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Book Fermi LAT Discovery of Extended Gamma Ray Emission in the Direction of Supernova Remnant W51C

Download or read book Fermi LAT Discovery of Extended Gamma Ray Emission in the Direction of Supernova Remnant W51C written by and published by . This book was released on 2012 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery of bright gamma-ray emission coincident with supernova remnant (SNR) W51C is reported using the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. W51C is a middle-aged remnant (≈104 yr) with intense radio synchrotron emission in its shell and known to be interacting with a molecular cloud. The gamma-ray emission is spatially extended, broadly consistent with the radio and X-ray extent of SNR W51C. The energy spectrum in the 0.2-50 GeV band exhibits steepening toward high energies. The luminosity is greater than 1 x 1036 erg s−1 given the distance constraint of D> 5.5 kpc, which makes this object one of the most luminous gamma-ray sources in our Galaxy. The observed gamma-rays can be explained reasonably by a combination of efficient acceleration of nuclear cosmic rays at supernova shocks and shock-cloud interactions. The decay of neutral p mesons produced in hadronic collisions provides a plausible explanation for the gamma-ray emission. The product of the average gas density and the total energy content of the accelerated protons amounts to {bar n}{sub H} W{sub p} ≃ 5 x 1051 (D/6 kpc)2 erg cm−3. Electron density constraints from the radio and X-ray bands render it difficult to explain the LAT signal as due to inverse Compton scattering. The Fermi LAT source coincident with SNR W51C sheds new light on the origin of Galactic cosmic rays.

Book Cosmic Rays in Star Forming Environments

Download or read book Cosmic Rays in Star Forming Environments written by Diego F. Torres and published by Springer Science & Business Media. This book was released on 2013-04-19 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: These are the proceedings of the Sant Cugat Forum 2nd Workshop on Cosmic-ray Induced Phenomenology in Stellar Environments, held April 16-19, 2012. The aim of this Workshop was to address the current knowledge and challenges of high-energy emission from stellar environments at all scales and provide a comprehensive review of the state of the field from the observational to the theoretical perspectives. In the meeting, the prospects for possible observations with planned instruments across the multi-wavelength spectrum were analyzed and also how they impact on our understanding of these systems.

Book Fermi LAT Observation of Supernova Remnant S147

Download or read book Fermi LAT Observation of Supernova Remnant S147 written by and published by . This book was released on 2012 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present an analysis of gamma-ray data obtained with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region around SNR S147 (G180.0-1.7). A spatially extended gamma-ray source detected in an energy range of 0.2-10 GeV is found to coincide with SNR S147. We confirm its spatial extension at>5? confidence level. The gamma-ray flux is (3.8 ± 0.6) x 10−8 photons cm−2 s−1, corresponding to a luminosity of 1.3 x 1034 (d/1.3 kpc)2 erg s−1 in this energy range. The gamma-ray emission exhibits a possible spatial correlation with prominent H? filaments of S147. There is no indication that the gamma-ray emission comes from the associated pulsar PSR J0538+2817. The gamma-ray spectrum integrated over the remnant is likely dominated by the decay of neutral? mesons produced through the proton-proton collisions in the filaments. Reacceleration of pre-existing CRs and subsequent adiabatic compression in the filaments is sufficient to provide the required energy density of high-energy protons.

Book Search for Evidence of Cosmic Ray Acceleration by Supernova Remnant Kes 41 Using the Fermi LAT

Download or read book Search for Evidence of Cosmic Ray Acceleration by Supernova Remnant Kes 41 Using the Fermi LAT written by Timothy Robert Joubert and published by . This book was released on 2013 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: The analysis presented in this paper incorporated photon events received during the full run time of the Fermi Gamma Space Telescope (FGST) Large Area Telescope (LAT) to date. By studying the [gamma]y emission of the supernova remnant (SNR) Kes 41 for the energy range ~ 200MeV-200GeV, the [gamma]-ray morphology and spectrum were measured. These measurements required the use of reduced log likelihood statistics mediated by the Fermi Science Tools toolkit, developed for LAT analysis. The spatial analysis of the [gamma]-ray emission was measured at 5[sigma] for the area within and around the contours established during radio measurements [25]. It also resembles Kes 41's observed, centrally bright, X-ray emission [18, 25]. Spectral analysis was also carried out and the resulting [gamma]-ray spectrum was successfully fit to a power-law model of emission consistent with [pi]0-decay, a form of non-thermal emission caused by cosmic ray acceleration. An overall approximation of the [gamma]-ray luminosity was then measured as L[gamma] = 1.94 x 1035 erg/s using a measure of the total [gamma]-ray flux. A calculation also measured the particle density associated with material interacting with Kes 41 emission as n = 0.15 particles/cm-3. This value resembles that from other calculations involving SNR-Molecular cloud interaction [22]. This interaction serves to constrain [gamma]-ray emission to the [pi]0-decay channel, so evidence of a similar density value may be evidence that the significant [gamma]-ray emission observed, was due to the acceleration of cosmic rays.

Book Search for Gamma ray Emission from Supernova Remnants with the Fermi LAT and MAGIC Telescopes

Download or read book Search for Gamma ray Emission from Supernova Remnants with the Fermi LAT and MAGIC Telescopes written by Ignasi Reichardt Candel and published by . This book was released on 2012 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant

Download or read book Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant written by and published by . This book was released on 2011 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present an analysis of the gamma-ray measurements by the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope in the region of the supernova remnant (SNR) Cygnus Loop (G74.0-8.5). We detect significant gamma-ray emission associated with the SNR in the energy band 0.2-100 GeV. The gamma-ray spectrum shows a break in the range 2-3 GeV. The gamma-ray luminosity is ≈ 1 x 1033 erg s−1 between 1-100 GeV, much lower than those of other GeV-emitting SNRs. The morphology is best represented by a ring shape, with inner/outer radii 0{sup o}.7 ± 0{sup o}.1 and 1{sup o}.6 ± 0{sup o}.1. Given the association among X-ray rims, H[alpha] filaments and gamma-ray emission, we argue that gamma rays originate in interactions between particles accelerated in the SNR and interstellar gas or radiation fields adjacent to the shock regions. The decay of neutral pions produced in nucleon-nucleon interactions between accelerated hadrons and interstellar gas provides a reasonable explanation for the gamma-ray spectrum.

Book Fermi Large Area Telescope Observations of the Supernova Remnant G8 7 0 1

Download or read book Fermi Large Area Telescope Observations of the Supernova Remnant G8 7 0 1 written by and published by . This book was released on 2012 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. The GeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200 MeV-100 GeV can be described by a broken power-law function with a break of 2.4 ± 0.6 (stat) ± 1.2 (sys) GeV, and photon indices of 2.10 ± 0.06 (stat) ± 0.10 (sys) below the break and 2.70 ± 0.12 (stat) ± 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of p0s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains the GeV gamma-ray spectrum. We also find that the GeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in the GeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

Book Fermi LAT Discovery of GeV Gamma ray Emission from the Vicinity of SNR W44

Download or read book Fermi LAT Discovery of GeV Gamma ray Emission from the Vicinity of SNR W44 written by and published by . This book was released on 2013 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Search for High Energy Gamma Rays in the Northern Fermi Bubble Region with the HAWC Observatory

Download or read book Search for High Energy Gamma Rays in the Northern Fermi Bubble Region with the HAWC Observatory written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : Gamma-ray astronomy is the study of very energetic photons, from E = mec2 = 0.5x106 eV to > 10 1020eV. Due to the large span of the energy range, the field focuses on non-thermal processes that include the acceleration and propagation of relativistic particles, which can be found in extreme environments such as pulsars, supernova remnants, molecular clouds, black holes, etc. The High Altitude Water Cherenkov (HAWC) observatory is an instrument designed for the study of gamma rays in the energy range of 100 GeV to 100 TeV. Using data from the HAWC observatory, a study for the search of very high energy gamma rays in the northern Fermi Bubble region was made. The Fermi Bubbles are large extended regions in the gamma-ray sky located above and below the galactic plane that present a hard emission between 1 GeV and 100 GeV. No significant excess is found an upper bounds at 95% C.L. are obtained. The implications of this result are that certain processes explaining the Fermi Bubble formation from the center of our galaxy are excluded. I will discuss and compare the scenarios that still present a possible hypothesis of the Fermi Bubble origin.

Book Gamma ray Flux Variation Studies from the Blazar B2 1215 30 with the Fermi LAT and the Crab Nebula with the H E S S Experiment

Download or read book Gamma ray Flux Variation Studies from the Blazar B2 1215 30 with the Fermi LAT and the Crab Nebula with the H E S S Experiment written by Floriana Zefi and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current state-of-the-art experiments in gamma-ray astronomy are the Fermi-LAT in space and the ground-based H.E.S.S., VERITAS and MAGIC experiments. The monitoring of the very-high-energy gamma-ray emitting sources indicates the diverse physics taking place in astrophysical environments. To study the most energetic form of radiation and the most violent phenomena taking place in the Universe, individual source analyses are important. BL Lac objects, a subcategory of active galaxies, are the most abundant source class detected both in the GeV andTeV energies, while pulsar wind nebulae represent the most numerous identified source class in the galactic plane. Both source classes exhibit gamma-ray flux variations.In this thesis, the gamma-ray variability of the BL Lac object B2 1215+30 is presented with Fermi-LAT data. A bright flare, with 16 times the average quiescent flux, was detected in February 2014.In collaboration with the VERITAS experiment, the gamma-ray variability was investigated over five decades in energy. This work resulted in the detection of a luminous flare, seen simultaneously in GeV and TeV energies by both instruments. These results were used to set constraints on the size of the emission region and on the Doppler factor of the relativistic jet. Additionally, the long-term variability was studied using nine years of Fermi-LAT data. This brought out new flux enhancements, which characterize the long-term lightcurve from 100 MeV up to 500 GeV. Other striking characteristics are a steady linear increase of the yearly average flux, together with a hardening of the spectral index. The investigation of the light curve indicates a hint of quasi-periodic behavior with a period of around 1083±32 days.This work includes spectrum and flux variability studies for the well-studied but ever-surprising Crab Nebula at TeV energies with more than a decade of H.E.S.S. observations. The spectrum measured in this work goes from 280 GeV to 62 TeV, making this the first measurement tha textends to such very-high-energies. Considered as a standard candle for ground-based gamma-ray astronomy, the Crab Nebula is also used for calibration and instrument studies. The detection of GeV flares by the Fermi-LAT were unexpected and motivated the search of flux variations at TeVenergies with the H.E.S.S. experiment. The position of the Crab Nebula in the northern hemisphere makes this investigation challenging due to the large systematic uncertainties introduced by the non-optimal observation conditions. This work showed that the systematic uncertainties can be reduced by taking into account the atmospheric transparency. No flux variations were found at energies above 1 TeV from the H.E.S.S. I data. A flare reported by the Fermi-LAT in October 2016 was also investigated. This analysis showed the GeV flare lasting for one month, while the flux withH.E.S.S. II had an excess variance of 15 %. This should be compared to the commonly quoted 20% systematic uncertainty by H.E.S.S. experiment.

Book Physics and Evolution of Supernova Remnants

Download or read book Physics and Evolution of Supernova Remnants written by Jacco Vink and published by Springer Nature. This book was released on 2020-11-10 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by a leading expert, this monograph presents recent developments on supernova remnants, with the inclusion of results from various satellites and ground-based instruments. The book details the physics and evolution of supernova remnants, as well as provides an up-to-date account of recent multiwavelength results. Supernova remnants provide vital clues about the actual supernova explosions from X-ray spectroscopy of the supernova material, or from the imprints the progenitors had on the ambient medium supernova remnants are interacting with - all of which the author discusses in great detail. The way in which supernova remnants are classified, is reviewed and explained early on. A chapter is devoted to the related topic of pulsar wind nebulae, and neutron stars associated with supernova remnants. The book also includes an extended part on radiative processes, collisionless shock physics and cosmic-ray acceleration, making this book applicable to a wide variety of astronomical sub-disciplines. With its coverage of fundamental physics and careful review of the state of the field, the book serves as both textbook for advanced students and as reference for researchers in the field.