Diffuse galactic gamma-ray line emission from nucleosynthetic Fe-60, Al-26, and Na-22 - Preliminary limits from HEAO 3

Mahoney, W. A.; Ling, J. C.; Jacobson, Allan; Lingenfelter, R. E.

doi:10.1086/160469

Cited by 237 publications

(202 citation statements)

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“…To illustrate the procedure that we employ, we consider the case of the radioisotope 26 Al. The characteristic 1809-keV γ -ray that follows the β-decay of 26 Al has been observed in the interstellar medium of our galaxy, 7,8 which FIG. 3.…”

Section: What To Measure?mentioning

confidence: 65%

Nuclear astrophysics in the laboratory and in the universe

2014

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Nuclear processes drive stellar evolution and so nuclear physics, stellar models and observations together allow us to describe the inner workings of stars and their life stories. This Information on nuclear reaction rates and nuclear properties are critical ingredients in addressing most questions in astrophysics and often the nuclear database is incomplete or lacking the needed precision. Direct measurements of astrophysically-interesting reactions are necessary and the experimental focus is on improving both sensitivity and precision. In the following, we review recent results and approaches taken at the Laboratory for Experimental Nuclear Astrophysics (LENA, http://research.physics.unc.edu/project/nuclearastro/Welcome.html).

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Section: What To Measure?mentioning

confidence: 65%

Nuclear astrophysics in the laboratory and in the universe

2014

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“…The first clear detection of an extra-solar gamma ray line was the positron annihilation line [8]. This was followed by detection of the gamma-ray line from 26 Al radioactivity [9], which proved experimentally that cosmic nucleosynthesis was an on-going process in our current Galaxy. But it took many years to further advance the techniques of gamma-ray telescopes.…”

Section: Measuring Cosmic Gamma-ray Linesmentioning

confidence: 78%

“…Characteristic gamma rays from the radioactive decay to 26 Al were first measured by NASA's High Energy Observatory satellite HEAO-C from the extended inner region of our Galaxy [9]. Apparently, synthesis of this isotope, and hence cosmic nucleosynthesis, was ongoing in our Galaxy.…”

Section: Al and 60 Fe From Cumulative Nucleosynthesismentioning

confidence: 94%

About cosmic gamma ray lines

Diehl

2017

AIP Conference Proceedings

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Abstract. Gamma ray lines from cosmic sources convey the action of nuclear reactions in cosmic sites and their impacts on astrophysical objects. Gamma rays at characteristic energies result from nuclear transitions following radioactive decays or highenergy collisions with excitation of nuclei. The gamma-ray line from the annihilation of positrons at 511 keV falls into the same energy window, although of different origin. We present here the concepts of cosmic gamma ray spectrometry and the corresponding instruments and missions, followed by a discussion of recent results and the challenges and open issues for the future. Among the lessons learned are the diffuse radioactive afterglow of massive-star nucleosynthesis in 26 Al and 60 Fe gamma rays, which is now being exploited towards the cycle of matter driven by massive stars and their supernovae; large interstellar cavities and superbubbles have been recognised to be of key importance here. Also, constraints on the complex processes making stars explode as either thermonuclear or core-collapse supernovae are being illuminated by gamma-ray lines, in this case from shortlived radioactivities from 56 Ni and 44 Ti decays. In particular, the three-dimensionality and asphericities that have recently been recognised as important are enlightened in different ways through such gamma-ray line spectroscopy. Finally, the distribution of positron annihilation gamma ray emission with its puzzling bulge-dominated intensity disctribution is measured through spatially-resolved spectra, which indicate that annihilation conditions may differ in different parts of our Galaxy. But it is now understood that a variety of sources may feed positrons into the interstellar medium, and their characteristics largely get lost during slowing down and propagation of positrons before annihilation; a recent microquasar flare was caught as an opportunity to see positrons annihilate at a source.

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“…The cosmologically short half-life of 26 Al g provides a date for the creation of the anomalous material. The other outstanding event was the detection of the 1.806 MeV γ-ray emission by γ-ray telescopes and the subsequent mapping of 26 Al material within the interstellar medium of our Galaxy [4]. Astrophysical sources of 26 Al production within our Galaxy are not well established.…”

Section: The 26 Al Radioisotopementioning

confidence: 98%

An alternative method for the measurement of stellar nuclear-reaction rates

Niello¹,

Arazi²,

Knie³

et al. 2003

Braz. J. Phys.

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For charged-particle induced reactions occurring in astrophysical scenarios, projectile energies are usually well below the Coulomb barrier of the reacting system. Hence, extremely small cross section reactions pose a difficult task for laboratory measurements. Most commonly, these energy-dependent cross sections are studied by detecting the emitted prompt gamma rays following the de-excitation of the produced compound nucleus. In this work we propose an alternative way for the measurement of the extremely small cross sections of the 25 Mg(p,γ) 26 Al resonant reaction, namely the use of the Accelerator Mass Spectrometry (AMS) technique. I IntroductionIn the understanding of the nucleosynthesis of the elements in stars, one of the most important quantities is the reaction rate. This quantity must be evaluated in terms of the stellar temperature T, and its determination involves the knowledge of the excitation function σ(E) of the specific nuclear reaction leading to the final nucleus. The particular case of proton capture reactions plays an important role in stellar process of intermediate-mass elements.In several cases, the formation of a compound nucleus is dominated by a resonant process: the entrance channel, formed by a projectile P impinging on a target nucleus A, evolves into an excited state of a compound nucleus B = P + A, which ultimately decays into lower-lying states with the subsequent emission of gamma rays. This process occurs at well-defined center of mass (CM) energies, E CM = E X − Q, where E X is the energy of the excited states of the compound nucleus B and Q is the Q-value of the reaction [1].In a stellar environment, the reaction rate per particle pair is calculated as [2]where σ is the energy-dependent reaction cross section, v the relative velocity between the reacting particles and φ(v) is the velocity distribution of these particles in the stellar plasma. Nuclei participating in thermonuclear reactions can be considered as non-relativistic and non-degenerate ones, therefore, their velocities v (and hence their energies E) follow a Maxwell-Boltzmann distribution,where E = 1 2 mv 2 represents the kinetic energy of the nucleus with mass m, and T refers to the temperature of the gas. This distribution reaches a maximum value at E = kT. The second term defining the reaction rate is the cross section for the compound nucleus formation. This can be described by three factors: a geometrical one, σ = πλ / 2 ∝ E −1 ; a second one resembling the exponential behavior for tunneling through a Coulomb barrier, σ ∝ exp(−Z P Z A e 2 / v); and finally by a nuclear S-factor, S(E), which depicts the specific nuclear characteristics of the particular reaction. Therefore, the reaction rate per particle pair can also be expressed as

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Diffuse galactic gamma-ray line emission from nucleosynthetic Fe-60, Al-26, and Na-22 - Preliminary limits from HEAO 3

Cited by 237 publications

References 0 publications

Nuclear astrophysics in the laboratory and in the universe

Nuclear astrophysics in the laboratory and in the universe

About cosmic gamma ray lines

An alternative method for the measurement of stellar nuclear-reaction rates

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