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The comptonized X-ray source X 1724-308 in the globular cluster Terzan 2

Stella, L.; Parmar, A. N.; Guainazzi, M. +3 more

We report on the BeppoSAX observation of the X-ray source X 1724-308 in the globular cluster Terzan 2. The broadband spectrum can be described as the superposition of a power-law with photon spectral index Gamma =~ 1.6-1.9 and a thermal component with typical temperature kT ~ 1 keV. X 1724-308 is detected in the PDS up to 150 keV with a S/N ratio …

Intraday variability in X-ray selected BL Lacertae objects

Wagner, S. J.; Heidt, J.

We present a study of the intraday variability behaviour of two samples of X-ray selected BL Lac objects, the EMSS and EXOSAT samples consisting of 22 and 11 sources, respectively. In both samples we were able to detect intraday variability in less than 40% of the sources only. The duty cycle (the fraction of time, when a BL Lac object is variable…

Discovery of a new 170 S X-ray pulsar 1SAX J1324.4-6200

Parmar, A. N.; Mineo, T.; Angelini, L. +2 more

We report the discovery with BeppoSAX of a new 170.84 +/- 0.04 s X-ray pulsar, XB 1323-619b, found serendipitously in the field of the X-ray binary XB 1323-619 in 1997 August. The source and periodicity are also detected in archival ASCA data taken in 1994. The X-ray spectrum is modeled by a power-law with a photon index of 1.0 +/- 0.4 and absorpt…

Analyzing short-term X-ray variability of Cygnus X-1 with Linear State Space Models

Pottschmidt, Katja; Wilms, Joern; Koenig, Michael +1 more

Cyg X-1 exhibits irregular X-ray variability on all measured timescales. The usually applied shot noise models describe the typical short-term behavior of this source by superposition of randomly occuring shots with a distribution of shot durations. We have reanalyzed EXOSAT ME observations of Cyg X-1\ using the more general Linear State Space Mod…

A comparison of the fast timing behaviour of 4U 1705-44 to that of 4U 1608-52 and Cygnus X-1

van der Klis, M.; Berger, M.

We studied the fast timing behaviour of the atoll source \leavevmode4U 1705-44 using the entire \mboxEXOSAT dataset, four observations covering a total of 230 000 seconds of 1-20 keV spectral and timing data. In one of the observations, \leavevmode4U 1705-44 was in a low intensity ``island'' state and had an unusually hard spectrum. The fast timin…

Broad band X-ray spectrum of Cygnus X-1

Rao, A. R.; Chitnis, V. R.; Agrawal, P. C.

We present the hard X-ray (20 - 100 keV) observations of Cygnus X-1 obtained using a large area balloon-borne Xenon filled Multi-anode Proportional Counter (XMPC) telescope. The observations were carried out during the gamma_2 state of the source and we obtain a power law photon index of 1.62+/-0.07. To constrain the spectral shape of the source, …