Cassiopeia A ( Cas A ) as the nearby young remnant of a core-collapse supernova is the best candidate for astrophysical studies in supernova explosion and its environment .
We studied hard X-ray emissions from Cas A using the ten-year data of INTEGRAL observations , and first detected non-thermal continuum emission from the source up to 220 keV .
The ^ { 44 } Ti line emissions at 68 and 78 keV are confirmed by our observations with a mean flux of \sim ( 2.2 \pm 0.4 ) \times 10 ^ { -5 } ph cm ^ { -2 } s ^ { -1 } , corresponding to a ^ { 44 } Ti yield in Cas A of ( 1.3 \pm 0.4 ) \times 10 ^ { -4 } M _ { \odot } .
The continuum emission from 3 – 500 keV can be fitted with a thermal bremsstrahlung of kT \sim 0.79 \pm 0.08 keV plus a power-law model of \Gamma \sim 3.13 \pm 0.03 .
The non-thermal emission from Cas A is well fitted with a power-law model without a cutoff up to 220 keV .
This radiation characteristic is inconsistent with the diffusive shock acceleration models with the remnant shock velocity of only 5000km s ^ { -1 } .
The central compact object in Cas A can not contribute to the emission above 80 keV significantly .
Some possible physical origins of the non-thermal emission above 80 keV from the remnant shock are discussed .
We deduce that the asymmetrical supernova explosion scenario of Cas A is a promising scenario to produce high energy synchrotron radiation photons , where a part of ejecta with the velocity of \sim 0.1 c and opening angle of \sim 10 ^ { \circ } can account for the 100-keV emission , consistent with the ” jet ” observed in Cas A .