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  • 1
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    The Wasilewski sample of emission-line galaxies - Follow-up CCD imaging and spectroscopic and IRAS observations (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The results of an extensive imaging and spectroscopic follow-up of the objective prism-selected emission line galaxy (ELG) sample of Wasilewski (1982) are presented. Fluxes at 12, 25, 60, and 100 microns were also obtained from the coadded IRAS survey data. ELGs found by objective prism surveys are found to be generally small and underluminous galaxies which usually have higher than average optical surface brightness. The Seyfert detection rate in objective prism surveys is roughly 10 percent and the ratio of the space densities of Seyfert 2 to Seyfert 1 galaxies is significantly larger than unity. Most of the galaxies selected by objective prism surveys are star-forming, late-type spirals which often show disturbed morphology. About 25 percent of the galaxies detected by the surveys are faint, high-excitation metal-poor compact H II regions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 70; 271-328
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  • 2
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    Analysis of IUE observations of CS in Comet Bradfield (1979 l) (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The high resolution rotational band profiles were fitted with theoretical band profiles which are derived using a Boltzmann temperature of 70 K. A very rapid variation with heliocentric distance for the CS brightness was found. The implications of these results for models of the coma along with the origin of the CS species are discussed.
    Keywords: ASTROPHYSICS
    Type: The Universe at Ultraviolet Wavelengths: The First Two Yrs. of Intern. Ultraviolet Explorer; p 55-64
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  • 3
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    X-ray spectrum and variability of 3C 120 (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The X-ray luminosity of 3C 120 is variable by a factor of 2.5 on time scales of days to months. The spectral slope of the 2-10 keV X-rays changes systematically in the sense that the higher intensity states are steeper. Simple power laws fitted to the data are consistent with an energy index alpha of 0.51 + or - 0.13 at minimum intensity and 0.83 + or - 0.03 at maximum, with a continuous variation in between. A more complicated spectral shape cannot be ruled out, but changes in absorbing column density alone cannot explain the data. The results are interpreted in terms of beamed synchrotron emission from a relativistic jet, a model which has been invoked previously for the spectra of BL Lac objects. The spectral variability is in marked contrast to the behavior of 3C 273, another superluminal source in which the X-ray spectral index is constant to a high degree of accuracy despite variability in time scales and amplitudes which are quite similar to those of 3C 120. The difference may be due to the degree of beaming of the respective core components. Another model which is consistent with the data involves thermal emission from isothermal shocks in a hot (approximately 10 to the 8th K) medium. Thermal Compton and spherical accretion X-ray source models do not reproduce the correct behavior of alpha versus flux.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 290; 130-135
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  • 4
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    1300 + 361 A,B is not a gravitational lens (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Spectroscopic observations toward 1300 + 361 B obtained at 320-940 nm using a double spectrograph with CCD detectors on the 5-m Hale telescope (resolution about 7 A at 470-940 nm and 10-12 A at 320-470 nm on April 4-5, 1984, are reported. Two objects with magnitude 20 and spectral characteristics resembling those of an interacting pair of metal-poor H II regions at redshift 0.107 are observed, separated by about 10.6 arcsec and with a velocity difference of less than 80 km/s. It is considered unlikely that these objects form a gravitational-lens system. The ratio of the dereddened flux of the 5007-A forbidden line of O III to that of H-beta is found to be 5.03 for 1300 + 361 A and 3.67 for 1300 + 361 B; the difference is attributed to the presence of star-forming regions in the interacting system.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 89; 1802-180
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  • 5
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    The nonstellar continuum of the Seyfert galaxy NGC 7213 (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The optical continuum of the nearby Seyfert galaxy NGC 7213 is decomposed into stellar and nonstellar components, and the spectrum at X-ray energies is derived from observations made with the Monitor Proportional Counter and the Imaging Proportional Counter aboard the Einstein Observatory. These results are used to obtain conclusions about the galaxy's column density and spectral index, covering fraction and visual extinction, and thermal emission. Ultraviolet, infrared, and radio observations published elsewhere are then combined with the new data to produce the overall continuum.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 475-482
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  • 6
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    NGC 7213 - A key to the nature of liners? (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: New optical spectra of the nearby S0 galaxy NGC 7213 are analyzed. The observations are described and a brief overview of the spectrum is given. The subtraction of the stellar component is presented, and the measurement of various emission lines is discussed in detail. Important physical parameters are derived, including those pertaining to atomic data, line widths, physical conditions, geometry and kinematics, the Balmer decrement, and ultraviolet emission lines. The Seyfert characteristics of NGC 7213 are reviewed, and the galaxy's shock features are reconciled with photoionization models. The presented arguments may apply to classical liners as well. Theoretical models that can help explain the relationships discovered among the emission lines are examined.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 285; 458-474
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  • 7
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    Variable X-ray absorption in the QSO MR 2251 - 178 (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The monitoring proportional counter of the Einstein Observatory has been used to observe the QSO MR 2251 - 178 on two occasions, approximately 1 year apart, in the 2-10 keV range. Evidence is found for an increase in the absorbing column density by a large factor over the 1 year interval. Simultaneous measurements with the high resolution imager are used to further constrain the soft X-ray flux and to show that the highly absorbed spectrum must have excess emission below 1 keV. A model is presented in which photoionization by the X-ray continuum ionizes a cloud or shell of material, so that the emergent spectrum is transparent below the K-edge of O VII at 739 eV, but is highly absorbed above this energy.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 90-94
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  • 8
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    Discovery of a 50 minute binary period and a likely 22 magnitude optical counterpart for the X-ray burster 4U 1915-05 (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Absorption dips which recur with a period of 2985 s have been observed from the X-ray burst source 4U 1915-05. It is suggested that the dips are caused by obscuration of the X-ray source by material at the point where the gas stream from the companion meets the accretion disk, and that the 2985 s periodicity is the orbital period of the binary system. These observations represent the first direct evidence of the binary nature of X-ray burst sources. In addition, a new optical identification of 4U 1915-05 is suggested: a 22 magnitude candidate observed in a CCD image of the optical field at the arcsec-accurate HRI X-ray position.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 253
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  • 9
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    Was 49: Mirror for a hidden Seyfert 1 galaxy (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Was 49 is an interacting pair of Seyfert galaxies at z = 0.063, one of which contains a hidden Seyfert 1 nucleus as evidenced by the highly polarized broad wings on its Balmer lines. The disk of the main galaxy, Was 49a, appears to be globally photoionized by a powerful continuum source, undoubtedly the hidden Seyfert 1 companion, Was 49b. The intrinsic luminosity of Was 49b is at least 100 times larger than the observed (scattered) luminosity. A single SWP spectrum of the pair, which can be spatially resolved in the large aperture was obtained. A narrow Ly-alpha line was detected from Was 49b, the hidden Seyfert 1, at a flux level consistent with that of an unreddened Seyfert 2 galaxy. The lack of detection of a continuum is consistent with a power-law of v(sup -1) or steeper extrapolated from the optical, again consistent with the spectrum of other Seyfert 2 and hidden Seyfert 1 galaxies.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-194537 , NAS 1.26:194537 , CAL-2139
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  • 10
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    Multiwavelength observations of unidentified high energy gamma ray sources (1993)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: As was the case for COS B, the majority of high-energy (greater than 100 MeV) gamma-ray sources detected by the EGRET instrument on GRO are not immediately identifiable with cataloged objects at other wavelengths. These persistent gamma-ray sources are, next to the gamma-ray bursts, the least understood objects in the universe. Even a rudimentary understanding of their nature awaits identifications and follow-up work at other wavelengths to tell us what they are. The as yet unidentified sources are potentially the most interesting, since they may represent unrecognized new classes of astronomical objects, such as radio-quiet pulsars or new types of active galactic nuclei (AGN's). This two-year investigation is intended to support the analysis, correlation, and theoretical interpretation of data that we are obtaining at x ray, optical, and radio wavelengths in order to render the gamma-ray data interpretable. According to plan, in the first year concentration was on the identification and study of Geminga. The second year will be devoted to studies of similar unidentified gamma-ray sources which will become available in the first EGRET catalogs. The results obtained so far are presented in the two papers which are reproduced in the Appendix. In these papers, we discuss the pulse profiles of Geminga, the geometry and efficiency of the magnetospheric accelerator, the distance to Geminga, the implications for theories of polar cap heating, the effect of the magnetic field on the surface emission and environment of the neutron star, and possible interpretations of a radio-quiet Geminga. The implications of the other gamma-ray pulsars which were discovered to have high gamma-ray efficiency are also discussed, and the remaining unidentified COS B sources are attributed to a population of efficient gamma-ray sources, some of which may be radio quiet.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-194536 , NAS 1.26:194536 , CAL-2140
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