scholarly journals Beryllium Radioactive Isotopes as a Probe to Measure the Residence Time of Cosmic Rays in the Galaxy and Halo Thickness: A “Data-Driven” Approach

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 183
Author(s):  
Francesco Nozzoli ◽  
Cinzia Cernetti
Keyword(s):  
Cosmic Rays ◽  
Residence Time ◽  
Galactic Halo ◽  
Flux Ratio ◽  
Cosmic Ray ◽  
Radioactive Isotopes ◽  
Data Driven ◽  
Data Driven Approach ◽  
A New Technique ◽  
Two Parameters

Cosmic rays are a powerful tool for the investigation of the structure of the magnetic fields in the Galactic halo and the properties of the inter-stellar medium. Two parameters of the cosmic ray propagation models, the Galactic halo (half) thickness, H, and the diffusion coefficient, D, are loosely constrained by current cosmic ray flux measurements; in particular, a large degeneracy exists, with only H/D being well measured. The 10Be/9Be isotopic flux ratio (thanks to the 2 My lifetime of 10Be) can be used as a radioactive clock providing the measurement of cosmic ray residence time in a galaxy. This is an important probe with which to solve the H/D degeneracy. Past measurements of 10Be/9Be isotopic flux ratios in cosmic rays are scarce, and were limited to low energy and affected by large uncertainties. Here a new technique to measure 10Be/9Be isotopic flux ratio, with a data-driven approach in magnetic spectrometers is presented. As an example, by applying the method to beryllium events published via PAMELA experiment, it is now possible to determine the important 10Be/9Be measurement while avoiding the prohibitive uncertainties coming from Monte Carlo simulations. It is shown how the accuracy of PAMELA data strengthens the experimental indication for the relativistic time dilation of 10Be decay in cosmic rays; this should improve the knowledge of the H parameter.

scholarly journals A Data Driven Approach for the Measurement of 10Be/9Be in Cosmic Rays with Magnetic Spectrometers

2020 ◽  
Author(s):  
Francesco Nozzoli ◽  
Cinzia Cernetti
Keyword(s):  
Cosmic Rays ◽  
Galactic Halo ◽  
Flux Ratio ◽  
Data Driven ◽  
A Value ◽  
The Galaxy ◽  
Data Driven Approach ◽  
Flux Measurements ◽  
A New Technique ◽  
Two Parameters

Cosmic Rays (CR) are a powerful tool for the investigation of the structure of the magnetic fields in the galactic halo and the property of the Inter-Stellar Medium. Two parameters of the CR propagation models: the galactic halo thickness, H, and the diffusion coefficient, D, are loosely constrained by current CR flux measurements, in particular a large degeneracy exist being only H/D well measured. The 10Be/9Be isotopic flux ratio (thanks to the 2 My lifetime of 10Be) can be used as a radioactive clock providing the measurement of CR residence time in the galaxy. This is an important tool to solve the H/D degeneracy. Past measurements of 10Be/9Be isotopic flux ratio in CR are scarce, limited to low energy and affected by large uncertainties. Here a new technique to measure 10Be/9Be isotopic flux ratio, with a Data-Driven approach, in magnetic spectrometers is presented. As an example by applying the method to Beryllium events published by PAMELA experiment it is now possible to determine the important 10Be/9Be measurement avoiding the prohibitive uncertainties coming from the Monte Carlo simulation. It is shown how the accuracy of PAMELA data permits to infer a value of the halo thickness H within 25% precision.

scholarly journals Discovery of s-process enhanced stars in the LAMOST survey

2019 ◽  
Vol 490 (2) ◽  
pp. 2219-2227 ◽  
Author(s):  
Brodie J Norfolk ◽  
Andrew R Casey ◽  
Amanda I Karakas ◽  
Matthew T Miles ◽  
Alex J Kemp ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Selection Bias ◽  
Galactic Halo ◽  
Asymptotic Giant Branch ◽  
The Other ◽  
Data Driven ◽  
Giant Stars ◽  
Show Evidence ◽  
Data Driven Approach ◽  
Red Giant

ABSTRACT Here we present the discovery of 895 s-process-rich candidates from 454 180 giant stars observed by the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) using a data-driven approach. This sample constitutes the largest number of s-process enhanced stars ever discovered. Our sample includes 187 s-process-rich candidates that are enhanced in both barium and strontium, 49 stars with significant barium enhancement only and 659 stars that show only a strontium enhancement. Most of the stars in our sample are in the range of effective temperature and log g typical of red giant branch (RGB) populations, which is consistent with our observational selection bias towards finding RGB stars. We estimate that only a small fraction (∼0.5 per cent) of binary configurations are favourable for s-process enriched stars. The majority of our s-process-rich candidates (95 per cent) show strong carbon enhancements, whereas only five candidates (<3  per cent) show evidence of sodium enhancement. Our kinematic analysis reveals that 97 per cent of our sample are disc stars, with the other 3 per cent showing velocities consistent with the Galactic halo. The scaleheight of the disc is estimated to be $z_{\rm h}=0.634 \pm {0.063}\, \mathrm{kpc}$, comparable with values in the literature. A comparison with yields from asymptotic giant branch (AGB) models suggests that the main neutron source responsible for the Ba and Sr enhancements is the 13C(α,n)16O reaction. We conclude that s-process-rich candidates may have received their overabundances via mass transfer from a previous AGB companion with an initial mass in the range $1\!-\!3\, \mathrm{M}_{\odot }$.

scholarly journals Cosmic Rays and the Parker Instability

1985 ◽  
Vol 107 ◽  
pp. 361-363
Author(s):  
A.H. Nelson
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Interstellar Medium ◽  
Galactic Halo ◽  
Cosmic Ray ◽  
Interstellar Gas ◽  
Horizontal Magnetic Field ◽  
Magnetic Buoyancy ◽  
Field Lines ◽  
Gas Layer

Parker (1966, 1969, 1979) has shown that the magnetic buoyancy of a uniform horizontal magnetic field will destabilize the Galactic gas layer. Perturbations of the form shown in Fig. 1 will grow in time with the magnetic loops ballooning up into the Galactic halo, and the interstellar gas draining down the field lines to collect in the mid-plane. Parker also showed that if the dynamical effect of the cosmic ray component of the interstellar medium is included, using an isotropic cosmic ray pressure, then the instability is enhanced.

scholarly journals Cosmogenic activation of materials

2017 ◽  
Vol 32 (30) ◽  
pp. 1743006 ◽  
Author(s):  
Susana Cebrián
Keyword(s):  
Cosmic Rays ◽  
Cross Sections ◽  
Direct Detection ◽  
Production Cross ◽  
Cosmic Ray ◽  
Double Beta Decay ◽  
Radioactive Isotopes ◽  
Isotope Production ◽  
Deep Underground ◽  
Cosmogenic Activation

Experiments looking for rare events like the direct detection of dark matter particles, neutrino interactions or the nuclear double beta decay are operated deep underground to suppress the effect of cosmic rays. But, the production of radioactive isotopes in materials due to previous exposure to cosmic rays is a hazard when ultra-low background conditions are required. In this context, the generation of long-lived products by cosmic nucleons has been studied for many detector media and for other materials commonly used. Here, the main results obtained on the quantification of activation yields on the Earth’s surface will be summarized, considering both measurements and calculations following different approaches. The isotope production cross-sections and the cosmic ray spectrum are the two main ingredients when calculating this cosmogenic activation; the different alternatives for implementing them will be discussed. Activation that can take place deep underground mainly due to cosmic muons will be briefly commented too. Presently, the experimental results for the cosmogenic production of radioisotopes are scarce and discrepancies between different calculations are important in many cases, but the increasing interest on this background source which is becoming more and more relevant can help to change this situation.

scholarly journals The Bulge of the Milky Way and cosmic rays

1993 ◽  
Vol 153 ◽  
pp. 283-284
Author(s):  
F. Jansen ◽  
K.-P. Wenzel ◽  
D.O' Sullivan ◽  
A. Thompson
Keyword(s):  
Cosmic Rays ◽  
Milky Way ◽  
Galactic Halo ◽  
Cosmic Ray ◽  
Proton Flux ◽  
The Sun ◽  
Good Agreement

The propagation of cosmic ray protons and anti–protons from the inner Galaxy via the galactic halo to the Sun supplies a good agreement with the observed cosmic ray gradient and is in the order of the measured anti-proton flux. Ultra heavy cosmic ray nuclei may have the same origin.

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