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Study of the variable broadband emission of Markarian 501 during the most extreme Swift X-ray activity
No full textContext. Markarian 501 (Mrk 501) is a very high-energy (VHE) gamma-ray blazar located at z = 0.034, which is regularly monitored by a wide range of multi-wavelength instruments, from radio to VHE gamma rays. During a period of almost two weeks in July 2014, the highest X-ray activity of Mrk 501 was observed in ∼14 years of operation of the Neil Gehrels Swift Gamma-ray Burst Observatory.Aims. We characterize the broadband variability of Mrk 501 from radio to VHE gamma rays during the most extreme X-ray activity measured in the last 14 years, and evaluate whether it can be interpreted within theoretical scenarios widely used to explain the broadband emission from blazars.Methods. The emission of Mrk 501 was measured at radio with Metsähovi, at optical–UV with KVA and Swift/UVOT, at X-ray with Swift/XRT and Swift/BAT, at gamma ray with Fermi-LAT, and at VHE gamma rays with the FACT and MAGIC telescopes. The multi-band variability and correlations were quantified, and the broadband spectral energy distributions (SEDs) were compared with predictions from theoretical models.Results. The VHE emission of Mrk 501 was found to be elevated during the X-ray outburst, with a gamma-ray flux above 0.15 TeV varying from ∼0.5 to ∼2 times the Crab nebula flux. The X-ray and VHE emission both varied on timescales of 1 day and were found to be correlated. We measured a general increase in the fractional variability with energy, with the VHE variability being twice as large as the X-ray variability. The temporal evolution of the most prominent and variable segments of the SED, characterized on a day-by-day basis from 2014 July 16 to 2014 July 31, is described with a one-zone synchrotron self-Compton model with variations in the break energy of the electron energy distribution (EED), and with some adjustments in the magnetic field strength and spectral shape of the EED. These results suggest that the main flux variations during this extreme X-ray outburst are produced by the acceleration and the cooling of the high-energy electrons. A narrow feature at ∼3 TeV was observed in the VHE spectrum measured on 2014 July 19 (MJD 56857.98), which is the day with the highest X-ray flux (>0.3 keV) measured during the entire Swift mission. This feature is inconsistent with the classical analytic functions to describe the measured VHE spectra (power law, log-parabola, and log-parabola with exponential cutoff) at more than 3σ. A fit with a log-parabola plus a narrow component is preferred over the fit with a single log-parabola at more than 4σ, and a dedicated Monte Carlo simulation estimated the significance of this extra component to be larger than 3σ. Under the assumption that this VHE spectral feature is real, we show that it can be reproduced with three distinct theoretical scenarios: (a) a pileup in the EED due to stochastic acceleration; (b) a structured jet with two-SSC emitting regions, with one region dominated by an extremely narrow EED; and (c) an emission from an IC pair cascade induced by electrons accelerated in a magnetospheric vacuum gap, in addition to the SSC emission from a more conventional region along the jet of Mrk 501.Key words: galaxies: active / BL Lacertae objects: individual: Mrk 501 / gamma rays: galaxies / X-rays: galaxies⋆ Corresponding authors: J. Becerra González, [email protected]; D. Paneque, [email protected]; C. Wendel, [email protected]
Femtosecond timing synchronization at megahertz repetition rates for an x-ray free-electron laser
No full textA critical challenge of pump-probe experiments with x-ray free-electron lasers (XFELs) is accurate synchronization of x-ray and optical pulses. At the European XFEL we observed megahertz rate timing jitter of 24.0±12.4fs
Deformations of Ti-6Al-4 V additive-manufacturing-induced isotropic and anisotropic columnar structures: In situ measurements and underlying mechanisms
No full textThe deformations of isotropic and anisotropic Ti-6Al-4V columnar structures fabricated by additive manufacturing were extensively examined. The distinct texture and microstructure distributions were characterised. In situ X-ray diffraction measurements show different lattice activities resulting from the different microstructure distributions. Spatially resolved mapping revealed manufacturing-induced crystallite-orientation distributions that determine the deformation mechanisms. We propose a self-consistent model to correlate the multi-scale characteristics, from the anisotropic-texture-distribution microstructure to the bulk mechanical properties. We determined that basal and pyramidal slip activities were activated by tension deformation. The underlying additive-manufacturing-induced crystal plasticity plays a major role. We find that the texture development of the columnar structures and the distribution of crystallite orientation achieved by different processing conditions during additive manufacturing have important effects on the mechanical properties. The dominant deformation mode for the anisotropic Ti-6Al-4V columnar structure is basal slip, and that for the isotropic Ti-6Al-4V columnar structure is pyramidal slip. The difference may be important for determining the fatigue behaviour
Search for supersymmetric particles in gluino-gluino pair production events at CMS
No full textA search for gluino pair production with events using 35.9 fb−1of data from ppcollisions at a center-of-mass energy of 13 TeV in 2016 is presented. Two differentcascade decay modes of gluinos are considered, and separate analyses for each of themodels are performed. The first model describes gluino pair production, where eachgluino decays to a top quark-antiquark pair and the lightest SUSY particle. Thefinal state contain an isolated lepton, b-tagged jets along with other jets and largemissing transverse momentum. The azimuthal angle between the lepton and the Wboson flight direction is used to suppress the background. The search is performedin exclusive search bins which differ in the number of jets, b-tagged jets, scalar sumof all jet transverse momenta and scalar sum of the scalar sum of the transversemissing momentum and transverse momentum of the lepton. The second modeltargets gluino decays to a chargino that is nearly mass degenerate with the lightestSUSY particle, a neutralino, and therefore long-lived. The final state consists ofa disappearing track, multiple jets, and large missing transverse energy. Eventvariables are constructed based on the topology of the final state for defining searchregions and facilitating background estimation.No significant deviation from the predicted Standard Model background is ob-served. The results are interpreted in terms of simplified models, resulting in theexclusion limits of particular gluino-neutralino mass configuration. The largest ex-cluded gluino mass ism ̃g= 2050 GeV, whereas the largest excluded neutralino massism ̃χ01= 1400 Ge
Testing binary dynamics in gravity at the sixth post-Newtonian level
No full textWe calculate the motion of binary mass systems in gravity up to the sixth post–Newtonian order to the GN3 terms ab initio using momentum expansions within an effective field theory approach based on Feynman amplitudes in harmonic coordinates. For these contributions we construct a canonical transformation to isotropic and to EOB coordinates at 5PN and agree with the results in the literature [1,2] by Bern et al. and Damour. At 6PN we compare to the Hamiltonians in isotropic coordinates either given in [1] or resulting from the scattering angle. We find a canonical transformation from our Hamiltonian in harmonic coordinates to [1] , but not to [2] . This implies that we also agree on all observables with [1] to the sixth post–Newtonian order to GN3
Improved kinetic behaviour of doped with nanostructured K-modified- for hydrogen storage
No full textIn situ monitoring of mechanochemical synthesis of calcium urea phosphate fertilizer cocrystal reveals highly effective water-based autocatalysis
No full textUsing the mechanosynthesis of the calcium urea phosphate fertilizer cocrystal as a model, we provide a quantitative investigation of chemical autocatalysis in a mechanochemical reaction. The application of in situ Raman spectroscopy and synchrotron X-ray powder diffraction to monitor the reaction of urea phosphate and either calcium hydroxide or carbonate enabled the first quantitative and in situ study of a mechanochemical system in which one of the products of a chemical reaction (water) mediates the rate of transformation and underpins positive feedback kinetics. The herein observed autocatalysis by water generated in the reaction enables reaction acceleration at amounts that are up to 3 orders of magnitude smaller than in a typical liquid-assisted mechanochemical reaction