530 research outputs found
Introduction:Religious Dimensions of Conspiracy Theories
In this introduction to Religious Dimensions of Conspiracy Theories, the editors explain the rationale for the book and introduce a set of definitions and methodological principles for the study of conspiracy theories and religion. In order to better understand both the continuities and discontinuities between old and new forms of conspiracy theories, especially as they connect with ‘religion’, ‘magic’, and ‘the occult’, the introduction advocates a historical and comparative approach operating in dialogue with disciplines such as anthropology, sociology, media studies, and psychology. It also provides a short introduction to the book’s chapters, which include cases spanning from the 2nd century BCE to the present day and locations as diverse as Zambia, Japan, Italy, and Norway
Correlations between X-ray Spectral and Timing Characteristics in Cyg X-2
Correlations between the quasi-periodic oscillations (QPOs) and the spectral
power-law index have been reported for a number of black hole candidate sources
and for four neutron star (NS) sources, 4U 0614+09, 4U 1608-52, 4U 1728-34 and
Sco X-1. An examination of QPO frequencies and index relationship in Cyg X-2 is
reported herein. The RXTE spectrum of Cyg X-2 can be adequately represented by
a simple two-component model of Compton up-scattering with a soft photon
electron temperature of about 0.7 keV and an iron K-line. Inferred spectral
power-law index shows correlation with the low QPO frequencies. We find that
the Thomson optical depth of the Compton cloud (CC) tau, in framework of
spherical geometry, is in the range of ~4-6, which is consistent with the
neutron star's surface being obscured. The NS high frequency pulsations are
presumably suppressed as a result of photon scattering off CC electrons because
of such high values of tau. We also point out a number of similarities in terms
timing (presence of low and high frequency QPOs) and spectral (high CC optical
depth and low CC plasma temperature) appearances between Cyg X-2 and Sco X-1.Comment: 7 pages, 4 figures, accepted for publication in ApJ (October 1, 2007,
v667n2 issue
The broad band spectral properties of binary X-ray pulsars
The X-ray telescopes on board BeppoSAX are an optimal set of instruments to
observe bright galactic binary pulsars. These sources emit very hard and quite
complex X-ray spectra that can be accurately measured with BeppoSAX between 0.1
and 200 keV. A prototype of this complexity, the source Her X-1, shows at least
seven different components in its spectrum. A broad band measure is therefore
of paramount importance to have a thorough insight into the physics of the
emitting region. Moreover the detection of cyclotron features, when present,
allows a direct and highly significant measure of the magnetic field intensity
in the emission region. In this paper we briefly report the results obtained
with BeppoSAX on this class of sources, with emphasis on the detection and on
the measured properties of the cyclotron lines.Comment: 10 Latex pages, 4 figures, uses psfig.sty. Accepted for publication
in Advances in Space Research, in Proceedings of 32nd Scientific Assembly of
COSPAR - Symposium E1.1: "Broad-Band X-ray Spectroscopy of Cosmic Sources
BeppoSAX observations of the atoll x-ray binary 4U0614+091
We report the first simultaneous measurement of the broad band X-ray (0.3-150 keV) spectrum of the neutron star x-ray binary 4U0614+091. Our data confirm the presence of a hard x-ray tail that can be modeled as thermal Comptonization of low-energy photons on electrons having a very high temperature, greater than 220 keV, or as a non-thermal powerlaw. We detected a spectral feature that can be interpreted as reprocessing, via Compton reflection, of the direct emission by an optically-thick disk and found a correlation between the photon index of the power-law tail and the fraction of radiation reflected which is similar to the correlation found for black hole candidate x-ray binaries and Seyfert galaxies
Broadband observations of the X-ray burster 4U 1705-44 with BeppoSAX
4U 1705-44 is one of the most-studied type I X-ray burster and Atoll sources.
This source represents a perfect candidate to test different models proposed to
self-consistently track the physical changes occurring between different
spectral states because it shows clear spectral state transitions. The
broadband coverage, the sensitivity and energy resolution of the BeppoSAX
satellite offers the opportunity to disentangle the components that form the
total X-ray spectrum and to study their changes according to the spectral
state. Using two BeppoSAX observations carried out in August and October 2000,
respectively, for a total effective exposure time of about 100 ks, we study the
spectral evolution of the source from a soft to hard state. Energy spectra are
selected according to the source position in the color-color diagram (CCD)
Results. We succeeded in modeling the spectra of the source using a physical
self-consistent scenario for both the island and banana branches (the double
Comptonization scenario). The components observed are the soft Comptonization
and hard Comptonization, the blackbody, and a reflection component with a broad
iron line. When the source moves from the banana state to the island state, the
parameters of the two Comptonization components change significantly and the
blackbody component becomes too weak to be detected. We interpret the soft
Comptonization component as emission from the hot plasma surrounding the
neutron star, hard Comptonization as emission from the disk region, and the
blackbody component as emission from the inner accretion disk. The broad
feature in the iron line region is compatible with reflection from the inner
accretion disk.Comment: 8 pages, 10 figures, accepted for publication by A&
A relativistic iron emission line from the neutron star low-mass X-ray binary GX 3+1
We present the results of a spectroscopic study of the Fe K{\alpha} emission
of the persistent neutron-star atoll low-mass X-ray binary and type I X-ray
burster GX 3+1 with the EPIC-PN on board XMM-Newton. The source shows a flux
modulation over several years and we observed it during its fainter phase,
which corresponds to an X-ray luminosity of Lx~10^37 ergs/s. When fitted with a
two-component model, the X-ray spectrum shows broad residuals at \sim6-7 keV
that can be ascribed to an iron K{\alpha} fluorescence line. In addition, lower
energy features are observed at \sim3.3 keV, \sim3.9 keV and might originate
from Ar XVIII and Ca XIX. The broad iron line feature is well fitted with a
relativistically smeared profile. This result is robust against possible
systematics caused by instrumental pile-up effects. Assuming that the line is
produced by reflection from the inner accretion disk, we infer an inner disk
radius of \sim25 Rg and a disk inclination of 35{\deg} < i < 44{\deg}.Comment: 4 pages, 3 figures Accepted for publication in Astronomy and
Astrophysic
Discovery of a Hard X-Ray Source, SAX J0635+0533, in the Error Box of the Gamma-Ray Source 2EG 0635+0521
We have discovered an x-ray source, SAX J0635+0533, with a hard spectrum
within the error box of the GeV gamma-ray source in Monoceros, 2EG J0635+0521.
The unabsorbed x-ray flux is 1.2*10^-11 erg cm^-2 s^-1 in the 2-10 keV band.
The x-ray spectrum is consistent with a simple powerlaw model with absorption.
The photon index is 1.50 +/- 0.08 and we detect emission out to 40 keV. Optical
observations identify a counterpart with a V-magnitude of 12.8. The counterpart
has broad emission lines and the colors of an early B type star. If the
identification of the x-ray/optical source with the gamma-ray source is
correct, then the source would be a gamma-ray emitting x-ray binary.Comment: Accepted to the Astrophysical Journal, 8 page
Testing reflection features in 4U 1705-44 with XMM-Newton, BeppoSAX and RXTE in the hard and soft state
We use data of the bright atoll source 4U 1705-44 taken with XMM-Newton,
BeppoSAX and RXTE both in the hard and in the soft state to perform a
self-consistent study of the reflection component in this source. Although the
data from these X-ray observatories are not simultaneous, the spectral
decomposition is shown to be consistent among the different observations, when
the source flux is similar. We therefore select observations performed at
similar flux levels in the hard and soft state in order to study the spectral
shape in these two states in a broad band (0.1-200 keV) energy range, with good
energy resolution, and using self-consistent reflection models. These
reflection models provide a good fit for the X-ray spectrum both in the hard
and in the soft state in the whole spectral range. We discuss the differences
in the main spectral parameters we find in the hard and the soft state,
respectively, providing evidence that the inner radius of the optically thick
disk slightly recedes in the hard state.Comment: Accepted for publication in A&A, 20 pages, 12 figure
Swift monitoring of Cygnus X-2: investigating the NUV-X-ray connection
The neutron star X-ray binary (NSXRB) Cygnus X-2 was observed by the Swift
satellite 51 times over a 4 month period in 2008 with the XRT, UVOT, and BAT
instruments. During this campaign, we observed Cyg X-2 in all three branches of
the Z track (horizontal, normal, and flaring branches). We find that the NUV
emission is uncorrelated with the soft X-ray flux detected with the XRT, and is
anticorrelated with the BAT X-ray flux and the hard X-ray color. The observed
anticorrelation is inconsistent with simple models of reprocessing as the
source of the NUV emission. The anticorrelation may be a consequence of the
high inclination angle of Cyg X-2, where NUV emission is preferentially
scattered by a corona that expands as the disk is radiatively heated.
Alternatively, if the accretion disk thickens as Cyg X-2 goes down the normal
branch toward the flaring branch, this may be able to explain the observed
anticorrelation. In these models the NUV emission may not be a good proxy for
in the system. We also discuss the implications of using Swift/XRT to
perform spectral modeling of the continuum emission of NSXRBs.Comment: 10 pages, 8 figures. ApJ Accepte
SEM/EDX analysis of stomach contents of a sea slug snacking on a polluted seafloor reveal microplastics as a component of its diet
Understanding the impacts of microplastics on living organisms in aquatic habitats is one of the hottest research topics worldwide. Despite increased attention, investigating microplastics in underwater environments remains a problematic task, due to the ubiquitous occurrence of microplastic, its multiple modes of interactions with the biota, and to the diversity of the synthetic organic polymers composing microplastics in the field. Several studies on microplastics focused on marine invertebrates, but to date, the benthic sea slugs (Mollusca, Gastropoda, Heterobranchia) were not yet investigated. Sea slugs are known to live on the organisms on which they feed on or to snack while gliding over the sea floor, but also as users of exogenous molecules or materials not only for nutrition. Therefore, they may represent a potential biological model to explore new modes of transformation and/or management of plastic, so far considered to be a non-biodegradable polymer. In this study we analysed the stomachal content of Bursatella leachii, an aplysiid heterobranch living in the Mar Piccolo, a highly polluted coastal basin near Taranto, in the northern part of the Ionian Sea. Microplastics were found in the stomachs of all the six sampled specimens, and SEM/EDX analyses were carried out to characterize the plastic debris. The SEM images and EDX spectra gathered here should be regarded as a baseline reference database for future investigations on marine Heterobranchia and their interactions with microplastics
- …