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SPECTRUM OF RELATIVISTIC AND SUBRELATIVISTIC COSMIC RAYS IN THE 100 pc CENTRAL REGION
Dogiel, V. A.,Chernyshov, D. O.,Kiselev, A. M.,Nobukawa, M.,Cheng, K. S.,Hui, C. Y.,Ko, C. M.,Nobukawa, K. K.,Tsuru, T. G. IOP Publishing 2015 The Astrophysical journal Vol.809 No.1
<P>From the rate of hydrogen ionization and the gamma-ray flux, we derived the spectrum of relativistic and subrelativistic cosmic rays (CRs) nearby and inside the molecular cloud Sgr B2 near the Galactic Center. We studied two cases of CR propagation in molecular clouds: free propagation and scattering of particles by magnetic fluctuations excited by the neutral gas turbulence. We showed that in the latter case CR propagation inside the cloud can be described as diffusion with a coefficient of similar to 3 x 10(27) cm(2) s(-1). For the case of hydrogen ionization by subrelativistic protons, we showed that their spectrum outside the cloud is quite hard with a spectral index of delta > -1. The energy density of subrelativistic protons (>50 eV cm(-3)) is one order of magnitude higher than that of relativistic CRs. These protons generate the 6.4 keV emission from Sgr B2, which was about 30% of the flux observed by Suzaku in 2013. Future observations for the period after 2013 may discover the background flux generated by subrelativistic CRs in Sgr B2. Alternatively, hydrogen ionization of the molecular gas in Sgr B2 may be caused by high energy electrons. We showed that the spectrum of electron bremsstrahlung is harder than the observed continuum from Sgr B2, and in principle, this X-ray component provided by electrons could be seen from the INTEGRAL data as a stationary high energy excess above the observed spectrum E-x(-2).</P>
CHANDRA DETECTION OF A NEW DIFFUSE X-RAY COMPONENT FROM THE GLOBULAR CLUSTER 47 TUCANAE
Wu, E. M. H.,Hui, C. Y.,Kong, A. K. H.,Tam, P. H. T.,Cheng, K. S.,Dogiel, V. A. University of Chicago Press for the American Astro 2014 ASTROPHYSICAL JOURNAL LETTERS - Vol.788 No.2
In re-analyzing the archival Chandra data of the globular cluster 47 Tucanae, we have detected a new diffuse X-ray emission feature within the half-mass radius of the cluster. The spectrum of the diffuse emission can be described by a power-law model plus a plasma component with photon index Gamma similar to 1.0 and plasma temperature kT similar to 0.2 keV. While the thermal component is apparently uniform, the non-thermal contribution falls off exponentially from the core. The observed properties could possibly be explained in the context of multiple shocks resulting from the collisions among the stellar wind in the cluster and the inverse Compton scattering between the pulsar wind and the relic photons.