Reported cosmic gamma-ray source in Cygnus.
High altitude balloon flights with gamma ray spark chamber for search of cosmic gamma ray source in Cygnus
BALLOON FLIGHT↗
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Solar and galactic cosmic ray abundances - A comparison and some comments
We have compared the abundances of galactic cosmic rays at their source and solar cosmic-rays utilizing new data which includes the first determination of the abundances of Na and Al in the solar cosmic ray population. We find the relative abundances of the solar and galactic species to be identical within experimental error for 8 elements. One clear abundance difference exists for C. He and Fe have a variable solar cosmic ray abundance, and the unbiased abundance of both of these nuclei is also probably different than that in the galactic cosmic ray sources. We also have compared the cosmic ray abundances with solar system and solar atmospheric abundance determinations. We find an abundance ratio which depends on the first ionization potential for galactic cosmic rays; however, in addition, we find this same dependence on ionization potential for solar cosmic ray abundance ratios. The implications of this result are discussed.
Webber, W. R.↗
The spectral archive of cosmic X-ray sources observed by the Einstein Observatory Focal Plane Crystal Spectrometer
The Einstein Observatory Focal Plane Crystal Spectrometer (FPCS) used the technique of Bragg spectroscopy to study cosmic X-ray sources in the 0.2-3 keV energy range. The high spectral resolving power (E/Delta-E is approximately equal to 100-1000) of this instrument allowed it to resolve closely spaced lines and study the structure of individual features in the spectra of 41 cosmic X-ray sources. An archival summary of the results is presented as a concise record the FPCS observations and a source of information for future analysis by the general astrophysics community. For each observation, the instrument configuration, background rate, X-ray flux or upper limit within the energy band observed, and spectral histograms are given. Examples of the contributions the FPCS observations have made to the understanding of the objects observed are discussed.
Lum, Kenneth S. K.↗
Analysis of New Orion Gamma Ray Data and Monte Carlo Simulations of BATSE Gamma Ray Bursts
These studies were stimulated by the reported COMPTEL detection of nuclear gamma ray line emission from the Orion star formation region. Although the observation have very recently been retracted, the detailed analyses that we carried out clearly showed that the low energy cosmic rays that would have been required to explain the reported fluxes were exceedingly restrictive and thus highly improbable. Moreover, these studies proved to be the trigger for very productive new work. In particular, they led us into carefully re-examining the problem of the origin of the light elements, Li, Be and B, where we showed that the light elements could, in fact, be produced primarily by Galactic cosmic rays and did not require an unobserved low energy cosmic ray source , as had been suggested. We further showed that the observed abundances of Be and B in old halo stars contradicted the common belief that the Galactic cosmic rays were accelerated out of the well mixed interstellar medium, and required instead that they be accelerated out of freshly synthesized matter from supernovae. This work, in turn, led us to propose a new origin of Galactic cosmic rays from the refractory grains in supernova enriched cores of superbubbles.
Lingenfelter, Richard E.↗
Theoretical Studies in Gamma-Ray Astrophysics
These studies were stimulated by the reported COMPTEL detection of nuclear gamma ray line emission from the Orion star formation region. Although the observation have very recently been retracted, the detailed analyses that we carried out clearly showed that the low energy cosmic rays that would have been required to explain the reported fluxes were exceedingly restrictive and thus highly improbable. More importantly, these studies proved to be the trigger for very productive new work. In particular, they led us into carefully re-examining the problem of the origin of the light elements, Li, Be and B, where we showed that the light elements could, in fact, be produced primarily by Galactic cosmic rays and did not require an unobserved low energy cosmic ray source , as had been suggested. We further showed that the observed abundances of Be and B in old halo stars contradicted the common belief that the Galactic cosmic rays were accelerated out of the well mixed interstellar medium, and required instead that they be accelerated out of freshly synthesized matter from supernovae. This work, in turn, led us to propose a new origin of Galactic cosmic rays from the refractory grains in supernova enriched core of superbubbles, which is now the subject of our on-going research under a new grant from the Astrophysics Theory Program.
Lingenfelter, Richard E.↗
Neutron-rich isotopes of cosmic rays with Z between 9 and 16
Data are reported on the isotopic composition of cosmic rays with charges between 9 and 16 at a temperature of 450 MeV per amu. The data show the presence of a considerable neutron-rich component of Mg and Ne, the measured mean masses being 24.3 plus or minus 0.1 and 20.8 plus or minus 0.1, respectively. Coupled with a calculation of the evolution of cosmic-ray isotopic abundances during propagation, these masses indicate that there is probably some neutron-rich material in this charge range at the cosmic-ray source. To explain the Ne mass requires more neutron-rich Ne at the source than is observed in solar-system material. This result is discussed in light of recent theories of nucleosynthesis and cosmic-ray propagation.
Maehl, R. C.↗
Optical characteristics of young quasars as sources of the cosmic X-ray background
The sources which dominate the thermal cosmic X-ray background cannot have X-ray spectra similar to the power laws measured for bright active galactic nuclei. The optical consequences of this disparity are pursued by considering a standard model for the photoexcitation and heating of the line emitting gas surrounding a central source (e.g., such as a quasar). The optical line emission to be associated with compact young quasar sources having the same X-ray spectrum as the X-ray background is found to be substantially different from that characteristic of typical quasars. Implications on quasar source counts and the identification of such new objects are discussed.
Boldt, E.↗
Optical characteristics of young quasars as sources of the cosmic X-ray background
The sources which dominate the thermal cosmic X-ray background cannot have X-ray spectra similar to the power laws measured for bright active galactic nuclei. The optical consequences of this disparity are pursued by considering a standard model for the photoexcitation and heating of the line-emitting gas surrounding a central source (e.g., such as a quasar). The optical line emission to be associated with compact young quasar sources having the same X-ray spectrum as the X-ray background is found to be substantially different from that characteristic of typical quasars. Implications on quasar source counts and the identification of such new objects are discussed.
Boldt, E.↗
The isotropic composition of cosmic ray B, C, N, and O nuclei
High resolution measurements are presented for the elemental and isotopic composition of galactic cosmic ray B, C, N, and O nuclei with about 30-130 MeV/nucleon. The isotopes are separately resolved, and the resulting abundances are limited by statistical rather than systematic uncertainties. N is found to be significantly depleted in the cosmic ray source with respect to the solar system and local interstellar medium, and it is concluded that the N-14/O-16 limit is inconsistent with models in which a majority of cosmic rays are accelerated interstellar material.
Mewaldt, R. A.↗
Neutron-rich nuclei in cosmic rays and Wolf-Rayet stars
Wolf-Rayet stars figure prominently in astrophysical research. As a bonus, they seem to offer, in the recent past, an interesting connection between classical astronomy and high energy astrophysics due to their unusual composition and their huge mechanical power. The material flowing from WC stars (carbon-rich WR stars) contains gas which has been processed through core-helium burning, i.e., considerably enriched into 12C,16O, 22Ne, and 25,26Mg. This composition is reminiscent of the cosmic ray source anomalies. Encouraging agreement is obtained with observation in the mass range 12 A 26 assuming acceleration of wind particles at the shock that delineates the WR cavity, and adequate dilution with normal cosmic rays, but silicon poses.
Prantzos, N.↗
On purported observations of partially ionized galactic cosmic rays
Galactic cosmic rays are generally believed to be bare nuclei, fully stripped of all orbital electrons during passage through several g/sq cm of interstellar matter. Over the years there have been numerous reports of so-called 'below-cutoff' Fe-group cosmic rays, with momentum below the minimum required for a fully ionized particle to reach Earth's inner magnetosphere. These reports comprised just a few tens of ions, but stimulated much speculation about partially ionized Galactic cosmic rays, suggesting a nearby source of Galactic cosmic rays. In this Letter we compare these previous reports to new observations of below-cutoff Fe-group ions from passive track detectors exposed for nearly 6 years in low-Earth orbit aboard NASA's Long Duration Exposure Facility (LDEF) satellite. The LDEF fluxes are only a few percent of the previously reported fluxes. This comparison suggests that the flux of below-cutoff ions must be out of phase with the observed solar-cycle variation of other (nonsolar) cosmic-ray sources and/or must strongly increase with decreasing altitude in low-Earth orbit. Both of these features are inconsistent with the notion of partially ionized Galactic cosmic rays as the source of the observed below-cutoff ions.
Tylka, A. J.↗
The isotopic composition of cosmic-ray calcium
We find that the relative abundance of cosmic ray calcium isotopes in the cosmic-ray source are very similar to those found in solar-system material, in spite of the fact that different types of stars are thought to be responsible for producing these two isotopes. This observation is consistent with the view that cosmic rays are derived from a mixed sample of interstellar matter.
cosmic rays calcium isotopes advanced composition ↗
The abundances of isotopes in the cosmic radiation
Studies of the isotopic composition of nuclei in the cosmic radiation are reviewed, including abundances of the isotopes of elements from H to Ni, together with their implications for cosmic ray origin, acceleration, and transport in the Galaxy. The review focuses on determinations of the composition of cosmic ray source material, and the extent to which the isotopic composition of this material is different from, or similar to, typical solar system material and other samples of Galactic matter. Theoretical models that have been advanced to explain the observed overabundance of neutron-rich isotopes in cosmic rays are described. Also discussed are studies of various radioactive clocks that record the time-scales associated with the nucleosynthesis, acceleration, and transport of cosmic ray nuclei, and studies of the so-called anomalous cosmic ray component, thought to represent a sample of the neutral interstellar medium.
Mewaldt, R. A.↗
Propagation of cosmic-ray nuclei in a diffusing galaxy with convective halo and thin matter disk
A diffusion model for cosmic-ray propagation in the galaxy that includes the effects of convection in the halo is presented. Calculations are made for 13 primary and secondary nuclei with rigidities between 1 and 1000 GV using interaction loss rates, secondary production rates, and radioactive decay on the basis of recent new cross-section measurements. It is found that, in order to fit the rather weak radial dependence of cosmic-ray protons derived from gamma-ray data, the radial profile of the cosmic-ray sources must also have a weak radial dependence. It is suggested that convection perpendicular to the disk of the Milky Way Galaxy may not be important even at rigidities less than a few GV. The obtained limits on halo thicknesses are consistent with what can be determined for the distribution of cosmic-ray electrons in the halo based on the distribution of radio synchrotron emission in this and other galaxies.
Webber, W. R.↗
The effects of newly measured cross sections in hydrogen on the production of secondary nuclei during the propagation of cosmic rays through interstellar H
The cross sections of six important cosmic ray source nuclei in hydrogen at several energies between 300 and 1800 MeV/nuc were measured. Significant differences, sometimes exceeding 50%, exist between these new measurements and the earlier semiempirical predictions, and a new set of semiempirical formulae are being determined that better describe this fragmentation. New cross sections were obtained so that the systematics of their effects on cosmic ray propagation through interstellar hydrogen can be examined.
Webber, W. R.↗
Solar sources and the cosmic ray transport equation
Cosmic ray transport equation for solar sources, using Fisk numerical method by applying transformation of independent variable U/r,T/
Gleeson, L. J.↗
Search for point sources of neutral cosmic rays above 10 super 12 ev.
Cerenkov light detection from extensive air showers used to search for point sources of high energy neutral cosmic rays
Cusimano, F. J.↗
The isotopic composition of galactic cosmic-ray iron nuclei
High-resolution observations made in interplanetary space of 83-284 MeV per nucleon galactic cosmic-ray iron isotopes are reported and it is directly established that Fe-56 is the dominant cosmic-ray Fe isotope. The following percentage abundances for Fe at the cosmic-ray source are found: Fe-54 = 9(+8, -5)%, Fe-55 is less than or equal to 7%, Fe-56 = 91(+5, -11)%, Fe-57 is less than or equal to 8%, and Fe-58 is less than or equal to 6%. When compared to calculated nucleosynthesis yields and other observations, these results place significant constraints on the neutron excess of the environment where cosmic-ray Fe originates.
Mewaldt, R. A.↗