722 research outputs found
A Pointing Solution for the Medium Size Telescopes for the Cherenkov Telescope Array
An important aspect of the calibration of the Cherenkov Telescope Array is
the pointing, which enables an exact alignment of each telescope and therefore
allows to transform a position in the sky to a point in the plane of the
Cherenkov camera and vice versa. The favoured approach for the pointing
calibration of the medium size telescopes (MST) is the installation of an
optical CCD-camera in the dish of the telescope that captures the position of
the Cherenkov camera and of the stars in the night sky simultaneously during
data taking. The adaption of this approach is presented in this proceeding.Comment: 6 pages, 9 figures, Proceedings of the 6th International Symposium on
High-Energy Gamma-Ray Astronomy (Gamma2016
The Active Mirror Control of the MAGIC Telescope
One of the main design goals of the MAGIC telescopes is the very fast
repositioning in case of Gamma Ray Burst (GRB) alarms, implying a low weight of
the telescope dish. This is accomplished by using a space frame made of carbon
fiber epoxy tubes, resulting in a strong but not very rigid support structure.
Therefore it is necessary to readjust the individual mirror tiles to correct
for deformations of the dish under varying gravitational load while tracking an
object. We present the concept of the Active Mirror Control (AMC) as
implemented in the MAGIC telescopes and the actual performance reached.
Additionally we show that also telescopes using a stiff structure can benefit
from using an AMC.Comment: Contribution to the 30th ICRC, Merida, Mexico, July 2007 on behalf of
the MAGIC Collaboratio
A method to measure the mirror reflectivity of a prime focus telescope
We have developed a method to measure the mirror reflectivity of telescopes. While it is relatively easy to measure the local reflectivity of the mirror material, it is not so straightforward to measure the amount of light that it focuses in a spot of a given diameter. Our method is based on the use of a CCD camera that is fixed on the mirror dish structure and observes simultaneously part of the telescope's focal plane and the sky region around its optical axis. A white diffuse reflecting disk of known reflectivity is fixed in the telescopes focal plane. During a typical reflectivity measurement the telescope is directed to a selected star. The CCD camera can see two images of the selected star, one directly and another one as a spot focused by the mirror on the white disk. The ratio of the reflected starlight integrated by the CCD from the white disk to the directly measured one provides a precise result of the product of (mirror area x mirror reflectivity)
Gamma-ray burst observations with new generation imaging atmospheric Cerenkov Telescopes in the FERMI era
After the launch and successful beginning of operations of the FERMI
satellite, the topics related to high-energy observations of gamma-ray bursts
have obtained a considerable attention by the scientific community.
Undoubtedly, the diagnostic power of high-energy observations in constraining
the emission processes and the physical conditions of gamma-ray burst is
relevant. We briefly discuss how gamma-ray burst observations with ground-based
imaging array Cerenkov telescopes, in the GeV-TeV range, can compete and
cooperate with FERMI observations, in the MeV-GeV range, to allow researchers
to obtain a more detailed and complete picture of the prompt and afterglow
phases of gamma-ray bursts.Comment: 9 pages, two figures. Proceeding for the 6th "Science with the New
Generation of High Energy Gamma-Ray Experiments" worksho
Investigation of the marine compound spongistatin 1 links the inhibition of PKCα translocation to nonmitotic effects of tubulin antagonism in angiogenesis
The aims of the study were to meet the demand of new tubulin antagonists with fewer side effects by characterizing the antiangiogenic properties of the experimental compound spongistatin 1, and to elucidate nonmitotic mechanisms by which tubulin antagonists inhibit angiogenesis. Although tubulin-inhibiting drugs and their antiangiogenic properties have been investigated for a long time, surprisingly little is known about their underlying mechanisms of action. Antiangiogenic effects of spongistatin 1 were investigated in endothelial cells in vitro, including functional cell-based assays, live-cell imaging, and a kinome array, and in the mouse cornea pocket assay in vivo. Spongistatin 1 inhibited angiogenesis at nanomolar concentrations (IC50: cytotoxicity>50 nM, proliferation 100 pM, migration 1.0 nM, tube formation 1.0 nM, chemotaxis 1.0 nM, aortic ring sprouting 500 pM, neovascularization in vivo 10 ÎŒg/kg). Further, a kinome array and validating data showed that spongistatin 1 inhibits the phosphorylation activity of protein kinase Cα (PKCα), an essential kinase in angiogenesis, and its translocation to the membrane. Thus, we conclude that PKCα might be an important target for the antiangiogenic effects of tubulin antagonism. In addition, the data from the kinase array suggest that different tubulin antagonists might have individual intracellular actions.âRothmeier, A. S., Ischenko, I., Joore, J., Garczarczyk, D., Fušrst, R., Bruns, C. J., Vollmar, A. M., Zahler, S. Investigation of the marine compound spongistatin 1 links the inhibition of PKCα translocation to nonmitotic effects of tubulin antagonism in angiogenesis
The MAGIC Telescope and the Observation of Gamma Ray Bursts
The MAGIC Telescope, now taking data with an energy threshold well below 100
GeV, will soon be able to take full advantage of the fast slewing capability of
its altazimuthal mount. Exploiting the link with the GCN network, the MAGIC
Telescope could be one of the first ground-based experiments able to see the
prompt emission of Gamma Ray Bursts in the few tens of GeV region.Comment: 4 pages, 1 figure (-> 3 subfigures), class file (cimento.cls)
included. To appear in: "Gamma-Ray Bursts in the Afterglow Era: 4rd
Workshop", Rome 200
GRB 050713A: High Energy Observations of the GRB Prompt and Afterglow Emission
Swift discovered GRB 050713A and slewed promptly to begin observing with its
narrow field instruments 72.6 seconds after the burst onset, while the prompt
gamma-ray emission was still detectable in the BAT. Simultaneous emission from
two flares is detected in the BAT and XRT. This burst marks just the second
time that the BAT and XRT have simultaneously detected emission from a burst
and the first time that both instruments have produced a well sampled,
simultaneous dataset covering multiple X-ray flares. The temporal rise and
decay parameters of the flares are consistent with the internal shock
mechanism. In addition to the Swift coverage of GRB 050713A, we report on the
Konus-Wind (K-W) detection of the prompt emission in the energy range 18-1150
keV, an upper limiting GeV measurement of the prompt emission made by the MAGIC
imaging atmospheric Cherenkov telescope and XMM-Newton observations of the
afterglow. Simultaneous observation between Swift XRT and XMM-Newton produce
consistent results, showing a break in the lightcurve at T+~15ks. Together,
these four observatories provide unusually broad spectral coverage of the
prompt emission and detailed X-ray follow-up of the afterglow for two weeks
after the burst trigger. Simultaneous spectral fits of K-W with BAT and BAT
with XRT data indicate that an absorbed broken powerlaw is often a better fit
to GRB flares than a simple absorbed powerlaw. These spectral results together
with the rapid temporal rise and decay of the flares suggest that flares are
produced in internal shocks due to late time central engine activity.Comment: 22 pages, 6 tables, 10 figures; Submitted to the Astrophysical
Journa
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