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  • 1
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    In-flight performance of the Broad-Band X-Ray Telescope (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Broad-Band X-Ray Telescope (BBXRT) was designed to carry out moderate resolution spectrophotometry of cosmic X-ray sources in the 0.3-12 keV band from the Space Shuttle. It consists of a pair of coaligned conical foil telescopes, with cryogenically cooled Si(Li) spectrometers as focal instruments. It was flown as part of the Astro-1 mission in December, 1990. The in-flight performance of the instrument was essentially as predicted on the basis of ground calibration and modelling. We discuss the performance of the system, with emphasis on the conical mirror systems, and present some preliminary scientific results which illustrate the power of broad band, high sensitivity X-ray spectrophotometry.
    Keywords: ASTRONOMY
    Type: In: Multilayer and grazing incidence X-ray(EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991 (A93-39658 15-74); p. 72-81.
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  • 2
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    Astrometric observations with the Space Telescope (1982)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Astrometry with the Space Telescope (ST) is performed using one of the fine guidance sensors (FGS). The FGS, which is based on a pair of Koester's prism interferometers, one for each axis, is capable of measuring the position of one object relative to another with an accuracy of 0.002 arcseconds. Astrometric Data Reduction Software (ADRS) available to the astrometric user of ST is described. The kinds of problems the space telescope astrometry team plans to investigate using ST are discussed.
    Keywords: ASTRONOMY
    Type: Space Telescope Science Inst. The Space Telescope Obs.; p 114-120
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  • 3
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    OSO-8 GSFC results on Cen X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Spectra of Cen X-3 during eclipse, in transition out of eclipse, and during several later phases of the binary orbit were obtained from quick look data of the July 16-25, 1975 observation by the Goddard X-ray spectroscopy experiment on OSO-8. In the high state there was no absorption turn over. Pulsations were present at least to 23 keV. The spectrum at the pulse minimum was flatter above 7 keV than that of the pulse peak. In transition out of eclipse Cen X-3 emerged above a small low energy flux seen during eclipse. The observations appear to indicate absorption by cold and ionized matter and the presence of iron in the companion's atmosphere. Decreased intensities were observed at late phases of some binary orbits in some cases corresponding to dips. Absorption appears although the low energy component remains. Variable features may be interpretable as absorption and emission by iron and possibly other trace elements.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 207-218
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  • 4
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    OSO-8 observations of Hercules X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The X-ray binary Her X-1 was observed by the GSFC cosmic X-ray detectors aboard OSO-8 between August 26 and September 3, 1975. The results reported are based on quick look tapes which contain less than 10% of the total time spent on source. Spectra were observed during different phases of the binary period including the anomalous low state (dip) in X-ray intensity. The normal high spectra is well represented by a power law with a short cutoff above approximately 25 keV. A significant and varying enhancement in the intensity around 6.7 keV was observed, suggesting the presence of an iron line. Absorption was seen in the spectrum immediately following eclipse. The dip spectrum is found to be considerably flattened. Also spectra are presented for different phases of the pulse period.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 161-168
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  • 5
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    New results from long-term observations of Cyg X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Observations of Cyg X-1 between October 1974 and July 1975 reveal a persistent 5.6 day modulation of the 3-6 keV X-ray intensity, having a minimum in phase with superior conjunction of the HDE 226868 binary system. The modulation is found to be most pronounced just prior to the April-May 1975 increase of Cyg X-1, after which both the modulation and intensity are at their lowest values for the entire duration of the observations. These data imply that the X-ray emission from Cyg X-1 arises from the compact member of HDE 226868, and that the increase of April-May 1975 may have represented the depletion of accreting material which had not yet been mixed into a cylindrically symmetric accretion disk about the compact member.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 391-405
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  • 6
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    The observation program for the GSFC cosmic X-ray spectroscopy experiment (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The cosmic X-ray spectroscopy experiment on OSO-8 will observe seven X-ray binary sources in its first six months of operation. If possible, each of these sources will be observed for one or more binary orbits so that the X-ray spectrum of each object can be observed through all phases of its orbit. For the two pulsing binaries, Her X-1 and Cen X-3, spectral variations over the pulse period will be studied. Simultaneous radio observations of Cyg X-1 and Cyg X-3 will search for any correlation between radio and X-ray emission. During the first year of operation, the detectors will observe over 50% of the known X-ray sources.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 737-738
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  • 7
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    Long term X-ray studies of Sco X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: No modulation of the 3-6 keV X-ray intensity of Sco X-1 at a level of excess of 1% is observed at the optical period of .787313d. Evidence is found for shot-noise character in a large fraction or the X-ray emission. Almost all of the Sco X-1 emission can be synthesized in terms of approximately 200 shots per day, each with a duration of approximately 1/3 day.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 703-716
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  • 8
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    High resolution measurements of Cyg X-1 from rockets (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Cyg X-1 was observed on two occasions (Oct. 4, 1973 and Oct. 3, 1974) by the Goddard X-ray rocket payload. This payload consisted of two gas proportional counters (xenon-methane with 710 sq cm and argon-methane with 610 sq cm using the same 128 channel pulse height analyzer and having 320 micro sec temporal resolution on the 1973 flight and 160 micro sec resolution on the 1974 flight. During both flights, bursts of 1 ms duration were observed with very high statistical certainty. To date all 13 of these bursts were analyzed for spectral and temporal character, and the results of this analysis are presented. The spectra of overall X-ray emission from both flights is also presented. In a source known for its variability, it is remarkable that the spectra taken one year apart are virtually identical.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 443-451
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  • 9
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    The early light curve of A0620-00 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The Ariel-5 All-Sky Monitor measured the 3-6 keV X-ray intensity of 0620-00 for two days shortly after peak emission in August 1975, and continuously throughout September 1975. The effective exposure each day for this source (and every other source in the 80% of the celestial sphere covered by the monitor) is approximately 250 sq cm sec. The light curve obtained through October 1 (when the spin axis was again pointed to A0620-00) is shown. The intensity difference at maximum is obviously a manifestation of the very soft spectrum of the source. Clearly, A0620-00 was approximately four times as bright as Sco X-1 at maximum in the band 3-6 keV. The decay is quite smooth, but cannot be fit with a single e-folding time. The interval between the early All-Sky Monitor points and the onset of continuous coverage has an inferred e-folding time of 22 days, but it is continually increasing throughout September. A0620-00 is apparently similar in its X-ray character to the very strong, long-lasting transient X-ray sources which presently number six. In contrast, only three can be sensibly reconciled with the lower-intensity, shorter-duration hard-spectrum transients which have been found to pulse on a time scale of minutes.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 311-316
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  • 10
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    A research proposal on spectroscopy of gases and solids observed in the solar system (1986)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: It is well recognized and accepted that the interpretation and analysis of any type of remote planetary spectroscopic observation requires that basic molecular parameters be available. Furthermore, the newly developed capabilities of air, ground, and space borne spectrometers trained on bodies in the solar system are producing results which are extremely difficult to understand on the basis of available data. This is particularly true in the case of spectral features arising from gases and volatiles condensed as ices. With the objective to continue to extend the understanding of spectroscopic observations of solar system objects (including comets) , laboratory studies of both gas phase molecules and ices and dusts are proposed.
    Keywords: ASTRONOMY
    Type: NASA, Washington Reports of Planetary Astronomy, 1985; p 167-168
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