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07 February 2025
 
  » arxiv » 1605.0360

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Hard X-ray emissions from Cassiopeia A observed by INTEGRAL
Wei Wang ; Zhuo Li ;
Date 2 May 2016
AbstractCassiopeia 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 $sim (2.2pm 0.4) imes 10^{-5}$ ph cm$^{-2}$ s$^{-1}$, corresponding to a $^{44}$Ti yield in Cas A of $(1.3pm 0.4) imes 10^{-4}$ ms. The continuum emission from 3 -- 500 keV can be fitted with a thermal bremsstrahlung of $kTsim 0.79pm 0.08$ keV plus a power-law model of $Gamma sim 3.13pm 0.03$. 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 cannot 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 $sim 0.1c$ and opening angle of $sim10^circ$ can account for the 100-keV emission, consistent with the "jet" observed in Cas A.
Source arXiv, 1605.0360
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