Gamma-ray Line Production Research Articles

New γ-ray production cross sections for the 4.439 and 6.129 MeV lines of 12C and 16O. Astrophysical implications

Gamma-ray line production cross sections from nuclear reactions induced by 30 - 200 MeV protons on natC and Mylar targets have been measured at the SSC facility of iThemba LABS. Results for the 4.439 and 6.129 MeV prominent lines of 12C and 16O of astrophysical concern are reported and discussed.

The Role of Nuclei-Nuclei Interactions in the Production of Gamma-ray Lines in Solar Flares

Dramatic extensions of experimental possibilities (spacecraft RHESSI, CORONAS-F and others) in solar gamma-ray astronomy call for urgent, detailed theoretical consideration of a set of physical problems of solar activity and solar-terrestrial relationships that earlier may have only been outlined. Here we undertake a theoretical analysis of issues related to the production of gamma-radiation in the processes of interactions of energetic (accelerated) heavy and middle nuclei with the nuclei of the solar atmosphere (the so-called i-j interactions). We also make an estimate of the contribution of these interactions to the formation of nuclear and isotopic abundances of the solar atmosphere in the range of light and rare elements. The analysis is carried out for solar flares in the wide range of their intensities. We compare our theoretical estimates with RHESSI observations for the flare of 2002 July 23. It was shown that the 24Mg gamma-ray emission in this event was produced by the newly generated Mg nuclei. With a high probability, the gamma-ray line emission of 28Si nuclei from this flare was generated by the same processes.

What gamma-ray deexcitation lines reveal about solar-flares

Gamma-ray emission from solar flares reveals information about the nature of the accelerated particles and about the physical conditions of the medium through which the accelerated particles are transported. In this paper, we present the gamma-ray line-production and loop transport models used in our calculations of high-energy emission. We discuss the calculated interaction time history, the depth distribution, the interacting-particle angular distribution, and fluence ratios of the narrow gamma-ray lines. We show the relationship between the γ-ray observables and the parameters of the transport and line-production models. For illustration, we use calculations of 4.44 MeV 12C nuclear deexcitation line-production. Applications of the calculations to flare observations by both SMM and RHESSI are also presented.

On Nonprimordial Deuterium Production by Accelerated Particles

Deuterium plays a crucial role in cosmology because the primordial D/H abundance, in the context of big bang nucleosynthesis (BBN) theory, yields a precise measure of the cosmic baryon content. Observations of D/H can limit or measure the true primordial abundance because D is thought to be destroyed by stars and thus D/H monotonically decreases after BBN. Recently, however, Mullan & Linsky have pointed out that D arises as a secondary product of neutrons in stellar flares that then capture on protons via n + p → d + γ and that this could dominate over direct D production in flares. Mullan & Linsky note that if this process is sufficiently vigorous in flaring dwarf stars, it could lead to significant non-BBN D production. We have considered the production of D in stellar flares, both directly and by n capture. We find that for reasonable flare spectra, n/d ≲ 10 and (n + d)/6Li ≲ 400, both of which indicate that the n-capture channel does not allow for Galactic D production at a level that will reverse the monotonic decline of D. We also calculate the 2.22 MeV gamma-ray line production associated with n capture and find that existing COMPTEL limits also rule out significant D production in the Galaxy today. Thus, we find that flares in particular and neutron captures in general are not an important Galactic source of D. On the other hand, we cannot exclude that flare production might contribute to recent Far Ultraviolet Spectroscopic Explorer (FUSE) observations of large variations in the local interstellar D/H abundance; we do, however, offer important constraints on this possibility. Finally, since flare stars should inevitably produce some n-capture events, a search for diffuse 2.22 MeV gamma rays by INTEGRAL can further constrain (or measure!) Galactic deuterium production via n-capture.

Nuclear Deexcitation Gamma‐Ray Lines from Accelerated Particle Interactions

Total cross sections for the production of gamma-ray lines from nuclear deexcitation as a function of the projectile energy are evaluated and presented. Included are proton and α reactions with He, C, N, O, Ne, Mg, Al, Si, S, Ca, and Fe. Such functions are essential for interpretation of gamma-ray line observations of astrophysical sites which contain large fluxes of energetic particles such as solar flares, the Earth's atmosphere, planetary atmospheres and surfaces, the interstellar medium, and galactic nebulae.

Photon yields of energetic particles in the interstellar medium: An easy way to calculate gamma-ray line emission

A gamma-ray line production calculation in astrophysics depends on i) the composition and energy source spectrum of the energetic particles, ii) the propagation model, and iii) the nuclear cross sections. The main difficulty for model predictions and data interpretation comes from the fact that the spectrum of the particles which actually interact in the ISM - the propagated spectrum, is not the same as the source spectrum coming out of the acceleration site, due to energy-dependent energy losses and nuclear destruction. We present a different approach to calculate gamma-ray line emission, based on the computation of the total number of photons produced by individual energetic nuclei injected in the interstellar medium at a given energy. These photon yields take into account all the propagation effects once and for all, and allow one to calculate quickly the gamma-ray line emission induced by energetic particles in any astrophysical situation by using directly their source spectrum. Indeed, the same photon yields can be used for any source spectrum and composition, as well as any target composition. In addition, these photon yields provide visual, intuitive tools for gamma-ray line phenomenology.

Nuclear gamma ray line astronomy in the perspective of the integral satellite

We present a broad overview of the principal processes and astrophysical sites of gamma-ray line production and review the main pre-INTEGRAL satellite observations to set the stage to the next European era of gamma-ray line astronomy.

Thermonuclear breakup reactions of light nuclei. II - Gamma-ray line production and other applications

The main consequence of nuclear breakup reactions in high-temperature plasmas is shown to be to reduce the production of the gamma-ray lines, due to the breakup of these species at high temperature. Results of the emissivities of all the relevant gamma-ray lines are discussed. It is shown that the magnitude of the breakup effect on the line emissivities depends strongly on temperature, but more importantly on the plasma density and on the available time for the ion processes. Other effects considered include the production of neutrons (from the breakup of helium) and its consequences (such as the production of gamma rays from n-capture reactions and dynamical effects in accretion disk plasmas).

Gamma-ray line production in astronomical objects

This review focuses on the conditions for γ-ray line production in the most interesting astronomical objects, in light of the planned experiments: ‘Gamma-1’, ‘GRO’, ‘Sigma’, ‘GRASP’, and others. Among these objects are the Sun, the galactic center region, molecular and dust clouds, accreting and exploding stars.

Nuclear line spectroscopy of solar flares

The study of nuclear line spectra from solar flares holds a rich promise for elucidating the properties of both the accelerated particles and the interaction or target region. We review the observations and the analysis of the large nuclear line rich flare which occurred near the west limb starting at 08:03 UT on 27 April, 1981. The observed spectrum from this flare contains three intense and isolated gamma-ray lines which can be analyzed in a model independent way. The measured energies are 1.628 ± 0.008, 4.430 ± 0.011, and 6.147 ± 0.022 MeV, identifying them as the de-excitation lines of 20Ne (1.634 MeV), 12C (4.438 MeV), and 16O (6.129 MeV). Elemental abundances of the ambient gas at the site of gamma-ray line production in the solar atmosphere are deduced using these gamma-ray line observations. The resultant abundances are different from local galactic abundances which are thought to be similar to photospheric abundances.

On the dust jet model of SS 433

The dust jet model for production of narrow gamma-ray lines from SS 433 is examined and shown to be implausible. Sputtering rates at disk temperatures are high, and self-absorption rates in the disk and jet are important; both imply that dust particles would easily be destroyed. The energy deposited in the dust jet particles by collisions with the ambient protons should be radiated in the optical and infrared in amounts greatly exceeding that observed. The dust momentum pumps ambient gas out of the beam at rates which imply that for the steady state, the ambient gas has to have an initial temperature exceeding one million K. The ambient medium is also required to have densities exceeding those postulated for the H-alpha-emitting gas jet, and the interaction within the gas jet material would result in appreciable broadening of the H-alpha emission lines. At present, there is no viable model for the steady state production of the gamma-ray line radiation.

Solar Gamma-Ray Lines and Interplanetary Solar Protons

Solar gamma-ray lines and protons were simultaneously observed for six flares on 1 April, 4 April, 27 April, 13 May 1981, 1 Feb., and 6 June, 1982 by Hinotori and Himawari satellites. The flare list is presented in Table I and the time histories of gamma-rays and protons are shown in Figs. 1 to 6. The relation-ship between the gamma-ray line fluences and peak proton fluxes for these flares is shown in Fig. 7. It does not reveal an apparent correlation between them. The present results imply that the protons producing gamma-ray lines in the flare region and protons observed near the Earth do not always belong to the same population, and favor the downward streaming model for the gamma-ray line production.

Nuclear gamma-rays from energetic particle interactions

view Abstract Citations (268) References (118) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Nuclear gamma-rays from energetic particle interactions. Ramaty, R. ; Kozlovsky, B. ; Lingenfelter, R. E. Abstract Gamma-ray line emission due to nuclear deexcitation following energetic particle interactions with abundant constituents of cosmic matter is studied. Reactions induced by energetic protons and alpha particles in ambient nuclei (He, C, N, O, Ne, Mg, Al, Si, S, Ca, and Fe) are considered, along with inverse reactions in which energetic nuclei interact with ambient H and He. Line-production cross sections are evaluated by analyzing a large body of laboratory nuclear data. Both prompt gamma rays, produced by direct excitation of nuclear levels and by spallation reactions that leave the secondary nucleus in an excited state, and delayed emission from long-lived radioactive nuclei also produced in the energetic particle reactions are investigated. A line list is provided, and the shapes of the gamma-ray lines are determined. Gamma-ray line production in the interstellar medium is evaluated in detail. Publication: The Astrophysical Journal Supplement Series Pub Date: July 1979 DOI: 10.1086/190596 Bibcode: 1979ApJS...40..487R Keywords: Energetic Particles; Gamma Ray Astronomy; Nuclear Reactions; Particle Interactions; Astronomical Spectroscopy; Cross Sections; Gamma Ray Spectra; Interstellar Matter; Line Spectra; Photons; Protons; Solar Radiation; Space Radiation; Galactic Center:Gamma Rays; Gamma Rays:Interstellar Matter; Gamma Rays:Nuclear Reactions full text sources ADS |

X-ray and gamma-ray line production by nonthermal ions

X-ray production was calculated at approximately 6.8 keV by the 2p to 1s transition in fast hydrogen- and helium-like iron ions, following both electron capture to excited levels and collisional excitation. A refinement of the OBK approximation was used to obtain an improved charge exchange cross section. This, and the corresponding ionization cross section were used to determine equilibrium charge fractions for iron ions as functions of their energy. The effective X-ray line production cross section was found to be sharply peaked in energy at about 8 to 12 MeV/amu. Because fast ions of similar energies can also excite nuclear levels, the ratio of selected strong gamma ray line emissivities to the X-ray line emissivity was also calculated. Limits set by this method on the intensity of gamma ray line emission from the galactic center and the radio galaxy Centaurus A are generally lower than those reported in the literature.

High Energy Gamma-Ray Radiation Above 300 KeV Associated with Solar Activity

The present status of our knowledge concerning the production of gamma-ray lines and continuum during the impulsive phase of solar flares is reviewed. Our data in this field is based solely on the OSO-7 observations made in 1972, August 4 and August 7. The experimental data will be reviewed. These observations along with theoretical work of Ramaty and Lingenfelter (1973a, b) and the charged secondary observations of the Chicago group (Anglin et al., 1973) lead to the investigation of different hypothetical models to explain the production of neutral and charged secondaries in the solar atmosphere. At the present time it is not possible to rule out the preflare and postflare accumulation models if all the data is considered. We will discuss the outstanding experimental questions to be answered in future investigations.

Gamma-Ray Lines from Solar Flares

We have treated in detail the theory of gamma-ray line production in solar flares. The strongest line, both predicted theoretically and detected observationally at 2.2 MeV, is due to neutron capture by protons in the photosphere. The neutrons are produced in nuclear reactions of flare accelerated particles which also produce positrons and prompt nuclear gamma rays. From the comparison of the observed and calculated intensities of the lines at 4.4 or 6.1 MeV to that of the 2.2 MeV line it is possible to deduce the spectrum of accelerated nuclei in the flare region; and from the absolute intensities of these lines it is possible to obtain the total number of accelerated nuclei at the Sun. The study of the 2.2 MeV line also gives information on the amount of He3 in the photosphere. The study of the line at 0.51 MeV resulting from positron annihilation complements the data obtained from the other lines; in addition it gives information on the temperature and density in the annihilation region and on the anisotropy of the accelerated electron beam which produces continuum gamma rays at energies greater than about 1 MeV.

Neutron propagation and 2.2 MeV gamma-ray line production in the solar atmosphere

We have calculated the 2.2 MeV gamma-ray line intensity from the Sun using a Monte Carlo method for neutron propagation in the solar atmosphere. We provide detailed results on the total gamma-ray yield per neutron and on the time profile of the 2.2 MeV line from an instantaneous and monoenergetic neutron source. The parameters which have the most significant effects on the line intensity are the energies of the neutrons, the position of the neutron source on the Sun, and the abundance of He3 in the photosphere. For an isotropic neutron source which is not too close to the limb of the Sun, the gamma-ray yield is between about 0.02 to 0.2 photons per neutron, provided that the neutron energies are in the range 1 to 100 MeV and the ratio He3/H is less than about 5 × 10−5.