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  • ASTROPHYSICS  (28)
  • Astrophysics  (1)
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  • 1
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    Colors of reflection nebulae. III - Ultraviolet scattering by small particles in reflection nebulae associated with 17, 20, and 23 Tauri (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: New surface brightness measurements in the reflection nebulae associated with the Pleiades stars 17, 20, and 23 Tau have been carried out with the IUE satellite. Each nebula was observed at two angular offsets south of the respective illuminating star. At the larger offsets (40, 40, and 60 arcsec respectively) each nebula exhibits a flux distribution which rises much more steeply with decreasing wavelengths than the corresponding stellar spectrum. At the smaller offsets (20 arcsec) the nebular spectra are more similar to those of the stars and fail to show the steep rise at wavelengths less than 2200 A. Independent observations of interstellar absorption lines as well as theoretical arguments by several previous authors lead to a model wherein the reflection nebulosity near the Pleiades stars is caused by a thin sheet of interstellar matter in front of the stars, at an approximate distance of a few x 10 to the -2nd pc. In the context of such a model the nebular spectra obtained near 17, 20, and 23 Tau can be understood only if the phase-function asymmetry of scattering declines with decreasing wavelengths throughout the spectral range. This result indicates that the role of scattering in the UV by particles in the 10 to the -6th cm size range appears more important than is generally recognized by current models.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 302; 421-431
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  • 2
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    Images in the rocket ultraviolet - The starburst in the nucleus of M83 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Ultraviolet images of the SAB(s)c I-II galaxy M83 (NGC 5236) obtained with a rocketborne telescope in broad bandpasses centered at 1540 A and 2360 A show a bright resolved nuclear source which accounts for approximately 20 percent of the flux of the galaxy in both bandpasses. Low-resolution International Ultraviolet Explorer spectra of this source reveal an energy distribution similar to that of the starburst nucleus of NGC 7714. Strong blueshifted absorption lines can be interpreted as evidence for a nuclear wind powered by supernovae. Observations from UV, X-ray, optical, and far-infrared bandpasses are consistent with a starburst approximately one-sixth as strong as that in M82. A scaling of the M82 models of Rieke et al. (1980) predicts that the nucleus of M83 contains 10 to the 6th - 3 x 10 to the 7th solar masses in young stars and has a supernova rate of approximately 0.01 per yr.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 274; L53-L56
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  • 3
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    The rocket-ultraviolet spectrum and models of the planetary nebula NGC 7662 (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Ultraviolet spectral analysis of NGC 7662 has revealed a Balmer line distribution indicating a C/O ratio of unity. This abundance of carbon is characteristic of mixing between the central star and the outer envelope of the planetary nebula. A continuum spectrum is observed from the star and the nebula, radiating its energy via the two photon process through neutral hydrogen. Spectral lines were fitted to apply to the predictions of three models of the nebular structure. UV observations were compared with visible, IR, and radio observations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 219
    Format: text
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  • 4
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    IUE observations of the interstellar medium (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results from a preliminary study of interstellar absorption lines in the spectra of the three stars HD149757, HD93521 and HD153919, observed by the IUE during its commissioning phase are presented. They demonstrate the capabilities of the IUE for interstellar research. Results from a preliminary study of the emission line spectrum of the planetary nebula NGC 7027 are outlined and used to study its interstellar reddening.
    Keywords: ASTROPHYSICS
    Type: Nature; 275; Oct. 5
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  • 5
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    Images in the rocket ultraviolet - The stellar population in the central bulge of M31 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Imagery of the bulge of M31 obtained with a rocket-borne telescope in two broad bands centered at 1460 A and 2380 A is discussed. The UV spatial profiles over a region about 200 arcsec wide are identical with those at visible wavelengths. The absence of detectable point sources indicates that main-sequence stars hotter than B0 V are not present in the bulge. It is suggested that the far-UV flux in old stellar populations originates in post-AGB stars. The UV flux from such stars is extremely sensitive to age and the physics of their previous mass loss.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 298; L37-L40
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  • 6
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    Discovery of a nitrogen-rich UV-bright star in the globular cluster M5 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Observations of a UV bright source in the globular cluster M5 using instrumentation on the Black Brant rocket are reported. Imagery was obtained by two cameras operating at 1540 A and 2360 A and bandpasses of 350 A and 880 A. The instruments are prototypes for cameras to be flown with the Spacelab. The UV-emitting object in the cluster was located off-center. Comparison of the data with data from the IUE for short-wavelength radiation indicated a temperature in the range 25,000-50,000 K, with a dereddened flux for the continuum near 1550 A of 4.2 x 10 to the -13th ergs/sq cm per sec per A. The object is concluded to be a post-AGB star with an envelope which has experienced CNO processing.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 267; April 15
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  • 7
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    Images in the rocket ultraviolet - The initial helium abundance and distance modulus of the globular cluster M5 from photometry of horizontal-branch stars (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A natural laboratory for the study of postmain-sequence evolution of low-mass (less than one solar mass) metal-poor stars is provided by globular clusters. These clusters are, therefore, a critical aid for developing an understanding of advanced stages of stellar evolution and of the chemical evolution of the Galaxy. Bohlin et al. (1983) have described a study of the postasymptotic branch star near the center of M5. The present investigation is concerned with the fainter horizontal-branch stars. The observations were made with the aid of a rocket-borne 38 cm f/9.0 Ritchey-Chretien telescope. Attention is given to payload and flight data, preflight bandpass calibration, the reduction of flight data, star selection, position measurement, photometry, the minimum observed horizontal-branch mass and inferences on mass loss, and individual UV-bright stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 687-695
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  • 8
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    Results of basic improvements to the extraction of spectra from IUE images (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Results of two methods of extracting spectra from IUE images are compared. The first method, which is presently implemented, performs a geometric correction of the image followed by a photometric correction. The spectral data are then extracted using a slit with an effective width and sampling interval of 2.4A for the SWP camera and 3.7A for the LWR camera in low dispersion. The second method performs the photometric correction without doing a geometric correction. The spectral data are then extracted from the photometrically corrected image by an extraction slit, which follows the spectral orders in the nongeometrically corrected space, with an effective width and sampling interval 1/2 that of the present method.
    Keywords: ASTROPHYSICS
    Type: The Universe at Ultraviolet Wavelengths: The First Two Yrs. of Intern. Ultraviolet Explorer; p 777-785
    Format: application/pdf
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  • 9
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    The diffuse interstellar feature at 4430 A and interstellar extinction in the far-ultraviolet (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: IUE measurements have been obtained for the UV extinction characteristics of 20 reddened stars previously reported to have anomalously high or low A(4430)/E(B-V) ratios, in order to conduct a first statistical study of the correlations between these ratios and interstellar extinction features in the UV. A marginally significant positive correlation is noted between A(4430)/E(B-V) and the normalized strength of the 2175 A extinction jump, but no correlation is found with the total extinction at the wavelength and a marginally negative correlation is found with the extinction rise at 1250 A. The hypothesis that 4430 A diffuse absorption is produced by very small interstellar grains is not supported by the present observations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 267
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  • 10
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    Interstellar abundances of oxygen and nitrogen (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Neutral nitrogen and oxygen column densities or limits are derived for 53 path lengths through the diffuse interstellar medium and compared with column densities of neutral hydrogen. For neither N nor O is a systematic increase of depletion found as reddening increases. The value found for forbidden O/N is 8, and the abundances of N and O are both between 40% and 70% of the solar values. Implications of these results for models of interstellar grains are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
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