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  • 1
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    Recent chaqnges in the IUE spectrum of the very young planetary nebula He 3-1357 (=SAO 244567) (1995)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We obtained the first high-dispersion IUE spectrum, and an additional low-dispersion spectrum of the very young planetary nebula He 3-1357 and its central star SDAO 244567. In 1988, it showed a very strong C IV lambda-1549 P Cygni profile which diminished and has disappeared by 1994, but C IV absorptions are seen in a high-resolution spectrum. The electron density from the C III F(lambda 1907)/F(lambda 1909) emission ratio is log N(sub e) = 4.1/cc. The older IUE data were reprocessed, and emission-line fluxes vary greatly for the period 1988-1994. The high-dispersion data show a rich Fe V and Fe VI absorption spectrum.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 443; 1; p. 245-248
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  • 2
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    Correction to the luni-solar precession from very long baseline interferometry (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The redetermination of the luni-solar precession is performed by using Very Long Baseline Interferometry (VLBI) catalogues of extragalactic radio sources containing positions at observation epochs which cover 9 years. The positions of the sources have been determined by the VLBI network of the Crustal Dynamics Project of NASA from measurements covering consecutive half year and one year intervals between 1981 and 1989. In the course of their reduction the International Astronomical Union (IAU) recommended precession terms were applied. On the assumption of an imperfection of the luni-solar precession it is expected that the positions of each source obtained at different epochs but uniformly reduced to the reference system J2000.0 exhibit an apparent proper motion. We attributed this motion tentatively to precession and solved for a correction of the luni-solar precession by making a least squares fit to the position differences between homonymous sources in the set of catalogues. The 18.6 yr terms of nutation entered the process as parameters the values of which were set by choice from the reservoir of recent determinations. Twenty-five sources contributed to the analysis with the effect that the annual and semi-annual catalogues contain 16 sources on the average. The analysis confirmed the slightly overestimated IAU value of the luni-solar precession yielding a mean correction of -3.59 +/- 1.14 mas/yr from the annual and -3.84 +/- 1.16 mas/yr from the semi-annual catalogues. We discuss these secular terms and their dependence on the adopted nutation terms.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 284; 3; p. 1000-1006
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  • 3
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    40 Eridani and the gravitational lens effect (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations covering a period of 20 years show that the large proper motion (4.08 arcsec/yr) of the nearly triple system 40 Eridani-ABC will cause its brightest member, A, to pass within 3 arcsec of a faint background star. The originally hoped-for primary gravitational lens effect will therefore not take place although a minor secondary effect may occur near the time of closest approach on June 1, 1987.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 98; 1199
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  • 4
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    The chromospheric rotation activity relation in late type close binary systems (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The IUE data on 36 late type close binary stars are presented. It is shown that the chromospheric and TR line fluxes increase with decreasing stellar rotation period, though not as rapidly as does the X-ray flux. There is an increasing dependence upon rotation with increasing line temperature. The data are consistent with the hypothesis that there exists a critical rotation rate, which depends on temperature, below which the emission flux is independent of rotation and above which it increases linearly with increasing angular velocity omega.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center Advan. in Ultraviolet Astron.; p 566-569
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  • 5
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    Spectral images of HD 199178 (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: High-resolution IUE spectra of the Mg II k line of HD 199178 were analyzed, applying spectral imaging techniques to derive an image of the chromospheric structure and to study the transient behavior of the chromosphere. All spectra in the IUE archives were uniformly reduced and analyzed. Results are compared with ground-based observations of the photosphere. Four ultraviolet flares on HD 199178 are observed; 3 of these occurred at roughly the same rotational phase. There is no clear phase-dependence of the SWP line fluxes, but there is for the Mg II k flux. The emission centroid of the Mg II k line varies in a quasi-sinusoidal fashion, presumably due to the rotation of a nonuniform chromosphere.
    Keywords: ASTRONOMY
    Type: ESA, A Decade of UV Astronomy with the IUE Satellite, Volume 1; p 291-293
    Format: application/pdf
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  • 6
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    Diffuse bands versus extinction parameters (1994)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: All recent available, high quality measurements of the strong diffuse bands 5780 A and 5797 A have been collected. This includes those measurement derived from the authors's recent observations (February, May, and November 1993, taken with a echelle spectrograph) as well as those from a coude spectrograph and from literature. Equivalent widths of the diffuse interstellar bands (DIB's) at 5780 A and 5797 A have been measured on spectrograms. The measured signal-to-noise ratio (S/N) on their own spectrograms ranged from 250 to 500. The Johnson UBV data were used to estimate the color excesses of our targets.
    Keywords: ASTRONOMY
    Type: NASA. Ames Research Center, The Diffuse Interstellar Bands: Contributed Papers; p 39-43
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  • 7
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    The ultraviolet spectrum of AS 201: A planetary nebula (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The spatially unresolved emission line object AS 201 was observed by IUE in the low dispersion mode. It shows a UV spectrum similar to that of planetary nebulae or symbiotic stars. The optical spectrum shows characteristics of a G2 III star, but the UV indicates that a hot companion is present, as evidenced by strong C III, C IV, and moderately strong He II emissions. A fairly strong continuum is also seen throughout the IUE range. The log R (I(C III)/I(Si III)) value of 1.44 strongly argues for AS 201 being a planetary nebula and not a symbiotic star.
    Keywords: ASTRONOMY
    Type: ESA, Proceedings of the Celebratory Symposium on a Decade of UV Astronomy with the IUE Satellite, Volume 2; p 179-181
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  • 8
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    X-ray emission from UX Arietis - RS Canum Venaticorum systems as a class of coronal X-ray sources (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 225
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  • 9
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    The IUE spectrum of Cn 1-2 (= PK 326-10 deg 1) - A southern counterpart to V1016 Cygni and HM Sagittae? (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Low-dispersion IUE spectra confirm that the emission-line object Cn 1-2 is a symbiotic star and not a planetary nebula. The UV spectrum of Cn 1-2 strongly resembles those of V1016 Cyg and HM Sge. The object is correctly identified in the finder field of Allen's Catalogue of Symbiotic Stars (1984) but misidentified in the Catalogue of Galactic Planetary Nebulae by Perek and Kohoutek (1967).
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 100; 1101-110
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  • 10
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    A search for the 13175 A infrared diffuse band in dense environments (1994)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Models of ionized interstellar C60 predict a strong transition in the 1.2 micrometer region, and two candidate bands have recently been detected in reddened stars. We have searched for the stronger of these bands (at 13175 A) in the Taurus dark cloud complex, to determine its response to the dark-cloud environment. None of the three lines of sight studied (two near the cloud surface, one reaching A(sub V) greater than 20(sup m)) give rise to a detectable band; in one case the equivalent width is a factor of order three below that predicted. Since such behaviour is also shown by the optical Diffuse Interstellar Bands, we suggest that the 13175 A band is a genuine DIB, but we caution against an automatic interpretation in terms of an ionic carrier.
    Keywords: ASTRONOMY
    Type: NASA. Ames Research Center, The Diffuse Interstellar Bands: Contributed Papers; p 17
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