Using optical lines to study particle acceleration at supernova remnants

Morlino, G.

doi:10.1016/j.nuclphysbps.2014.10.006

Cited by 6 publications

(4 citation statements)

References 33 publications

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“…This choice appears to be in good qualitative agreement with observations when the shock speed is > ∼ 1000 km s −1 (see e.g. Ghavamian et al (2013) for a review and Morlino (2014)) and also with results from PICS simulations . We also notice that values of β e that are below 0.1 do not change our results, while if β e approaches unity, the ionization rate of neutrals due to electrons increases and the effect of the NRF is reduced.…”

Section: Resultssupporting

confidence: 82%

“…Magnetic field amplification plays a crucial role in this discussion: reaching high energies requires amplification to occur in the the so-called CR driven regime (Bell, 2004), but in this case the conditions in which the supernova explosion occurs seem to determine how high the maximum energy can be. For instance, Schure & Bell (2013, 2014 and Cardillo, Amato & Blasi (2015) point out that only core collapse supernova (SN) explosions taking place in the wind of their pre-supernova red giant parent star could possibly ⋆ email: giovanni.morlino@gssi.infn.it ⋆⋆ email: blasi@arcetri.astro.it achieve maximum energy in the PeV region (within a few tens of years after the explosion), while standard SNe type Ia, exploding in the interstellar medium (ISM), can only reach maximum energy around a few hundred TeV. Realistic estimates of the maximum energy may be affected by damping processes.…”

Section: Introductionmentioning

confidence: 99%

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Spectra of accelerated particles at supernova shocks in the presence of neutral hydrogen: the case of Tycho

Morlino

Blasi

2016

A&A

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Context. The presence of neutral hydrogen in the shock proximity changes the structure of the shock and affects the spectra of particles accelerated through the first-order Fermi mechanism. This phenomenon has profound implications for the interpretation of the multifrequency spectra of radiation from supernova remnants. Aims. Neutrals that undergo charge exchange with hot ions downstream of the shock may result in fast neutrals moving towards the upstream gas, where they can suffer additional charge exchange or ionisation reactions, thereby depositing energy and momentum upstream. Here we discuss the implications of this neutral return flux, which was already predicted in our previous work on neutral mediated supernova shocks, and show how the spectra of accelerated particles turn out to be appreciably steeper than p −4 , thereby affecting the gamma ray spectra from supernova remnants in general and from Tycho specifically. Methods. The theory that describes non-linear diffusive shock acceleration in the presence of neutral hydrogen has been developed in recent years. Here we use a semi-analytical theory developed in previous work and specialise our predictions to the case of the Tycho supernova shock, where there is evidence from gamma ray observations that the spectrum of the parent cosmic rays is steeper than expected from the traditional theory of diffusive shock acceleration. Results. We show that, if the fraction of neutral hydrogen in the vicinity of the Tycho supernova shock is, as suggested by observations, ∼70−90%, then spectra of accelerated protons steeper than p −4 may be a natural consequence of charge exchange reactions and the associated neutral return flux. The spectral shape is affected by this phenomenon for particles with energies below ∼100−1000 GeV, for which the diffusion length is less than or at most comparable to the path length of charge exchange and ionisation upstream of the shock.

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Section: Resultssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Spectra of accelerated particles at supernova shocks in the presence of neutral hydrogen: the case of Tycho

Morlino

Blasi

2016

A&A

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“…As a consequence the expected width of the broad Blamer line is smaller when efficient acceleration takes place. It is very intriguing that such reduction of the broad Balmer line width has been inferred in at least two SNRs, namely RCW 86 and SN 0509-67.5 (Morlino, 2014). On the other hand, as shown in Section 3.3, the existence of a CR precursor could be responsible for a temperature increase of the upstream plasma resulting in a larger width of the narrow Balmer lines.…”

Section: (4) Compression Ratiosmentioning

confidence: 86%

High-Energy Cosmic Rays from Supernovae

Morlino

2017

Handbook of Supernovae

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Cosmic rays are charged relativistic particles that reach the Earth with extremely high energies, providing striking evidence of the existence of effective accelerators in the Universe. Below an energy around ∼ 10 17 eV cosmic rays are believed to be produced in the Milky Way while above that energy their origin is probably extragalactic. In the early '30s supernovae were already identified as possible sources for the Galactic component of cosmic rays. After the '70s this idea has gained more and more credibility thanks to the the development of the diffusive shock acceleration theory, which provides a robust theoretical framework for particle energization in astrophysical environments. Afterwards, mostly in recent years, much observational evidence has been gathered in support of this framework, converting a speculative idea in a real paradigm. In this Chapter the basic pillars of this paradigm will be illustrated. This includes the acceleration mechanism, the non linear effects produced by accelerated particles onto the shock dynamics needed to reach the highest energies, the escape process from the sources and the transportation of cosmic rays through the Galaxy. The theoretical picture will be corroborated by discussing several observations which support the idea that supernova remnants are effective cosmic ray factories.

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“…Two SNRs are analyzed in [63], with resulting ε esc comprised between 6% and 70%. Morlino et al [64], Morlino [65] present an in depth analysis of the SNRs RCW 86, SNR 0509-67.5 and Tycho (the first two were analyzed also in [63]), concluding that, even if a value of ε esc ∼ 0 cannot be excluded because of uncertainties in the source distance, ε esc is probably in the range 10-20%.…”

Section: Production Of Cosmic-ray Electronsmentioning

confidence: 99%

A review of Cosmic-ray electrons and fermi-LAT

Tinivella

2016

Preprint

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The study of Galactic Cosmic Ray Electrons (CREs) saw important developments in recent years, with the assumption of e + production only in interaction of hadronic Cosmic-rays with interstellar matter challenged by new measurements of CRE spectrum and related quantities. Indeed, all recent experiments seem to confirm an hardening in the e + , a feature that is totally in contrast with the allsecondaries hypothesis, even if significant disagreements are present about the CRE spectral behavior and the possible presence of spectral features. Together with insufficient precision of current measurements, these disagreements prevent the identification of the primary e + source, with models involving Dark matter or astrophysical sources like SuperNova Remnants (SNRs) and Pulsar Wind Nebulae (PWNe) all able to explain current data.The Fermi-LAT contribution to the CRE study was fundamental, with the 2009 measurement of the e + +e − spectrum extended to the 7 MeV -1 TeV range with a statistics already exceeding previous results by many order of magnitude; since then, the last statistic has largely increased, while the LAT event reconstruction was significantly improved.In this article the reader will find an extensive and historical review of the CRE science, a summary of the history of gamma astronomy before Fermi, an accurate description of the LAT and of its data analysis, a review of the present knowledge about CRE spectrum and on the theories that try to explain it, and finally a description of the changes and improvements introduced in the LAT event reconstruction process at the beginning of 2015.

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Using optical lines to study particle acceleration at supernova remnants

Cited by 6 publications

References 33 publications

Spectra of accelerated particles at supernova shocks in the presence of neutral hydrogen: the case of Tycho

Spectra of accelerated particles at supernova shocks in the presence of neutral hydrogen: the case of Tycho

High-Energy Cosmic Rays from Supernovae

A review of Cosmic-ray electrons and fermi-LAT

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