Therefore radiation from the stellar surface is behind the stronger radiation for the circumstellar gas. Absorption column increases as we go back to the evolution history. Therefore soft X-rays, if any, can not arrive to us. Accordingly hard X-ray imaging is essentially important to observe the protostar itself. The ASCA results of a star forming region the RCrA dark cloud shown in figure is very demonstrative.
Contours show the column of the molecular gas.
Moving to the hard X-ray band, the center becomes bright. It shows complex X-ray structure. The positions of class I objects are given by the blue circles. The protostars exhibit typical flare similar to T-Tauri's. Also clear emission line from iron K-shell emission is found.