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The average X-ray/gamma-ray spectrum of radio-quiet Seyfert 1s
Zdziarski, Andrzej A.; George, Ian M.; Gondek, Dorota +5 more
We have obtained the average 1-500 keV spectrum of radio-quiet Seyfert 1s using data from EXOSAT, Ginga, HEAO-1 and GRO OSSE. The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE, confirming results from an earlier Ginga/OSSE sample. The average spectrum is well fitted by a power-law X-ray …
Periodic UV modulation of X1850-087: a double degenerate binary in the globular cluster NGC 6712?
van Paradijs, J.; Charles, P. A.; Naylor, T. +3 more
We report the discovery with the Hubble Space Telescope (HST) of a short-period (20.6 min) UV modulation in X1850-087, the luminous X-ray source in the globular cluster NGC 6712. The low-amplitude modulation (0.044+/-0.007 mag) is not detected in archival X-ray observations with EXOSAT. We compare the properties of X1850-087 with the 11-min binary…
The origin of the correlation between the UV and X-rays in NGC 4151
Zdziarski, Andrzej A.; Magdziarz, Pawel
We propose that the UV/X-ray correlation observed in NGC 4151 by EXOSAT and IUE is due to re-emission of the X-ray flux absorbed by cold clouds in the line of sight. This transmission model satisfies the energy balance, provides a good fit to the X-ray and UV data, and predicts no Compton reflection of X-rays (as observed). Alternatively, the corr…