the D25 ellipse of NGC 4088 were converted to source fluxes by applying a conversion factor calculated assuming a power-law spectrum of $\Gamma$ = 1.8 and line-of-sight Galactic absorption[^5] $N_\mathrm{H} = 2 \times 10^{20}$ cm$^{-2}$ using WebPIMMS[^6]. A $\Gamma$ = 1.4$\sim$2 (e.g., @2002ApJ...577..726Z) and $\Gamma$ = 1.4–1.8 (e.g., @2011ApJ...729...12B) was found for HMXBs and LMXBs, respectively. We note that the average value of $\Gamma$ = 1.8 used here may not be applicable to our case since those studies have a deeper detection limit that includes also XRBs in the low/hard state (dominated by a hard power-law component), while we can only see those in the high/soft state (dominated by a disk blackbody). To make sure that we are using a plausible slope, we used the [XSPEC]{} task [*fakeit*]{} to simulate a distribution of [*Chandra*]{} spectra for disk-blackbody models with column densities equal to the line-of-sight and twice the line-of-sight values, and inner-disk temperatures distributed between 0.6 and 1.0 keV (typical disk temperatures in the high/soft state; e.g., @2006csxs.book..157M). We then re-fitted the simulated spectra with a power-law model, fixing the column density to the line-of-sight value and leaving the photon index as a free parameter. We find that low signal-to-noise 