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Abstract The population-wide properties and demographics of extragalactic X-ray binaries (XRBs) correlate with the star formation rates (SFRs), stellar masses (M_⋆), and environmental factors (such as metallicity,Z) of their host galaxy. Although there is evidence that XRB scaling relations (L_X/SFR for high-mass XRBs (HMXBs) andL_X/M_⋆for low-mass XRBs) may depend on metallicity and stellar age across large samples of XRB-hosting galaxies, disentangling the effects of metallicity and stellar age from stochastic effects, particularly on subgalactic scales, remains a challenge. We use archival X-ray through IR observations of the nearby galaxy NGC 300 to self-consistently model the broadband spectral energy distribution and examine radial trends in its XRB population. We measure a current (<100 Myr) SFR of 0.18 ± 0.08 M_⊙yr⁻¹and stellar massM_⋆= $\left({2.15}_{-0.14}^{+0.26}\right)\times {10}^9$M_⊙. Although we measure a metallicity gradient and radially resolved star formation histories that are consistent with the literature, there is a clear excess in the number of X-ray sources below ∼10³⁷erg s⁻¹that are likely a mix of variable XRBs and additional background active galactic nuclei. When we compare the subgalacticL_X/SFR ratios as a function ofZto the galaxy-integratedL_X-SFR-Zrelationships from the literature, we find that only the regions hosting the youngest (≲30 Myr) HMXBs agree with predictions, hinting at time evolution of theL_X–SFR–Zrelationship. 

ABSTRACT We present an analysis of the two-point spatial correlation functions of high-mass X-ray binary (HMXB) and young star cluster (YSC) populations in M31 and M33. We find evidence that HMXBs are spatially correlated with YSCs to a higher degree than would be expected from random chance in both galaxies. When supplemented with similar studies in the Milky Way, Small Magellanic Cloud, and NGC 4449, we find that the peak value of the spatial correlation function correlates strongly with the specific star formation rate of the host galaxy. We additionally perform an X-ray stacking analysis of 211 non-X-ray detected YSCs in M31 and 463 YSCs in M33. We do not detect excess X-ray emission at the stacked cluster locations down to 3σ upper limits of ∼1033 erg s−1 (0.35–8 keV) in both galaxies, which strongly suggests that dynamical formation within YSCs is not a major HMXB formation channel. We interpret our results in the context of (1) the recent star formation histories of the galaxies, which may produce differences in the demographics of compact objects powering the HMXBs, and (2) the differences in natal kicks experienced by compact objects during formation, which can eject newly formed HMXBs from their birth clusters.