ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • ASTROPHYSICS  (578)
  • Chemical Engineering  (547)
  • 1980-1984  (1,125)
  • 1925-1929
  • 1983  (1,125)
  • 101
    facet.materialart.
    Unknown
    Possible evidence for the driving of the winds of hot stars by Alfven waves (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Ultraviolet spectra of the supergiants Alpha Cam (09.5 Ia), HD 105056 (ON9.7 Iae), and 15 Sgr (O9.7 Iab) are compared, and it is shown that the terminal outflow velocity, TOV, of HD 105056 is one-half that of the other two stars even though HD 105056 has the highest effective temperature of the three stars. This anomaly, together with the fact that the observed TOV values for early-type stars scatter about an empirical correlation between TOV and log T(eff) by an amount which is larger than the amount expected according to the observational errors in determining TOV and log T(eff), leads to the conclusion that an agent in addition to radiation, Alfven waves, is driving the winds of early-type stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 268; May 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 102
    facet.materialart.
    Unknown
    An X-ray survey on nine algol systems (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The observed X-ray luminosities seen from an Einstein survey of nine Algol like systems are similar to those found by Pallavicini, et al. (1981) for single or widely separated rapidly rotating late stars, but fall an order of magnitude below those seen from RS CVn stars with similar orbital periods and spectral types. It is concluded that the X-ray emission is most probably associated with a hot coronae surrounding the secondary. Possible explanations for the lower luminosity of the Algol systems relative to the RS CVn systems are considered. Previously announced in STAR as N83-22074
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 268; May 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 103
    facet.materialart.
    Unknown
    Distribution of forbidden neutral carbon emission in the ring nebula (NGC 6720) (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The spatial distribution of forbidden C I 9823, 9850 A emission in NGC 6720 is reported. Like forbidden O I, the forbidden C I radiation appears enhanced in the region of the bright filaments. A few percent of the carbon atoms in the filaments are neutral. The neutral fraction is consistent with ionization equilibrium calculations made under the assumption of complete shielding of direct stellar radiation by hydrogen. The observed carbon lines are excited by photoelectrons produced from hydrogen by the nebular diffuse radiation field. The forbidden C I observations confirm that the filaments in NGC 6720 are regions of locally enhanced shielding.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 268; May 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 104
    facet.materialart.
    Unknown
    A survey of spectral morphology and rotational velocities among the helium-rich stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A spectroscopically homogeneous listing of all known members of the helium-rich B star category is presented together with uniform estimates of their rotational velocities. Equivalent widths of hydrogen, helium, and metal lines in the spectra of the helium-rich and comparison stars are given. The distribution of rotational velocities is found to be indistinguishable from that of normal early B dwarfs, except for a possible excess of rapid rotators. The existence of metal abundance anomalies in the helium-rich spectra is critically discussed, as is the identification of helium-rich stars as massive Population I objects with normal main sequence cores and surface helium enhancements, or as low mass highly evolved objects with processed cores.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 268; May 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 105
    facet.materialart.
    Unknown
    Dynamical evolution of interplanetary magnetic fields and flows between 0.3 AU and 8.5 AU - Entrainment (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An analysis is presented of the radial evolution of interplanetary flows and associated magnetic fields between 0.3 AU and 8.5 AU using data from Helios 1 and B Voyager 1, respectively. The results indicate that in moving to 8 AU the largest corotating streams swept up the slower flows and shocks into a relatively thin region in which they coalesced to form a single large-amplitude compression. As a result of this process, referred to as entrainment, memory of the sources and flow configurations near the sun is lost, while small-scale features are erased as the flows move outward and energy is transferred from small scales to large scales.It is concluded that in the outer solar system the structure of the solar wind may be dominated by large scale pressure waves separated by several AU, while beyond several AU most of the compression waves are no longer driven by streams, and the compression waves expand freely. At large distances (greater than 25 AU) these compression waves will have interacted extensively with one another producing another state of the solar wind, with fewer large-scale nonuniformities and more small-scale nonuniformities.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; May 1983
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 106
    facet.materialart.
    Unknown
    The opacity of the universe and the strong equivalence principle (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A possible explanation of why the advanced solutions of Maxwell's equations are not observed in nature is by way of absorption by an opaque universe. As Davies has shown, the ever expanding, general relativistic cosmological models fail to provide the needed absorption. The absorption mechanism calling for an interplay between local physics and cosmology, is usually developed adopting the strong equivalence principle, SEP, which precludes such interplay. It is shown that complete absorption of electromagnetic radiation by ionized intergalactic plasma is obtained provided a violation of the SEP, of the order of the Hubble's constant, is allowed to occur. The same degree of violation was previously found to be compatible with a large body of observational data.
    Keywords: ASTROPHYSICS
    Type: Physics Letters (ISSN 0031-9163); 95A; April 11
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 107
    facet.materialart.
    Unknown
    The Mg II h and k lines in Vega (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: High resolution h (2802.7 A) and k (2795.5 A) lines Mg II obtained for the star Vega (Alpha Lyr, A0V) with Copernicus satellite and a balloon-borne ultraviolet stellar spectrometer (BUSS) are interpreted by means of theoretical NLTE line profiles in the frame work of complete (CR) and partial (PR) redistribution hypothesis. The PR profiles are remarkably coincident with the observed ones for a magnesium abundance Mg/H = 0.00001 and a projected rotation velocity v sin i = 17 km/s. LTE and NLTE atmospheric models with a temperature plateau or with temperature rises (depending on whether the atmosphere is in radiative equilibrium or not) are used to account for the possible presence of a chromosphere on Vega. The possible presence of an interstellar Mg II absorption line superimposed on the stellar ones is also discussed.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 121; 1, Ma; May 1983
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 108
    facet.materialart.
    Unknown
    Hydrogen sulfide in a circumstellar envelope (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A search for hydrogen sulfide in the cool circumstellar envelopes of 25 stars was made using the 1(10)-1(01) rotational line at 1.8 mm. It was detected in the bipolar nebula/OH maser OH231.8+4.2, an object having a high rate of mass loss. An approximate analysis indicates that 1/60 of the sulfur in this outflowing envelope is in the form of H2S, a fraction which may be similar to that in the atmosphere of the central star. In addition, the shape of the observed line profile is discussed in terms of a possible variation of the outflow velocity with latitude above the system's equatorial plane.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 121; 1, Ma; May 1983
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 109
    facet.materialart.
    Unknown
    High spatial resolution VLA observations of the R Aquarii jet (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The Very Large Array was used to observe the jet feature of the symbiotic variable R Aquarii. A steady emission at 6 cm was confirmed for the past year, with the jet located 6.4 arcsec from R Aquarii at 29.3 deg PA. A velocity for the jet has been calculated as 40 km/sec, and may be accompanied by an ejection velocity in the range of 760-1800 km/sec. Since R Aquarii is the closest known object with a jet, further monitoring is recommended in order to detect any episodic mass transfer in what may be a binary system. The mass transfer, monitored at various wavelengths, would account for the observed optical and radio properties.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 267; April 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 110
    facet.materialart.
    Unknown
    Discovery of a nitrogen-rich UV-bright star in the globular cluster M5 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observations of a UV bright source in the globular cluster M5 using instrumentation on the Black Brant rocket are reported. Imagery was obtained by two cameras operating at 1540 A and 2360 A and bandpasses of 350 A and 880 A. The instruments are prototypes for cameras to be flown with the Spacelab. The UV-emitting object in the cluster was located off-center. Comparison of the data with data from the IUE for short-wavelength radiation indicated a temperature in the range 25,000-50,000 K, with a dereddened flux for the continuum near 1550 A of 4.2 x 10 to the -13th ergs/sq cm per sec per A. The object is concluded to be a post-AGB star with an envelope which has experienced CNO processing.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 267; April 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 111
    facet.materialart.
    Unknown
    The period history of the X-ray pulsar in MSH 15-52 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: New and refined mesurements of the pulse period of the X-ray pulsar in the supernova remnant MSH 15-52 are presented. The data were obtained with the Monitor proportional Counter on board the HEAO 2 observatory. The period measurements were obtained by analyzing pulse arrival times determined by cross-correlating sample pulse profiles with a master template. The period history for the source and a representative 0.15 s X-ray light curve are shown. The X-ray measurements alone lead to a refined value of the period derivative of (1.5382 + or -0.0024) x 10 to the -12th s/s, while including the results of more recent radio observations leads to a value of (1.54029 + or -0.00095) x 10 to the -12th s/s. These results indicate a hard-point source surrounded by diffuse nebular emission.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 267; April 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 112
    facet.materialart.
    Unknown
    Stellar contributions to the hard X-ray galactic ridge (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The number density of serendipitous sources in galactic plane Einstein Observatory IPC fields are compared with predictions based on the intensity of the HEAO 1 A-2 unresolved hard X-ray galactic ridge emission. It is concluded that it is unlikely that X-ray sources with 2-10 keV luminosities from about 8 x 10 to the 32nd to about 3 x 10 to the 34th ergs/s are dominant contributors to the hard X-ray galactic ridge. Their surfacea density is less than about 8 x 10 to the -4th/L(32)/sq pc. In particular, Be/neutron star systems such as X Per are not expected to be dominant contributors, both because the 2-10 keV luminosity is roughly 10 to the 33rd ergs/s and their scale height is too small. Lower luminosity stellar systems are likely to be major contributors to the ridge. RS CVn and CV systems with 2-10 keV luminosities between 2 x 10 to the 30th and 4 x 10 to the 32nd ergs/s contribute about 43 + or 18 percent.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 267; April 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 113
    facet.materialart.
    Unknown
    UV radiation field inside dense clouds - Its possible existence and chemical implications (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Interstellar UV radiation cannot penetrate into the interior of dense clouds, and cosmic ray ionization is thought to be the sole driver of the gas phase chemistry. However, cosmic ray energy deposition also involves electronic excitation of the absorbing gas. It appears, therefore, possible that emissions resulting from these excitations might maintain a significant flux of chemically effective UV photons in the interior of dense clouds. The present investigation is concerned with this possibility, taking into account a simplified approach. This approach involves a consideration of Lyman and Werner band photons of molecular hydrogen and their relevance to C and CO chemistry. The results of this investigation suggest that a chemically significant flux of UV photons may exist inside dense clouds due to cosmic ray excitation of the various band systems of hydrogen. These photons would recover C I from the CO reservoir in dense clouds via photodissociation at an order of magnitude faster rate than that possible in connection with the reaction of CO with He(+).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 267; April 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 114
    facet.materialart.
    Unknown
    Two newly discovered S stars in a list of faint red objects (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A list of 103 faint red stars in a 0.7-square-degree area located near NGC 6820/23 on the galactic plane in the constellation Vulpecula is presented. The stars were chosen from Near Infrared Photographic Sky Survey visual and near-IR photographic pairs and were selected for their visual faintness as well as their red colors. Positions, approximate magnitudes, and finding charts for these stars are presented. It is noted that two members of the list, 1548C858 and 1548C869, have already been determined to be faint, pure S stars.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; March 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 115
    facet.materialart.
    Unknown
    The optical emission from the supernova remnant HB 3 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The supernova remnant HB 3 was first detected as a radio source by Brown and Hazard (1953). On the basis of subsequent radio studies, it was concluded that the object was a supernova remnant (SNR). HB 3 is located at the far western edge of the H II region/molecular cloud complex W3-W4-W5 (IC 1795-1805-1848). However, a physical association of HB 3 with this complex is uncertain. In the present investigation, attention is called to the probability that HB 3 exhibits a more extensive optical emission structure than previously realized, and one which agrees well with both the position and morphology of the radio emission. It is found that narrow-passband optical images strongly suggest an almost complete optical emission shell for HB 3. Spectroscopic observations are, however, required to confirm that this emission is characteristic of a SNR.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; March 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 116
    facet.materialart.
    Unknown
    Questions on universal constants and four-dimensional symmetry from a broad viewpoint. I (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: It is demonstrated that there is a flexibility in clock synchronizations and that four-dimensional symmetry framework can be viewed broadly. The true universality of basic constants is discussed, considering a class of measurement processes based on the velocity = distance/time interval, which always yields some number when used by an observer. The four-dimensional symmetry framework based on common time for all observers is formulated, and related processes of measuring light speed are discussed. Invariant 'action functions' for physical laws in the new four-dimensional symmetry framework with the common time are established to discuss universal constants. Truly universal constants are demonstrated, and it is shown that physics in this new framework and in special relativity are equivalent as far as one-particle systems and the S-matrix in field theories are concerned.
    Keywords: ASTROPHYSICS
    Type: Nuovo Cimento B; vol. 74B
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 117
    facet.materialart.
    Unknown
    The nature of NML Cygnus (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Since the discovery of NML Cyg by Neugebauer et al. (1965), its nature has been uncertain because its distance and luminosity are not known. NML Cyg is partially surrounded by an H II region which is heavily obscured by intervening interstellar matter. This H II region has been mapped in the continuum at 21 cm, and it seems clearly associated with the star. In the present investigation it is proposed that the H II region has been created by ionizing radiation from the Cyg OB2 association. The close agreement between the observed structure of the H II region and that predicted by the considered model provides strong evidence that NML Cyg is indeed at the distance of the association, 2 kpc. At this distance it is among the most luminous red stars shown. Because of its high luminosity, NML Cygnus is probably a massive star of perhaps 50 solar masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 267
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 118
    facet.materialart.
    Unknown
    Dependence of interstellar depletion on hydrogen column density - Possibilities and implications (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A reexamination of the observed column densities of various elements in diffuse clouds suggests that almost all elements including oxygen, nitrogen, sulfur, and argon may be depleted with respect to hydrogen in interstellar clouds with large hydrogen column density. The amount of depletion varies from element to element and increases with increasing column density of hydrogen nuclei. This result is in qualitative agreement with the depletion of oxygen and sulfur independently inferred from the gas phase chemistry of sulfur in dense clouds. The rate of increase of depletion with hydrogen column density implied by the present study is large. It is possible that observational selection effects may have amplified the real dependence on N(H). A broad spectrum of C/O ratios ranging from values greater than unity to values less than unity appears possible for interstellar clouds, which would have the effect of a large variation in chemical composition from cloud to cloud.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 267
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 119
    facet.materialart.
    Unknown
    X-ray observations of 4U 1626-67 by the monitor counter on the Einstein /HEAO 2/ observatory (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The pulsing X-ray source 4U 1626-67 was observed with the Monitor Proportional Counter (MPC) on board the Einstein X-Ray Observatory on three occasions in early 1979. The MPC is a sealed, argon-filled proportional counter with a 1.5 mil beryllium window and is coaligned with the X-ray telescope on board the observatory. The spectral data spanning the energy range from 1.1 to 21 keV are divided into eight logarithmically spaced energy channels which integrate for 2.56 s. The Time Interval Processor (TIP) circuitry of the MPC measures time intervals between events to within 1 microsecond or 1.6%, whichever is larger, for a count rate dependent fraction of all events in all eight energy channels. It is found that in the energy range from 1 to 21 keV, the spectrum and 7.7 s pulse shape of 4U 1626-67 are variable on a time scale of minutes. The pulse shape variations correlate in a complex way with the intensity variations in this source.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 120
    facet.materialart.
    Unknown
    The molecular cloud complex associated with ON 1 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observations of CO with different resolutions near the compact H II region/maser source ON 1 are presented, as well as new H2CO and HCO(+) observations. ON 1 is part of an extended molecular cloud complex with overall dimensions of 25 x 60 pc at a distance of 1.4 kpc; it appears to be the only site of star formation in at least the western part of the complex. ON 1 coincides with a compact and dense molecular cloud core (size 0.8 pc) that shows little sign of disruption indicating that ON 1 has only recently turned on. The isolation and apparent youth of ON 1 suggest that the very beginning of the star formation phase of a molecular cloud complex is observed here.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 121
    facet.materialart.
    Unknown
    A laboratory study of the infrared spectra of interstellar ices (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The 3 micron 'ice' band observed in absorption and polarization and other absorption features in interstellar infrared spectra are studied in the laboratory in low temperature (10-130 K) solid mixtures of H2O and other molecules. General empirical rules are derived which relate the shape and relative intensity of the H2O infrared absorptions to thermal history, degree of H2O dilution and hydrogen bonding capacity of the dilutant. Observations of specific features anticipated in low noise medium resolution spectra will yield potentially valuable information on the degree of H2O dilution, the nature of the dilutant and the thermal history of the absorbing solid mixture. Under well defined conditions the peak of the hitherto unobserved librational '12 micron' H2O absorption is shifted to outside the current infrared observation window beyond 13.5 microns.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics Supplement Series; 51; Mar. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 122
    facet.materialart.
    Unknown
    First detection of radio emission from a dwarf nova (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The detection of 4.75 GHz radio emissions from a white dwarf star in SU UMa is reported, and the source of the emission is discussed. The emission was discovered during a survey of six dwarf stars with a double horn receiver system. SU UMa was successfully scanned 123 times, with each scan comprising 31 3-sec integrations 30 arcsec apart. Average fluxes for each beam position were calculated, as was the X ray emission of 7.6 x 10 to the 54th/cu cm in the 0.1-4.5 keV band. The small mass outflow projected for the object indicates a source of suprathermal electrons for the radio emissions A cyclotron maser instability is suggested as the mechanism, and future measurements to detect circular polarization as proof of a coherent source are indicated.
    Keywords: ASTROPHYSICS
    Type: Nature; 302; Mar. 3
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 123
    facet.materialart.
    Unknown
    The mass of the Oort cloud (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The total mass of comets in the Oort cloud is calculated. The distribution of cometary masses is found based on the observed distribution of cometary magnitudes corrected for observational selection effects by Everhart (1967), and a derived relationship between brightness and nucleus mass. A cloud population of 1.4 trillion comets brighter than an absolute magnitude of 11 as found by Weissman (1982) is used. The estimated total mass is 1.9 earth masses. The probable error in the estimate is about one order of magnitude. Most of the mass of the Oort cloud is concentrated in the size range of the observed long-period comets. The mass estimate is consistent with either cometary formation among the outer planets, or in satellite fragments of the primordial solar nebula.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 118; 1, Fe; Feb. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 124
    facet.materialart.
    Unknown
    From dwarfs to giants - Signposts of galaxy formation (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A two-dimensional parametrization of galactic evolution from the primordial state involving mean surface density and velocity dispersion is presented. A dissipation diagram for large-scale structure is presented and its evolutionary significance explored while considering both the pancake and the hierarchical clustering models of galaxy formation. Gaseous dissipation is studied by assuming that individual clouds or turbulent elements of gas interact supersonically, producing strong shocks. It is found that many diverse properties of galaxies can be understood in terms of an evolutionary sequence operative during an early gas-rich protogalactic phase in which dissipation played a key role. Dwarf galaxies may be the fossilized link between primordial fluctuations and the giant galaxies observed today, relics of a past era of prolific galaxy formation.
    Keywords: ASTROPHYSICS
    Type: Nature; 301; Feb. 17
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 125
    facet.materialart.
    Unknown
    Ice in Comet Bowell (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Results of observations of the reflected light in the 1-5 micron region of the spectrum from the Comet Bowell are presented as part of the attempt to directly detect the presence of frozen volatiles in the nucleus of a comet. A deep absorption at 3.25 microns is detected in Comet Bowell which is due to the presence of H2O ice. While other volatile ices have absorption features near 3 microns, it is shown that only H2O ice is a plausible identification at the heliocentric distance of Comet Bowell during the observations (3.4 AU) since only H2O grains are stable enough to have produced the observed absorption. The implications of these findings for models of cometary nuclei are examined.
    Keywords: ASTROPHYSICS
    Type: Nature; 301; Feb. 3
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 126
    facet.materialart.
    Unknown
    A QSO in a rich, distant cluster of galaxies (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The detection of a 'classical' QSO in a previously studied, distant rich cluster of visible galaxies is reported. The blue and red/IR spectra of the QSO are shown. The QSO occurs at a redshift essentially identical to that of the cluster 0016+16, colocated on the 0.01 of the plate which contains the cluster. The simplest explanation of this association is that the QSO is a member of the cluster. The consequences of the finding are discussed. The QSO-cluster association is further confirmation of the cosmological nature of QSO-cluster association is further confirmation of the cosmological nature of QSOs, and it suggests that QSOs do not necessarily avoid the environment of rich clusters. The fact that this QSO is not well centered adds credence to the suggestion that 3C345 and QSO 1641+3998 constitute an additional case of QSOs in high redshift cluster. The location of this QSO could make it a unique probe to study the physical state of the intracluster gas that is common in rich clusters.
    Keywords: ASTROPHYSICS
    Type: Nature; 301; Jan. 20
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 127
    facet.materialart.
    Unknown
    On the origin of relativistic particles and gamma-rays in quasars (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-33329)
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 265
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 128
    facet.materialart.
    Unknown
    Gravitational waves and red shifts - A space experiment for testing relativistic gravity using multiple time-correlated radio signals (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A two-step satellite mission for improving the accuracy of gravitational wave detection and for observing actual gravity waveforms is proposed. The spacecraft would carry both a highly stable hydrogen maser, which would control a transmitter sending signals to earth, and a Doppler transponder operating in the two-way mode. The use of simultaneous one- and two-way Doppler transmissions offers four time records of frequency pulsations, which can reveal gravitational radiation at 1-10 MHz with an amplitude accuracy of a factor of six. The first mission phase would consist of a Shuttle launch into a highly eccentric orbit to obtain measurements of the gravitational redshift using gravitational potentials of different earth regions to establish that gravity is describable by a metric theory. Then, after a boost into a heliocentric orbit at 6 AU, the earth-satellite system could detect gravitational waves in the solar system, as well as bursts emitted by the collisions of supermassive black holes.
    Keywords: ASTROPHYSICS
    Type: General Relativity and Gravitation; 15; Feb. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 129
    facet.materialart.
    Unknown
    The three micron 'ice' band in grain mantles (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Attention is given to the influence of different mantle constituents on extinction and polarization due to H2O absorption in grain mantles, particularly the 3250/cm band. With respect to BN, the simultaneous reproduction of the extinction and polarization band shapes occurs by normal size particles containing mixtures of H2O with other molecules. As regards the 3-micron absorption in OH 231.8 plus 4.2, the data can be best fitted with pure amorphous H2O grains which have been heated to (or created at) about 80 K. The variation in grain mantle composition between young stellar objects and late-type stars loosing mass is attributed to a fundamental difference in grain formation and evolution.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics; 117; 1, Ja; Jan. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 130
    facet.materialart.
    Unknown
    Large-amplitude hydromagnetic waves in collisionless relativistic plasma - Exact solution for the fast-mode magnetoacoustic wave (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: An exact nonlinear solution is found to the relativistic kinetic and electrodynamic equations (in their hydromagnetic limit) that describes the large-amplitude fast-mode magnetoacoustic wave propagating normal to the magnetic field in a collisionless, previously uniform plasma. It is pointed out that a wave of this kind will be generated by transverse compression of any collisionless plasma. The solution is in essence independent of the detailed form of the particle momentum distribution functions. The solution is obtained, in part, through the method of characteristics; the wave exhibits the familiar properties of steepening and shock formation. A detailed analysis is given of the ultrarelativistic limit of this wave.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 131
    facet.materialart.
    Unknown
    Identification of the emission feature near 3.5 microns in the pre-main-sequence star HD 97048 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-34320)
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 265
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 132
    facet.materialart.
    Unknown
    Modeling of G333.6-0.2 as a spherical H II region (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The radio and IR observations of the H II region G333.6-0.2 are matched with a detailed spherical model with a density distribution which has a uniform-density core of radius 0.05 pc, a power-law intermediate zone, and a uniform-density halo. A stellar radiation field is required that is somewhat different from those predicted by available model atmospheres. Of the stellar models of Kurucz, the Teff = 34,000 K and log g = 3.5 model best fits the observed ratio of helium to hydrogen recombination lines. A good fit to all the observations in obtained with an S(2+) ionizing flux which is a factor of 20 times less than predicted by the Kurucz atmosphere. Current model atmospheres may not be appropriate because a single stable star with Teff = 34,000 K fails by at least an order of magnitude to produce the ionizing luminosity. The small radius of the constant-density core implies a short dynamical lifetime of approximately 5000 years for this spherical model; this may indicate that a nonspherical blister geometry is more appropriate for this H II region.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 265
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 133
    facet.materialart.
    Unknown
    Gravitationally induced spurs in spiral galaxies - An example in M31 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Radio and optical morphological data are consistent with a gravitational mechanism for the anomalous structure between the S4 and SS arms of M31, with the large complex of H I and H II in and around NGC 206 being implicated in the creation of the anomalous spur. Computer models of the gravitational effects of the spur show that its gravitational induction explains the observed velocity distortions. It is speculated that spurs in more distant galaxies, for which high resolution data as complete as that presented are not yet available, are also gravitational. This implicitly applies not only to spurs in galaxies with well defined spiral structure, but also for galaxies with more chaotic spiral arm patterns.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 134
    facet.materialart.
    Unknown
    The grains and gas in Comet Bowell 1980b (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The importance of coordinating different types of observations of a comet is illustrated in terms of spectral data on Comet Bowell. Photometric data in 1980 indicated that OH emissions were occurring when the comet was still more than 4 AU from the sun. Further measurements were arranged with the IUE satellite, the photoelectric scanner at Cerro Tololo and the IR telescope on Mauna Kea. Several sizes of diaphragms were used in order to estimate variations with respect to aperture. Calculations were made to quantify the wavelengths observed as a function of the grains' cross-sections. The OH emission was confirmed by the spectrographic and photometric data. It is suggested that sufficient dark materials are present on the cometary surface to have enhanced the absorption of solar radiation to levels sufficient for heating and dissociating surface ice particles.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 135
    facet.materialart.
    Unknown
    Properties of ices and grains - An experimental study (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Proton irradiation of a variety of ice mixtures was carried out to study the effect of galactic cosmic ray irradiation of comets in the Oort Cloud. Three significant effects were noted: (1) production of new molecules; (2) production of a more energetic ice at low temperatures; (3) production of a non-volatile, complex organic residue. These phenomena suggest various effects on new comets approaching the sun including enhanced activity. Experiments on the condensation of silicate grains provide information on the condensation mechanism and properties of grains. Controlled annealing of the amorphous condensates shows how crystallization occurs. Infrared spectra of different stages of crystallization contain features that may identify composition, structure and history of refractory material.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 136
    facet.materialart.
    Unknown
    Interstellar ice (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The 3250/cm 'ice' band observed in absorption and polarization in interstellar spectra is studied in the laboratory in low-temperature solid mixtures of H2O and other molecules. General empirical rules are derived which relate the shape and relative intensity of the H2O infrared absorptions to the degree of H2O dilution and hydrogen-bonding capacity of the dilutant. The chemical composition of mantles accreting on interstellar grains inside dense (1000-100,000/cu cm) molecular clouds has been calculated numerically. The reaction scheme comprises gas-phase as well as grain surface reactions. The results show that in most circumstances grain mantles consist of the molecules H2O, H2CO, NH3, N2, O2, CO, and CO2. The expected infrared characteristics of the calculated grain mantles are discussed with an emphasis on the observed 3250/cm 'ice' band. Grain mantles accreted at a density of about 10,000/cu cm contain large concentrations of H2O (about 60 percent) and produce a broad 3250/cm 'ice' band.
    Keywords: ASTROPHYSICS
    Type: Journal of Physical Chemistry (ISSN 0022-3654); 87; 21, 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 137
    facet.materialart.
    Unknown
    The high energy X-ray spectra of supernova remnants (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The results of fitting an ionization-nonequilibrium (INE) model to the high-energy (above 5-keV) X-ray spectra of the young supernova remnants Cas A and Tycho are presented. As an additional constraint, the models must simultaneously fit lower-energy, higher-resolution data. For Cas A, a single INE component cannot adequately reproduce the features for the entire X-ray spectrum because the ionization structure of iron ions responsible for the K emission is inconsistent with that of the ions responsible for the lower-energy lines, and the flux of the highest-energy X-rays is underestimated. The iron K line and the high-energy continuum could arise from the same INE component, but the identification of this component with either the blast wave or the ejecta in the standard model is difficult. In Tycho, the high-energy data rule out a class of models for the lower-energy data which have too large a continuum contribution.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 138
    facet.materialart.
    Unknown
    Gamma-rays from active galactic nuclei (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Gamma-ray observations of active galactic nuclei (AGNs) are reviewed and the best candidate mechanisms for gamma ray production in AGNs are examined. Both nonthermal and thermal mechanisms are considered. Hot accretion disks around massive black holes in the centers of AGNs could provide the required thermal electrons, pions, and relativistic lectrons and positrons to explain both the X-ray and gamma emission.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 139
    facet.materialart.
    Unknown
    Observational Basis for Velocity Fields in Stellar Atmospheres, Workshop, Trieste, Italy, August-September 1982, Proceedings (1983)
    In:  Other Sources
    Details
    Publication Date: 2016-03-09
    Description: Solar and stellar winds and mass-loss phenomena are discussed in reviews of recent observations and current theory. Topics examined include mass loss from the sun, the O-type stars, Wolf-Rayet stars, the Parker theory, B stars, T Tauri stars, Balmer line emission from Be stars, novae, symbiotic stars, planetary nebulae, and dwarf novae. Graphs, tables, diagrams, sample spectra, and extensive discussion on each contribution are provided.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 140
    facet.materialart.
    Unknown
    Pair Production near Threshold in Pulsar Magnetic Fields (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: In pulsar polar cap models, curvature radiation gamma rays produce e(+)e(-) pairs in the strong magnetic fields near the surface of the neutron star. While these gamma rays have energies E sub gamma mc(2), they also propagate at very small angles to the fields, such that the threshold condition, E gamma 2mc(2)/sin theta is just barely satisfied when they pair produce. Threshold effects on the pair production attenuation coefficient, which are due to the discreteness of the e(+)e(-) Landau states, must therefore be considered when computing the mean free paths of curvature radiation photons in pulsar magnetic fields. These effects, which are not incorporated in the asymptotic expression for the attenuation coefficient, have some interesting consequences for pulsar models. Since pair production is suppressed near threshold, the photon mean free paths are longer than previously thought. In magnetic fields approximately 6x10 approximately G, the pairs tend to be produced in the ground state Landau level and will not synchrotron radiate. Since synchrotron radiation is an essential ingredient in the electromagnetic cascades which produce low energy pairs above the acceleration region, pulsars with very high magnetic fields may not produce many pairs.
    Keywords: ASTROPHYSICS
    Type: NASA(Goddard Space Flight Center Contrib. to the Workshop on Positron-Electron Pairs in Astrophys.; p 45-49
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 141
    facet.materialart.
    Unknown
    Comparison of Photon-photon and Photon-magnetic Field Pair Production Rates (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: Neutron stars were proposed as the site of gamma-ray burst activity and the copious supply of MeV photons admits the possibility of electron-positron pair production. If the neutron star magnetic field is sufficiently intense ( 10 to the 12th power G), both photon-photon (2 gamma) and photon-magnetic field ( gamma) pair production should be important mechanisms. Rates for the two processes were calculated using a Maxwellian distribution for the photons. The ratio of 1 gamma to 2 gamma pair production rates was obtained as a function of photon temperature and magnetic field strength.
    Keywords: ASTROPHYSICS
    Type: NASA(Goddard Space Flight Center Contrib. to the Workshop on Positron-Electron Pairs in Astrophys.; p 7-12
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 142
    facet.materialart.
    Unknown
    Pair Production and Annihilation in Strong Magnetic Fields (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: Electromagnetic phenomena occurring in the presence of strong magnetic fields are currently of great interest in high-energy astrophysics. In particular, the process of pair production by single photons in the presence of fields of order 10 to the 12th power Gauss is of importance in cascade models of pulsar gamma ray emission, and may also become significant in theories of other radiation phenomena whose sources may be neutron stars (e.g., gamma ray bursts). In addition to pair production, the inverse process of pair annihilation is greatly affected by the presence of superstrong magnetic fields. The most significant departures from annihilation processes in free space are a reduction in the total rate for annihilation into two photons, a broadening of the familiar 511-keV line for annihilation at rest, and the possibility for annihilation into a single photon (which dominates the two-photon annihilation for B ( 10 the 13th power Gauss). The physics of these pair conversion processes, which is reviewed briefly, can become quite complex in the teragauss regime, and can involve calculations which are technically difficult to incorporate into models of emission mechanisms in neutron star magnetospheres. However, theoretical work, especially the case of pair annihilation, also suggests potential techniques for more direct measurements of field strengths near the stellar surface.
    Keywords: ASTROPHYSICS
    Type: NASA(Goddard Space Flight Center Contrib. to the Workshop on Positron-Electron Pairs in Astrophys.; p 13-26
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 143
    facet.materialart.
    Unknown
    An Electron-positron Jet Model for the Galactic Center (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: High energy observations of the galactic center on the subparsec scale seem to be consistent with electron-positron production in the form of relativistic jets. These jets could be produced by an approximately 1,000,000 solar mass black hole dynamo transportating pairs away from the massive core. An electromagnetic cascade shower would develop first from ambient soft protons and then nonlinearly; the shower using itself as a scattering medium. This is suited to producing, cooling and transporting pairs to the observed annihilation region. It is possible the center of our galaxy is a miniature version of more powerful active galactic nuclei that exhibit jet activity.
    Keywords: ASTROPHYSICS
    Type: NASA(Goddard Space Flight Center Contrib. to the Workshop on Positron-Electron Pairs in Astrophys.; p 1-6
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 144
    facet.materialart.
    Unknown
    Criteria for Grasar Action in Astrophysical Sources (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: The theory of gamma ray amplification through stimulated annihilation radiation (grasar) was developed by Ramaty, McKinley and Jones. For gamma ray bursts similar to the March 5, 1979 burst, an observed annihilation line of width 0.03 MeV would imply a grasar source. The minimum pair density needed for the onset of grasar action is approx. 10 to the 30th power/cu cm and the peak of the grasar line, without a gravitational redshift, is at 0.5 MeV.
    Keywords: ASTROPHYSICS
    Type: NASA(Goddard Space Flight Center Contrib. to the Workshop on Positron-Electron Pairs in Astrophys.; p 63-67
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 145
    facet.materialart.
    Unknown
    Activity and magnetic fields on stars from radio observations (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Radio observations explain certain kinds of stellar activity and reliable estimates of magnetic field strengths are derived for the radio emitting regions. Radio observation of flare stars shows rapidly varying bursts of radiation with frequencies of up to 5 GHz. The inferred brightness temperatures of these bursts (10 to the 10th power to 10 to the 14th power) imply that the radiation is coherent. Two mechanisms are proposed to generate such radiation: (1) plasma radiation, and (2) electron cyclotron masers. The high brightness temperatures of the bursts up to 10 to the 20th power K) makes the latter the most plausible. For bursts in the 5 GHz range, the magnetic field strength would be approximately 900 Gauss.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-175966 , NAS 1.26:175966
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 146
    facet.materialart.
    Unknown
    Ages of Extragalactic Intermediate-Age Star Clusters (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A dating technique for faint, distant star clusters observable in the local group of galaxies with the space telescope is discussed. Color-magnitude diagrams of Magellanic Cloud clusters are mentioned along with the metallicity of star clusters.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-173927 , NAS 1.26:173927
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 147
    facet.materialart.
    Unknown
    Shock processing of interstellar grains (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Theoretical and observational evidence is presented that shock processing of interstellar dust grains by supernova blast waves affects both heavy element depletions and ultraviolet extinction curves. By coupling a realistic model of grain sizes and populations with a radiative shock code, significant grain destruction at velocities as low as 40 km/s is demonstrated. Nonthermal sputtering and grain-grain collisions destroy relatively more large grains than small, and more silicates than graphite. Consequently, both the 2175 A extinction 'bump' and the far-ultraviolet normalized extinction are increased in strength. Ultraviolet extinction studies with the International Ultraviolet Explorer of nine stars near three supernova remnants (the Monoceros Loop, Shajn 147, and Vela) exhibit strong 2175 A bumps and normal or high far-ultraviolet extinction. Diffuse bands, if they are created by small grains, should show little correlation with such activity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 652-660
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 148
    facet.materialart.
    Unknown
    X-ray observations of M33 with the high resolution imager on the Einstein Observatory (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Three observations, separated by 6 months, of the Local Group galaxy M33 using the high resolution imager (HRI) on the Einstein Observatory are reported. Eight X-ray sources with luminosites ranging from 8 x 10 to the 36th to 1.2 x 10 to the 39th ergs/s have been detected. For seven of these sources, finding charts with positions accurate to less than 5 arcsec are provided. The X-ray properties and possible identifications are discussed for the eight HRI-detected sources and for two other sources, previously described by Long et al. (1981), for which upper limits are provided. It is found that most of the sources are associated with Population I markers. One source may be coincident with an optical supernova remnant. The most luminous source (by a factor of at least 25) is that associated with the optical nucleus. Because the X-ray flux from the nucleus decreased by a factor of 1/2 between the first and second observations, it is most likely that a single, compact object is responsible for the X-ray emission. It is possible that this source may be an active galactic nucleus, a massive binary X-ray source, or a low-mass X-ray binary such as are found in globular clusters within the Galaxy.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 571-577
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 149
    facet.materialart.
    Unknown
    X-ray studies of BL Lacertae objects with the Einstein Observatory - Confrontation with the synchrotron self-Compton predictions (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: X-ray flux densities measured with the Einstein Observatory are presented for a set of LB Lac objects with available VLBI angular sizes. The static, single-component synchrotron self-Compton formalism is used to predict the X-ray flux densities. Ratios of 10 to the -6th to the 10 to the -8th are found for the observed to predicted flux densities and it is concluded that such a model, at least in its simplest form, does not explain the X-ray emission from these objects as a class. The hypothesis that the compact source is in relativistic motion allows a simple resolution of the discrepancy. The results agree qualitatively with a broad distribution of bulk Lorentz factors Gamma with a fairly low typical value of Gamma approximately equal to and with a quasi-isotropic distribution of the direction of ejection relative to our line of sight.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 467-471
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 150
    facet.materialart.
    Unknown
    Ultraviolet carbon lines in the spectrum of the white dwarf BPM 11668 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The southern hemisphere DC white dwarf BPM 11668 has been found to show strong ultraviolet lines of neutral carbon using observations from the IUE satellite. This star seems typical of the growing number of DC white dwarfs found to be of this type and appears to have a carbon abundance near C:He = 0.0001, with an effective temperature of 8500 K.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 128; 1; 258
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 151
    facet.materialart.
    Unknown
    The star-forming history of the young cluster NGC 2264 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: UBVRI H-alpha photographic photometry was obtained for a sample of low-mass stars in the young open cluster NGC 2264 in order to investigate the star-forming history of this region. A theoretical H-R diagram was constructed for the sample of probable cluster members. Isochrones and evolutionary tracks were adopted from Cohen and Kuhi (1979). Evidence for a significant age spread in the cluster was found amounting to over ten million yr. In addition, the derived star formation rate as a function of stellar mass suggests that the principal star-forming mass range in NGC 2264 has proceeded sequentially in time from the lowest to the highest masses. The low-mass cluster stars were the first cluster members to form in significant numbers, although their present birth rate is much lower now than it was about ten million yr ago. The star-formation rate has risen to a peak at successively higher masses and then declined.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 53; 893-936
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 152
    facet.materialart.
    Unknown
    Ultraviolet spectroscopic observations of some Be stars of later type and A-F type shell stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: High-dispersion IUE spectra of 18 later type Be and A-F type shell stars as well as eight standard nonemission line stars have been analyzed for anomalous ionization and mass loss effects. It is found that superionization in the Be stars extends to the latest spectral subtypes but does not seem to be present in the A-F type stars. The superionized lines in the Be stars appear to be correlated with v sin i. Asymmetrical or violet-displaced resonance lines suggesting mass loss are observed in all the Be stars except one, in some of the standard stars, but not in the A-F stars. Lower limits to the mass loss rates computed from Si IV lines range between 5.3 x 10 to the -12th and 3.5 x 10 to the -11th solar masses/yr, with Be shell stars showing the largest values. Mass loss is correlated with luminosity and effective temperature but not with rotation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 53; 869-892
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 153
    facet.materialart.
    Unknown
    Mass loss from evolved stars. II - Radio continuum emission and evolution to planetary nebulae (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The radio continuum properties of cool evolved stars are investigated from the viewpoint of mass loss mechanisms and evolution through the planetary nebula stage. The VLA was used to search 32 high mass loss rate objects for 6-cm continuum emission, leading to the detection of NGC 7027, CRL 618, R Aqr, IRC + 10216, and Omicron Ceti. The evolution of such objects to the planetary nebula stage was studied by calculating the propagation of an ionization front into the remnant neutral envelope that is produced by continuous mass loss in the red giant stage. It is found that none of the stars has a hot, compact companion, except for the known cases of R Aqr and Mira, and that envelope fractional ionization is in most cases as small as less than about 0.001.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 330-341
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 154
    facet.materialart.
    Unknown
    Far-ultraviolet emission lines in U Cephei - Evidence for a hot, turbulent circumstellar envelope (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The numerous emission lines in the far-UV spectrum which have been found in the Algol-type eclipsing binary U Cephei are similar to those observed in the W Serpentis stars, although they are weaker and appear only during the primary eclipse. The line-emitting region is studied in both emission and absorption.It surrounds the hotter component and extends to a distance of several of its radii. A model is proposed in which the emission originates in a highly turbulent circumstellar region, at an electron temperature of about 10,000 K. The energy needed for ionization is derived from collisions, and is probably extracted from the accretion energy.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 251-270
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 155
    facet.materialart.
    Unknown
    The cool DC white dwarf Stein 2051B (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Visual scans from the Kitt-Peak 2.1-m telescope and UV spectra from the IUE satellite are combined in a spectroscopic study of the bright DC white dwarf, Stein 2051B. With a cooling age near 2 billion years, and a resulting atmospheric mass of hydrogen of the order of 6 x 10 to the 17th g, the accretion rate over the star's lifetime is less than 2 x 10 to the -25th solar masses/year. This is far below the predictions of standard accretion theories, and requires unreasonably strong suppression of hydrogen accretion in this star if the accretion-diffusion theory is to account for the carbon abundance found. It is suggested that the carbon may have been brought to the surface by convective mixing.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 240-246
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 156
    facet.materialart.
    Unknown
    H2O heating in molecular clouds - Line transfer and thermal balance in a warm dusty medium (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An investigation is undertaken into the possibility of the heating of molecular gas through collisions with radiatively pumped H2O, in the context of the overall thermal balance of optically thick molecular clouds with embedded sources. In order to solve the line transfer equation, which includes warm dust grains, an extended method of escape probability approximation is developed in which the equilibrium gas temperature arises from the balance of heating by cosmic ray ionization of H2, and by collisions with warm dust grains and radiatively pumped H2O molecules against cooling by collisions with CO and C I. The equilibrium gas temperature for a given dust temperature strongly depends on the efficiency of the cooling species, and is therefore most sensitive to the cloud optical depth. It is less dependent, in decreasing order, on H2O abundance, gas density, and velocity dispersion.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 145-162
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 157
    facet.materialart.
    Unknown
    An ionization gradient across the front in M17 SW (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Measurements of forbidden Ne II lines at 12.8 microns and forbidden S IV at 10.5 microns are presented along a line through and perpendicular to the ionization front in M17 SW. These observations give evidence for ionization stratification within the front, with the most highly ionized material lying toward the east, opposite to the peak molecular emission and far-IR flux. This result supports the picture of M17 SW as a region where a molecular cloud is heated externally. The ionization equilibrium within the ridge and the nebular energetics suggest that the M17 H II region is largely excited by one or more nearby early O stars. The properties of the recently discovered radio point source in M17 are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 130-134
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 158
    facet.materialart.
    Unknown
    Luminosity correlations in quasars (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Simulations are conducted with and without flux thresholds in an investigation of quasar luminosity correlations by means of a Monte Carlo analysis, for various model distributions of quasars in X-rays and optical luminosity. For the case where the X-ray photons are primary, an anticorrelation between X-ray-to-optical luminosity ratio and optical luminosity arises as a natural consequence which resembles observations. The low optical luminosities of X-ray selected quasars can be understood as a consequence of the same effect, and similar conclusions may hold if the X-ray and optical luminosities are determined independently by a third parameter, although they do not hold if the optical photons are primary. The importance of such considerations is demonstrated through a reanalysis of the published X-ray-to-optical flux ratios for the 3CR sample.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 275; 45-52
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 159
    facet.materialart.
    Unknown
    The ionization structure of planetary nebulae. 4: NGC 6853 (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Spectrophotometric observations of emission line intensities were made in seven positions in the planetary nebula NGC 6853; for five of the positions, coverage is across the entire spectral range 1400A to 9600A. Standard equations used to correct for the existence of elements in other than the optically-observable ionization stages give results over a wide range of ionization that are generally consistent and in agreement with abundances calculated using ultraviolet lines. As in the previous studies in this series, the lambda 4267 CII line implies a c(2+) abundance that is higher than that determined from UV lines. Although this effect is much smaller than in NGC 6720 and NGC 7009, it is again largest nearest the central star, giving more evidence that the excitation mechanism for the lambda 4267 line is not understood.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-173240 , NAS 1.26:173240
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 160
    facet.materialart.
    Unknown
    Chromospheric and coronal emissions from the giants in the Hyades (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The visible Ca II K and International Ultraviolet Explorer spectra from the four K0 III stars (theta-1, gamma, delta, and epsilon Tau) in the Hyades, along with a field giant of similar spectral type, beta Gem, have been measured. Among the Hyades giants, the range of the high-temperature emissions can be a factor of 6 or more for C IV and an order of magnitude in the X-ray luminosity measured by Stern et al. (1981). For these presumably coeval cluster giants with similar macroscopic parameters, such as age, mass, effective temperature, gravity, and projected rotational velocity, the observed range in chromospheric and coronal emissions is not easily explained by the dominant factors thought to control these emissions in cool stars. It is possible that the emissions are time variable, on a time scale longer than six months. This would be the first evidence that giants undergo magnetic activity cycles similar to those of dwarf stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 271; Aug. 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 161
    facet.materialart.
    Unknown
    The Riemann disks. I - Equilibrium and secular evolution (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The two-dimensional analogs to Riemann S-type ellipsoids are considered as simple fluid models for galactic bars. Their equilibrium is discussed and their evolution under the effects of viscosity, gravitational radiation, and external torques from other components of the galaxy is computed. As a bar loses angular momentum due to external torques, it generally becomes less elongated, and its figure speed may either increase or decrease.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 271; Aug. 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 162
    facet.materialart.
    Unknown
    X-rays from radio pulsars - The detection of PSR 1055-52 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The short-period pulsar PSR 1055-52 has been detected as a soft X-ray source in the course of an Einstein Observatory survey of radio pulsars. Its X-ray to radio luminosity ratio is about 10,000, although the X-rays are not modulated at the neutron star's rotation frequency. High spatial resolution observations suggest that a significant fraction of the emission comes from an extended region surrounding the pulsar. Several possible scenarios for the origin of both point and extended X-ray emission from isolated neutron stars are investigated: radiation from the hot stellar surface, from hot polar caps, and from an optically thick atmosphere, as well as from a circumstellar nebula emitting thermal bremsstrahlung or synchrotron radiation. It is concluded that the spatial, spectral, and temporal characteristics of this source are most consistent with a model in which relativistic particles generated by the pulsar are radiating synchrotron X-rays in the surrounding magnetic field; i.e., that PSR 1055 is embedded in a mini-Crab nebula. Observational tests of this hypothesis are suggested, and the implications of this result for pulsar evolution are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 271; Aug. 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 163
    facet.materialart.
    Unknown
    SS Bootis - A totally eclipsing binary of the RS CVn type (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Photoelectric photometry gathered for SS Bootis over the 1976-1981 period shows a distortion wave amplitude variation from 0.05 to 0.20 mag, with no apparent pattern. From the rectified light curve, a new time of midprimary eclipse was found to be 2444332.0335 + or - 0.0005 days. Solutions of the primary eclipse data, rectified for star spots as well as for ellipticity and reflection, are presented.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 88; Aug. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 164
    facet.materialart.
    Unknown
    The 0.9-2.5 micron spectrum of Comet West 1976 VI (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Analyses of IR data of Comet West in the region 0.9-2.5 microns are presented. The spectra were observed with a resolution of 4.6/cm, and the solar-type star Eta Boo was also observed for comparison purposes. The cometary continuum was found to increase slightly from 10,000-5500/cm, and display thermal emission above 5500/cm due to dust particles in the coma. The cometary emissions were identified with CN and C2, with the C2 transitions displaying unblended singlet and triplet systems. It is noted that no emissions or absorptions due to ice of any form were detected.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 165
    facet.materialart.
    Unknown
    On the evolutionary status of bright, low-mass X-ray sources (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A model of bright, low-mass X-ray binaries is proposed which features a lower giant-branch star losing mass on a nuclear time scale to an accreting compact companion. Simple numerical models show that mass transfer rates equal to or greater than 10 to the -9th solar masses per yr are sustained at very nearly a constant rate until the envelope of the donor star is exhausted. The model predicts orbital periods in the range 1-200 days and X-ray to optical luminosity ratios Lx/Lopt = 200-1000 for these sources. It accounts in a natural way for the large fraction of the total galactic bulge luminosity emitted by a few bright (10 to the 37th erg/s or greater) sources. It also accords very well with the observed X-ray and optical properties of the halo source Cyg X-2 and also with those of 2S 0921-63, provided this latter system contains a massive accreting white dwarf rather than a neutron star. Problems of the prior evolution of low-mass X-ray sources are also briefly delineated.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 166
    facet.materialart.
    Unknown
    Radio and X-ray observations of the radio halo source in A1367 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Radio and X-ray observations of the 'radio halo' in A1367 are presented. The radio spectral index distribution is derived combining data at 610 and 1415 MHz taken with the Westerbork Synthesis Radio Telescope (WSRT). A high-resolution Very Large Array (VLA) map allows us to discriminate between the extended cluster emission and a triple radio source associated with a background stellar object (most probably a QSO) which appears projected onto it. X-ray observations taken with the high-resolution imager on board the Einstein satellite reveal an X-ray source associated with this background object. A second weak X-ray enhancement is found projected onto the extended radio component. Inverse Compton scattering of the synchrotron-emitting particles provides a possible interpretation of such a source. The presence of large-scale magnetic fields and particle acceleration due to the turbulent motion of galaxies through the intergalactic medium is discussed in relationship to the observed peculiarities of the galaxies found in this region.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 167
    facet.materialart.
    Unknown
    On the contributions of the Orion reflection nebulosity to the continuous UV spectrum of the Herbig-Haro objects HH 1 and HH 2 and of the C-S Star (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 168
    facet.materialart.
    Unknown
    Constraints on the inclination and masses of the HDE 226868/Cygnus X-1 system from the observations (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Analyses of two high-dispersions IUE spectra of HDE 226868 (the optical counterpart of Cygnus X-1) are combined with studies of low-dispersion IUE spectra to provide a more accurate determination of the variation of C IV stellar wind absorption as a function of orbital phase. By incorporating these observational results into an analysis of the structure of the X-ray ionization cavity in the stellar wind, it is found that the orbital inclination must lie between 36 and 67 deg, leading to a mass for the compact object between 5.7 and 11.2 solar masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 169
    facet.materialart.
    Unknown
    Theory of molecular formation by radiative association in interstellar clouds (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A theory of molecular formation by radiative association is presented which is consistent with angular momentum being conserved during the encounter and which incorporates explicitly the long-range attraction between the reactants. It is pointed out that the activated complex would not have a Boltzmann energy distribution should the rotational and kinetic temperatures of the reactants differ, and it is shown how allowance for this may be made. Account is taken of the inaccessibility of a considerable fraction of the nuclear spin states of the complex. Methods are given for treating the effect which the finiteness of the dissociation frequency may have on the association rate. Calculations on some reactions of interest are performed. A very simple semiempirical formula for the rate coefficient for radiative association is also given.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 170
    facet.materialart.
    Unknown
    Determinations of S III, O IV, and Ne V abundances in planetary nebulae from infrared lines (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Twelve planetary nebulae have been subjected to airborne observations of the S III (18.71 microns), Ne V (24.28 microns) and O IV (25.87 microns) IR forbidden lines, of which one or more lines were detected in seven of the nebulae. These results are insensitive to nebula temperatures, in contrast to optical or UV lines, although density estimates from the latter were required to obtain abundances. The Ne V electron temperature of 11,200 + 2000 or - 1100 K temperature obtained overlaps O III temperature measurements. Since the ionization potential of Ne IV is much greater than that of O II, the electron temperature of Ne V should be much greater than that of O III. This discrepancy may indicate inaccuracies in currently available atomic parameters for Ne V.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 171
    facet.materialart.
    Unknown
    Hydromagnetic wave dissipation in molecular clouds (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The damping of long wavelength, hydromagnetic waves in molecular cloud environments is studied with the aim of determining whether the supersonic motions observed in such clouds are likely to be due to the waves. It is found that Alfven waves propagating parallel to the average magnetic field are the longest lived wave modes. Such waves can typically survive for as long as one-million years if the wavelength is as long as a few tenths of a pc and the magnetic field is 0.1-1 milligauss. Nonlinear steepening of the waves followed by ion-neutral friction in the steepened wave profiles appears to be the most effective damping mechanism.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 172
    facet.materialart.
    Unknown
    Progress toward the origin of the solar system (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: In recent years, considerable progress has been made toward understanding the origin of the solar system. There exists a broad consensus that the planets are derived from a nebular disk which formed with the sun itself. There are, however, disagreements regarding the assumed mass of the solar nebula. Estimates range from a few percent of the sun's mass, the minimum required to make the planets, up to one solar mass. The two extremes lead to very different models of planet formation. The general problem of star formation is considered, taking into account the production of a circumsolar disk nebula due to angular momentum in the protostellar cloud. Collapse of a rotating cloud is modeled by computer codes. Attention is given to the chemical evidence concerning the solar nebula, relations regarding planetesimals and terrestrial planets, and protoplanets and giant planets.
    Keywords: ASTROPHYSICS
    Type: (ISSN 0034-6853)
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 173
    facet.materialart.
    Unknown
    Interstellar photoelectric absorption cross sections, 0.03-10 keV (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An effective absorption cross section per hydrogen atom has been calculated as a function of energy in the 0.03-10 keV range using the most recent atomic cross section and cosmic abundance data. Coefficients of a piecewise polynomial fit to the numerical results are given to allow convenient application in automated calculations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 174
    facet.materialart.
    Unknown
    Waves observed upstream of interplanetary shocks (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The properties of the waves that are present upstream of interplanetary, collisionless, quasi-parallel shocks are described. Two types of such waves have been detected, a higher frequency whistler mode wave and a lower frequency fast mode MHD wave. Both are typically circular or elliptically polarized right-hand waves which propagate along the ambient magnetic field with a 15 deg angle cone. The high frequency waves have sufficient group velocities to outrun the shock, and may be generated by cyclotron resonance with 100 eV to 1 keV shock electrons. The lower frequency waves must be generated locally by particles upstream of the shock, probably by 1-10 keV ions flowing away from the shock. Distinct changes in the spectra of upstream waves as a function of distance from the shock have been noted.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; July 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 175
    facet.materialart.
    Unknown
    ISEE/IMP observations of simultaneous upstream ion events (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Propagation of upstream energetic (50-200 keV) ions is analyzed in sixteen events observed simultaneously by solid state detectors on ISEE 3 at about 200 earth radii and on IMP 8 at about 35 earth radii from the earth. Conclusions are based on comparisons of the pitch angle distributions observed at the two spacecraft and transformed into the solar wind frame. They are beamlike at ISEE 3 and are confined to the outward hemisphere. When IMP 8 is furthest from the bow shock, they are also usually beamlike, or hemispheric. However, when IMP 8 is closer to the bow shock, pancakelike distributions are observed. This systematic variation in the IMP 8 pitch angle distributions delimits a scattering region l less than about 15 earth radii upstream of the earth's bow shock (l measured along the interplanetary magnetic field) that dominates ion propagation, influences the global distribution of fluxes in the foreshock, and may play a role in acceleration of the ions. When IMP 8 is beyond l of about 15 earth radii the propagation appears to be essentially scatter-free between IMP 8 and ISEE 3; this is deduced from the absence of earthward fluxes at IMP 8 as well as the tendency for the spin-averaged fluxes to be comparable at the two spacecraft.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; July 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 176
    facet.materialart.
    Unknown
    Dependence of 50-keV upstream ion events at IMP 7 and 8 upon magnetic field bow shock geometry (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results are presented for a statistical study of four years (1972-1976) of IMP 7 and 8 observations at approximately 40 R(E) of 50-200 keV upstream ion events measured with the Energetic Particle Experiment. A monotonic increase in the probability of observing upstream particle events is found with a decrease in the angle (theta-Bn) between the interplanetary magnetic field (IMF) and the local shock normal at the point where the IMF intersects the bow shock, independent of the length of time of bow shock connections exceeding approximately 10 min. Approximately equal probabilities are found for observing an event above a given flux from any portion of the bow shock with the same value of theta-Bn, a growth time of the 50-200 keV events of approximately 10 min, a maximum attainable flux of approximately 25,000/sq cm s sr, and a positive correlation between the probability of exceeding a given flux and the 3 hr Kp index. It is concluded that the local structure of the bow shock in the immediate vicinity of the field line connection is the dominant influence in the generation process of energetic upstream particle events and that wave-particle interactions produce a self-throttling mechanism that limits the maximum flux of ions escaping the upstream foreshock.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; July 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 177
    facet.materialart.
    Unknown
    On the possibly low H2 formation rate in dense clouds (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: It has been found for the Rho Ophiuchi cloud, and suggested for diffuse cloud cores in general, that H2 has a lower formation rate than normally expected in diffuse clouds. It is proposed that this may be due to a reduction in grain surface area per unit volume, if the grains in these regions are enlarged due to coagulation. For the Rho Oph cloud, there is independent evidence that grain coagulation has occurred, so this hypothesis regarding H2 formation has a more substantial basis than for other clouds, where the evidence for suppressed H2 formation is less certain, and for which there is little information on grain sizes.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 269; June 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 178
    facet.materialart.
    Unknown
    H0547-14 - X-ray flux from a weak gamma-ray burst? (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Data concerning a fast X ray transient observed by the HEAO 1 on March 17, 1978 are discussed. The object, labeled H0547-14, was located in Lepus, with galactic coordinates 219.37 deg longitude, b = -20.12 deg in the anticenter direction. A 10 sec scan of the transient was obtained with proportional counter detectors. An X ray luminosity of more than 5.1 x 10 to the 31st ergs/sec was measured as a lower limit, with the decay taking 17 min. A lower limit to the flare was set at 30 sec. The flux intensity resided in the range 4.4/1 billion-4/100 million erg/sq cm per sec, with a rise time of a factor of 10 in about 5 sec. Possible characterizations of the object, as either a gamma ray burst or as an M dwarf star, are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 179
    facet.materialart.
    Unknown
    On the penetration of the solar wind into the cometary ionosphere (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Questions of interaction between the cometary ionosphere and the solar wind are considered, taking into account present steady-state models of the global flow pattern. The stability of the ionopause and the feasibility of its penetration by the solar wind magnetic field and plasma are found to be central factors in connection with a consideration of the flow patterns. An investigation is conducted regarding a magnetic field penetration of the ionopause. It is concluded that a 'magnetic barrier' is expected to form ahead of the cometary ionopause. The stability of the ionopause is studied in some detail, taking into consideration a four-component fluid (neutrals, ions, protons, and electrons). The present study leads to the conclusion that any deep penetration of the solar wind magnetic field into the cometary ionosphere should be due to the Kelvin-Helmholtz instability of the ionopause, rather than due to the continuous diffusion process recently proposed by Marochnik (1982).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 180
    facet.materialart.
    Unknown
    On the large-scale dynamics of rapidly rotating convection zones (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The fact that the values of the eight basic waves present in turbulent flows in the presence of rotation prohibit a tilt of eddy towards the axis of rotation is incorporated into a formalism for rapidly rotating convection zones. Equations for turbulent velocities are defined in a rotating coordinate system, assuming that gravity and grad delta T act in a radial direction. An expression is derived for the lifetime of a basic wave and then for the average velocity vector. A real convective eddy is formulated and the wave vectors are calculated. The velocity amplitude and the stress tensor amplitude are integrated over the eddy domain. Applied to the solar convective zone, it is found that the convective cells are aligned along the axis of rotation at the poles and at the equator, a model that conflicts with nonrotating mixng length theory predictions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 181
    facet.materialart.
    Unknown
    Infrared observations of OB star formation in NGC 6334 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Infrared photometry and maps from 2 to 100 microns are presented for three of the principal far infrared sources in NGC 6334. Each region is powered by two or more very young stars. The distribution of dust and ionized gas is probably strongly affected by the presence of the embedded stars; one of the sources is a blister H II region, another has a bipolar structure, and the third exhibits asymmetric temperature structure. The presence of protostellar objects throughout the region suggests that star formation has occurred nearly simultaneously in the whole molecular cloud rather than having been triggered sequentially from within. Previously announced in STAR as N83-16263
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 182
    facet.materialart.
    Unknown
    X-ray observations of 20 3CR radio galaxies and their environs (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: X-ray observations of 20 3CR radio galaxies using the Imaging Proportional Counter on the Einstein Observatory are reported. Fourteen of the 18 galaxies, plus two sources without optical identification, are detected with soft X-ray luminosities (Lx) ranging from 10 to the 40.9th to 10 to the 44.4th ergs/s. In four of the galaxies there is evidence for extended X-ray structure. Lx is statistically correlated with the radio power of the core, the lobe radio power (especially below 1 GHz), and the steepness of the lobe radio spectrum at high frequencies. The complex interrelations between X-ray luminosities and radio core, radio lobe, optical nuclei, and galaxy clustering are examined; and it is found that a cluster origin of the X-rays provides the best explanation of these effects. Constraints on synchrotron and inverse Compton production of X-rays in radio lobes and on mechanisms of lobe confinement are also discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 183
    facet.materialart.
    Unknown
    X-ray observations of radio-jet galaxies (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The possibility that the morphology of radio-galaxy jets may be influenced by interaction with X ray emitting gaseous halos led to a study of several jet galaxies with the Einstein Observatory. These observations carried out with the IPC had a high detection rate (5 out of the 6 radio galaxies observed). The X ray data for these objects are presented. The X ray luminosities lie between about 10 to the 42nd and 10 to the 45th erg/sec. The X ray emission was found to be extended for the two galaxies with the most counts. 3C130 and 3C449. Three of the detected galaxies are known to be associated with clusters and we suggest that 3C130 may also be associated with a cluster.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 122; 1-2; June 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 184
    facet.materialart.
    Unknown
    Transition probability of the Si III 189.2-nm intersystem line (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Measurement of the lifetime of the metastable 3s3p(3)P(0)1 level of Si(2+) (Si III), which decays by photon emission at 189.2 nm to the 3s2(1)S0 state, is reported. The data were taken from spontaneous emission from metastable Si III stored in an RF ion trap. The Si III ions were produced through electron bombardment of SiH4 and SiF4 at pressures of 1/100,000,000-1/10,000,000 Torr. A photomultiplier was employed to count the photon emissions from the transitions. A total of 11 decay curves were generated for analysis, with Poisson statistics used to set the uncertainties at within 8 pct. Significant systematic effects were controlled, and the lifetime was found to be within 3.6 microsec of 59.9 microsec. The method used is concluded valid for determining the lifetimes of metastable levels of low-Z ions with low charge, and thereby the transition probabilities.
    Keywords: ASTROPHYSICS
    Type: Physical Review A - General Physics, 3rd Series (ISSN 0556-2791); 27; June 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 185
    facet.materialart.
    Unknown
    MM Herculis - An eclipsing binary of the RS CVn (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: V, B and U differential photoelectric photometry has been obtained for the RS Canum Venaticorum-class eclipsing binary star MM Her, with the light outside the eclipse being Fourier-analyzed to study wave migration and amplitude. These, together with the mean light level of the system, have been monitored from 1976 through 1980. Observations within the eclipse have revealed eclipses to be partial, rather than total as previously thought. The geometric elements of the presently rectified light curve are forced on the pre-1980 light curves and found to be compatible. With these elements, and previously obtained double line radial velocity curves, new absolute dimensions of 1.18 solar masses and 1.58 solar radii are calculated for the hotter star and 1.27 solar masses and 2.83 solar radii for the cooler star. The plotting of color indices on the color-color curve indicates G2V and K2IV spectral types.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 90; 2 Fe; Feb. 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 186
    facet.materialart.
    Unknown
    Studies of proton-irradiated cometary-type ice mixtures (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Cometary ice mixtures are studied in a laboratory experiment designed to simulate the temperature, pressure and radiation environments of the interstellar Oort cloud region, in order to test the hypothesized radiation synthesis mechanism for changing the characteristics of the outer few meters of a comet stored in the Oort cloud for 4.6 billion years. All experiments conducted confirm the synthesis of new molecular species in solid phase mixtures at 20 K. When CH4 is present in the irradiated ice mixture, long chained, voltaile hydrocarbon and CO2 are synthesized together with high molecular weight C compounds present in the room temperature residue. Due to radiation synthesis, about 1 percent of the ice was converted into a nonvolatile residue containing complicated C compounds not present in the blank samples. These results suggest that initial molecular abundances can be altered, and new species created, as a result of radiation synthesis. Irradiated mixtures exhibited thermoluminescence and pressure enhancements during warming, showing the synthesis of reactive species. Outbursts in new comets resulting from similar irradiation-induced exothermic activity would be expected to begin occurring at distances of the order of 100 AU.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 54; June 198
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 187
    facet.materialart.
    Unknown
    Detection of interstellar NH3 in the far-infrared - Warm and dense gas in Orion-KL (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results of an investigation are presented which show the detection of the (J,K) = a(4,3)-s(3,3) rotation-inversion transition of ammonia at 124.6 microns toward the center of the Orion-KL region. The line is found to be in emission and has a FWHM greater than or equal to 30 km/s, while the far-IR ammonia line emission probably comes mainly from the 'hot core', a compact region of warm, very dense gas previously identified by the radio inversion lines of NH3. The a(4,3)-s(3,3) line is very optically thick and it is determined that radiative excitation of the (4,3) NH3 level by far-IR emission from dust within the source can be ruled out. It is concluded that the (4,3) level is probably collisionally excited and the gas in the hot core region is warmer than the dust. Densities of approximately 10 to the 7th/cu cm are high enough to explain the observations, while shock heating by the mass outflow from IRc2 may account for the high gas temperatures in the hot core region.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 188
    facet.materialart.
    Unknown
    High-velocity iron absorption lines in supernova remnant 1006 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The very strong, broad absorption lines of a sdOB star continuum shown in the International Ultraviolet Explorer spectrum of the Schweizer-Middleditch star projected near the center of supernova remnant SNR 1006 are investigated. It is found that strong Fe(+) resonance absorption lines are present whose centers show zero radial velocity while their profiles are broadened by approximately 5000-6000 km/s. Also identified are redshifted Si(+), Si(2+), and Si(3+) lines at velocities of approximately 5000 km/s. Results show that the absorptions must occur in the ejecta of the supernova. The strength and symmetric width of the Fe(+) line indicates that the bulk of the ejecta is iron, in agreement with the current theory for the origin of Type I supernova. It is suggested that the previous failure to detect strong Fe emission lines in the X-ray spectra of this and other young Type I SNRs may be a result of the ejecta not having had time to interact significantly with the ambient medium. In addition, the presence of redshifted adsorption lines due to supernova ejecta in its spectrum shows that this star is located behind the SNR and is not physically associated with it.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 189
    facet.materialart.
    Unknown
    The pulse profile of the Crab pulsar in the energy range 45 keV-1.2 MeV (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The Crab Nebula pulsar (PSR 0531+21) is the best studied and most intense of the nontransient X-ray pulsars. However, since its spectrum drops rapidly with energy, a well-resolved pulse profile has not previously been obtained above 200 keV. In the hard X-ray and low-energy gamma-ray region, an accurate pulse profile can be obtained with a balloon-borne detector of sufficient area during a single transit of the source. A new measurement of the pulse profile of PSR 0531+21 in the energy range above 45 keV obtained with a large-area scintillation detector array is reported. The detector array was flown on a balloon launched from Palestine, Texas on 1980 October 6, reaching a float altitude 4.5 g/sq cm at 0230 UTC October 7. The primary objective of the experiment was to detect and study weak gamma-ray bursts.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 190
    facet.materialart.
    Unknown
    Observations of suspected low-mass post-T Tauri stars and their evolutionary status (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The results of a study of five X-ray discovered weak emission pre-main-sequence stars in the Taurus-Auriga star formation complex are presented. All are of spectral type K7-M0, and about 1-2 mag above the main sequence. One is a double-lined spectroscopic binary, the first spectroscopic binary PMS star to be confirmed. The ages, masses, and radii of these stars as determined by photometry and spectroscopy are discussed. The difference in emission strength between these and the T Tauri stars is investigated, and it is concluded that these 'post-T Tauri' stars do indeed appear more evolved than the T Tauri stars, although there is no evidence of any significant difference in ages.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 191
    facet.materialart.
    Unknown
    The X-ray absorption spectrum of 4U 1700-37 and its implications for the stellar wind of the companion HD 153919 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The first high resolution non-dispersive 2-60 keV X-ray spectra at 4U1700-37 is presented. The continuum is typical of that found from X-ray pulsars; that is a flat powr law between 2 and 10 keV and, beyond 10 keV, an exponential decay of characteristic energy varying between 10 and 20 keV. No X-ray pulsations were detected between 160 ms and 6 min with an amplitude greater than approximately 2 percent. The absorption measured at binary phases approximately 0.72 is comparable to that expected from the stellar wind of the primary. The gravitational capture of material in the wind is found to be more than enough to power the X-ray source. The increase in the average absorption after phi of approximately 0.5 is confirmed. The minimum level of adsorption is a factor of 2 or 3 lower than that reported by previous observers, which may be related to a factor of approximately 10 decline in the average X-ray luminosity over the same interval. Short term approximately 50 percent variations in adsorption are seen for the first time which appear to be loosely correlated with approximately 10 min flickering activity in the X-ray flux. These most likely originate from inhomogeneities in the stellar wind of the primary. Previously announced in STAR as N83-14034
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 192
    facet.materialart.
    Unknown
    Velocity dispersions of knots in Vela X and Puppis A (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Very high resolution spectroscopy of optical emission lines indicates that the velocity dispersions of knots in Vela X and Puppis A result primarily from turbulence within the emitting regions. Line-of-sight velocity dispersions (half-widths at half-maximum) for the observed knots in both remnants are about 20-30 km/s. In Vela X, these include thermal velocity dispersions of roughly 16 km/s for hydrogen and 4 km/s for nitrogen. The knots themselves move randomly relative to each other, with speeds up to 30 km/s in Vela X and between 30-80 km/s in Puppis A. Occasionally, diffuse components of the filaments are observed in Puppis A. These diffuse components have velocity dispersions between 55 and 80 km/s, but the relative contributions of turbulent and thermal motions to the dispersions are unknown. The results are compared with theory and previous observations. Direct photographs may be able to show if the forbidden O III knots are less spatially dispersed than the forbidden N II, forbidden S II, forbidden O II, and H I knots.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 193
    facet.materialart.
    Unknown
    The soft X-ray spectrum of the Vela supernova remnant (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: An X-ray spectrum of a major fraction of the Vela supernova remnant has been obtained during scanning observations with the low energy proportional counters of the A-2 experiment, flown on HEAO 1. A deconvolution analysis of the data shows that the spectrum exhibits pronounced line emission near 0.6 keV due primarily to oxygen ions. Model fits using the Raymond-Smith hot plasma emission calculations indicate that the spectrum can be well described by a model involving two collisional equilibrium components with temperatures of 2.4 x 10 to the 6th and 1.9 x 10 to the 7th K, respectively. The abundances of oxygen and iron are found to be constrained to lie near their normal cosmic values.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 194
    facet.materialart.
    Unknown
    Relativistic thermal plasmas - Effects of magnetic fields (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Processes and equilibria in finite, relativistic, thermal plasmas are investigated, taking into account electron-positron creation and annihilation, photon production by internal processes, and photon production by a magnetic field. Inclusion of the latter extends previous work on such plasmas. The basic relations for thermal, Comptonized synchrotron emission are analyzed, including emission and absorption without Comptonization, Comptonized thermal synchrotron emission, and the Comptonized synchrotron and bremsstrahlung luminosities. Pair equilibria are calculated, including approximations and dimensionless parameters, the pair balance equation, maximum temperatures and field strengths, and individual models and cooling curves.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 195
    facet.materialart.
    Unknown
    Analysis of complete quasar samples to obtain parameters of luminosity and evolution functions (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A parametric likelihood analysis of the joint redshift-luminosity distribution is presented for a composite, complete sample of 32 quasars with B between 17.0 and 19.2 selected on the basis of ultraviolet excess. Best estimates and joint confidence regions are determined for the parameters of several models of the quasar optical luminosity and evolution function. These models are also tested explicitly for their acceptability. A steeper luminosity function is found than was found for previous samples. A model invoking pure density evolution is rejected on the basis of its extrapolation to fainter magnitudes through comparisons with the optical number counts and independently with the observed 2 keV X-ray background. Assuming an average value for L(x)/L(opt), the contribution of quasars to the X-ray background at 2 keV is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 269; June 1
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 196
    facet.materialart.
    Unknown
    The waiting point approximation in R-process calculations (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The steady flow approximation to the r-process has been used to evaluate the validity of the waiting point assumption (that, for a given charge number Z, neutron captures become balanced by neutron photodisintegrations) under a variety of conditions. The criterion for the accuracy of the approximation for any set of nuclei with the same value of Z is that the ratio of the total rate of neutron photodisintegration in those nuclei to the total rate of neutron captures should be close to unity. No set of conditions involving neutron production by helium thermonuclear reactions (at temperatures up to 10 to the 9th K) could be found for which the waiting point approximation is useful for all values of Z, and it is recommended that all such r-process calculations not use this approximation. At higher temperatures, such as those characteristic of explosive carbon burning (2 x 10 to the 9th K), the waiting point approximation is much better.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 91; 2 Ap; April 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 197
    facet.materialart.
    Unknown
    Steady flow approximations to the helium r-process (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A steady flow approximation to the r-process is presented and used for numerical experiments with physical quantities to determine the sensitivity of the process to variations in those quantities. The effect of neutron capture cross sections along the capture path and of recently available improved beta decay rates on the r-process are discussed. The peaks in the observed r-process yield curve near mass numbers 80 and 130 are roughly characterized by a neutron number density of 10 to the 20th per cu/cm; the mean beta decay rates are about 10/s, and the freezing time is comparable to or less than 0.1 s. The peak near mass number 195 is roughly characterized by a neutron number density of 10 to the 21st/cm, the mean beta decay rates are about 100/s, and the freezing time is comparable to or less than 0.01 s. The flow path of the steady state r-process is sensitively dependent upon the neutron capture cross sections in the flow network and on the values of the beta decay rates.
    Keywords: ASTROPHYSICS
    Type: Astrophysics and Space Science (ISSN 0004-640X); 91; 2 Ap; April 19
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 198
    facet.materialart.
    Unknown
    The magnetic field on the RS Canum Venaticorum star Lambda Andromedae (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A program to detect and measure magnetic flux on the surfaces of late-type stars is discussed. A technique is adopted to deconvolve magnetically insensitive lines from similar, magnetically sensitive lines to infer the degree of Zeeman splitting in the latter lines. These measurements yield values for the magnetic field strength and filling factor (flux). To illustrate the approach, observations of the RS CVn star Lambda And are presented. At the epoch of observation, 1981 April 26, a field strength of 1290 + or - 320 gauss covering 48 + or - 7 percent of this star's surface is found. This measurement compares with an estimate of coronal magnetic flux in the cooler component of the stellar corona of 1110 gauss with a coronal volume filling factor of 75 percent, based on X-ray data for Lambda And.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 268; May 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 199
    facet.materialart.
    Unknown
    G29.7-0.3: another supernova remnant with an identity crisis (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: New radio and X-ray observations of the galactic supernova remnant G29.7-0.3 show that it is composed of two spectrally distinct components: a steep-spectrum, incomplete shell 3 arcmin in extent enclosing a flat-spectrum, X-ray emitting region 30 arcsec across. Thus, G29.7-0.3 joins the ranks of supernova remnants which exhibit a combination of Crab-like and shell remnant attributes. The Crab-like core has the highest ratio of X-ray radio luminosity of all the Crab-like remnants observed to date, suggesting that it is an extremely young object.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 268; May 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 200
    facet.materialart.
    Unknown
    Charge exchange in solar wind-cometary interactions (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A simple model of a cometary spherically symmetrical atmosphere and ionosphere is considered. An analytic solution of the governing equations describing the radial distribution of the neutral and ion densities is found. The new solution is compared to the well-known solution of the equations containing only ionization terms. Neglecting recombination causes a significant overestimate of the ion density in the vicinity of the comet. An axisymmetric model of the solar wind-cometary interaction is considered, taking into account the loss of solar wind ions due to charge exchange. The calculations predict that for active comets, solar wind absorption due to charge exchange becomes important at a few thousand kilometers from the nucleus, and a surface separating the shocked solar wind from the cometary ionosphere develops in this region. These calculations are in reasonable agreement with the few observations available for the ionopause location at comets.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 268; May 15
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...