1915+105. We also point out the exciting possibility for thefirst astrophysical detection of XAFS attributed to material in interstellargrains. We place constraints on the ionization parameter, temperature, andhydrogen equivalent number density of the absorber near the accretion diskbased on the detection of the H- and He-like Fe absorption. Observed spectralchanges in the ionized lines which track the light curve point to changes inboth the ionizing flux and density of the absorber, supporting the presence ofa flow. Details can be found in Lee et al., 2002, ApJ., 567, 1102Comment: Proceedings of the 4th Microquasar Workshop, 2002, eds. Durouchoux, Fuchs & Rodriguez, published by the Center for Space Physics : Kolkata ; The main findings as presented in Lee et al., 2002, ApJ., 567, 1102 are summarize