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In this work, we characterize the properties of HB stars in the GCs $\omega$Cen and NGC 6752. We use dedicated model atmospheres and synthetic spectragrids computed using a hybrid LTE/NLTE modeling approach to fit the MUSEspectra of HB stars hotter than 8000 K in both clusters. The spectral fitsprovide estimates of the effective temperature, surface gravity, and heliumabundance of the stars. The model grids are further used to fit the HSTmagnitudes, meaning the spectral energy distributions (SED), of the stars. Fromthe SED fits, we derive the average reddening, radius, luminosity, and mass ofthe stars in our sample. The atmospheric and stellar properties that we derivefor the stars in our sample are in good agreement with the theoreticalexpectations. In particular, the stars cooler than $\sim$15 000 K follow neatlythe theoretical predictions on the radius, log $g$, and luminosity forhelium-normal models. In $\omega$ Cen, we show that the majority of thesecooler HB stars cannot originate from a helium-enriched population with$Y>$0.35. The properties of the hotter stars (radii and luminosities) are stillin reasonable agreement with theoretical expectations, but the individualmeasurements have a large scatter. We use three different diagnostics, namelythe position of the G-jump and changes in metallicity and helium abundances toplace the onset of diffusion in the stellar atmospheres at Teff between 11 and11.5 kK. Our sample includes two stars known as photometric variables, weconfirm one to be a bona fide extreme HB object but the other is a bluestraggler star. Finally, unlike what has been reported in the literature, we donot find significant differences between the properties of the stars in bothclusters. We showed that our analysis method combining MUSE spectra and HSTphotometry of HB stars in GC is a powerful tool to characterize their stellarproperties.

SHOTGLAS II. MUSE spectroscopy of blue horizontal branch stars in the core of $\omega$ Centauri and NGC 6752