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  • 1
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    Spectral variations of LMC X-3 observed with Ginga (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The prime black hole candidate LMC X-3 was observed over three years with the Ginga satellite, and a characteristic spectral variation was found accompanying the periodic intensity variation of about 198 (or possibly about 99) days (Cowley et al., 1991). The energy spectrum of LMC X-3 consists of the soft, thermal component and the hard, power-law component, which are respectively dominant below and above about 9 keV. The soft component, which carries most of the X-ray intensity, shows a clear correlation between the intensity and the hardness, while the hard component varies independently of the soft component. It was found that the spectral variation of the soft component is well described by an optically thick accretion disk model with a remarkably constant innermost radius and variable mass accretion rate. The constancy of the innermost radius suggests it is related to the mass of the central object.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 403; 2; p. 684-689.
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  • 2
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    The interacting binary SCO X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Spectroscopic observations of Sco X-1 show conclusively that the emission lines vary in radial velocity with a period of .787 sup d + or - .006 and a full range of approximately 120 km/s. The period is identical to that found by Gottleib et al (1975) from photometric data; light minimum occurs when the emission line region is at superior conjunction. The observations indicate that the emission lines originate in an accretion disk surrounding a neutron star which is orbiting about a normal, although somewhat evolved companion. The light variation is due to a heating effect on the non degenerate star, viewed at a small inclination angle.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 683-690
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  • 3
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    Ultraviolet observations of accretion disk in LMC X-3 (1994)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We report information obtained from a series of International Ultraviolet Explorer (IUE) low-resolution spectra and two HST UV spectra of LMC X-3. The HST spectra are used to identify disk emission lines and interstellar absorptions as well as to fit continuum models, which indicate the presence of a hot disk component. The IUE observations, mainly taken over approximately 1.5 years, were intended to study how the observed characteristics of the accretion disk change through the precessional cycle. It is shown that although the emission line strengths and short-wavelength ultraviolet flux are well correlated, both optical and UV data show little long-term periodic modulation was present during our observations, indicating LMC X-3 had dropped into a 'low' state.
    Keywords: ASTROPHYSICS
    Type: The Astrophysical Journal (ISSN 0004-637X); 429; 2, pt; p. 826-831
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  • 4
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    Energetic water-group ions at Comet Giacobini-Zinner - An overview of observations by the EPAS instrument (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: An overview is presented of the observations of energetic (45-480 keV) cometary water group ions made by the EPAS instrument on the ICE spacecraft during the fly-by of Comet Giacobini-Zinner in September 1985. The discussion covers ion observations in the large-scale ion pick-up region surrounding the comet on about 10 exp 6 km spatial scales, observations of the cometary shock at about 100,000 km and the region of slowed mass-loaded flows which occur downstream, and the finite gyroradius effects which occur near the closest approach.
    Keywords: ASTROPHYSICS
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  • 5
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    Comparison of magnetosonic wave and water group ion energy densities at Comet Giacobini-Zinner (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Measurements of the Comet Giacobini-Zinner (GZ) are presented to determine to what extent wave-particle scattering redistributed the initial pick-up energy of the ion population. Also examined is the difference between the ion thermal energy and the energy in the magnetic fields of the waves. In spite of uncertainty of about a factor of 2 noted in the pick-up and mass-loaded regions, it is shown that less than approximately 50 percent of the pick-up energy is converted into wave magnetic energy in the inbound pick-up region.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 11; 9, 19; 83-86
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  • 6
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    The ultraviolet spectra of M31 globular clusters (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Ultraviolet spectra of 11 of the brightest globular clusters in M31 show that some exhibit residual flux below 3000 A, greater than that expected from the bright, evolved stars in the cluster. There seems to be no apparent correlation of the strength of this ultraviolet flux with parameters such as metallicity, U-B color, visual magnitude, X-ray emission, or location within the parent galaxy. However, comparison of the ultraviolet colors of the M31 globular clusters with those in the Galaxy and in the Large Magellanic Cloud suggests that the M31 clusters may contain a high percentage of blue horizontal-branch stars or that some clusters could be as young as about 2 x 10 to the 9th yr.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 95; 1071-108
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  • 7
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    Optical and UV spectroscopy of the black hole binary candidate LMC X-1 (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Both further optical spectroscopy of the binary star identified with LMC X-1, obtained between 1983 and 1985, and a series of IUE UV spectra taken during a 5 day interval in 1984 are presented. The optical data are used to refine the orbital period to 4.2288 days, and improved orbital parameters are derived. The velocity of the optical emission lines is antiphased with the absorption lines and has twice the velocity amplitude. These new results support the estimates of the masses in the system given earlier. The most probable component masses are approximately 20 solar masses for the primary and near 6 solar masses (for the x-ray star), suggesting the the latter may be a black hole. The UV spectra show very weak, low-velocity stellar-wind lines. It is suggested that much of the surrounding medium is highly ionized by the X-ray flux. The 'nonwind' UV spectral lines and the UV continuum temperature are consistent with the optical data, indicating a late O type star of M(bol) = -8.5. There is a weak modulation of absorption-line strengths with orbital phase, suggestive of a lack of axisymmetry in the X-irradiation of the primary star and indicative of a fairly low orbital inclination.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal (ISSN 0004-6256); 94; 340-344
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  • 8
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    In-situ observations of cometary pick-up ions greater than 0.2 AU upstream of Comet Halley - ICE observations (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Burst-like enhancements of energetic ions were observed by the EPAS instrument on the International Cometary Explorer (ICE) during its closest approach to (28 x 10 to the 6th km upstream of) Comet P/Halley, in late March 1986. The ion intensity was modulated by the varying solar wind speed (the latter reaching maxima of around 600 km/s), as was found to be the case for heavy cometary ions accelerated by pick-up in the solar wind flow, during the ICE encounter with Comet P/Giacobini-Zinner (G-Z). Therefore it is concluded that the observed pick-up ions (most probably greater than or equal to 65 keV oxygen ions) are produced by heavy neutrals from Comet Halley. The observations of energetic ions at such large distances suggest the presence, in the neutral atmosphere surrounding the nucleus, of a component with an ionization scale length of 5-10 million km, resulting from a relatively high expansion speed of a few km/s and/or an ionization time scale of a few times 10 to the 6ths.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 13; 861-864
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  • 9
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    Observations of the interactions of heavy ions from Comet P/Giacobini-Zinner with the solar wind (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: During the encounter between the ICE spacecraft and Comet Giacobini-Zinner, intense fluxes of energetic heavy ions were observed up to 4 x 10 to the 6th km from the comet. In this paper the authors correlated observations of heavy ions, the solar wind velocity and the magnetic field direction, and compare the observations of the ions with the theoretical predictions for their variations with distance from the comet, wih the solar wind velocity and with the magnetic field direction.
    Keywords: ASTROPHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 6; 1, 19
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  • 10
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    Gyroradius effects on the energetic ions in the tail lobes of Comet P/Giacobini-Zinner (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: It is reported that during the ICE fly-by of comet P/Giacobini-Zinner, a depletion was seen in the energetic ion intensities (E greater than 65 keV for 'water group' ions) extending to about 40 min on either side of the time of closest approach (1102 UT on September 11, 1985). It is demonstrated that the physical size of this hole is a few ion gyroradii (about 1.5 x 10 to the 4 km). Angular analysis of the ion distributions in the 'gyroradius region' can distinguish those ions whose gyromotion is entirely in one comet lobe from those that cross the current sheet into the other lobe. In the central tail within a few minutes of closest approach, the single-lobe ions exhibit high intensities and little pitch angle dependence, whereas the ions crossing the current sheet have lower intensities and are streaming along the magnetic field away from the comet. The derived density gradients are used to determine the orientation of the current sheet at closest approach, as 44 degrees east of north.
    Keywords: ASTROPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 13; 419-422
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