  Solar hard X-rays (HXRs) appear in the form of either footpoint sources or
coronal sources, and each individual source provides its own critical
information on acceleration of nonthermal electrons and plasma heating. Earlier
studies found that the HXR emission in some events manifests a broken-up
power-law spectrum with the break energy around a few hundred keV based on
spatially-integrated spectral analysis, without distinguishing the
contributions from individual sources. In this paper, we report the broken-up
spectra of a coronal source studied using HXR data recorded by Ramaty High
Energy Solar Spectroscopic Imager (RHESSI) during the SOL2017-09-10T16:06 (GOES
class X8.2) flare. The flare occurred behind the western limb with its
foot-point sources mostly occulted by the disk, and we could clearly identify
such broken-up spectra pertaining solely to the coronal source during the flare
peak time and after. Since a significant pileup effect on the RHESSI spectra is
expected for this intense solar flare, we have selected the pileup correction
factor, $p = 2$. In this case, we found the resulting \textit{RHESSI}
temperature (~30 MK) similar to the GOES soft X-ray temperature and break
energies of 45--60 keV. Above the break energy the spectrum hardens with time
from spectral index of 3.4 to 2.7, and the difference of spectral indices below
and above the break energy increases from 1.5 to 5 with time. We, however, note
that when $p = 2$ is assumed, a single power-law fitting is also possible with
the RHESSI temperature higher than the GOES temperature by ~10 MK. Possible
scenarios for the broken-up spectra of the loop-top HXR source are briefly
discussed.

Solar and Stellar Astrophysics