161 research outputs found
Analysis of the Data from Compton X-ray Polarimeters which Measure the Azimuthal and Polar Scattering Angles
X-ray polarimetry has the potential to make key-contributions to our
understanding of galactic compact objects like binary black hole systems and
neutron stars, and extragalactic objects like active galactic nuclei, blazars,
and Gamma Ray Bursts. Furthermore, several particle astrophysics topics can be
addressed including uniquely sensitive tests of Lorentz invariance. In the
energy range from 10 keV to several MeV, Compton polarimeters achieve the best
performance. In this paper we evaluate the benefit that comes from using the
azimuthal and polar angles of the Compton scattered photons in the analysis,
rather than using the azimuthal scattering angles alone. We study the case of
an ideal Compton polarimeter and show that a Maximum Likelihood analysis which
uses the two scattering angles lowers the Minimum Detectable Polarization (MDP)
by ~20% compared to a standard analysis based on the azimuthal scattering
angles alone. The accuracies with which the polarization fraction and the
polarization direction can be measured improve by a similar amount. We conclude
by discussing potential applications of Maximum Likelihood analysis methods for
various polarimeter experiments.Comment: Accepted for publication in Astroparticle Physics (14 pages, 4
figures
Time Dependent Modeling of the Markarian 501 X-ray and TeV Gamma-Ray Data Taken During March and April, 1997
If the high-energy emission from TeV blazars is produced by the Synchrotron
Self-Compton (SSC) mechanism, then simultaneous X-ray and Gamma-ray
observations of these objects are a powerful probe of the electron (and/or
positron) populations responsible for this emission. Understanding the emitting
particle distributions and their evolution in turn allow us to probe physical
conditions in the inner blazar jet and test, for example, various acceleration
scenarios. By constraining the SSC emission model parameters, such observations
also allow us to predict the intrinsic (unabsorbed) Gamma-ray spectra of these
sources, a major uncertainty in current attempts to use the observed Gamma-ray
spectra to constrain the intensity of the extragalactic background at
optical/infrared wavelengths. As a next step in testing the SSC model and as a
demonstration of the potential power of coordinated X-ray and Gamma-ray
observations, we attempt to model in detail the X-ray and Gamma-ray light
curves of the TeV Blazar Mrk 501 during its April-May 1997 outburst using a
time dependent SSC emission model. Extensive, quasi-simultaneous X-ray and
gamma-ray coverage exists for this period. We discuss and explore
quantitatively several of the flare scenarios presented in the literature. We
show that simple two-component models (with a soft, steady X-ray component plus
a variable SSC component) involving substantial pre-acceleration of electrons
to Lorentz factors on the order of 1E+5 describe the data train surprisingly
well. All considered models imply an emission region that is strongly out of
equipartition and low radiative efficiencies (ratio between kinetic jet
luminosity and comoving radiative luminosity) of 1 per-mill and less.Comment: 16 pages, Refereed Manuscript. Minor changes to previous versio
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