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  • 1.
    Dieckmann, Mark E
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Bret, Antoine
    ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain..
    Electrostatic and magnetic instabilities in the transition layer of a collisionless weakly relativistic pair shock2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 1, 198-209 p.Article in journal (Refereed)
    Abstract [en]

    Energetic electromagnetic emissions by astrophysical jets like those that are launched during the collapse of a massive star and trigger gamma-ray bursts are partially attributed to relativistic internal shocks. The shocks are mediated in the collisionless plasma of such jets by the filamentation instability of counterstreaming particle beams. The filamentation instability grows fastest only if the beams move at a relativistic relative speed. We model here with a particle-in-cell simulation, the collision of two cold pair clouds at the speed c/2 (c: speed of light). We demonstrate that the two-stream instability outgrows the filamentation instability for this speed and is thus responsible for the shock formation. The incomplete thermalization of the upstream plasma by its quasi-electrostatic waves allows other instabilities to grow. A shock transition layer forms, in which a filamentation instability modulates the plasma far upstream of the shock. The inflowing upstream plasma is progressively heated by a two-stream instability closer to the shock and compressed to the expected downstream density by the Weibel instability. The strong magnetic field due to the latter is confined to a layer 10 electron skin depths wide.

  • 2.
    Dieckmann, Mark Eric
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Sarri, Gianluca
    Queen's University Belfast. BT7 1NN, Belfast, United Kingdom.
    Markoff, Sera
    University of Amsterdam, 1098 XH Amsterdam, The Netherlands.
    Borghesi, Marco
    Queen's University Belfast, BT7 1NN, Belfast, United Kingdom.
    Zepf, Matt
    Queen's University Belfast, BT7 1NN, Belfast, United Kingdom.
    PIC simulation study of the interaction between a relativisticallymoving leptonic micro-cloud and ambient electrons.2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 577, no A137, 1-10 p.Article in journal (Refereed)
    Abstract [en]

    Context. The jets of compact accreting objects are composed of electrons and a mixture of positrons and ions. These outflows impinge on the interstellar or intergalactic medium and both plasmas interact via collisionless processes. Filamentation (beam-Weibel) instabilities give rise to the growth of strong electromagnetic fields. These fields thermalize the interpenetrating plasmas.

    Aims. Hitherto, the effects imposed by a spatial non-uniformity on filamentation instabilities have remained unexplored. We examine the interaction between spatially uniform background electrons and a minuscule cloud of electrons and positrons. The cloud size is comparable to that created in recent laboratory experiments and such clouds may exist close to internal and external shocks of leptonic jets. The purpose of our study is to determine the prevalent instabilities, their ability to generate electromagnetic fields and the mechanism, by which the lepton micro-cloud transfers energy to the background plasma.

    Methods. A square micro-cloud of equally dense electrons and positrons impinges in our particle-in-cell (PIC) simulation on a spatially uniform plasma at rest. The latter consists of electrons with a temperature of 1 keV and immobile ions. The initially charge- and current neutral micro-cloud has a temperature of 100 keV and a side length of 2.5 plasma skin depths of the micro-cloud. The side length is given in the reference frame of the background plasma. The mean speed of the micro-cloud corresponds to a relativistic factor of 15, which is relevant for laboratory experiments and for relativistic astrophysical outflows. The spatial distributions of the leptons and of the electromagnetic fields are examined at several times.

    Results. A filamentation instability develops between the magnetic field carried by the micro-cloud and the background electrons. The electromagnetic fields, which grow from noise levels, redistribute the electrons and positrons within the cloud, which boosts the peak magnetic field amplitude. The current density and the moduli of the electromagnetic fields grow aperiodically in time and steadily along the direction that is anti-parallel to the cloud’s velocity vector. The micro-cloud remains conjoined during the simulation. The instability induces an electrostatic wakefield in the background plasma.

    Conclusions. Relativistic clouds of leptons can generate and amplify magnetic fields even if they have a microscopic size, which implies that the underlying processes can be studied in the laboratory. The interaction of the localized magnetic field and high-energy leptons will give rise to synchrotron jitter radiation. The wakefield in the background plasma dissipates the kinetic energy of the lepton cloud. Even the fastest lepton micro-clouds can be slowed down by this collisionless mechanism. Moderately fast charge- and current neutralized lepton micro–clouds will deposit their energy close to relativistic shocks and hence they do not constitute an energy loss mechanism for the shock.

  • 3.
    Marcowith, Alexandre
    et al.
    Laboratoire Univers et Particules de Montpellier CNRS/Université de Montpellier, Place E. Bataillon, 34095 Montpellier, France.
    Bret, Antoine
    ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain.
    Bykov, Andrei
    A.F. Ioffe Institute for Physics and Technology, 194021, St. Petersburg, Russia.
    Dieckmann, Mark Eric
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Drury, Luke
    School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland.
    Lembege, Bertrand
    LATMOS—CNRS—UVSQ—IPSL, 11 Bd. d’Alembert , 78280, Guyancourt, France.
    Lemoine, Martin
    Institut d’Astrophysique de Paris, CNRS—UPMC, 98 bis boulevard Arago, F-75014 Paris, France.
    Morlino, Guiseppe
    INFN, Gran Sasso Science Institute, viale F. Crispi 7, 67100 LAquila, Italy.
    Murphy, Gareth Charles
    Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17 Copenhagen 2100 Denmark.
    Pelletier, Guy
    Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), UMR 5274 F-38041 Grenoble, France.
    Plotnikov, Ilya
    Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), UMR 5274 F-38041 Grenoble, France.
    Reville, Brian
    Department of Physics and Astronomy, Queen’s University Belfast, University Road, Belfast, BT7 1NN, UK.
    Riquelme, Mario
    Department of Physics, (FCFM)—University of Chile, Santiago, Chile.
    Sironi, Lorenzo
    Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA.
    Stockem Novo, Anne
    Institut fur Theoretische Physik, Lehrstuhl IV: Weltraum- Astrophysik, Ruhr-Universität, 44801 Bochum, Germany.
    The microphysics of collisionless shock waves2016In: Reports on progress in physics (Print), ISSN 0034-4885, E-ISSN 1361-6633, Vol. 79, no 4, 046901Article, review/survey (Refereed)
    Abstract [en]

    Collisionless shocks, that is shocks mediated by electromagnetic processes, are customary in space physics and in astrophysics. They are to be found in a great variety of objects and environments: magnetospheric and heliospheric shocks, supernova remnants, pulsar winds and their nebulæ, active galactic nuclei, gamma-ray bursts and clusters of galaxies shock waves. Collisionless shock microphysics enters at different stages of shock formation, shock dynamics and particle energization and/or acceleration. It turns out that the shock phenomenon is a multi-scale non-linear problem in time and space. It is complexified by the impact due to high-energy cosmic rays in astrophysical environments. This review adresses the physics of shock formation, shock dynamics and particle acceleration based on a close examination of available multi-wavelength or in situ observations, analytical and numerical developments. A particular emphasis is made on the different instabilities triggered during the shock formation and in association with particle acceleration processes with regards to the properties of the background upstream medium. It appears that among the most important parameters the background magnetic field through the magnetization and its obliquity is the dominant one. The shock velocity that can reach relativistic speeds has also a strong impact over the development of the micro-instabilities and the fate of particle acceleration. Recent developments of laboratory shock experiments has started to bring some new insights in the physics of space plasma and astrophysical shock waves. A special section is dedicated to new laser plasma experiments probing shock physics.

  • 4.
    Meng, Fanqi
    et al.
    Goethe University of Frankfurt, Germany.
    Thomson, Mark D.
    Goethe University of Frankfurt, Germany.
    Sernelius, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Roskos, Hartmut G.
    Goethe University of Frankfurt, Germany.
    Relativistic Doppler Frequency Up-conversion and Probing the Initial Relaxation of a Non-Equilibrium Electron-Hole Plasma in Silicon2015In: 2015 40TH INTERNATIONAL CONFERENCE ON INFRARED, MILLIMETER AND TERAHERTZ WAVES (IRMMW-THZ), IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    we demonstrate experimentally the relativistic Doppler frequency up-conversion of the THz pulses from the counter-propagating ionized plasma front in silicon. The observed frequency up-conversion can be well modeled by the 1D FDTD simulations if significant short scattering time (well below 10 fs) in the plasma is assumed. To further elucidate the scattering rate in the electro-hole plasma, we performed pump probe experiment employing ultra-broadband (150 THz) THz-Mid-Infrared pulse. The results show the scattering time decreases from similar to 200 fs down to similar to 20 fs when the carrier density increases up to 10(19)-cm(-3), and then saturates for higher densities. Such scattering time dependence on plasma carrier density can be very well fitted by the Drude model for thermalized electron-holes, and the saturation behavior is attributed to electron-hole phase-space restriction as the plasma becomes degenerate. The resultant much shorter scattering time measured with non-thermalized plasma is in good accordance with the Doppler experiment, which demonstrates Doppler geometry an effective method for probing non-equilibrium plasma dynamics.

  • 5.
    Petrushevska, T.
    et al.
    Stockholm University, Sweden.
    Amanullah, R.
    Stockholm University, Sweden.
    Goobar, A.
    Stockholm University, Sweden.
    Fabbro, S.
    NRC Herzberg Institute Astrophys, Canada.
    Johansson, J.
    Weizmann Institute Science, Israel.
    Kjellsson, T.
    Stockholm University, Sweden.
    Lidman, C.
    Australian Astron Observ, Australia.
    Paech, K.
    Ludwig Maximilians University of Munchen, Germany; Excellence Cluster University, Germany.
    Richard, J.
    University of Lyon 1, France.
    Dahle, H.
    University of Oslo, Norway.
    Ferretti, R.
    Stockholm University, Sweden.
    Kneib, J. P.
    EPFL, Switzerland.
    Limousin, M.
    University of Provence, France.
    Nordin, J.
    Humboldt University, Germany.
    Stanishev, Vallery
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    High-redshift supernova rates measured with the gravitational telescope A 16892016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 594, A54Article in journal (Refereed)
    Abstract [en]

    Aims. We present a ground-based, near-infrared search for lensed supernovae behind the massive cluster Abell 1689 at z = 0.18, which is one of the most powerful gravitational telescopes that nature provides. Methods. Our survey was based on multi-epoch J-band observations with the HAWK-I instrument on VLT, with supporting optical data from the Nordic Optical Telescope. Results. Our search resulted in the discovery of five photometrically classified, core-collapse supernovae with high redshifts of 0.671 amp;lt; z amp;lt; 1.703 and magnifications in the range Delta m = -0.31 to -1.58 mag, as calculated from lensing models in the literature. Owing to the power of the lensing cluster, the survey had the sensitivity to detect supernovae up to very high redshifts, z similar to 3, albeit for a limited region of space. We present a study of the core-collapse supernova rates for 0.4 amp;lt; z amp;lt; 2.9, and find good agreement with previous estimates and predictions from star formation history. During our survey, we also discovered two Type Ia supernovae in A 1689 cluster members, which allowed us to determine the cluster Ia rate to be 0.14(-0.09)(+0.19) SNuB h(2) (SNuB 10(-12) SNe L-circle dot,B(-1) yr(-1)), where the error bars indicate 1 sigma confidence intervals, statistical and systematic, respectively. The cluster rate normalized by the stellar mass is 0.10(-0.06)(+0.13) +/- 0.02 in SNuM h(2) (SNuM = 10(-12) SNe M-1 yr(-1)). Furthermore, we explore the optimal future survey for improving the core-collapse supernova rate measurements at z greater than or similar to 2 using gravitational telescopes, and for detections with multiply lensed images, and we find that the planned WFIRST space mission has excellent prospects. Conclusions. Massive clusters can be used as gravitational telescopes to significantly expand the survey range of supernova searches, with important implications for the study of the high-z transient Universe.

  • 6.
    Rådbo, Marie
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Science & Engineering.
    Stjärnhimlen: bortom gatlyktor och neonljus2015Book (Other academic)
    Abstract [sv]

    Prickar.

    Vita prickar mot en becksvart bakgrund. Det är allt.

    Eller?

    Ingen kan riktigt förklara varför detta enkla motiv berör oss så djupt. Kanske beror det på att våra förfäder såg samma vy, att den finns inpräntad i vårt kollektiva minne. För den väcker tveklöst känslor, inte åsikter. Men det måste vara riktigt mörkt.

    Alla dessa prickar vill jag visa min lille prins, mitt första barnbarn.”

    Det tycks finnas något i människans natur som gör att just stjärnhimlen i alla tider har stimulerat till att ställa de stora frågorna om oss själva, om vårt ursprung och om vår plats i tid och rum. Astronomin ger oss redskap att placera in oss i ett större sammanhang, samtidigt som den påminner oss om att vi alla är rymdvarelser på vårt naturliga rymdskepp. Stjärnhimlen, av Sveriges mest folkkära astronom Marie Rådbo, är en bok för alla som vill lära sig mer om dessa fantastiska prickar, och en handbok i hur man kan dela upplevelsen med sitt barn eller barnbarn.

  • 7.
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology.
    X-ray Analysis of a Complete Sample of Giga-Hertz Peaked Spectrum Galaxies2008Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates the X-ray properties of the entire Stanghellini et al. (1998) complete sample of GHz Peaked Spectrum galaxies with redshift lower than 1. In total 19 sources are included mainly from observations made by the European space telescope, XMM-Newton. Out of these the analysis of seven "new" observations made between 2006 and 2008 are throughout described. Data from the new observations shows consistency with already analysed data. As a new result a tentative discovery of a bi-modal structure in the X-ray to radio luminosity ratio within the sample is presented.

  • 8.
    Winroth, Gustaf
    Linköping University, The Department of Physics, Chemistry and Biology.
    Energy Calibration of Different Modes of a pn-CCD-camera on board the X-Ray Observatory XMM-Newton2007Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    The X-ray Multi-mirror Mission, XMM-Newton was launched by the European Space Agency, ESA, in 1999. XMM-Newton carries six cameras, including a silicon pn-junction Charge Coupled Device, or pn-CCD camera. This camera has six operating modes, spatially as well as time resolved. The main objective of this project is to refine the Burst mode energy correction in order to align the measured energy spectra observed in the Burst mode with the spectra taken in the Full Frame mode. An observation of the line-rich supernova remnant called Cassiopeia A is used to evaluate the line positions in each mode such that the energy correction function used for the alignment can be modified accordingly. The analysis further treats the application of the correction on a source with a continuous spectrum, the Crab nebula. Discussion shows how to reduce eventual residuals in the Crab spectrum by modifying the correction function while keeping the alignment of the Cas-A spectra. The final product is an update of the corresponding published calibration file.

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