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Hard tail detection in the LMXB 4U1636-53 from INTEGRAL

M. Fiocchi, A. Bazzano, P. Ubertini, M. federici

astro-pharXiv:astro-ph/0610320

Abstract

Recent INTEGRAL observations and archival BeppoSAX data have been analyzed to deeply investigate the hard X-ray behavior of the neutron star, atoll type, low mass X-ray Binary 4U1636-53. Our investigation in three different periods outline three corresponding different sates. Infact, the source was detected in both the canonical high and low state and moreover in one occasion ∫egral spectrum shows, for first time in this source, a hard tail dominating the emission above 30 keV. This spectrum is fitted as the sum of a Comptonized component similar to soft state and a power-law component (Γ=2.76), indicating the presence of a non thermal electron distribution of velocities.

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