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  • 11
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    X-ray nova A0620-00 - Celestial position and low-energy flux (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The X-ray nova A0620-00 (Nova Monocerotis 1975) has been observed with the SAS-3 satellite. The 1-10 keV intensity was observed to increase by a factor of 2.3 from August 8 to August 11, 1975. It reached and maintained a constant intensity of 1.7 by 10 to the -6 power erg/sq cm/sec from August 11 to August 13. Limits on periodicities of not more than 2 per cent of the power were obtained for periods from 0.2 ms to 435 s. A precise position was obtained with the SAS-3 modulation collimators on August 15. This led directly to optical and radio identifications. Observations with the SAS-3 low-energy concentrator system on August 27 showed an intense 0.4-0.8 keV flux emanating from the nova. A hydrogen column density of 3.5 (plus or minus 0.3) by 10 to the 21st power per sq cm was inferred from these data.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 203; Jan. 1
    Format: text
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  • 12
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    X-ray and radio observations of the structure of Abell 478 (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The complex X-ray and radio structures of the cluster of galaxies Abell 478 have been observed in the 2-11-keV energy band by the rotating modulation collimators on the SAS-3 X-ray observatory and at 1415 MHz by the Westerbork synthesis radio telescope. The X-ray data imply an extended source (X-ray luminosity of the order of 10 to the 45th power erg/s) and are consistent with the presence of a coincident pointlike source X-ray luminosity of the order of 10 to the 45th power erg/s. The X-ray source position is also coincident with a cD radio galaxy at the core of the cluster.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 217
    Format: text
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  • 13
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    The binary pulsar - Post-Newtonian timing effects (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Certain post-Newtonian effects may be observable in the arrival times of pulses from the binary pulsar PSR 1913+16. Such effects include the gravitational propagation delay and the post-Newtonian corrections to the elliptical binary orbit. Fitting a model of these effects as they are predicted by general relativity to the pulse arrival times permits the estimation of more parameters than are necessary to determine the orbit and masses of the system. This redundancy provides an important check of the assumption that the observed periastron precession rate is entirely due to the effect of general relativity on compact masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 216
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  • 14
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    Variability of LMC X-4 (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: X-rays in the 2-11-keV band were detected from LMC X-4 using the rotating modulation collimator system on SAS-3. The derived X-ray luminosity of LMC X-4 is of the order of 10 to the 38th power ergs/s. A transition to a high-intensity state which lasted about 40 minutes was detected during which short-time-scale flares (about 20 s) were observed. The temporal and spectral behavior of LMC X-4 is found to be similar to that of several X-ray binaries. A derived 90% error circle with a radius of 1 arcmin is also presented.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 216
    Format: text
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  • 15
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    Search for X-ray emission from AO0235+164 (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Limits to the first-order Compton scattering, brightness temperature, and angular size of the compact radio source AO0235+164 were calculated on the basis of a flux density of less than about 1 microJy at 10 to the 18th Hz calculated from observations of the source with the rotating modulation collimator aboard the SAS 3 X-ray observatory. It was found that the maximum brightness temperature at this frequency is less than 2.4 times 10 to the 11th K, corresponding to a minimum angular size of 0.38 msec of arc, assuming the synchrotron self-absorption turnover coefficient is 0.5. On the basis of the distance implied by the largest redshift present, the energy contained in relativistic particles and the magnetic field are calculated, and the ratio of particle to magnetic energy is greater than 10, so the dynamics must be particle dominated. This indicates relativistic expansion if the mean energy per particle is comparable to or greater than the rest of those particles that neutralize the electron plasma.
    Keywords: ASTRONOMY
    Type: Nature; 276; Nov. 23
    Format: text
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  • 16
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    Si XIII and Si XIV line emission search with the ANS crystal spectrometer (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The final results of the search for Si XIII and Si XIV line emission, using the ANS Bragg crystal spectrometer, are presented. No positive line detection was achieved in any of the measurements made on several types of cosmic object; i.e., a transient X-ray source, close binary systems, supernova remnants, GX sources, and clusters of galaxies. Three-sigma upper limits for discrete line emission from these objects are reported and compared with line strengths inferred from other proportional-counter and Bragg spectrometer data. The present upper limit of 1.0 eV for the equivalent width of a narrow Si XIV line emission from the X-ray nova A0620-00 is an order of magnitude lower than previous limits set by other experiments.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 226
    Format: text
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  • 17
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    Neutrino angular momentum loss in rotating stars (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: We consider how an axisymmetric, uniformly and slowly rotating homogeneous star might be affected by the loss of energy and angular momentum via neutrino emission. For example, these losses can cause a collapsing, rotating star to flatten either faster or slower than would be the case if these losses were not taken fully into account, depending on the efficiency of the angular momentum loss mechanism.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 219
    Format: text
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  • 18
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    Detection of X-rays from Algol /beta Persei/ (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: X-rays in the 2-6 keV band were detected from the Algol system using the rotating modulation collimator system on SAS-3 during an observation in October 1975. The measured X-ray flux is 3.8 x 10 to the -11th ergs/sq cm/s/keV. No positive detection was made in the 6-11 keV band. The data are consistent with either a power-law spectrum with photon spectral index not less than 2.5 or a thermal bremsstrahlung spectrum with a temperature not greater than 3 x 10 to the 7th K.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 210; Dec. 1
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  • 19
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    X-ray and radio emission from the compact galaxy III Zw 2 (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: X-rays from the compact galaxy III Zw 2 have been detected with the rotating modulation collimator on board SAS 3. The (2-10-keV) flux is (4.3 + or - 0.5) by 10 to the -11th power erg/sq cm per sec, which corresponds to a luminosity of 1.4 by 10 to the 45th power erg/s at 530 Mpc. Subsequent radio observations between 1.46 and 90 GHz were made at the NRAO Very Large Array and 36-foot (11-m) installations. The radio spectrum rises sharply toward higher frequencies and, below about 100 GHz, is indicative of a self-absorbed synchrotron spectrum from an extremely compact, rapidly evolving object.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 222
    Format: text
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  • 20
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    The X-ray structure of NGC 5128 (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: During an observation of NGC 5128 (Cen A) by the rotating modulation collimator on board the SAS-3 X-ray observatory in early June 1975, data were obtained which suggest the presence of an extended source with about 3 arcmin FWHM surrounding an extremely compact object located at the radio/IR nucleus. The point component exhibited a 25% increase in intensity over a period of 2 to 5 hours.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 219
    Format: text
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