43 research outputs found
The X-ray Telescope of the CAST Experiment
The CERN Axion Solar Telescope (CAST) searches for solar axions employing a 9
Tesla superconducting dipole magnet equipped with 3 independent detection
systems for X-rays from axion-photon conversions inside the 10 m long magnetic
field. Results of the first 6 months of data taking in 2003 imply a 95 % CL
upper limit on the axion-photon coupling constant of 1.16x10(-10) GeV(-1) for
axion masses < 0.02 eV. The most sensitive detector of CAST is a X-ray
telescope consisting of a Wolter I type mirror system and a fully depleted
pn-CCD as focal plane detector. Exploiting the full potential of background
suppression by focussing X-rays emerging from the magnet bore, the axion
sensitivity obtained with telescope data taken in 2004, for the first time in a
controlled laboratory experiment, will supersede axion constraints derived from
stellar energy loss arguments.Comment: 5 pages, 9 figure
News, intelligence and 'little lies' : rumours between the Cherokees and the British 1740-1785
Rumour and information are one of the most fundamental ways in which people engage
with one another. Rumours can change the way that individuals and groups see each other
and the actions that they take. Sociologists and anthropologists have long used rumour as a
way to explore the experiences of their subjects. Historians of early America have, in recent
years, begun to make use of rumour as a way of examining the, often hidden, world of
interactions between American Indians and white Europeans. This thesis will expand upon
this work by exploring the changing role of rumour within an intercultural relationship over
several decades. This thesis will focus on rumour in the relationship between the Cherokee
Nation and the colonists of the British Empire. It will explore the ways that rumour
influenced these interactions and the impact of the rapidly changing backcountry
environment of the latter eighteenth century, both on rumour and on the wider Cherokee-
British relationship. This thesis will argue that rumour shifted in the course of the
eighteenth century from being a diplomatic tool which could be used- either to create
further panic and confusion or to calm and smooth over problems- to an uncontrollable
force which would deepen and exacerbate the divisions between Cherokees and the
British. Rumour played an important role in politics and society in the eighteenth century
backcountry and its changing function offers a way to better understand the shifting
currents of life in early America
The dynamical state of the Coma cluster with XMM-Newton
We present in this paper a substructure and spectroimaging study of the Coma
cluster of galaxies based on XMM-Newton data. XMM-Newton performed a mosaic of
observations of Coma to ensure a large coverage of the cluster. We add the
different pointings together and fit elliptical beta-models to the data. We
subtract the cluster models from the data and look for residuals, which can be
interpreted as substructure. We find several significant structures: the
well-known subgroup connected to NGC4839 in the South-West of the cluster, and
another substructure located between NGC 4839 and the centre of the Coma
cluster. Constructing a hardness ratio image, which can be used as a
temperature map we see that in front of this new structure the temperature is
significantly increased (higher or equal 10 keV). We interpret this temperature
enhancement as the result of heating as this structure falls onto the Coma
cluster. We furthermore reconfirm the filament-like structure South-East of the
cluster centre. This region is significantly cooler than the mean cluster
temperature. We estimate the temperature of this structure to be equal or below
1keV. A possible scenario to explain the observed features is stripping caused
by the infall of a small group of galaxies located around the two galaxies
NGC4921 and NGC4911 into the Coma cluster with a non-zero impact parameter. We
also see significant X-ray depressions North and South-East of NGC4921, which
might either be linked to tidal forces due to the merger with the Western
structure or connected to an older cluster merger.Comment: 12 pages, 4 figures accepted for publication in A&
The eROSITA X-ray telescope on SRG
eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. By the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. At the end of this program, the eROSITA all-sky survey in the soft X-ray band (0.2-2.3 keV) will be about 25 times more sensitive than the ROSAT All-Sky Survey, while in the hard band (2.3-8 keV) it will provide the first ever true imaging survey of the sky. The eROSITA design driving science is the detection of large samples of galaxy clusters up to redshifts z > 1 in order to study the large-scale structure of the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGNs, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astrophysical phenomena, including X-ray binaries, active stars, and diffuse emission within the Galaxy. Results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. With this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements