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X-ray Spectrum of the Black Hole Candidate X1755-338

H. C. Pan·G. K. Skinner·R. A. Sunyaev·K. N. Borozdin
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Abstract

We report the first detection of a hard power-law tail in the X-ray spectrum of the black hole candidate (BHC) binary X1755-338, which was observed in 1989 March-September during the TTM Galactic Centre survey. In addition, an ultrasoft thermal component with a temperature of ~1.1-1.4 keV was also detected. We demonstrate that the soft and hard X-ray components of X1755-338 vary independently, as in the spectra of the well known BHCs LMC X-1, LMC X-3 and GX339-4 in their high (intensity) state. If the hard tail observed from X1755-338 is generated near the black hole by energetic electrons up-scattering low energy photons, the un-correlated variations imply that the soft X-rays from accretion disc may not be the main photon seeds needed for inverse Comptonization. The TTM observations strongly suggest that X1755-338 does indeed belong to the family of BHCs.

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H. C. Pan, G. K. Skinner, R. A. Sunyaev, K. N. Borozdin. 1995-02-27. X-ray Spectrum of the Black Hole Candidate X1755-338. https://doi.org/10.1093/mnras%2F274.1.l15

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