Download or read book Observations of Galactic Positron Annihilation Radiation written by Michael S. Briggs and published by . This book was released on 1991 with total page 239 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book OSSE Observations of Galactic 511 KeV Positron Annihilation Radiation Initial Phase 1 Results written by and published by . This book was released on 1993 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory (GRO) has performed numerous observations of the galactic plane and galactic center region to measure the distribution of galactic 511 keV positron annihilation radiation and to search for time variability of the emission; the initial 511 keV line fluxes for the observations performed during the first 18 months of the GRO mission are presented. The 511 keV line flux for a typical galactic center observation is (2:5 plus or minus 0:3) x 10(exp -1) gamma sq cm s(exp -1), where the quoted uncertainty represents the 1 sigma statistical uncertainty. No statistically significant time variability of the line flux has been observed; the 3 sigma upper linit to daily variations from the mean is 3 x 10(exp -4) gamma sq cm s(exp -1). The distribution of galactic 511 keV positron annihilation radiation implied by the OSSE observations is discussed and compared with observations by other instruments.
Download or read book OSSE Observations of Galactic 511 KeV Annihilation Radiation written by and published by . This book was released on 1991 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory has performed several observations of the Galactic plane and Galactic center region to measure the distribution of Galactic 511 keV positron annihilation radiation. Preliminary analysis of data collected during the observation of the Galactic center region over the period July 13[24, 1991, indicates the presence of a 511 keV line and positronium continuum superimposed on a power-law continuum.
Download or read book The Distribution of Galactic 511 KeV Positron Annihilation Radiation written by and published by . This book was released on 1994 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Oriented Scintillation Spectrometer Experiment (OSSE) on NASA's Compton Gamma-Ray Observatory has completed numerous observations of the Galactic plane and Galactic center region. A principle objective of these observations was to measure the distribution of the Galactic positron annihilation radiation. Most of these observations provided positive detections of the narrow 511 keV annihilation line. These data were fitted using several diffuse distribution models representing various populations of progenitor objects. The only model investigated which is not rejected is a two-component distribution consisting of spheroidal and disk components; all other models investigated can be rejected at the> 4:5 sigma confidence level. The size of the spheroidal component is found to be
Download or read book OSSE Observations of Positron Annihilation in the Galactic Plane written by and published by . This book was released on 1996 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: OSSE has measured the galactic longitude distribution of both the 511 keV annihilation line radiation and the three-photon positronium continuum within ~40 degrees of the center. They have similar shapes, with a composite longitude distribution well represented by an ~11 degrees FWHM Gaussian central bulge together with a possible broad disk component comprising as much as 15% of the integral flux between 40 degrees and 320 degrees longitude. Contributions from one or more discrete source(s) at or near the center with total annihilation radiation (line plus continuum) intensities of up to ~4 x 10(exp -4) photons cu cm sec(exp -1) (2 sigma upper limit) are compatible with the observed distribution. The best estimate of the positronium fraction is 0.97 plus or minus 0.03. No evidence for variation in the positronium fraction is observed.
Download or read book Observations of Galactic Positron Annihilation Radiation written by Michael S. Briggs and published by . This book was released on 1991 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Positron Distribution in the Inner Galactic Ridge written by and published by . This book was released on 1997 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: OSSE was used to measure the longitude and latitude distribution of positron annihilation in the inner galactic ridge using differential measurements relative to intensities at latitudes of plus or minus 10 degrees. An improved understanding of the 50 keV to 10 MeV continua has recently permitted accurate determinations of the positronium continuum flux intensities; this provides an - 5 times greater signal than was available in previous analyses which used only the 511 keV annihilation line. Within the statistical precision of the measurements, the line and positronium continuum components show indistinguishable distributions in both latitude and longitude. A differential measurement of their latitude distributions near the center indicates a narrow Gaussian ridge of -4.4 degrees FWHM. The longitude distribution of the ridge intensity differs from other known galactic ridge radiation distributions in that it shows a narrowly peaked maximum around the center. It can be characterized by an -12 degrees FWHM Gaussian central bulge plus a broad disk-like component. The only physical model based on plausibly associated galactic ridge distributions which can fit the observations well in longitude is the predicted galactic nova spheroid distribution, but scaled down by -2/3 from the latitude-integrated model bulge longitude width. The best fit has no additional discrete source or broad-disk components, although small contributions are permitted by the data. Novae are thought to be progenitors of Type I supernovae, probable sources of positrons in the galaxy, so this correlation suggests that Type I supernovae are the primary source of the positrons producing the observed galactic ridge annihilation radiation.
Download or read book Diffuse Galactic Positron Annihilation Radiation and the Underlying Continuum written by Jeffrey George Skibo and published by . This book was released on 1993 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Positrons from Supernova and the Origin of the Galactic center Positron annihilation Radiation written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The emission of positrons from supernova ejecta is dicussed in terms of the galactic-center annihilation radiation. The positrons from the radioactive sequences 56Ni.-->.56Co.-->.56Fe are the most numerous source from supernova. Only type I supernova will allow a significant fraction to escape the expanding ejecta. For a neutron star model of a type I SN a fraction 4 x 10−3 of the escaped positron is enough to create the observed several year fluctuation of the annihilation radiation. The likelihood of this model is discussed in terms of other astrophysical evidence as well as the type I SN light curve.
Download or read book Positron Annihilation in the Galactic Center written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two separate observations of the .gamma.-ray spectrum originating from the Galactic Center were made by HEAO-3 in the fall of 1979 and in the spring of 1980. The 2.gamma. 511 KeV annihilation line flux decreased by a factor of three over the corresponding six month period, whereas the excess .gamma.-ray continuum below the 511 KeV line, often interpreted as 3.gamma. decay of orthopositronium, barely changed. This apparent discrepancy in the temporal behavior makes it difficult to associate the bulk of the excess continuum with the 3.gamma. decay of positronium. We will show that Compton scattering of the line and high energy radiation provides a natural explanation for the surprisingly small change seen in the excess continuum. 11 refs., 2 figs.
Download or read book A Hard X ray and Gamma ray Observation of the Galactic Center Region written by David Miles Smith and published by . This book was released on 1993 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book OSSE Observations of Active Galactic Nuclei written by and published by . This book was released on 1995 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The principal results on active galactic nuclei obtained by the Oriented Scintillation Spectrometer Experiment (OSSE) on the COMPTON Gamma Ray Observatory are presented. These include observations of 26 Seyfert galaxies in low energy gamma rays and observations of several of the high-energy gamma ray sources detected by EGRET. OSSE observes a thermal-like spectrum from NGC 4151, and the average gamma ray spectrum of weak Seyferts is significantly softer (consistent with a 45 keV thermal spectrum) than the spectrum below 50 keV. OSSE has not detected any positron annihilation radiation from any Seyfert, and has not detected an MeV excess from these sources. The OSSE observations of several blazars, when combined with the COMPTEL and EGRET data, indicate that the spectral characteristics of these sources vary dramatically, exhibiting power-law spectra with breaks or changes in spectral index in the MeV region which vary from 0 to greater than 1.
Download or read book The Center of the Galaxy written by Mark Morris and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt: The investigation of the Galactic nucleus and its surroundings is necessarily a modem endeavor, for traditional observations made at visual wavelengths have not even begun to penetrate the veil of -30 magnitudes of visual extinction that intercedes. On the other hand, infrared, and especially radio observers find a relatively unobstructed view of the central portion of the Galaxy, so the study of this arena has proceeded apace with the development of these branches of astronomy. Thus, it is no accident that the first IAU sponsored conference to be held on the Galactic center is timed to coincide with the initiation, or the immediate aftennath, of major technical developments at long wavelengths, including infrared array detectors, millimeter-wavelength aperture synthesis, and self-calibration and refmed deconvolution algorithms in aperture synthesis radio astronomy. The center of the Galaxy is also accessible to X and gamma-ray observers, and progress at high energies has been steady, especially as imaging capabilities are being realized at X-ray wavelengths. However, one might expect that the revolution in the high energy domain is still ahead of us, as instruments with larger collecting areas and improved spatial resolution are now being developed. The youth of this subject is evidenced by the relatively small number of meetings that have been devoted to it.
Download or read book High Energy Astrophysics Models And Observations From Mev To Tev written by Peter L Biermann and published by World Scientific. This book was released on 1994-06-21 with total page 297 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a collection of comprehensive reviews on astrophysics at the highest energies. It puts together, for the first time, discussions of astrophysics from MeV to EeV energies and beyond. Observations at these energies reveal nuclear and particle physics throughout our galaxy as well as in the most extreme environments in the entire cosmos. These reports range from the recent spectacular results from the Compton Gamma Ray Observatory, including the latest information on enigmatic gamma ray bursts, to cosmic rays at the highest energies ever observed by man.
Download or read book Detection of the 511 KeV Positron Annihilation Line with the Compton Spectrometer and Imager written by Carolyn Kierans and published by . This book was released on 2018 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: The signature of positron annihilation, namely the 511~keV $\gamma$-ray line, was first detected coming from the direction of the Galactic center in the 1970's, but the source of Galactic positrons still remains a puzzle. The measured flux of the annihilation corresponds to an intense steady source of positron production, with an annihilation rate of $\sim$10$^{43}$~e$^+$/s. Spatially, the 511~keV intensity is strongest in the Galactic center region, with an additional component that is consistent with the Galactic disk; however, the unique morphology is not well constrained. The Compton Spectrometer and Imager (COSI) is a balloon-borne soft $\gamma$-ray (0.2--5~MeV) telescope designed to perform wide-field imaging and high-resolution spectroscopy, with a goal of furthering our understanding of Galactic positrons. COSI employs a compact Compton telescope design, using 12 cross-strip germanium detectors to track the trajectory of incident photons, where position and energy deposits from Compton interactions allow for a reconstruction of the source sky position and significant background reduction. COSI had a record-breaking 46-day balloon flight from Wanaka, New Zealand, in May--July 2016, and here we report on the detection and analyses of the 511~keV emission from those observations. To isolate the Galactic positron annihilation emission, we have developed a background subtraction technique utilizing the COMPTEL Data Space. With this new method, we find a 7.2~$\sigma$ detection of the 511~\keV line and a broader spatial distribution of the emission than has been previously reported.
Download or read book High Energy Astrophysics written by James Matthews and published by World Scientific. This book was released on 1994 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a collection of comprehensive reviews on astrophysics at the highest energies. It puts together, for the first time, discussions of astrophysics from MeV to EeV energies and beyond. Observations at these energies reveal nuclear and particle physics throughout our galaxy as well as in the most extreme environments in the entire cosmos. These reports range from the recent spectacular results from the Compton Gamma Ray Observatory, including the latest information on enigmatic gamma ray bursts, to cosmic rays at the highest energies ever observed by man.
Download or read book Focusing Telescopes in Nuclear Astrophysics written by Peter Ballmoos and published by Springer Science & Business Media. This book was released on 2007-11-25 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is the first of its kind on focusing gamma-ray telescopes. Forty-eight refereed papers provide a comprehensive overview of the scientific potential and technical challenges of this nascent tool for nuclear astrophysics. The book features articles dealing with pivotal technologies such as grazing incident mirrors, multilayer coatings, Laue- and Fresnel-lenses - and even an optic using the curvature of space-time.
