478-keV and 431-keV Line Emissions from Alpha-Alpha Reactions

Kozlovsky, B.; Ramaty, R.

doi:10.1086/181542

Cited by 46 publications

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“…Based on these pioneering observations, several expla nations of the feature were put forth; (i) Fishman and Clayton C1972) and Kozlovsky and Ramaty -(1974) suggested cosmic ray exci tation of 478 keV interstellar 7Li nuclear radiation via the 7 Li*, and 4 HeCt,p) 7 Li*, respectively; (ii) reactions 7 Li(p,p') Ramaty, Borner, and Cohen (1973) and Guthrie and Tademaru (1973) suggested 511 keV position annihilation radiation gravitationally redshifted from the surface of small neutron stars, and (iii) - Leventhal (1973) suggested interstellar positronium (e+e bound state) annihilation radiation. In the lbtter case an apparent redshift arises when the three-photon annihilation spectrum of 3 S 1 ortho-positronium is combined with the 511 keV annihilation line of is, para-positronium and the sum is convoluted with the Since this inherently poor energy resolution of a NaI system.…”

Section: N78-31978mentioning

confidence: 99%

Gamma-ray spectroscopy in astrophysics

Ramaty

Kline

Weaver

1978

Nature

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This was the first symposium devoted entirely to spectroscopy in gamma ray astronomy. Its purposes were to bring together most of the scientists contributing to all the aspects, experimental and theoretical, of this new field and to discuss and compare ideas, measurements, calcu lations and technical experience in what we confidently expect to be a very important new discipline in high energy astrophysics.This goal was achieved, we feel, in that a very large fraction of all that is known about gamma ray spectroscopy in astrophysics was indeed presented or discussed at the Symposium, yet many of these results are new, presented here for the first time. Further, the discipline is on the brink of moving to the next level of development within the coming year, with a number of satellite experiments and major balloon experiments in gamma ray spectroscopy and in related astrophysical sciences about to be launched. We therefore felt that we should publish the Proceedings as soon as possible, without the delays involved in reformatting the manuscripts and extensive editing. We hope that the information that will thus become available will prove to be useful to all workers in these fields.We have ordered the papers approximately as presented, with experimental and theoretical papers combined in each session. The introductory session is followed by the sessions on solar, stellar, and planetary gamma ray spectroscopy, and on cosmic gamma ray spectroscopy, with the technical discussions and previews of new experiments in the last two sessions.The Symposium was organized by the editors of these proceedings, T. L. Cline and R. Ramaty. We wish to thank the Symposium Session Chairmen, D. D. Clayton, and M. M. Shapiro, and the Workshop Session Chairmen, G. J. Fishman and N. S. Wall, for their assistance. We are grateful to R. C. Reedy for supplying us the manuscript on Planetary Gamma Ray Spectro scopy which was not presented at the Symposium. This paper is taken from the Proceedings of the Ninth Lunar and Planetary Science Conference (Pergamon Press 1978, with permission). We are also indebted to R. W. Bussard and R. P. Weaver for their help in running the conference. We thank F. B. McDonald for his continued support of this Symposium, and R. S. Cooper for his interest and his contribution. We thank Barbara Pratt in particular for her excellent secretarial help with both the organization of the Symposium and the preparation of this document. It is a pleasure for me to be here and welcome you all to the Goddard Space Flight Center. I noticed from the agenda that we have speakers from all the major groups that are interested in high energy astronomy and in particular in gamma ray astronomy virtually in the entire free world. The agenda is particularly interesting to me and I intend to spend as much of my time here over the next day as I can. I would like to make a couple of points. The people here at Goddard know that when they give me an oppor tunity to come and welcome you, the potential is always there for me to say something...

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Section: N78-31978mentioning

confidence: 99%

Gamma-ray spectroscopy in astrophysics

Ramaty

Kline

Weaver

1978

Nature

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“…The question is how can the positrons annihilate at such low densities. Kozlovsky et al 2004 show that positrons produced by 3He interactions form higher in the solar atmosphere; however, in order to explain the line width, it would require a much higher 3He/ 4He ratio than the upper limit set for this flare by RHESSI. Alternatively, all the observations are consistent with densities> 10 12 H cm-3.…”

Section: Positron Production and Annihilationmentioning

confidence: 87%

Solar Gamma-Ray Line Spectroscopy – Physics of a Flaring Star

Murphy

2004

Symp. - Int. Astron. Union

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Abstract. We discuss how gamma-ray spectroscopy provides information about the acceleration and transport of electrons and ions in solar flares, and their interaction with the solar atmosphere. Temporal studies illuminate differences in the acceleration and transport of electrons and ions. Nuclear line studies reveal the elemental abundance, density, and temperature of the ambient solar atmosphere; and the spectrum, composition, and directionality of the accelerated ions.

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“…Nuclear interactions of flare accelerated ct-particles with ambient He, 4 He(a,p) 7 Li* 0478 and 4 He(a,n) 7 Be* 0,429 , result in two gamma ray lines which due to Doppler broadening blend into a broad feature from ~0.35 to ~0.55 MeV, usually referred to as the act line [11]. Using the intensities of this line together with the 6.13 MeV 1 6 0 deexcitation line observed with SMM/GRS [12] we determined [10] the ambient He/O abundance ratio for 13 flares.…”

Section: Heliummentioning

confidence: 99%

Gamma Rays from Solar Flares

Mandzhavidze

Ramaty

1998

Highlights astron.

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A b s t r a c t .We review recent results obtained from the analysis of the solar flare gamma ray line emission: (a) The gamma ray derived ambient elemental abundances show that the First Ionization Potential (FIP) effect already sets in at relatively low altitudes in the solar atmosphere. (b) The composition of the flare accelerated particles that produce the gamma rays exhibit heavy element and 3 He abundance enhancements that are typical for impulsive flares. Unlike the solar energetic particle (SEP) observations in interplanetary space, the gamma ray method allows us to trace the time development of these enhancements. (c) Solar flare gamma ray spectroscopy provides the most direct measure of the abundances of the two very high FIP elements, He and Ne, in subcoronal regions leading to somewhat higher abundances than the generally accepted values. (d) The high intensities of the aa lines observed from a number of flares imply a high ( Z, 0.1) ambient He/H and/or accelerated a / p . (e) There are indications for the isotopic fractionation of He from the photosphere to corona that has important implications on the mechanism of solar wind acceleration, the protosolar deuterium abundance and Galactic chemical evolution.

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478-keV and 431-keV Line Emissions from Alpha-Alpha Reactions

Cited by 46 publications

References 0 publications

Gamma-ray spectroscopy in astrophysics

Gamma-ray spectroscopy in astrophysics

Solar Gamma-Ray Line Spectroscopy – Physics of a Flaring Star

Gamma Rays from Solar Flares

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