Academic literature on the topic 'Outflows supernova remnants ISM'
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Journal articles on the topic "Outflows supernova remnants ISM"
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Chu, You-Hua. "CSI in Supernova Remnants." Proceedings of the International Astronomical Union 12, S331 (February 2017): 81–85. http://dx.doi.org/10.1017/s1743921317004926.
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AbstractSupernovae (SNe) explode in environments that have been significantly modified by the SN progenitors. For core-collapse SNe, the massive progenitors ionize the ambient interstellar medium (ISM) via UV radiation and sweep the ambient ISM via fast stellar winds during the main sequence phase, replenish the surroundings with stellar material via slow winds during the luminous blue variable (LBV) or red supergiant (RSG) phase, and sweep up the circumstellar medium (CSM) via fast winds during the Wolf-Rayet (WR) phase. If a massive progenitor was in a close binary system, the binary interaction could have caused mass ejection in certain preferred directions, such as the orbital plane, and even bipolar outflow/jet. As a massive star finally explodes, the SN ejecta interacts first with the CSM that was ejected and shaped by the star itself. As the newly formed supernova remnant (SNR) expands further, it encounters interstellar structures that were shaped by the progenitor from earlier times. Therefore, the structure and evolution of a SNR is largely dependent on the initial mass and close binarity of the SN progenitor. The Large Magellanic Cloud (LMC) has an excellent sample of over 50 confirmed SNRs that are well resolved by Hubble Space Telescope, Chandra X-ray Observatory, and Spitzer Space Telescope. These multi-wavelength observations allow us to conduct stellar forensics in SNRs and understand the wide variety of morphologies and physical properties of SNRs observed.
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Gusdorf, Antoine. "Feedback from young stars, the molecular signature of shocks and outflows." EPJ Web of Conferences 265 (2022): 00035. http://dx.doi.org/10.1051/epjconf/202226500035.
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Why do we study shocks ? Because they are there. Shocks are ubiquitous in the interstellar medium (ISM), where they constitute a major source of energy injection, together with photons and cosmic rays (CRs). Galactic shocks, and converging flows at the basis of the formation of molecular clouds and filaments, are examples of interstellar shocks. Shock waves are also generated during the birth, life and death of stars in the form of jets and protostellar outflows, stellar winds and supernovae and supernova remnants (SNRs). Hence, they are a major route of feedback of stars on galaxies. As such, they are a proficient tool to better understand the cycle of matter and energy in galaxies, but also the formation of stars. In this review, I will describe the recent advances on the study of shocks that can be observed and characterized with the IRAM instruments, with emphasis on the study of protostellar jets and outflows.
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Petre, R. "Supernova Remnants in the Magellanic Clouds." Symposium - International Astronomical Union 190 (1999): 74–77. http://dx.doi.org/10.1017/s0074180900117425.
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Over the past decade, substantial progress has been made in understanding the properties of Magellanic Cloud supernova remnants and their role in the ISM. Among the notable results are the “typing” of progenitors via the X-ray spectra of their remnants, the use of X-ray spectra to measure ISM abundances, and the discovery of remnants with unique properties. I summarize recent studies of MC SNRs, and describe how a refined understanding of the SNR population requires consideration of the unique attributes of each remnant.
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Wu, D., M. F. Zhang, S. S. Shan, and W. W. Tian. "MHD Simulation of Supernova Remnants." Proceedings of the International Astronomical Union 12, S331 (February 2017): 174–77. http://dx.doi.org/10.1017/s1743921317004902.
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AbstractWe present some Magnetohydrodynamic (MHD) simulations for supernova remnants (SNRs), which hints the thicknesses of SNRs’ shells are likely related to the density and density distribution of surrounding interstellar medium (ISM). The simulations show clear formation and evolution of reverse shocks. In addition, we find that stellar winds can blow a bubble around the progenitor stars then lead to weaker radio emission at the center of SNRs.
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Wandel, Amri. "Supernova Remnants and the ISM: Constraints from Cosmic-Ray Acceleration." International Astronomical Union Colloquium 101 (1988): 325–29. http://dx.doi.org/10.1017/s0252921100102581.
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AbstractSupernova remnants can reaccelerate cosmic rays and modify their distribution during the cosmic ray propagation in the galaxy. Cosmic ray observations (in particular the boron-to-carbon data) strongly limit the permitted amount of reacceleration, which is used to set an upper limit on the expansion of supernova remnants, and a lower limit on the effective density of the ISM swept up by supernova shocks. The constraint depends on the theory of cosmic ray propagation: the standard Leaky Box model requires a high effective density, > 1cm−3, and is probably inconsistent with the present picture of the ISM. Modifying the Leaky Box model to include a moderate amount of weak-shock reacceleration, a self consistent solution is found, where the effective density in this solution is ≈ 0.1 cm−3, which implies efficient evaporation of the warm ISM component by young supernova remnants, during most of their supersonic expansion.
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Zhu, Hui, and Wenwu Tian. "Distances of Galactic supernova remnants." Proceedings of the International Astronomical Union 9, S296 (January 2013): 378–79. http://dx.doi.org/10.1017/s1743921313009915.
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AbstractSupernova remnants (SNRs) play a key role in understanding supernovae explosion mechanisms, exploring the likely sources of Galactic cosmic rays and the chemical enrichment of interstellar medium (ISM). Reliable distance determinations to Galactic SNRs are key to obtain their basic parameters, such as size, age, explosion energy, which helps us to study their environment and interstellar medium. We review the methods to determine the distances to SNRs and highlight the kinematic distance measurement by Hi absorption and CO emission observations.
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Fujita, Y., J. Fukumoto, and K. Okoshi. "Evolution of Multiphase Hot Interstellar Medium in Elliptical Galaxies." Symposium - International Astronomical Union 188 (1998): 281–82. http://dx.doi.org/10.1017/s007418090011513x.
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Theoretical arguments indicate that the ISM is inhomogeneous; Mathews estimated that the ~ 1M⊙ of metal ejected by each supernova event into the ISM is trapped locally within the hot bubbles. Since in elliptical galaxies, there is no overlapping of expanding supernova remnants after galactic wind period, it is expected that this inhomogeneity persists for a long time. The observations also suggests that the ISM of elliptical galaxies is inhomogeneous. Based on these arguments, we studied the evolution of the multiphase (inhomogeneous) ISM.
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Meyer, D. M.-A., M. Pohl, M. Petrov, and L. Oskinova. "Non-thermal radio supernova remnants of exiled Wolf–Rayet stars." Monthly Notices of the Royal Astronomical Society 502, no. 4 (February 17, 2021): 5340–55. http://dx.doi.org/10.1093/mnras/stab452.
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ABSTRACT A signification fraction of Galactic massive stars (${\ge}8\, \rm M_{\odot }$) are ejected from their parent cluster and supersonically sail away through the interstellar medium (ISM). The winds of these fast-moving stars blow asymmetric bubbles thus creating a circumstellar environment in which stars eventually die with a supernova explosion. The morphology of the resulting remnant is largely governed by the circumstellar medium of the defunct progenitor star. In this paper, we present 2D magneto-hydrodynamical simulations investigating the effect of the ISM magnetic field on the shape of the supernova remnants of a $35\, \mathrm{M}_{\odot }$ star evolving through a Wolf–Rayet phase and running with velocity 20 and $40\, \rm km\, \rm s^{-1}$, respectively. A $7\, \mu \rm G$ ambient magnetic field is sufficient to modify the properties of the expanding supernova shock front and in particular to prevent the formation of filamentary structures. Prior to the supernova explosion, the compressed magnetic field in the circumstellar medium stabilizes the wind/ISM contact discontinuity in the tail of the wind bubble. A consequence is a reduced mixing efficiency of ejecta and wind materials in the inner region of the remnant, where the supernova shock wave propagates. Radiative transfer calculations for synchrotron emission reveal that the non-thermal radio emission has characteristic features reflecting the asymmetry of exiled core-collapse supernova remnants from Wolf–Rayet progenitors. Our models are qualitatively consistent with the radio appearance of several remnants of high-mass progenitors, namely the bilateral G296.5+10.0 and the shell-type remnants CTB109 and Kes 17, respectively.
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McKee, Christopher F. "Supernova Remnant Shocks in an Inhomogeneous Interstellar Medium." International Astronomical Union Colloquium 101 (1988): 205–22. http://dx.doi.org/10.1017/s0252921100102386.
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AbstractThe inhomogeneity of the interstellar medium (ISM) has a profound effect on the propagation of the interstellar shock generated by a supernova and on the appearance of the resulting supernova remnant (SNR). Low mass supernovae produce remnants that interact with the “pristine” ISM, which has density inhomogeneities (clouds) on a wide range of scales. The shock compresses and accelerates the clouds it encounters; inside the blast wave, the clouds are hydrodynamically unstable, and mass is injected from the clouds into the intercloud medium. Embedded clouds interact thermally with the shock also, adding mass to the hot intercloud medium via thermal evaporation or subtracting it via condensation and thermal instability. Mass injection into the hot intercloud medium, whether dynamical or thermal, leads to infrared emission as dust mixes with the hot gas and is thermally sputtered. The remnants of massive supernovae interact primarily with circumstellar matter and with interstellar material which has been processed by the ionizing radiation and wind of the progenitor star. After passing through any circumstellar material which may be present, the shock encounters a cavity which tends to “muffle” the SNR. The remnants of massive supernovae therefore tell us more about the late stages of the evolution of massive stars than about the ISM.
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Kemball, Athol J. "Stellar masers, circumstellar envelopes and supernova remnants." Proceedings of the International Astronomical Union 3, S242 (March 2007): 236–45. http://dx.doi.org/10.1017/s1743921307013063.
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AbstractThis paper reviews recent advances in the study or circumstellar masers and masers found toward supernova remnants. The review is organized by science focus area, including the astrophysics of extended stellar atmospheres, stellar mass-loss processes and outflows, late-type evolved stellar evolution, stellar maser excitation and chemistry, and the use of stellar masers as independent distance estimators. Masers toward supernova remnants are covered separately. Recent advances and open future questions in this field are explored.
Dissertations / Theses on the topic "Outflows supernova remnants ISM"
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Bock, Douglas Carl-Johan. "Wide Field Aperture Synthesis Radio Astronomy." University of Sydney. Physics, 1998. http://hdl.handle.net/2123/377.
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This thesis is focussed on the Molonglo Observatory Synthesis Telescope (MOST), reporting on two primary areas of investigation. Firstly, it describes the recent upgrade of the MOST to perform an imaging survey of the southern sky. Secondly, it presents a MOST survey of the Vela supernova remnant and follow-up multiwavelength studies. The MOST Wide Field upgrade is the most significant instrumental upgrade of the telescope since observations began in 1981. It has made possible the nightly observation of fields with area ~5 square degrees, while retaining the operating frequency of 843 MHz and the pre-existing sensitivity to point sources and extended structure. The MOST will now be used to make a sensitive (rms approximately 1 mJy/beam) imaging survey of the sky south of declination -30°. This survey consists of two components: an extragalactic survey, which will begin in the south polar region, and a Galactic survey of latitudes |b| < 10°. These are expected to take about ten years. The upgrade has necessitated the installation of 352 new preamplifiers and phasing circuits which are controlled by 88 distributed microcontrollers, networked using optic fibre. The thesis documents the upgrade and describes the new systems, including associated testing, installation and commissioning. The thesis continues by presenting a new high-resolution radio continuum survey of the Vela supernova remnant (SNR), made with the MOST before the completion of the Wide Field upgrade. This remnant is the closest and one of the brightest SNRs. The contrast between the structures in the central pulsar-powered nebula and the synchrotron radiation shell allows the remnant to be identified morphologically as a member of the composite class. The data are the first of a composite remnant at spatial scales comparable with those available for the Cygnus Loop and the Crab Nebula, and make possible a comparison of radio, optical and soft X-ray emission from the resolved shell filaments. The survey covers an area of 50 square degrees at a resolution of 43" x 60", while imaging structures on scales up to 30'. It has been used for comparison with Wide Field observations to evaluate the performance of the upgraded MOST. The central plerion of the Vela SNR (Vela X) contains a network of complex filamentary structures. The validity of the imaging of these filaments has been confirmed with Very Large Array (VLA) observations at 1.4 GHz. Unlike the situation in the Crab Nebula, the filaments are not well correlated with H-alpha emission. Within a few parsec of the Vela pulsar the emission is much more complex than previously seen: both very sharp edges and more diffuse emission are present. It has been postulated that one of the brightest filaments in Vela X is associated with the X-ray feature (called a `jet') which appears to be emanating from the region of the pulsar. However, an analysis of the MOST and VLA data shows that this radio filament has a flat spectral index similar to another more distant filament within the plerion, indicating that it is probably unrelated to the X-ray feature.
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Brantseg, Thomas Felton. "Core-Collapse Supernova Remnants and Interactions with Their Surroundings." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4823.
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This thesis examines three core-collapse supernova remnants (SNR) - the Cygnus Loop in the Milky Way and 0453-68.5 and 0540-69.3 in the Large Magellanic Cloud - of varying ages and in varying states of interaction with the surrounding interstellar medium (ISM), using X-ray imaging spectroscopy with Chandra and supplemental data from other wavelengths. We use results from our analysis to address three main questions. First, we examine the applicability of the common Sedov-Taylor adiabatic blast wave model to core-collapse supernovae. Second, we determine the elemental abundances around the shell of these supernova remnants to determine if the use of SNRs as a gauge of abundances in the ISM is justified. Finally, we examine the pulsar wind nebulae (PWNe) in 0453-68.5 and 0540-69.3 and search for evidence of interaction between these PWNe and their immediate surroundings.
We see highly inhomogeneous ISM surrounding all three surveyed SNRs, contrary to the key assumption in the Sedov-Taylor model of a uniform surrounding medium. In all three studied SNRs, we find that shock speeds are dependent on the density of the surrounding material. As subsidiary results, we also find depleted elemental abundances of oxygen, magnesium, and silicon, relative to typical ISM, around all three studied supernova remnants. Although this subsidiary result is not conclusive, we believe that it merits a followup study.
In 0540-69.3 and 0453-68.5, which contain central pulsars, we find that the explosion directionality, which can be inferred from the pulsar's proper motion relative to the SNR, is not related to the morphology of the SNR itself. We conclude from this that the asymmetric shapes common in core-collapse supernova remnants can be more a function of the complex environments surrounding the progenitors of core- collapse supernovae than of the supernova explosions themselves.
Finally, we see that the PWN in 0453-68.5 shows signs of having mixed with the surrounding thermal- emitting material, while the PWN in 0540-69.3 appears to have not mixed with or interacted with the surrounding SNR material to any substantial degree. We believe that this result may indicate that the degree of interaction between a PWN and its surroundings is dependent on age and possibly shell morphology, although further study is needed.
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Zeng, Houdun, Yuliang Xin, Siming Liu, J. R. Jokipii, Li Zhang, and Shuinai Zhang. "EVOLUTION OF HIGH-ENERGY PARTICLE DISTRIBUTION IN MATURE SHELL-TYPE SUPERNOVA REMNANTS." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623101.
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Multi-wavelength observations of mature supernova remnants (SNRs), especially with recent advances in gamma-ray astronomy, make it possible to constrain energy distribution of energetic particles within these remnants. In consideration of the SNR origin of Galactic cosmic rays and physics related to particle acceleration and radiative processes, we use a simple one-zone model to fit the nonthermal emission spectra of three shell-type SNRs located within 2 degrees on the sky: RX J1713.7-3946, CTB 37B, and CTB 37A. Although radio images of these three sources all show a shell (or half-shell) structure, their radio, X-ray, and gamma-ray spectra are quite different, offering an ideal case to explore evolution of energetic particle distribution in SNRs. Our spectral fitting shows that (1) the particle distribution becomes harder with aging of these SNRs, implying a continuous acceleration process, and the particle distributions of CTB 37A and CTB 37B in the GeV range are harder than the hardest distribution that can be produced at a shock via the linear diffusive shock particle acceleration process, so spatial transport may play a role; (2) the energy loss timescale of electrons at the high-energy cutoff due to synchrotron radiation appears to be always a bit (within a factor of a few) shorter than the age of the corresponding remnant, which also requires continuous particle acceleration; (3) double power-law distributions are needed to fit the spectra of CTB 37B and CTB 37A, which may be attributed to shock interaction with molecular clouds.
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Foight, Dillon R., Tolga Güver, Feryal Özel, and Patrick O. Slane. "PROBING X-RAY ABSORPTION AND OPTICAL EXTINCTION IN THE INTERSTELLAR MEDIUM USING CHANDRA OBSERVATIONS OF SUPERNOVA REMNANTS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621375.
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We present a comprehensive study of interstellar X-ray extinction using the extensive Chandra supernova remnant (SNR) archive and use our results to refine the empirical relation between the hydrogen column density and optical extinction. In our analysis, we make use of the large, uniform data sample to assess various systematic uncertainties in the measurement of the interstellar X-ray absorption. Specifically, we address systematic uncertainties that originate from (i) the emission models used to fit SNR spectra; (ii) the spatial variations within individual remnants; (iii) the physical conditions of the remnant such as composition, temperature, and non-equilibrium regions; and (iv) the model used for the absorption of X-rays in the interstellar medium. Using a Bayesian framework to quantify these systematic uncertainties, and combining the resulting hydrogen column density measurements with the measurements of optical extinction toward the same remnants, we find the empirical relation N-H = (2.87 +/- 0.12) x 10(21) A(V) cm(-2), which is significantly higher than the previous measurements.
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Rho, J., J. W. Hewitt, J. Bieging, W. T. Reach, M. Andersen, and R. Güsten. "DISCOVERY OF BROAD MOLECULAR LINES AND OF SHOCKED MOLECULAR HYDROGEN FROM THE SUPERNOVA REMNANT G357.7+0.3: HHSMT, APEX, SPITZER , AND SOFIA OBSERVATIONS." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622645.
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We report a discovery of shocked gas from the supernova remnant (SNR) G357.7+0.3. Our millimeter and submillimeter observations reveal broad molecular lines of CO(2-1), CO(3-2), CO(4-3), (CO)-C-13 (2-1), and (CO)-C-13 (3-2), HCO+, and HCN using the Heinrich Hertz Submillimeter Telescope, the Arizona 12 m Telescope, APEX, and the MOPRA Telescope. The widths of the broad lines are 15-30 km s(-1), and the detection of such broad lines is unambiguous, dynamic evidence showing that the SNR G357.7+0.3 is interacting with molecular clouds. The broad lines appear in extended regions (>4'.5 x 5'). We also present the detection of shocked H-2 emission in the mid-infrared but lacking ionic lines using Spitzer/IRS observations to map a few-arcminute area. The H2 excitation diagram shows a best fit with a two-temperature local thermal equilibrium model with the temperatures of similar to 200 and 660 K. We observed [C II] at 158 mu m and high-J CO(11-10) with the German Receiver for Astronomy at Terahertz Frequencies (GREAT) on the Stratospheric Observatory for Infrared Astronomy. The GREAT spectrum of [C II], a 3 sigma detection, shows a broad line profile with a width of 15.7 km(-1) that is similar to those of broad CO molecular lines. The line width of [C II] implies that ionic lines can come from a low-velocity C-shock. Comparison of H2 emission with shock models shows that a combination of two C-shock models is favored over a combination of C- and J-shocks or a single shock. We estimate the CO density, column density, and temperature using a RADEX model. The best-fit model with n(H-2) = 1.7 x 10(4) cm(-3), N(CO) = 5.6 x 10(16) cm(-2), and T = 75 K can reproduce the observed millimeter CO brightnesses.
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Litke, Katrina C., You-Hua Chu, Abigail Holmes, Robert Santucci, Terrence Blindauer, Robert A. Gruendl, Chuan-Jui Li, Kuo-Chuan Pan, Paul M. Ricker, and Daniel R. Weisz. "Nature of the Diffuse Source and Its Central Point-like Source in SNR 0509-67.5." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624374.
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We examine a diffuse emission region near the center of SNR 0509-67.5 to determine its nature. Within this diffuse region we observe a point-like source that is bright in the near-IR, but is not visible in the B and V bands. We consider an emission line observed at 6766 angstrom and the possibilities that it is Ly alpha, H alpha, and [O II] lambda 3727. We examine the spectral energy distribution (SED) of the source, comprised of Hubble Space Telescope B, V, I, J, and H bands in addition to Spitzer/IRAC 3.6, 4.5, 5.8, and 8 mu m bands. The peak of the SED is consistent with a background galaxy at z approximate to 0.8 +/- 0.2 and a possible Balmer jump places the galaxy at z approximate to 0.9 +/- 0.3. These SED considerations support the emission line's identification as [O II] lambda 3727. We conclude that the diffuse source in SNR 0509-67.5 is a background galaxy at z approximate to 0.82. Furthermore, we identify the point-like source superposed near the center of the galaxy as its central bulge. Finally, we find no evidence for a surviving companion star, indicating a double-degenerate origin for SNR 0509-67.5.
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Sato, Toshiki, Satoru Katsuda, Mikio Morii, Aya Bamba, John P. Hughes, Yoshitomo Maeda, Manabu Ishida, and Federico Fraschetti. "X-Ray Measurements of the Particle Acceleration Properties at Inward Shocks in Cassiopeia A." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/626534.
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We present new evidence that the bright nonthermal X-ray emission features in the interior of the Cassiopeia A supernova remnant are caused by inward-moving shocks, based on Chandra and NuSTAR observations. Several bright inward-moving filaments were identified using monitoring data taken by Chandra in 2000-2014. These inward-moving shock locations are nearly coincident with hard X-ray (15-40 keV) hot spots seen by NuSTAR. From proper-motion measurements, the transverse velocities were estimated to be in the range of similar to 2100-3800 km s(-1) for a distance of 3.4 kpc. The shock velocities in the frame of the expanding ejecta reach values of similar to 5100-8700 km s(-1), which is slightly higher than the typical speed of the forward shock. Additionally, we find flux variations (both increasing and decreasing) on timescales of a few years in some of the inward-moving shock filaments. The rapid variability timescales are consistent with an amplified magnetic field of B similar to 0.5-1 mG. The high speed and low photon cut-off energy of the inward-moving shocks are shown to imply a particle diffusion coefficient that departs from the Bohm regime (k(0) = D-0/D-0,D-Bohm similar to 3-8) for the few simple physical configurations we consider in this study. The maximum electron energy at these shocks is estimated to be similar to 8-11 TeV, which is smaller than the values of similar to 15-34 TeV that were inferred for the forward shock. Cassiopeia A is dynamically too young for its reverse shock to appear to be moving inward in the observer frame. We propose instead that the inward-moving shocks are a consequence of the forward shock encountering a density jump of 5-8 in the surrounding material.
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Fraschetti, F., and M. Pohl. "Particle acceleration model for the broad-band baseline spectrum of the Crab nebula." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625798.
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We develop a simple one-zone model of the steady-state Crab nebula spectrum encompassing both the radio/soft X-ray and the GeV/multi-TeV observations. By solving the transport equation for GeV-TeV electrons injected at the wind termination shock as a log-parabola momentum distribution and evolved via energy losses, we determine analytically the resulting differential energy spectrum of photons. We find an impressive agreement with the observed spectrum of synchrotron emission, and the synchrotron self-Compton component reproduces the previously unexplained broad 200-GeV peak that matches the Fermi/Large Area Telescope (LAT) data beyond 1 GeV with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) data. We determine the parameters of the single log-parabola electron injection distribution, in contrast with multiple broken power-law electron spectra proposed in the literature. The resulting photon differential spectrum provides a natural interpretation of the deviation from power law customarily fitted with empirical multiple broken power laws. Our model can be applied to the radio-to-multi-TeV spectrum of a variety of astrophysical outflows, including pulsar wind nebulae and supernova remnants, as well as to interplanetary shocks.
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Giacalone, J. "The Acceleration of Charged Particles at a Spherical Shock Moving through an Irregular Magnetic Field." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/626061.
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We investigate the physics of charged-particle acceleration at spherical shocks moving into a uniform plasma containing a turbulent magnetic field with a uniform mean. This has applications to particle acceleration at astrophysical shocks, most notably, to supernovae blast waves. We numerically integrate the equations of motion of a large number of test protons moving under the influence of electric and magnetic fields determined from a kinematically defined plasma flow associated with a radially propagating blast wave. Distribution functions are determined from the positions and velocities of the protons. The unshocked plasma contains a magnetic field with a uniform mean and an irregular component having a Kolmogorov-like power spectrum. The field inside the blast wave is determined from Maxwell's equations. The angle between the average magnetic field and unit normal to the shock varies with position along its surface. It is quasi-perpendicular to the unit normal near the sphere's equator, and quasi-parallel to it near the poles. We find that the highest intensities of particles, accelerated by the shock, are at the poles of the blast wave. The particles "collect" at the poles as they approximately adhere to magnetic field lines that move poleward from their initial encounter with the shock at the equator, as the shock expands. The field lines at the poles have been connected to the shock the longest. We also find that the highest-energy protons are initially accelerated near the equator or near the quasi-perpendicular portion of the shock, where the acceleration is more rapid.
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Dexter, J., A. Deller, G. C. Bower, P. Demorest, M. Kramer, B. W. Stappers, A. G. Lyne, et al. "Locating the intense interstellar scattering towards the inner Galaxy." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/625730.
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We use VLBA+VLA observations to measure the sizes of the scatter-broadened images of six of the most heavily scattered known pulsars: three within the Galactic Centre (GC) and three elsewhere in the inner Galactic plane (Delta l < 20 degrees). By combining the measured sizes with temporal pulse broadening data from the literature and using the thin-screen approximation, we locate the scattering medium along the line of sight to these six pulsars. At least two scattering screens are needed to explain the observations of the GC sample. We show that the screen inferred by previous observations of SGR J1745-2900 and Sgr A*, which must be located far from the GC, falls off in strength on scales less than or similar to 0 degrees.2. A second scattering component closer to (Delta < 2 kpc) or even (tentatively) within (Delta < 700 pc) the GC produces most or all of the temporal broadening observed in the other GC pulsars. Outside the GC, the scattering locations for all three pulsars are similar or equal to 2 kpc from Earth, consistent with the distance of the Carina-Sagittarius or Scutum spiral arm. For each object the 3D scattering origin coincides with a known H II region (and in one case also a supernova remnant), suggesting that such objects preferentially cause the intense interstellar scattering seen towards the Galactic plane. We show that the H II regions should contribute greater than or similar to 25 per cent of the total dispersion measure (DM) towards these pulsars, and calculate reduced DM distances. Those distances for other pulsars lying behind H II regions may be similarly overestimated.
Book chapters on the topic "Outflows supernova remnants ISM"
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Oliva, E., S. Drapatz, D. Lutz, E. Sturm, and A. F. M. Moorwood. "First Results From ISO Spectra of Supernova Remnants Heavily Interacting with the ISM." In Astrophysics and Space Science, 211–20. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5076-7_33.
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