M31 supersoft and quasi-soft X-ray sources

In a survey that was most sensitive to soft sources in four 8'x8' regions covered by Chandra's ACIS-S S3 CCD, we find 33 VSSs that appear to belong to M31. Fifteen VSSs have spectral characteristics mirroring the supersoft X-ray sources studied in the Magellanic Clouds and Milky Way (kT_eff_<=100eV); we therefore call these "classical" supersoft sources, or simply supersoft sources (SSSs).

Eighteen VSSs may have either small (<10%) hard components or slightly higher effective temperatures (but still less than 350eV). We refer to these VSSs as quasi-soft sources (QSSs).