We analyze 3.5 years of public Fermi/LAT data around the position of the supernova remnant HB 21, where four point-like sources from the 2nd Fermi/LAT catalog are located. We determine that the ...gamma-ray source is produced by a single extended source. We model the observed morphology as a uniform circle. The spectral energy distribution is best described by a curved power law, with a maximum at 413 ± 11 MeV. We divide the circle into three regions defined by previously identified shocked molecular clouds, and find that one of these regions has a softer spectrum. The >3 GeV gamma-ray emission of the soft spectrum region is bow-shaped and coincident with the supernova remnant shell seen at radio wavelengths. We suggest that the gamma-ray emission from HB 21 can be understood as a combination of emission from shocked/illuminated molecular clouds, one of them coincident with the supernova remnant shell itself.
Telomeres are essential for chromosome stability, but their functions at specific cell-cycle stages are unknown. Telomeres are now shown to have a role in chromosome separation during mitosis. In ...telomeric DNA mutants of Tetrahymena thermophila, created by expression of a telomerase RNA with an altered template sequence, division of the germline nucleus was severely delayed or blocked in anaphase. The mutant chromatids failed to separate completely at the midzone, becoming stretched to up to twice their normal length. These results suggest a physical block in mutant telomere separation.
Massive star-forming regions assemble a large number of young stars with remnants of stellar evolution and a very dense environment. Therefore, particles accelerated in supernova remnants and pulsar ...wind nebulae encounter optimal conditions for interacting with target material and photon fields, and thus produce gamma-ray emission. However, observations are challenging because multiple phenomena may appear entangled within the resolution of current gamma-ray telescopes. We report on MAGIC observations aimed to understand the nature of the emission from the star-forming region W51 and the unidentified source HESS J1857+026. While gamma-ray emission from W51 is dominated by the interaction of the supernova remnant W51C with dense molecular clouds, HESS J1857+026 is associated to the pulsar wind nebula from PSR J1856+0245. However, an additional source is resolved north of HESSJ1857+026, with sufficient separation to determine that it cannot be powered by the same pulsar. We search for multiwavelength data to determine the origin of the new source.
Supernova remnants are a probable site of acceleration of particles via diffusive shock processes. High energies carried by electrons or protons are radiated into photons detectable from radio to γ ...rays. MAGIC has recently observed W51C, one of the most luminous galactic supernova remnants, and completed its spectrum between 50 GeV and 5 TeV. We modelled different processes for high energy photon emission of this source, and compared the predictions with the measured spectral energy distribution. It is plausible that hadrons are accelerated in the expansion front of this source, in interaction with the surrounding molecular cloud, and photons are produced in the decay of neutral mesons created in hadronic collisions.
We present an agile, hardware independent analysis methodology based on the spectral windows technique to detect and quantify the environmental activity concentration of artificial isotopes of ...interest. The method removes counts from Compton scattering, peak overlapping, intrinsic background and other unconsidered contributions to the spectral region where photopeaks from artificial elements are expected. Taking into account the varying concentration of 214Bi, 214Pb, and 212Pb, we compute the activity concentration of the artificial isotopes (when detectable), or a variable Minimum Detectable Activity Concentration (MDAC). This allows to set statistically robust early-warning levels. In the scenario with the lowest concentration of natural occurring isotopes, and for 10-min integration time, we achieve a MDAC of 5.4/4.1/3.9 (Bq/m³) for 131I/137Cs/60Co using a LaBr3(Ce) detector; and 4.2/2.8/2.7 (Bq/m³) for 131I/137Cs/60Co with a SrI2(Eu) detector.
•A fast algorithm monitors environmental artificial radioisotopes in real-time.•The algorithm subtracts natural isotopes contributions avoiding overestimations.•2″ × 2″ LaBr3(Ce) and SrI2(Eu) scintillation detectors results are compared.•We give minimum detectable activity concentrations (MDAC) for 131I, 137Cs and 60Co.•MDAC is affected by variations of natural isotopes activity concentrations.
The MAGIC data processing pipeline Curcoll, R Firpo; Delfino, M; Neissner, C ...
Journal of physics. Conference series,
12/2011, Letnik:
331, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The MAGIC data center has recently introduced a new computing service, which is available to the whole collaboration. This service will be complemented with DataCooker, an analysis system currently ...in development. This system implements the MAGIC data analysis chain and integrates it in the data center infrastructure. DataCooker is designed to provide an easy access to the computing service without the need to know its details or deal with the complexities of its use.
The e-ASTROGAM mission De Angelis, A.; Tatischeff, V.; Tavani, M. ...
Experimental astronomy,
10/2017, Letnik:
44, Številka:
1
Journal Article
Recenzirano
Odprti dostop
e-ASTROGAM (‘enhanced ASTROGAM’) is a breakthrough Observatory space mission, with a detector composed by a Silicon tracker, a calorimeter, and an anticoincidence system, dedicated to the study of ...the non-thermal Universe in the photon energy range from 0.3 MeV to 3 GeV – the lower energy limit can be pushed to energies as low as 150 keV, albeit with rapidly degrading angular resolution, for the tracker, and to 30 keV for calorimetric detection. The mission is based on an advanced space-proven detector technology, with unprecedented sensitivity, angular and energy resolution, combined with polarimetric capability. Thanks to its performance in the MeV-GeV domain, substantially improving its predecessors, e-ASTROGAM will open a new window on the non-thermal Universe, making pioneering observations of the most powerful Galactic and extragalactic sources, elucidating the nature of their relativistic outflows and their effects on the surroundings. With a line sensitivity in the MeV energy range one to two orders of magnitude better than previous generation instruments, e-ASTROGAM will determine the origin of key isotopes fundamental for the understanding of supernova explosion and the chemical evolution of our Galaxy. The mission will provide unique data of significant interest to a broad astronomical community, complementary to powerful observatories such as LIGO-Virgo-GEO600-KAGRA, SKA, ALMA, E-ELT, TMT, LSST, JWST, Athena, CTA, IceCube, KM3NeT, and the promise of eLISA.
Abstract
It is widely believed that the bulk of the Galactic cosmic rays is accelerated in supernova remnants (SNRs). However, no observational evidence of the presence of particles of PeV energies ...in SNRs has yet been found. The young historical SNR Cassiopeia A (Cas A) appears as one of the best candidates to study acceleration processes. Between 2014 December and 2016 October, we observed Cas A with the MAGIC telescopes, accumulating 158 h of good quality data. We derived the spectrum of the source from 100 GeV to 10 TeV. We also analysed ∼8 yr of Fermi-LAT to obtain the spectral shape between 60 MeV and 500 GeV. The spectra measured by the LAT and MAGIC telescopes are compatible within the errors and show a clear turn-off (4.6σ) at the highest energies, which can be described with an exponential cut-off at
$E_c = 3.5(^{+1.6}_{-1.0})_{{\rm stat}} (^{+0.8}_{-0.9})_{{\rm sys}}$
TeV. The gamma-ray emission from 60 MeV to 10 TeV can be attributed to a population of high-energy protons with a spectral index of ∼2.2 and an energy cut-off at ∼10 TeV. This result indicates that Cas A is not contributing to the high energy (∼PeV) cosmic ray sea in a significant manner at the present moment. A one-zone leptonic model fails to reproduce by itself the multiwavelength spectral energy distribution. Besides, if a non-negligible fraction of the flux seen by MAGIC is produced by leptons, the radiation should be emitted in a region with a low magnetic field (B⪅180 μG) like in the reverse shock.
Imaging Atmospheric Cherenkov Telescopes (IACTs) represent a class of instruments which are dedicated to the ground-based observation of cosmic VHE gamma ray emission based on the detection of the ...Cherenkov radiation produced in the interaction of gamma rays with the Earth atmosphere. One of the key elements of such instruments is a pixelized focal-plane camera consisting of photodetectors. To date, photomultiplier tubes (PMTs) have been the common choice given their high photon detection efficiency (PDE) and fast time response. Recently, silicon photomultipliers (SiPMs) are emerging as an alternative. This rapidly evolving technology has strong potential to become superior to that based on PMTs in terms of PDE, which would further improve the sensitivity of IACTs, and see a price reduction per square millimeter of detector area. We are working to develop a SiPM-based module for the focal-plane cameras of the MAGIC telescopes to probe this technology for IACTs with large focal plane cameras of an area of few square meters. We will describe the solutions we are exploring in order to balance a competitive performance with a minimal impact on the overall MAGIC camera design using ray tracing simulations. We further present a comparative study of the overall light throughput based on Monte Carlo simulations and considering the properties of the major hardware elements of an IACT.
Spontaneous breaking of Lorentz symmetry at energies on the order of the Planck energy or lower is predicted by many quantum gravity theories, implying non-trivial dispersion relations for the photon ...in vacuum. Consequently, gamma-rays of different energies, emitted simultaneously from astrophysical sources, could accumulate measurable differences in their time of flight until they reach the Earth. Such tests have been carried out in the past using fast variations of gamma-ray flux from pulsars, and more recently from active galactic nuclei and gamma-ray bursts. We present new constraints studying the gamma-ray emission of the galactic Crab Pulsar, recently observed up to TeV energies by the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) collaboration. A profile likelihood analysis of pulsar events reconstructed for energies above 400 GeV finds no significant variation in arrival time as their energy increases. Ninety-five percent CL limits are obtained on the effective Lorentz invariance violating energy scale at the level of ( ) for a linear, and ( ) for a quadratic scenario, for the subluminal and the superluminal cases, respectively. A substantial part of this study is dedicated to calibration of the test statistic, with respect to bias and coverage properties. Moreover, the limits take into account systematic uncertainties, which are found to worsen the statistical limits by about 36%-42%. Our constraints would have been much more stringent if the intrinsic pulse shape of the pulsar between 200 GeV and 400 GeV was understood in sufficient detail and allowed inclusion of events well below 400 GeV.
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