HEXTE Studies of Sco X-1 Spectra: Detections of Hard X-Ray Tails Beyond 200 keV

Abstract

Using the HEXTE experiment on-board the RXTE satellite, we performed a search for hard X-ray tails in Sco X-1 spectra. We found strong evidence for the presence of such a non-thermal component on several occasions. Using the PCA/RXTE we were able to track the position of the source along the Z diagram, and we observed that the presence of the hard X-ray tail is not confined to a particular region. However, we found a correlation between the power law index of the non-thermal component and the position of the source in the Z diagram, suggesting that the hard X-ray spectrum (i.e., E > 50 keV) becomes flatter as the mass accretion rate increases. We were also able to study the temporal variation of the appearance/absence of the hard X-ray component. With our derived luminosities, we were also able to test the idea that X-ray luminosities can be used to distinguish between X-ray binary systems containing neutron stars and black holes.

arXiv comment6 pages, 2 figures; Presented at the 33rd COSPAR Scientific Assembly (Warsaw, Poland, 2000 July); Accepted for publication in Advances in Space Research

References in corpus (5)

• In-flight Performance of the High Energy X-ray Timing Experiment on the Rossi X-ray Timing Explorer
• Hard X-ray Emission From Low Mass X-ray Binaries
• The Discovery of a State Dependent Hard Tail in the X-ray Spectrum of the Luminous Z-source GX 17+2
• The X-ray Spectrum of SAX J1808.4-3658
• HEXTE Detections of Hard X-Ray Tails in Sco X-1

Cited by in corpus (4)

• An XMM Observation of IGR J16320-4751=AX J1631.9-4752
• The Galactic LMXB Population and the Galactic Centre Region
• INTEGRAL observations of Sco X-1: evidence for Comptonization up to 200 keV
• Long Term Studies of Z sources with HEXTE/RXTE