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  • ASTROPHYSICS  (1,391)
  • ASTRONOMY  (615)
  • 1990-1994  (1,279)
  • 1975-1979  (727)
  • 1
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    Discovery of an X-ray QSO (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The discovery of X-ray QSO MR2251-178 at a distance of 410 Mpc is reported. The observations are based on signals (2-11 keV) from NRAO's Very Large Array (VLA) radio telescope and from two independent rotating modulation collimators (RMC). Coordinates are given and positional identification with X-ray source 2A2251-179 is made. Examination of POSS plates and redshift has given rise to speculation that MR2251-178 could actually be a Seyfert galaxy; but its high luminosity would tend to support the contention that it is, indeed, a QSO.
    Keywords: ASTRONOMY
    Type: Nature; 271; Jan. 5
    Format: text
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  • 2
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    Observations of an X-ray QSO (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper reports X-ray, optical, radio, and IR measurements of the z = 0.068 QSO MR2251-178, which was initially discovered on the basis of its X-ray emission. Data are provided on the position, optical colors, and 2-10-keV X-ray luminosity of this low-redshift QSO. An absolute V magnitude of -24.2 is implied, and the X-ray/optical luminosity ratio is estimated to be about 3:1 at peak X-ray brightness. It is shown that the optical spectrum of MR2251-178 is quite normal for a QSO, except for an extremely broad H-alpha emission line with a FWZI of 30,000 to 40,000 km/s. The overall spectrum of MR2251-178 from the radio to the X-ray region is plotted, and the photometric history of this QSO since 1889 is briefly discussed.
    Keywords: ASTROPHYSICS
    Type: X-ray astronomy; May 29, 1978 - Jun 10, 1978; Innsbruck; Austria
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  • 3
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    High-energy X-ray observations of the transient source A0535+26 from a balloon-borne telescope (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 204; Mar. 1
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  • 4
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    Observations of Cygnus X-3 from a balloon-borne X-ray telescope (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: X-ray measurements in the energy range 20-150 keV were made from a balloon-borne telescope on June 1 1975. Three scans, centered at phases 0.45, 0.60, and 0.70, respectively, of the 4.8 hr cycle, were conducted. The observed relative intensity as a function of phase differs significantly from previously reported X-ray measurements.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 279-283
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  • 5
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    Radiative widths and splitting of cyclotron lines in superstrong magnetic fields (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The radiative line widths of the Landau levels in a superstrong magnetic field are calculated and simple analytic expressions and fits are given for these which are valid over a wide range of the principal quantum number and the magnetic field strength. If QED corrections are not taken into account, all levels but the first are doubly degenerate, corresponding to the two possible spin projections. However, the interaction with the QED vacuum removes this degeneracy, leading to an energy splitting of each level which exceeds the radiative linewidth for low Landau levels if the magnetic field is not too large (B is less than approximately 10 exp 13 G). Estimations are presented of the splitting in various limits as a function of field strength and Landau number. The possibility of observing this splitting in accreting X-ray pulsars and in gamma-ray bursters is discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 380; 541-549
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  • 6
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    COBE diffuse infrared background experiment observations of Galactic reddening and stellar populations (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This Letter describes the results of an initial study of Galactic extinction and the colors of Galactic stellar populations in the near-IR using the Diffuse Infrared Background Experiment (DIRBE) aboard the Cosmic Background Explorer (COBE) spacecraft. The near-IR reddening observed by DIRBE is consistent with the extinction law tabulated by Rieke & Lebofsky (1985). The distribution of dust and stars in most of the first and fourth quadrants of the Galactic plane (0 deg less than l less than 90 deg, and 270 deg less than l less than 360 deg, respectively) can be modeled as a stellar background source seen through up to approximately 4 mag of extinction at 1.25 micrometers. The unreddened near-IR colors of the Galactic disk are similar to those of late-K and M giants. The Galactic bulge exhibits slightly bluer colors in the 2.2-3.5 micrometers range, as noted by Terndrup et al. (1991). Star-forming regions exhibit colors that indicate the presence of a approximately 900 K continuum produced by hot dust or polycyclic aromatic hydrocarbons (PAHs) contributing at wavelengths as short as 3.5 micrometers.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 425; 2; p. L85-L88
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  • 7
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    Ultraviolet continuum variability and visual flickering in the peculiar object MWC 560 (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: High-speed U-band photometry of the peculiar emission object MWC 560 obtained with the ground-based instrumentation, and V-band photometry obtained with the International Ultraviolet Explorer-Fine Error Sensor indicates irregular brightness variations are quasi-periodic. Multiple peaks of relative brightness power indicate statistically significant quasi periods existing in a range of 3-35 minutes, that are superposed on slower hourly varying components. We present a preliminary model that explains the minute and hourly time-scale variations in MWC 560 in terms of a velocity-shear instability that arises because a white dwarf magnetosphere impinges on an accretion disk. We also find evidence for Fe II multiplet pseudocontinuum absorption opacity in far-UV spectra of CH Cygni which is also present in MWC 560. Both CH Cyg and MWC 560 may be in an evolutionary stage that is characterized by strong UV continuum opacity which changes significantly during outburst, occurring before they permanently enter the symbiotic nebular emission phase.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 409; 2; p. L53-L56.
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  • 8
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    Near-infrared images of MG 1131+0456 with the W. M. Keck telescope: Another dusty gravitational lens? (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Images of the gravitational lens system MG 1131+0456 taken with the near-infrared camera on the W. M. Keck telescope in the J and K(sub s) bands show that the infrared counterparts of the compact radio structure are exceedingly red, with J - K greater than 4.2 mag. The J image reveals only the lensing galaxy, while the K(sub s) image shows both the lens and the infrared counterparts of the compact radio components. After subtracting the lensing galaxy from the K(sub s) image, the position and orientation of the compact components agree with their radio counterparts. The broad-band spectrum and observed brightness of the lens suggest a giant galaxy at a redshift of approximately 0.75, while the color of the quasar images suggests significant extinction by dust in the lens. There is a significant excess of faint objects within 20 sec of MG 1131+0456. Depending on their mass and redshifts, these objects could complicate the lensing potential considerably.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 420; 1; p. L9-L12
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  • 9
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    Turbulization of shear flows in astrophysics (1991)
    In:  CASI
    Details
    Publication Date: 2006-06-13
    Description: The problem of instability in shear flows is treated in a number of works which present a global analysis of irrotational (potential) modes in a 2-D compressible shear flow, implying that, in the presence of reflecting boundaries, those modes can increase and that the characteristic time of the increase is several orders as high as the dynamic time in the medium. Due to the slowness of the increase of irrotational modes and to the problematic character of the theory's applicability for thin accretion disks, an attempt was made to develop an alternative theory of turbulization shear flows. It is quite contrary to the above theory. Instead of the global analysis, a local one is made far from the flow boundaries. Instead of irrotational perturbations, vortical ones are examined. Lastly, the medium is considered to be incompressible. The flow in the accretion disk can be modeled by a plane Couette flow, without regard for boundary conditions: it can be modeled by a plane shear flow in infinite incompressible fluid. According to this scenario, there is a critical perturbation level in the free shear flow. If the level of initial perturbations exceeds the critical one, the flow is turbulized.
    Keywords: ASTROPHYSICS
    Type: NAS-NRC, High-Energy Astrophysics. American and Soviet Perspectives; p 55-64
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  • 10
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    Manifestations of dynamo driven large-scale magnetic field in accretion disks of compact objects (1991)
    In:  CASI
    Details
    Publication Date: 2006-06-13
    Description: A turbulent dynamo nonlinear theory of turbulence was developed that shows that in the compact objects of accretion disks, the generated large-scale magnetic field (when the generation takes place) has a practically toroidal configuration. Its energy density can be much higher than turbulent pulsations energy density, and it becomes comparable with the thermal energy density of the medium. On this basis, the manifestations to which the large-scale magnetic field can lead at the accretion onto black holes and gravimagnetic rotators, respectively, are presented.
    Keywords: ASTROPHYSICS
    Type: NAS-NRC, High-Energy Astrophysics. American and Soviet Perspectives; p 46-54
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