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

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.

4 pages, compressed and uuencoded postscript file, to be published in MNRAS (Letters)

Cited by in corpus (7)

• WATCHDOG: A Comprehensive All-Sky Database of Galactic Black Hole X-ray Binaries
• An XMM-Newton Observation of 4U1755-33 in Quiescence: Evidence for a Fossil X-Ray Jet
• Optical Studies of the Transient Dipping X-ray Sources X1755-338 and X1658-298 in Quiescence
• Evolution of the X-Ray Jets from 4U 1755--33
• A Chandra Observation of the Diffuse Emission Centered on the Low Mass X-ray Binary 4U 1755-33
• What can we learn from the surface chemical composition of the optical companions of Soft X-ray transients?
• Spectral and timing properties of the black hole candidate X1755-338 observed in 1989-1995