We present the properties of the discrete X-ray sources detected in our monitoring program of the globular cluster ( GC ) rich elliptical galaxy , NGC 4278 , observed with Chandra ACIS-S in six separate pointings , resulting in a co-added exposure of 458-ks .
From this deep observation , 236 sources have been detected within the region overlapped by all observations , 180 of which lie within the D _ { 25 } ellipse of the galaxy .
These 236 sources range in L _ { \mathrm { X } } from 3.5 \times 10 ^ { 36 } \mbox { erg } ~ { } \mbox { s } ^ { -1 } ( with 3 \sigma upper limit \leq 1 \times 10 ^ { 37 } \mbox { erg } ~ { } \mbox { s } ^ { -1 } ) to \sim 2 ~ { } \times 10 ^ { 40 } \mbox { erg } ~ { } \mbox { s } ^ { -1 } , including the central nuclear source which has been classified as a LINER .
From optical data , 39 X-ray sources have been determined to be coincident with a globular cluster , these sources tend to have high X-ray luminosity , with ten of these sources exhibiting L _ { \mathrm { X } } > 1 \times 10 ^ { 38 } \mbox { erg } ~ { } \mbox { s } ^ { -1 } .
From X-ray source photometry , it has been determined that the majority of the 236 point sources that have well constrained colors , have values that are consistent with typical LMXB spectra , with 29 of these sources expected to be background objects from the logN - logS relation .
There are 103 sources in this population that exhibit long-term variability , indicating that they are accreting compact objects .
3 of these sources have been identified as transient candidates , with a further 3 possible transients .
Spectral variations have also been identified in the majority of the source population , where a diverse range of variability has been identified , indicating that there are many different source classes located within this galaxy .