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Solar hard X-rays (HXRs) appear in the form of either footpoint sources orcoronal sources, and each individual source provides its own criticalinformation on acceleration of nonthermal electrons and plasma heating. Earlierstudies found that the HXR emission in some events manifests a broken-uppower-law spectrum with the break energy around a few hundred keV based onspatially-integrated spectral analysis, without distinguishing thecontributions from individual sources. In this paper, we report the broken-upspectra of a coronal source studied using HXR data recorded by Ramaty HighEnergy Solar Spectroscopic Imager (RHESSI) during the SOL2017-09-10T16:06 (GOESclass X8.2) flare. The flare occurred behind the western limb with itsfoot-point sources mostly occulted by the disk, and we could clearly identifysuch broken-up spectra pertaining solely to the coronal source during the flarepeak time and after. Since a significant pileup effect on the RHESSI spectra isexpected for this intense solar flare, we have selected the pileup correctionfactor, $p = 2$. In this case, we found the resulting \textit{RHESSI}temperature (~30 MK) similar to the GOES soft X-ray temperature and breakenergies of 45--60 keV. Above the break energy the spectrum hardens with timefrom spectral index of 3.4 to 2.7, and the difference of spectral indices belowand above the break energy increases from 1.5 to 5 with time. We, however, notethat when $p = 2$ is assumed, a single power-law fitting is also possible withthe RHESSI temperature higher than the GOES temperature by ~10 MK. Possiblescenarios for the broken-up spectra of the loop-top HXR source are brieflydiscussed.

Broken-up Spectra of the Loop-top Hard X-ray Source during a Solar Limb Flare