Long-term studies of Z sources with hexte/rxte

Scritto il 06 Giu 2012 alle 01:40 in Pubblicazioni

Using the High Energy X-Ray Timing Experiment (HEXTE) on-board the Rossi
XRay Timing Explorer (RXTE) we perform a spectral study of the Z
sources, with emphasis on the production of hard X-ray tails (HXT). Data
from the Proportional Counter Array (PCA) were used to determine the
position of the source in the Z diagram. We present current results of
this ongoing study. Previous results show that, at least for Sco X-1,
there is no correlation between the presence of a HXT and the position
on the Z. For GX 5-1, in 1 out of 12 observations, the presence of a HXT
is compelling, although…

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Testing the Standard Model of Active Galactic Nuclei through Quasar Variability

Scritto il 06 Giu 2012 alle 01:39 in Pubblicazioni

The standard model of Active Galactic Nuclei (AGNs) predicts that Type 2
AGNs and Type 1 AGNs only differ in the orientation of a dust torus,
which does or does not allow one to observe the central region. If the
model is correct, the time-scales and the amplitudes of observed
temporal variations should be different between obscured and unobscured
objects. In order to test this hypothesis, we started a multi-wavelength
(BRIJK<SUB>s</SUB>) monitoring campaign of a sample of quasars of both
types. Here we present the data and preliminary results of that project.