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  • 1
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    The Goddard High Resolution Spectrograph: Instrument, goals, and science results (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Goddard High Resolution Spectrograph (GHRS), currently in Earth orbit on the Hubble Space Telescope (HST), operates in the wavelength range 1150-3200 A with spectral resolutions (lambda/delta lambda) of approximately 2 x 10(exp 3), 2 x 10(exp 4), and 1 x 10(exp 3). The instrument and its development from inception, its current status, the approach to operations, representative results in the major areas of the scientific goals, and prospects for the future are described.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 106; 702; p. 890-908
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  • 2
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    The High Resolution Spectrograph for the Space Telescope (1982)
    In:  CASI
    Details
    Publication Date: 2009-11-16
    Description: The High Resoltuion Spectrograph (HRS) in conjunction with the Space Telescope (ST), extends ultraviolet astronomical spectroscopy to higher spectra, spatial, and time resolutions than previously achieved, as well as to fainter and more distant celestial objects. Other significant advances inherent in the instrument are high photometric accuracy and efficient operation via exposure meter control and real time rejection of bad data. These capabilities are provided to accomplish the scientific programs of the HRS investigation definition team, which concern the interstellar medium, stellar winds, and evolutionary aspects of stellar atmosphere studies; the determination of chemical abundances relevant to stellar evolution; the investigation of quasars and Seyfert galaxy nuclei; and the analysis of the atmospheres of solar system objects, including comets.
    Keywords: ASTRONOMY
    Type: Space Telescope Science Inst. The Space Telescope Obs.; p 76-105
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  • 3
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    X-ray emission from chemically peculiar stars (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We have searched the Roentgen Satellite (ROSAT) All-Sky Survey (RASS) database at the positions of about 100 magnetic Bp-Ap stars of the helium-strong, helium-weak, silicon, and strontium-chromium subclasses. We detect X-ray sources at the positions of 10 of these stars; in four cases the X-ray emission presumably arises from an early-type companion with a radiatively driven wind, while we believe that the magnetic chemically peculiar (CP) star is the most likely X-ray source (as opposed to a binary companion) in at least three and at most five of the six remaining cases. The helium-strong stars have X-ray emission levels that are characteristic of the luminous OB stars with massive winds (log L(sub x)/L(sub bol) is about -7), whereas the He-weak and Si stars (which generally show no evidence for significant mass loss) have log L(sub x)/L(sub bol) values that can reach as high as about -6. In contrast, we find no convincing evidence that the cooler SrCrEu-type CP stars are intrinsic X-ray sources. We discuss the X-ray and radio emission properties of our sample of CP stars, and argue that both types of emission may be magnetospheric in origin; however, there is clearly not a simple one-to-one correspondence between them, since many of the magnetic stars that are detected radio sources were not detected as X-ray sources in the present survey.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 420; 1; p. 387-391
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  • 4
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    Studies of H I and D I in the local interstellar medium (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: High-dispersion IUE spectra are presented of the hydrogen Ly-alpha chromospheric emission line of two nearby late-type stars, Capella and Lambda And. Both interstellar H I and D I Ly-alpha absorption can be seen against the chromospheric line, and the density, velocity dispersion, and bulk velocity of the gas in those lines of sight are derived. Limits are placed on the D/H ratio. The results are consistent with the current picture of the local interstellar medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 356; 223-228
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  • 5
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    The HRS GTO program to study the neutral hydrogen column density and D/H ratio in the local interstellar medium (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Theoretical line profiles are presented that demonstrate why 100,000 spectral resolution and high S/N are needed to derive accurate column densities from spectral lines that lie close to the flat part of the curve of growth and may contain multiple velocity components. The aim of the Space Telescope high-resolution-spectrograph observing program is to obtain column densities in the hydrogen and deuterium Lyman alpha lines along a variety of lines of sight within and extending beyond the local cloudlet, in which the sun is located near an edge. The broad chromospheric Lyman alpha emission lines of late-type stars are used as background sources against which to measure the interstellar absorption features. Profiles of interstellar absorption features in Mg II and Fe II lines will be obtained to derive the broadening parameter and/or identify possible multiple velocity components in the lines of sight.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 6; 2, 19; 91-94
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  • 6
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    IUE observations of neutral hydrogen and deuterium in the local interstellar medium (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Small-aperture, high-dispersion IUE spectra have been obtained of seven late-type stars that, in general, confirm previous Copernicus results concerning the distribution of hydrogen and deuterium in the local interstellar medium. In addition, the IUE Ly Alpha spectra of Altair, and of the Alpha Cen components, suggest that multiple velocity components exist in these two directions.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 6; 2, 19
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  • 7
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    IUE observations of interstellar hydrogen and deuterium toward Alpha Centauri B (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A high dispersion profile is presented of the Lyman-alpha emission toward Alpha Cen B as recorded in two images taken with the IUE spacecraft. The spectra were examined with a three-parameter Gaussian or five-parameter solar-type profile to derive the intrinsic background stellar emission. Voight absorption profiles were calculated for the intervening H I and D I gas. A uniform, thermally broadened medium was assumed, with the calculations being based on the free stellar parameters of density, velocity dispersion and the bulk velocity of H I, and the density of D I. The use of a small aperture is shown to have been effective in eliminating geocoronal and interplanetary diffuse Ly-alpha contamination. The H I absorption profile toward Alpha Cen B is found to be equivalent to that toward Alpha Cen A, indicating that the H I profiles derived are essentially independent of stellar emission. Less success, however, was attained in obtaining any definitive D I profile, although an asymmetry in the blue and red wings of the Lyman-alpha emissions did show the presence of absorption by interstellar deuterium and allow setting a lower limit of 0.00001 for the D I/H I ratio.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 303; 791-796
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  • 8
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    One- and multi-component models of the upper photosphere based on molecular spectra. II - CN/1, 1/ of the CN violet system (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: SPACE SCIENCES
    Type: Solar Physics; 35; Apr. 197
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  • 9
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    One- and multi-component models of the upper photosphere based on molecular spectra. I - The violet system of CN /0, 0/ (1973)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Spectroheliograms taken in the CN (0, 0) violet band near 3883 A show very small scale network and cell structures with high contrast. The bandhead itself, which is a broad feature due to overlap of several CN lines, allows the diagnostic simplicity of a continuum since motions, magnetic fields, and broadening mechanisms are unimportant. We have obtained spectroheliograms in the bandhead and center-to-limb photoelectric spectra of CN (0, 0) at Kitt Peak National Observatory. From the photoelectric spectra and a detailed analysis of the formation of the CN (0, 0) spectrum we derive a best-fit one-component upper photospheric model differing from that of the HSRA and recommend a change in solar carbon abundance from the HSRA value.
    Keywords: SPACE SCIENCES
    Type: Solar Physics; 32; Sept
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  • 10
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    One- and multi-component models of the upper photosphere based on molecular spectra. IV - Non-LTE treatment of the CN violet system (1975)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 41; Mar. 197
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