Can Galactic Cosmic Rays Account for Solar
                    <sup>6</sup>
                    Li without Overproducing Gamma Rays?

Prodanovic, Tijana; Fields, Brian D.

doi:10.1086/506205

Cited by 8 publications

(10 citation statements)

References 34 publications

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“…Compared to the solar abundance of lithium ( 6 Li/H) ⊙ = 1.53 × 10 −10 [4] we get ( 6 Li/H) MW ≈ 0.76( 6 Li/H) ⊙ . This also means that if we assume that the entire solar 6 Li abundance is produced by GCRs, the corresponding gamma-ray intensity of the MW-like galaxies would be larger and would violate the observed IGRB, which is consistent with the conclusions in [15,33].…”

Section: Formalism and Resultssupporting

confidence: 78%

Galactic cosmic-ray induced production of lithium in the Small Magellanic Cloud

Ćiprijanović

2016

Astroparticle Physics

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Recently, the first lithium detection outside of the Milky Way was made in low-metallicity gas of the Small Magellanic Cloud, which was at the level of the expected primordial value. Part of the observed lithium in any environment has primordial origin, but there is always some post-BBN (Big Bang Nucleosynthesis) contamination, since lithium can also be produced in cosmic-ray interactions with the interstellar medium. Using the fact that processes involving cosmic rays produce lithium, but also gamma rays through neutral pion decay, we use the Small Magellanic Cloud gamma-ray observations by Fermi-LAT to make predictions on the amount of lithium in this galaxy that was produced by galactic cosmic rays accelerated in supernova remnants. By including both fusion processes, as well as spallation of heavier nuclei, we find that galactic cosmic rays could produce a very small amount of lithium. In the case of 6 Li isotope (which should only be produced by cosmic rays) we can only explain 0.16% of the measured abundance. If these cosmic rays are indeed responsible for such small lithium production, observed abundances could be the result of some other sources, which are discussed in the paper.

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Section: Formalism and Resultssupporting

confidence: 78%

Galactic cosmic-ray induced production of lithium in the Small Magellanic Cloud

Ćiprijanović

2016

Astroparticle Physics

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“…In this work, we have implemented source evolution based on the PF06 (Prodanović & Fields 2006) analytical model of cosmic accretion shocks around virialized structures within different environments, with spectral index of the source gamma-ray emission as a free parameter. The results of our analysis are, in some cases, consistent with previous estimates that this component is subdominant to all other EGRB sources ; however, we also show that there are scenarios where accretion shocks on clusters can have an important contribution to the EGRB.…”

Section: Discussionmentioning

confidence: 99%

“…Nonetheless, given the importance of disentangling the origin of the EGRB and identifying its dominant components, in this work we build an improved and more detailed model of SFCR contribution to the EGRB. Since the history of this cosmic-ray population is unknown, as its tracer, we implement a semi-analytical source evolution of accretion shocks (Prodanović & Fields 2006). Another unknown required to make a prediction of their collective emission contributing to the EGRB is the gamma-ray flux expected from a single, average, large-scale shock.…”

Section: Introductionmentioning

confidence: 99%

DIFFUSE PIONIC GAMMA-RAY EMISSION FROM LARGE-SCALE STRUCTURES IN THEFERMIERA

Dobardžić

Prodanovic

2014

ApJ

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For more than a decade now the complete origin of the diffuse gamma-ray emission background (EGRB) has been unknown. Major components like unresolved star-forming galaxies (making < ∼ 50% of the EGRB) and blazars ( < ∼ 23%), have failed to explain the entire background observed by Fermi. Another, though subdominant, contribution is expected to come from the process of large-scale structure formation. The growth of structures is accompanied by accretion and merger shocks, which would, with at least some magnetic field present, give rise to a population of structure-formation cosmic rays (SFCRs). Though expected, this cosmic-ray population is still hypothetical and only very weak limits have been placed to their contribution to the EGRB. The most promising insight into SFCRs was expected to come from Fermi -LAT observations of clusters of galaxies, however, only upper limits and no detection have been placed. Here, we build a model of gamma-ray emission from large-scale accretion shocks implementing a source evolution calibrated with the Fermi -LAT cluster observation limits. Though our limits to the SFCR gamma-ray emission are weak (above the observed EGRB) in some case, in others, some of our models can provide a good fit to the observed EGRB. More importantly, we show that these largescale shocks could still give an important contribution to the EGRB, especially at high energies. Future detections of cluster gamma-ray emission would help place tighter constraints on our models and give us a better insight into large-scale shocks forming around them.

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“…A full calculation including all the light elements would be necessary to ascertain that. We also note that there are astrophysical scenarios wherein the observed abundance of 6 Li finds an explanation (e.g., [39,40,41,42,43,44,45]). The processes we have described here are clearly relevant for determining the light element abundances.…”

Section: Discussionmentioning

confidence: 75%