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  • ASTROPHYSICS  (3,387)
  • Inorganic Chemistry
  • 1
    Publication Date: 2011-08-19
    Description: High-resolution radio images of PKS1830 - 211 are obtained to study the possibility that the double structure is a gravitationally lensed object. The VLBI observations, taken from interferometric radiotelescope networks, reveal an elliptical ring that connects two bright spots of similar composition. Because the lens and the lensed object are closely aligned, and because of the structure of the two spots, the source is concluded to be a radio Einstein ring. The source is found to be close to the galactic plane, and the lens and the lensed object are extragalactic. The source is also found to be unusually bright, suggesting that it is aligned with a bright background source or amplified by some mechanism related to a source that is not so bright.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 352; 132-134
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  • 2
    Publication Date: 2019-06-28
    Description: Motivated by recent work which hints at a possible deficiency of hydrogen in non-Mira N-type carbon stars and to further explore the parameter space of chemical composition, computations have been made of a series of hydrogen-deficient models for carbon stars. For these models Teff = 3000 K, and log g = 0.0. Solar abundances are used for all elements except for carbon (which is enhanced to give C/O = 1.05), hydrogen, and helium. As the fractional abundance of hydrogen is decreased, being replaced by helium, the temperature-optical depth relation is affected only slightly, but the temperature-pressure relation is changed. The most striking change in the emergent flux is the decrease of the H(-) peak at 1.65 micron compared with the blackbody peak at 1.00 micron.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 228-230
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  • 3
    Publication Date: 2019-07-12
    Description: The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory has observed SN 1987A for two 2 week periods during the first 9 months of the mission. Evidence for gamma-ray line and continuum emission from Co-57 is observed with an intensity of about 10 exp -4 gamma/sq cm/s. This photon flux between 50 and 136 keV is demonstrated by Monte Carlo calculations to be independent of the radial distribution of Co-57 for models of low optical depth, viz., models having photoelectric absorption losses of 122 keV photons no greater than several percent. For such models the observed Co-57 flux indicates that the ratio Ni-57/Ni-56 produced in the explosion was about 1.5 times the solar system ratio of Fe-57/Fe-56. When compared with nearly contemporaneous bolometric estimates of the luminosity for SN 1987A, our observations imply that Co-57 radioactivity does not account for most of the current luminosity of the supernova remnant in low optical depth models. We suggest alternatives, including a large optical depth model that is able to provide the SN 1987A luminosity and is consistent with the OSSE flux. It requires a 57/56 production ratio about twice solar.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 399; 2; p. L137-L140.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 845-852 
    ISSN: 0044-2313
    Keywords: Nickel orthoperiodate ; i.r., Raman spectra ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: NiH3IO6 · 6 H2O  -  Crystal Structures and Vibrational SpectraThe crystal structure of NiH3IO6 · 6 H2O has been determined by X-ray single-crystal diffraction (Pc, Z = 2, a = 516.74(9), b = 981.5(2), c = 1052.5(2) pm, β = 116.496(8)°) on the basis of 4169 unique reflections (R = 1.96%). The structure is built up of distorted Ni(H2O)62+ and H3IO62- octahedra linked by hydrogen bonding. IR and Raman spectra of both the title compound and isostructural MgH3IO6 · 6 H2O as well as of deuterated specimens are given. There are up to 14 different OH(OD) modes in the spectra of isotopically dilute samples due to the 15 different hydrogen positions of the structure. The internal modes of the meridional H3IO62- ions (pseudo C2v symmetry) are discussed with respect to that double T-shaped entity, which gives rise to only two instead of 3I—O, I—O(H), and OH stretches in the IR and Raman spectra, i.e. the same as for facial (C3v) structured ions.
    Notes: Die Kristallstruktur (Pc, Z = 2) von NiH3IO6 · 6 H2O wurde mittels Röntgen-Einkristallmessungen auf der Basis von 4169 symmetrieunabhängigen Reflexen bestimmt (R = 1,96%). IR- und Raman-Spektren von NiH3IO6 · 6 H2O und der isotypen Verbindung MgH3IO6 · 6 H2O sowie von deuterierten Präparaten werden mitgeteilt. Die Spektren isotypenverdünnter Proben zeigen bis zu 14 OH(OD)-Streckschwingungen entsprechend den 15 verschiedenen Wasserstoff-Positionen der Struktur. Die meridionalen H3IO62--Ionen (Pseudosymmetrie C2v) besitzen wegen der T-förmigen Anordnung der je 3 IO-und IOH-Gruppen nur je 2 IO-, IO(H)- und OH-Streckschwingungen in den IR- und Raman-Spektren und können daher schwingungsspektroskopisch nicht von H3IO62--Ionen mit facialer Struktur (C3v) unterschieden werden.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2011-08-24
    Description: Gamma radiation above 100 MeV in energy has been detected from the radio pulsar PSR1706-44. The gamma emission forms a single broad peak within the pulsar period of 102 ms, in contrast to the two narrow peaks seen in the other three known high-energy gamma-ray pulsars. The emission mechanism in all cases is probably the same, the differences arising from the geometry of the magnetic and rotation axes and the line of sight. Gamma-ray emission accounts for as much as 1 percent of the total neutron star spindown energy in these pulsars, much more than emerges at optical or radio frequencies. Thus, study of this emission is important in understanding pulsar emission and evolution.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 359; 6396; p. 615, 616.
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  • 6
    Publication Date: 2011-08-24
    Description: During its full-sky survey, the Energetic Gamma Ray Experiment Telescope (EGRET) high-energy instrument aboard the Compton Gamma-Ray Observatory detected gamma-ray emission in the energy range above 30 MeV from a source identified as the blazar PKS 0420-014. This object was observed during two separate viewing periods in 1992 February/March and May/June. An intensity decrease above 100 MeV of a factor of at least 1.5 from a maximum of (5.0 +/- 1.4) x 10(exp -7) photons 1 sq cm/s was observed during that time interval indicating extensive variability. The photon spectrum in the range between 30 and 10,000 MeV at the time of the maximum intensity is well represented by a power law with an exponent of -1.9 +/- 0.3. Some similarities with other EGRET detected blazars are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 438; 2; p. 659-662
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  • 7
    Publication Date: 2019-07-13
    Keywords: ASTROPHYSICS
    Type: Extragalactic radio sources; Aug 03, 1981 - Aug 07, 1981; Albuquerque, NM
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  • 8
    Publication Date: 2019-08-28
    Description: In order to test gas-phase reaction schemes for the production of small oxides of carbon in cold, dense interstellar clouds, we have searched for the radical CCO and for propadienone (H2C3O) in Taurus Molecular Cloud 1, a nearby cloud which exhibits a rich organic chemistry. The radical CCO has been detected with a fractional abundance some two orders of magnitude less than that of CCS, about one order of magnitude less than that of H2CCO, and slightly less than that of C3O. An upper limit has been obtained on the abundance of propadienone which is slightly less than that of its isomer propynal (HC2CHO).
    Keywords: ASTROPHYSICS
    Type: Origins of Life and Evolution of the Biosphere (ISSN 0169-6149); 21; 6-May; p. 399-405.
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  • 9
    Publication Date: 2019-07-13
    Description: The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory observed high-energy gamma rays (50 - 2000 MeV) from quasar 0836 + 710 (z = 2.16) during observations in 1992 January, near the time of an optical fare (von Linde et al., 1993). The gamma-ray spectrum can be fitted with a power law with photon number index 2.4 +/- 0.2. EGRET identifies quasars 0454 - 234, 0804 + 499, 0906 + 430, 1510 - 089, and 2356 + 196 at a statistical significance of between 4 and 5 standard deviations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 415; 1; p. L13-L16.
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  • 10
    Publication Date: 2011-08-24
    Description: We present radio observations of the gravitational lens PKS 1830-211 at 8.4 and 15 GHz acquired using the Very Large Array. The observations were made over a 13 month period. Significant flux density changes over this period provide strong constraints on the time delay between the two lensed images and suffest a value of 44 +/- 9 days. This offers new direct evidence that this source is indeed a gravitational lens. The lens distance is dependent upon the model chosen, but reasonable limits on the mass of the lensing galaxy suggest that it is unlikely to be at a redshift less than a few tenths, and may well be significantly more distant.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 444; 2; p. 561-566
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