Using ASCA , spatially integrated X-ray spectra of the central regions of M31 were studied .
Data were accumulated over three different circular regions , with the radii of 3 ^ { \prime } , 6 ^ { \prime } and 12 ^ { \prime } , all centered on the nucleus .
The spectra are relatively similar among the three regions .
In the energy range above 1.5 keV , the spectra are reproduced by a combination of a disk black-body component and a black-body component , implying that the emission mainly comes from an assembly of low-mass X-ray binaries .
In energies below 1.5 keV , the spectra involves two additional softer components , expressed with thin-thermal plasma emission models of temperatures \sim 0.9 keV and \sim 0.3 keV .
Over the central 12 ^ { \prime } ( 2.4 kpc ) region and in the 0.5–10 keV energy band , the binary component has a luminosity of 2.6 \times 10 ^ { 39 } erg s ^ { -1 } , while the two softer components both exhibit luminosities of \sim 2 \times 10 ^ { 38 } erg s ^ { -1 } .
These results are compared with those from other missions , including Chandra and XMM-Newton in particular .
Discussion is made on the nature of the two softer spectral components besides the binary one .