| Abstract: | The Hitomi SXS spectrum of the Perseus cluster, with $sim$5 eV resolution in
the 2-9 keV band, offers an unprecedented benchmark of the atomic modeling and
database for hot collisional plasmas. It reveals both successes and challenges
of the current atomic codes. The latest versions of AtomDB/APEC (3.0.8), SPEX
(3.03.00), and CHIANTI (8.0) all provide reasonable fits to the broad-band
spectrum, and are in close agreement on best-fit temperature, emission measure,
and abundances of a few elements such as Ni. For the Fe abundance, the APEC and
SPEX measurements differ by 16%, which is 17 times higher than the statistical
uncertainty. This is mostly attributed to the differences in adopted
collisional excitation and dielectronic recombination rates of the strongest
emission lines. We further investigate and compare the sensitivity of the
derived physical parameters to the astrophysical source modeling and
instrumental effects. The Hitomi results show that an accurate atomic code is
as important as the astrophysical modeling and instrumental calibration
aspects. Substantial updates of atomic databases and targeted laboratory
measurements are needed to get the current codes ready for the data from the
next Hitomi-level mission. |
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