Download or read book Observations of radio recombination lines toward supernova remnants at 428 four hundred and twenty eight MHz written by Vernon Pankonin and published by . This book was released on 1975 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Supernova Remnants and their X Ray Emission written by John Danziger and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 597 pages. Available in PDF, EPUB and Kindle. Book excerpt: IAU Symposium 101, Supernova Remnants and Their X-ray Emission, was held on the Island of San Giorgio, Venice, 30 August - 2 September 1982. It was co-sponsored by the National Research Council, Italy, the University of Padua, the Observatory of Padua, and the International Astronomical Union, and was hosted by the Cini Foundation. The contents of this volume show the wide range of disciplines that are involved in supernova remnant research. Many new results were presented, not only from the X-ray observations from the Einstein Observatory but also from observations at optical and radio wavelengths. This has led to the stimulation of theoretical work, much of which attempts to accommodate in a more unified way all of these observations. Research on supernova remnants of all ages was reported. Perhaps the most impressive part of all this work is the way in which observations at all wavelengths have extended well outside the Galaxy to other members of the Local Group and beyond. The Symposium was attended by scientists from 15 countries. Twenty five invited papers and sixty-eight shorter contributions were presented during the 4-day meeting. Thirty-three of these shorter contributions were presented in poster sessions. This volume contains almost all (89) of those contributions. They are followed by discussions which took place after each verbal presentation. Since the availability of the discussions was left to the individual contributors, they are not complete, but those contained in this volume convey some idea of the nature of the exchanges.
Download or read book High Frequency Observations and Theoretical Interpretation of Recombination Line Emission in the Direction of the Supernova Remnant 3C391 written by Diego A. Cesarsky and published by . This book was released on 1973 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: The comparison of radio recombination line intensities and the amount of low frequency absorption along the same line of sight provides a unique method of obtaining information on the electron temperature of the regions involved. This method, when applied to high frequency line observations in the direction of the remnant 3C391, suggests that the line emission originates in regions having an electron temperature Te
Download or read book The origin of radio recombination lines seen toward supernova remnants written by Vernon Pankonin and published by . This book was released on 1986 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radio Continuum and 21 Cm Hydrogen Line Observations of Galactic Supernova Remnants written by Linda Kay DeNoyer and published by . This book was released on 1972 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Radio Recombination Lines written by P.A. Shaver and published by Springer. This book was released on 1980-03-31 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since their first detection 15 years ago, radio recombination lines from several elements have been observed in a wide variety of objects including HII regions, planetary nebulae, molecular clouds, the diffuse interstellar medium, and recently, other galaxies. The observations span almost the entire range from 0.1 to 100 GHz, and employ both single djsh and aperture synthesis techniques. The theory of radio recombination lines has also advanced strongly, to the point where it is perhaps one of the best-understood in astro physics. In a parallel development, it has become possible over the last decade to study these same highly-excited atoms in the laboratory; this work provides further confirmation of the theoretical framework. However there has been continuing controversy over the astrophysical interpre tation of radio recombination line observations, especially regarding the role of stimulated emission. A workshop was held in Ottawa on 24-25 August, 1979, bringing together many of the active scientists to review the field and discuss these questions of interpretation. A broad concensus has emerged: the subtleties of the line-formation process are understood, and the conditions under which reliable in formation can easily be extracted from the line measurements are known. It thus appears likely that the emphasis will shift increasingly from the study of the line phenomenon itself to further application in other areas of astrophysics, ranging from physical processes in plasmas (temperatures, densities, ionization structure), to the large-scale properties of our galaxy (abundances, kinematics, structure), and studies of extragalactic systems.
Download or read book Observations of Recombination Line Emission in the Direction of Two Supernova Remnants 2 written by Diego A. Cesarsky and published by . This book was released on 1973 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recombination line emission were detected in the direction of the supernova remnant 3C391 at 18 cm and 21 cm and in the direction of remnant 3C398 at 21 cm. The spectrum of 3C391 shows three emission features, one of which may be due to carbon recombination emission. The spectrum of 3C398 shows a hydrogen line at the same radial velocity as a recently reported carbon line in the same general direction. The observations suggest that the line emission originates in the cold component of the interstellar medium. (Modified author abstract).
Download or read book Radio Recombination Lines written by P.A. Shaver and published by Springer. This book was released on 1980-03-31 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since their first detection 15 years ago, radio recombination lines from several elements have been observed in a wide variety of objects including HII regions, planetary nebulae, molecular clouds, the diffuse interstellar medium, and recently, other galaxies. The observations span almost the entire range from 0.1 to 100 GHz, and employ both single djsh and aperture synthesis techniques. The theory of radio recombination lines has also advanced strongly, to the point where it is perhaps one of the best-understood in astro physics. In a parallel development, it has become possible over the last decade to study these same highly-excited atoms in the laboratory; this work provides further confirmation of the theoretical framework. However there has been continuing controversy over the astrophysical interpre tation of radio recombination line observations, especially regarding the role of stimulated emission. A workshop was held in Ottawa on 24-25 August, 1979, bringing together many of the active scientists to review the field and discuss these questions of interpretation. A broad concensus has emerged: the subtleties of the line-formation process are understood, and the conditions under which reliable in formation can easily be extracted from the line measurements are known. It thus appears likely that the emphasis will shift increasingly from the study of the line phenomenon itself to further application in other areas of astrophysics, ranging from physical processes in plasmas (temperatures, densities, ionization structure), to the large-scale properties of our galaxy (abundances, kinematics, structure), and studies of extragalactic systems.
Download or read book March 1966 Observations of the Galactic Spur in the 20 to 40 MHz Range written by Donald A. Guidice and published by . This book was released on 1967 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: In March 1966 observations were made at the Arecibo Ionospheric Observatory to map the region of the Galactic Spur (North Polar Spur) in the 20-40 MHz range. Simultaneous observations were made at 38.75, 33.45, 26.70, and 22.30 MHz using a log-periodic feed, a four-way power divider, and individual null-balancing radiometers. Antenna half-power beamwidths were roughly 2.0 degrees at 38.75 and 3.3 degrees at 22.30 MHz. The observations were confined to the 2300-0500 local time period to minimize ionospheric effects. The area observed was between 12h and 16h right ascension, +32 degrees and +2 degrees declination. Results are given in the report.
Download or read book Low Frequency Observations of Galactic Supernova Remnants and the Distribution of Low Density Ionized Gas in the Interstellar Medium written by and published by . This book was released on 1989 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: New long-wavelength observations of Galactic supernova remnants (SNRs) at 30.9 and 57.5 MHz are used to derive detailed low-frequency radio spectra for 32 SNRs. Of these, approximately two-thirds show turnovers at low frequencies, implying the presence of a widespread, but inhomogeneous, ionized absorbing medium along the lines of sight. These observations are combined with other low-frequency data to derive free-free optical depths toward 47 SNRs and to constrain the physical properties of the ionized gas responsible for the absorption. Three generally accepted ionized components of the interstellar medium (ISM) which absorb low-frequency radio emission are (1) H II regions; (2) extended H II region envelopes (EHEs); and (3) the warm ionized medium (WIM).
Download or read book X ray Spectra of Supernova Remnants written by Andrew E. Szymkowiak and published by . This book was released on 1985 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray spectra were obtained from fields in three supernova remnants with the solid state spectrometer of the HEAO 2 satellite. These spectra, which contain lines from K-shell transitions of several abundant elements with atomic numbers between 10 and 22, were compared with various models, including some of spectra that would be produced by adiabatic phase remnants when the time-dependence of the ionization is considered.
Download or read book Spatially Resolved Thermal Continuum Absorption Against Supernova Remnant W49B written by and published by . This book was released on 2001 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present subarcminute resolution imaging of the Galactic supernova remnant W49B at 74 MHz (25") and 327 MHz (6"), the former being the lowest frequency at which the source has been resolved. While the 327 MHz image shows a shell-like morphology similar to that seen at higher frequencies, the 74 MHz image is considerably different, with the southwest region of the remnant almost completely attenuated. The implied 74 MHz optical depth (approximately 1.6) is much higher than the intrinsic absorption levels seen inside two other relatively young remnants, Cas A and the Crab Nebula, nor are natural variations in the relativistic electron energy spectra expected at such levels. The geometry of the absorption is also inconsistent with intrinsic absorption. We attribute the absorption to extrinsic free-free absorption by an intervening cloud of thermal electrons. Its presence has already been inferred from the low-frequency turnover in the integrated continuum spectrum and from the detection of radio recombination lines toward the remnant. Our observations confirm the basic conclusions of those measurements, and our observations have resolved the absorber into a complex of classical H II regions surrounded either partially or fully by low-density H II gas. We identify this low-density gas as an extended H II region envelope (EHE), whose statistical properties were inferred from low-resolution meter- and centimeter-wavelength recombination line observations. Comparison of our radio images with H I and H2CO observations shows that the intervening thermal gas is likely associated with neutral and molecular material as well. This EHE may be responsible for the enhanced radio-wave scattering seen in the general direction of the W49 complex.
Download or read book Radio recombination lines in the direction of supernova remnants written by Dennis Downes and published by . This book was released on 1974 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 330 MHz VLA Observations of 20 Galactic Supernova Remnants written by and published by . This book was released on 1992 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present 330 MHz images and integrated flux densities for 20 previously identified 1st quadrant Galactic Supernova Remnants (SNRs). The observations were made in the D configuration of the VLA giving an angular resolution of -3' and providing good sensitivity to extended structure. Such emission, particularly if it is nonthermal, might be missed on higher frequency surveys due to confusion with the Galactic background and confusion with thermal sources in complex regions. Both problems are reduced by interferometric observations at this lower frequency. The flux densities presented can be used to anchor the low frequency end of the radio spectra of these sources, which are often poorly determined by previous observations at both high and low frequencies. The measurements presented here are also useful for distinguishing steeper spectrum shell-type emission from flatter spectrum plerionic emission for SNRs whose intrinsic morphological type is not well established.
Download or read book Radio Recombination Lines 25 Years of Investigation written by M.A. Gordon and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt: Text no 1 Radio Recombination Lines (RRLs), discovered in the USSR in 1964, have become a powerful research tool for astronomers. Available throughout the radio spectrum, these lines carry information regarding the density, temperature, turbulence and velocity of thermal plasmas. Their very existance shows the presence of thermal gas. They also can carry information regarding magnetic fields if Zeeman splitting were to be detected. Containing the proceedings of an IAU Colloquium celebrating the 25th anniversary of their detection, this volume tells us what has happened since. It contains the story of the detection of RRLs and reviews of many areas of physics of the interstellargas from which stars form, HII regions excited by newly formed stars, planetary nebulae involving dying stars, and the structure of our Milky Way and other galaxies reflecting the large-scale morphology of the star formation process. In addition there is an article describing modern laboratory studies of Rydberg atoms to probe the basic physics of atomic structure, and articles describing the theory of collisions and radiation upon Rydberg atoms leading to observate effects to be used as diagnostic tools in astromony. This book focuses on the 25 years of astronomical research with radio recombination lines (RRLs) since their discovery in 1965. It covers a wide range of topics: papers dealing with research into Rydberg atoms both in the laboratory and in the interstellar medium of our galaxy and others; papers on the interaction of radiation and atomic systems, as well as with the effects of inadiabatic collisions between these atoms and both ions and electrons. It deals with astronomical observations of atoms with `diameters' ranging from 0.08 to 50 mum a size factor of 625. It deals with RRLs in absorption, in emission and as true masers. And it deals with plasmas with temperatures ranging from 10 to greater than 104 kelvins, and with an even greater range of volume densities. Much new work is reported, including low frequency RRLs discovered in 1980 and the maser RRLs from the star MWC349, discovered in 1989. The advent of aperture synthesis telescopes and large single-element telescopes have made possible RRL studies with high angular resolution. The sum total of the work reported here will make the volume a platform from which to search new horizons in RRL research.
Download or read book Observations of the California Institute of Technology Radio Observatory Owens Valley California 1961 6 the Radio Spectrum of Supernova Remnants written by D. E. HARRIS and published by . This book was released on 1961 with total page 1 pages. Available in PDF, EPUB and Kindle. Book excerpt: 960 Mc/s observations of thirteen galactic sources generally assumed to be supernova remnants, are coupled with previous observations at other frequencies to derive spectral indices. Although several values of spectral index are found in the neighborhood of zero, arguments are presented that free-free transitions are not the primary cause of the radio emission. An interpretation of the relatively large range of spectral indices is suggested on the basis of an evolutionary sequence in which young, bright objects with relatively steep spectra gradually evolve into old, faint objects with flat or inverted spectra. (Author).
Download or read book High Resolution Radio Investigations of Four Supernova Remnants written by Roelf Marten Duin and published by . This book was released on 1974 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
