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Correlated X-ray spectral and fast-timing behaviour of 4U 1636-53.
van der Klis, M.; Prins, S.
We present a study of the persistent X-ray emission from the low-mass X-ray binary 4U 1636-53 based on the entire archival EXOSAT ME data set. We performed a homogeneous analysis of all five EXOSAT observations in terms of the correlated rapid X-ray variability and X-ray spectral properties by means of power spectra, and colour-colour and hardness…
Doppler imaging of stellar surface structure. III. The X-ray source HD 116544 = IN Virginis.
Strassmeier, K. G.
We present the first Doppler image of the EXOSAT X-ray source EXO 1321.8-0203, recently identified to be a chromospherically active star exhibiting periodic light variations and consequently named INVirginis. Our high-resolution spectra show INVirginis to be a single-lined spectroscopic binary with an orbital period of 8.2 days, very strong CaII e…
The ultraviolet to X-ray spectrum of the Seyfert 1 galaxy E 1615+061: accretion disk and reflection models.
Piro, L.; Perola, G. C.; Fiore, F. +4 more
The Seyfert 1 galaxy E 1615+061 is a candidate for the strongest variability in soft X-rays, changing from a very steep high state ({GAMMA}=~4), as implied by HEAO1 observations performed in 1977, to a two orders of magnitude dimmer state with a flatter spectrum ({GAMMA}=~2), as observed by EXOSAT in 1985. In this paper we present the results of a…
Correlation between variability time scale and X-ray spectral index in AGN.
Wilms, J.; Staubert, R.; Koenig, M.
We have analysed EXOSAT ME X-ray light curves of a sample of AGN assuming a stochastic process in these sources. The result is a significant anti-correlation between the relaxation timescale τ, derived from this stochastic model fit, and the photon index {GAMMA} of the X-ray spectrum. This establishes for the first time a relationship between vari…