<i>FERMI</i>
                    LARGE AREA TELESCOPE DETECTION OF THE YOUNG SUPERNOVA REMNANT TYCHO

Giordano, F.; Naumann-Godó, M.; Ballet, J.; Bechtol, K.; Funk, Stefan; Landé, J.; Mazziotta, M. N.; Rainò, S.; Tanaka, Takaaki; Tibolla, O.; Uchiyama, Y.

doi:10.1088/2041-8205/744/1/l2

Cited by 158 publications

(147 citation statements)

References 26 publications

(38 reference statements)

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“…However, in young SNRs where the hadronic hypothesis is preferred, the measured spectral indices are softer than or equal to 2.0 as in Cassiopeia A (2.0 ± 0.1 stat ± 0.1 syst , Abdo et al 2010) and Tycho (2.3 ± 0.2 stat ± 0.1 syst , Giordano et al 2012).…”

Section: Source Class Comparison At He and Vhementioning

confidence: 91%

Study of TeV shell supernova remnants at gamma-ray energies

Acero

Lemoine‐Goumard

Renaud

et al. 2015

A&A

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Context. The breakthrough developments of Cherenkov telescopes in the past decade have led to angular resolution of 0.1 • and an unprecedented sensitivity. This has allowed the current generation of Cherenkov telescopes (H.E.S.S., MAGIC, and VERITAS) to discover a population of supernova remnants (SNRs) radiating in very-high-energy (VHE; E > 100 GeV) γ-rays. A number of those VHE SNRs exhibit a shell-type morphology that is spatially coincident with the shock front of the SNR. Aims. The members of this VHE shell SNR club are RX J1713.7−3946, RX J0852.0−4622, RCW 86, SN 1006, and HESS J1731−347. The last two objects have been poorly studied in high-energy (HE; 0.1 < E < 100 GeV) γ-rays and need to be investigated in order to draw the overall picture of this class of SNRs and to constrain the characteristics of the underlying population of accelerated particles. Methods. Using 6 years of Fermi-LAT P7 reprocessed data, we studied the GeV counterpart of the SNRs HESS J1731−347 and SN 1006. The two SNRs are not detected in the data set, and given that there is no hint of detection, we do not expect any detection in coming years from the SNRs. However in both cases, we derived upper limits that significantly constrain the γ-ray emission mechanism and can rule out a standard hadronic scenario with a confidence level >5σ. Results. With this Fermi analysis, we now have a complete view of the HE to VHE γ-ray emission of TeV shell SNRs. All five sources have a hard HE photon index (Γ < 1.8), which suggests a common scenario where the bulk of the emission is produced by accelerated electrons radiating from radio to VHE γ-rays through synchrotron and inverse Compton processes. In addition when correcting for the distance, all SNRs show a surprisingly similar γ-ray luminosity supporting the idea of a common emission mechanism. While the γ-ray emission is likely to be leptonic-dominated at the scale of the whole SNR, this does not rule out efficient hadron acceleration in those objects.

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Section: Source Class Comparison At He and Vhementioning

confidence: 91%

Study of TeV shell supernova remnants at gamma-ray energies

Acero

Lemoine‐Goumard

Renaud

et al. 2015

A&A

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“…The most intriguing aspect of Tycho's broadband spectrum is its gamma-ray emission, which has been detected before in the TeV band by VERITAS (Acciari et al 2011) and then in the GeV band by Fermi-LAT, too (Giordano et al 2012). Gammaray emission from SNRs has been considered for long time a possible evidence of hadron acceleration in this class of objects (Drury et al 1994), even if there are two distinct physical mechanisms that may be responsible for such an emission; in the socalled hadronic scenario, the gamma-rays are produced by the decay of neutral pions produced in nuclear collisions between CRs and the background gas, while in the so-called leptonic scenario the emission is due to ICS or relativistic bremsstrahlung of relativistic electrons.…”

Section: Gamma-ray Emissionmentioning

confidence: 96%

“…For VERITAS data the systematic error is found to be ∼30% (Acciari et al 2011), while for Fermi-LAT the systematic uncertainties are comparable to or even larger than the statistical error especially for the lowest energy bins due to difficulties in evaluating the galactic background (see Fig. 3 in Giordano et al 2012, and the related discussion).…”

Section: Gamma-ray Emissionmentioning

confidence: 98%

“…The TeV emission is compatible with a point like source since the telescope's point spread function (PSF) of ∼15 arcmin is larger than the angular size of the remnant (8 arcmin). Even more recently, the Fermi-LAT has reported a detection of Tycho as well, assessing an integral flux above 400 MeV of ∼(3.5 ± 1.1 stat ± 0.7 sys ) × 10 −9 ph cm −2 s −1 and a spectral slope 2.3 ± 0.2 stat ± 0.1 sys (Giordano et al 2012).…”

Section: Introductionmentioning

confidence: 97%

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Strong evidence for hadron acceleration in Tycho’s supernova remnant

Morlino

Caprioli

2012

A&A

290

313

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Context. Very recent gamma-ray observations of G120.1+1.4 (Tycho's) supernova remnant (SNR) by Fermi-LAT and VERITAS have provided new fundamental pieces of information for understanding particle acceleration and nonthermal emission in SNRs. Aims. We want to outline a coherent description of Tycho's properties in terms of SNR evolution, shock hydrodynamics, and multiwavelength emission by accounting for particle acceleration at the forward shock via first-order Fermi mechanism. Methods. We adopt here a quick and reliable semi-analytical approach to nonlinear diffusive shock acceleration. It includes magnetic field amplification due to resonant streaming instability and the dynamical backreaction on the shock of both cosmic rays (CRs) and self-generated magnetic turbulence. Results. We find that Tycho's forward shock accelerates protons up to at least 500 TeV, channelling into CRs about 10% of its kinetic energy. Moreover, the CR-induced streaming instability is consistent with all the observational evidence of very efficient magnetic field amplification (up to ∼300 μG). In such a strong magnetic field, the velocity of the Alfvén waves scattering CRs in the upstream is expected to be enhanced and to make accelerated particles feel an effective compression factor lower than 4, in turn leading to an energy spectrum steeper than the standard prediction ∝E −2 . This effect is crucial for explaining GeV-to-TeV gamma-ray spectrum as the result of neutral pions decay produced in nuclear collisions between accelerated nuclei and the background gas. Conclusions. The self-consistency of such hadronic scenario, along with the inability of the concurrent leptonic mechanism (inverse Compton scattering of relativistic electrons on several photon backgrounds) to reproduce both the shape and the normalization of the detected gamma-ray emission, represents the first clear and direct radiative evidence that hadron acceleration occurs efficiently in young Galactic SNRs.

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“…If this were correct, particle spectra should follow a power-law with index, s = 2, with an exponential cut-off at very high energy. However, the wealth of recent observational data on, e.g., RX J0852.0-4622 (Aharonian et al 2007), RCW 86 (Aharonian et al 2009), SN 1006 (Acero et al 2010), Cas A (Acciari et al 2010;Abdo et al 2010), and Tycho's SNR (Acciari et al 2011;Giordano et al 2012) provide strong evidence that the particle spectra are significantly softer. Moreover, the spectral shape is not a pure power law with exponential cut-off, as for example in Cas A.…”

Section: Introductionmentioning

confidence: 99%

Acceleration of cosmic rays by young core-collapse supernova remnants

Telezhinsky

Dwarkadas

Pohl

2013

A&A

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Context. Supernova remnants (SNRs) are thought to be the primary candidates for the sources of Galactic cosmic rays. According to the diffusive shock acceleration theory, SNR shocks produce a power-law spectrum with an index of s = 2, perhaps nonlinearly modified to harder spectra at high energy. Observations of SNRs often indicate particle spectra that are softer than that and show features not expected from classical theory. Known drawbacks of the standard approach are the assumption that SNRs evolve in a uniform environment, and that the reverse shock does not accelerate particles. Relaxing these assumptions increases the complexity of the problem, because one needs reliable hydrodynamical data for the plasma flow as well as good estimates for the magnetic field (MF) at the reverse shock. Aims. We show that these two factors are especially important when modeling young core-collapse SNRs that evolve in a complicated circumstellar medium shaped by the winds of progenitor stars. Methods. We used high-resolution numerical simulations for the hydrodynamical evolution of the SNR. Instead of parametrizations of the MF profiles inside the SNR, we followed the advection of the frozen-in MF inside the SNR, and thus obtained the B-field value at all locations, in particular at the reverse shock. To model cosmic-ray acceleration we solved the cosmic-ray transport equation in test-particle approximation. Results. We find that the complex plasma-flow profiles of core-collapse SNRs significantly modify the particle spectra. Additionally, the reverse shock strongly affects the emission spectra and the surface brightness.

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FERMI LARGE AREA TELESCOPE DETECTION OF THE YOUNG SUPERNOVA REMNANT TYCHO

Cited by 158 publications

References 26 publications

Study of TeV shell supernova remnants at gamma-ray energies

Study of TeV shell supernova remnants at gamma-ray energies

Strong evidence for hadron acceleration in Tycho’s supernova remnant

Acceleration of cosmic rays by young core-collapse supernova remnants

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