scholarly journals Pan‐Spectrum Fitting Formula for Suprathermal Particles

2020 ◽  
Vol 125 (12) ◽  
Author(s):  
Zixuan Liu ◽  
Linghua Wang ◽  
Robert F. Wimmer‐Schweingruber ◽  
Säm Krucker ◽  
Glenn M. Mason
Keyword(s):  
Spectrum Fitting ◽  
Suprathermal Particles

General Spectrum Fitting for Energetic Particles

2020 ◽  
Author(s):  
Zixuan Liu ◽  
Linghua Wang ◽  
Haobo Fu ◽  
Krucker Sam ◽  
Wimmer-Schweingruber Robert
Keyword(s):  
Energy Spectrum ◽  
Power Law ◽  
Energetic Particles ◽  
Particle Energy ◽  
X Rays ◽  
Amplitude Coefficient ◽  
Spectral Break ◽  
Particle Intensity ◽  
Spectrum Fitting ◽  
Suprathermal Particles

<p>We propose a general fitting formula of energy spectrum of suprathermal particles, J=AE<sup>-β1</sup>[1+(E/E<sub>0</sub>)<sup>α</sup>]<sup>(β1-β2)/α</sup>, where J is the particle flux (or intensity), E is the particle energy, A is the amplitude coefficient, E<sub>0</sub> represents the spectral break energy, α (>0) describes the sharpness of energy spectral break around E<sub>0</sub>, and the power-law index β<sub>1</sub> (β<sub>2</sub>) gives the spectral shape before (after) the break.  When α tends to infinity (zero), this spectral formula becomes a classical double-power-law (logarithmic-parabola) spectrum. When both β<sub>2</sub> and E<sub>0</sub> tend to infinity, this formula can be simplified to an Ellison-Ramaty-like equation. Under some other specific parameter conditions, this formula can be transformed to a Kappa or Maxwellian function. Considering  the uncertainties both in particle intensity and energy, we fit this general formula well to the representative energy spectra of various suprathermal particle phenomena including solar energetic particles (electrons, protons,  <sup>3</sup>He and heavier ions), shocked particles, anomalous cosmic rays, hard X-rays, solar wind suprathermal particles, etc. Therefore, this general spectrum fitting formula would help us to comparatively examine the energy spectrum of different suprathermal particle phenomena and understand their origin, acceleration and transportation.</p>

Tailoring the optical properties of tin oxide thin films via gamma irradiation

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ateyyah M. Al-Baradi ◽  
Ahmed A. Atta ◽  
Ali Badawi ◽  
Saud A. Algarni ◽  
Abdulraheem S. A. Almalki ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Absorption Spectrum ◽  
Gamma Irradiation ◽  
Tin Oxide ◽  
Free Charge Carrier ◽  
Oxide Thin Films ◽  
Dispersion Parameters ◽  
Absorption Spectrum Fitting ◽  
Spectrum Fitting

Abstract In the current work, the optical properties of tin oxide thin films have been tailored via gamma irradiation for energy applications. The effect of Gamma radiation (50, 100, 150, 200 and 250 kGy) on the microstructural, absorption and oscillator parameters of SnO2 thin films has been investigated. XRD results reveal that the SnO2 films have the symmetry of the space group P42/mnm belonging to the tetragonal system. The crystallite size of γ-irradiated SnO2 thin film slightly increases as the irradiation dose increases. The allowed optical band gaps are estimated by applying various methods such as Tauc’s method, derivation of absorption spectrum fitting and absorption spectrum fitting approaches. The dispersion parameters are extracted from the dispersion curve of the real part of the refractive index. The single-effective-oscillator and Drude models for free charge carrier absorption are applied to obtain the dispersion parameters before and after γ-irradiation.

Suprathermal Particles. III. Electrons

1958 ◽  
Vol 112 (5) ◽  
pp. 1429-1435 ◽  
Author(s):  
E. N. Parker
Keyword(s):  
Suprathermal Particles

scholarly journals Photospheric nitrogen abundances and carbon 12C$/$13C ratios of red giant stars

2019 ◽  
Author(s):  
Yoichi Takeda ◽  
Masashi Omiya ◽  
Hiroki Harakawa ◽  
Bun’ei Sato
Keyword(s):  
Carbon Isotope ◽  
Observational Studies ◽  
Rotational Velocity ◽  
Isotope Ratios ◽  
Red Giants ◽  
Carbon Isotope Ratios ◽  
Giant Stars ◽  
Abundance Anomalies ◽  
Red Giant ◽  
Spectrum Fitting

Abstract Nitrogen abundances and carbon isotope ratios (12C$/$13C) in the atmospheres of red giants are known to be influenced by dredge-up of H-burning products, and serve as useful probes to study the nature of evolution-induced envelope mixing. We determined the [N/Fe] and 12C$/$13C ratios for 239 late-G/early-K giant stars by applying the spectrum-fitting technique to the 12CN and 13CN lines in the ∼8002–8005 Å region, with the aim of investigating how these quantities are related to other similar mixing-affected indicators which were already reported in our previous work. It was confirmed that [N/Fe] values are generally supersolar (typically by several tenths of a dex, though widely differing from star to star), anti-correlated with [C/Fe], and correlated with [Na/Fe], as expected from theory. As seen from their dependence upon stellar parameters, it appears that mixing tends to be enhanced with an increase of stellar luminosity (or mass) and rotational velocity, which is also reasonable from the theoretical viewpoint. In contrast, the resulting 12C$/$13C ratios turned out to be considerably diversified in the range of ∼5–50 (with a peak around ∼20), without showing any systematic dependence upon C or N abundance anomalies caused by the mixing of CN-cycled material. It thus appears that our understanding of the photospheric 12C$/$13C ratios in red giants is still incomplete, requiring more observational studies.

scholarly journals On the precision of full-spectrum fitting of simple stellar populations – I. Well-sampled populations

2020 ◽  
Vol 498 (2) ◽  
pp. 2814-2832
Author(s):  
Randa Asa’d ◽  
Paul Goudfrooij
Keyword(s):  
Random Noise ◽  
Star Clusters ◽  
Stellar Populations ◽  
Asymptotic Giant Branch ◽  
Full Spectrum ◽  
Red Giant ◽  
Set Up ◽  
Age Range ◽  
Spectrum Fitting ◽  
Giant Branch Stars

ABSTRACT We investigate the precision of the ages and metallicities of 21 000 mock simple stellar populations (SSPs) determined through full-spectrum fitting. The mock SSPs cover an age range of 6.8 < log (age/yr) < 10.2, for three wavelength ranges in the optical regime, using both Padova and MIST isochrone models. Random noise is added to the model spectra to achieve S/N ratios between 10 and 100 per wavelength pixel. We find that for S/N ≥ 50, this technique can yield ages of SSPs to an overall precision of ∆log (age/yr)∼01 for ages in the ranges 7.0 ≤ log (age/yr) ≤ 8.3 and 8.9 ≤ log (age/yr) ≤ 9.4. For the age ranges of 8.3 ≤ log (age/yr) ≤ 8.9 and log (age/yr) ≥ 9.5, which have significant flux contributions from asymptotic giant branch and red giant branch stars, respectively, the age uncertainty rises to about ±0.3 dex. The precision of age and metallicity estimation using this method depends significantly on the S/N and the wavelength range used in the fitting. We quantify the systematic differences in age predicted by the MIST and Padova isochrone models, due to their different assumptions about stellar physics in various important (i.e. luminous) phases of stellar evolution, which needs to be taken in consideration when comparing ages of star clusters obtained using these popular models. Knowing the strengths and limitations of this technique is crucial in interpreting the results obtained for real star clusters and for deciding the optimal instrument set-up before performing the observations.

Terahertz absorbance spectrum fitting method for quantitative detection of concealed contraband

2007 ◽  
Vol 102 (11) ◽  
pp. 113108 ◽  
Author(s):  
Yingxin Wang ◽  
Ziran Zhao ◽  
Zhiqiang Chen ◽  
Kejun Kang ◽  
Bing Feng ◽  
...  
Keyword(s):  
Quantitative Detection ◽  
Absorbance Spectrum ◽  
Fitting Method ◽  
Spectrum Fitting
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