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  • 1
    Electronic Resource
    Electronic Resource
    Time Variation of the Optical Intensity of the Sco X -1 X-ray Source (1969)
    [s.l.] : Nature Publishing Group
    Nature 222 (1969), S. 864-865 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In order to look for periodicities in the optical emission from Sco X-l, we have subjected all the available data from Hiltner and Mook, and from Stepien, to a power spectral analysis. Fig. 1 shows some of the data used in the analysis. Fig. 2 shows as a typical example the results of the power ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/222864a0
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  • 2
    Electronic Resource
    Electronic Resource
    Time variation of the X-ray spectrum and optical luminosity of SCO X-1 (1971)
    Springer
    Astrophysics and space science 12 (1971), S. 378-393 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results of rocket observations of SCO X-1 over the spectral range of 2∼20 keV are presented. The observations have been performed partly in India and partly in Japan under the collaboration of the three groups. The present results are compared with results of similar observations carried out by the LRL (Lawrence Radiation Laboratory) group. Some of these X-ray observations were accompanied by simultaneous optical observations. Relationships between the hardness of the X-ray spectrum and the X-ray intensity and between the hardness and the optical luminosity are compiled. The relationships among the parameters (temperature, density and size) which characterize the postulated isothermal cloud model of SCO X-1 are given. They indicate that SCO X-1 is characterized by a temperature of about 107–108K, a density of about 1016–1017 cm−3 and a radius of about 108–109 cm respectively. We further show that the temperature is inversely correlated with the size of the source; an increase in temperature corresponds to a decrease in the radius and an increase in density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651426
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  • 3
    Electronic Resource
    Electronic Resource
    Diffuse X-ray background measurements in the energy range 2–18 keV (1971)
    Springer
    Astrophysics and space science 10 (1971), S. 150-155 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Rocket measurements, of the diffuse X-ray background in the energy range 2–18 keV, conducted from Thumba Equatorial Rocket Launching Station (TERLS), India, are presented. The estimates of the cosmic background are derived by the method which employs the Earth and its atmosphere as a shutter to intercept the celestial X-rays. The results are shown to be consistent with a power law photon spectrum. 13.6 −3.3 +4.3 E −1.73±0.15 photons/cm2-sec-keV-ster the spectrum being much flatter than that observed at higher energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654613
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  • 4
    Electronic Resource
    Electronic Resource
    High fluences of low energy (10–25 MeV/amu) C, N, O and heavier ions at 450 km altitude; results from the skylab experiment (1975)
    Springer
    Astrophysics and space science 35 (1975), S. 337-347 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High fluences (i.e. the integrated fluxes) of C, N, O group of nuclei and some of the heavier ones, in the energy interval 10–25 MeV/amu, have been identified in a Lexan polycarbonate detector assembly exposed on the exterior of the Skylab for 73 days. The existence of large flux of low energy nuclei in the Skylab orbit is surprising since the minimum geomagnetic cut-off energy for fully stripped nuclei (A/Z=2) is ≃50 MeV/amu at the orbit of the satellite, and the period of exposure was a ‘quiet’ one, free from significant solar particle events. We have considered two sources for these particles: (i) partly ionized interplanetary ions accelerated within the magnetosphere and (ii) heavy nuclei trapped in the Earth's radiation belt. The flux and composition of the nuclei observed by us seem to be significantly different from those in the trapped radiation as known at present; hence it seems likely that the major part of the observed flux may be interpreted, in terms of partly ionized interplanetary ions that are further accelerated in the magnetosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637002
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  • 5
    Electronic Resource
    Electronic Resource
    Balloon observations of fast intensity fluctuations and flare-like enhancements of X-ray emission from Cygnus X-1 (1976)
    Springer
    Astrophysics and space science 42 (1976), S. 193-199 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The paper presents the results of the investigation on the short term X-ray emission characteristics of Cyg X-1 in the 20–150 keV range. The observations were made with balloon-borne oriented scintillation telescope and the flights were conducted from Hyderabad, India. The source was tracked over a duration of 1 hr that enabled detailed observations with time resolution of the order of 1 min. Fluctuations in the intensity of Cyg X-1 with time scales of the order of minutes have been detected besides short-term flare-like enhancements. The spectral characteristics of the flare emission features are discussed and their relationship to the phase of the binary is examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645542
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  • 6
    Electronic Resource
    Electronic Resource
    2.2 MeV gamma-ray line observed during two SN solar flares (1982)
    Springer
    Solar physics 79 (1982), S. 121-127 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract On December 15, 1978, an omnidirectional gamma-ray detector for the energy range 0.3 to 10 MeV was flown from São José dos Campos, Brazil at a latitude of about -23°. Around noon time, when the Sun was in the field of view of the detector, various solar flares of importance SN and SF occurred. The 2.2 MeV line flux was monitored during this time. A statistically significant line flux of (1.55 ± 0.50) × 10−2 photons cm−2 s−1 and (9.97 ± 4.85) × 10−3 photons cm−2 s−1 was observed within a few minutes of t maxima of the two long-duration SN flares respectively, whereas during SF flares only upper limits were obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146977
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  • 7
    Electronic Resource
    Electronic Resource
    X-ray Observation of Cen XR-4 and Nor XR-2 (1971)
    [s.l.] : Nature Publishing Group
    Nature 229 (1971), S. 248-250 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 shows the plot of count rate in the 2-9 keV range as a function of spin azimuth. Various sources within the scan region of the detector are marked in the figure, the source positions having been obtained from earlier observations2"4. As the figure shows, the fluxes from Cen XR-1, Cen XR-2 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/229248b0
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  • 8
    Electronic Resource
    Electronic Resource
    Low-energy gamma-rays from pulsar GX 1+4-balloon results (1987)
    Springer
    Astrophysics and space science 138 (1987), S. 183-189 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results from a search of pulsed emission in low-energy gamma-rays from GX 1+4 source observed during zenith transit in a balloon experiment in April 1982. The observed pulsar period is 120.6±0.2 s with pulsed emission flux of (1.3±0.4)×10−5 photons cm−2s−1 keV−1 at an average energy ∼342 keV. These pulsations, observed at gamma-ray energies perhaps for the first time from any X-ray pulsar, in conjunction with the period determined in X-rays, indicate a spin-down in contrast with the spin-up behaviour observed by others at earlier epochs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00642876
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  • 9
    Electronic Resource
    Electronic Resource
    Balloon observations of Sco X-1 in the energy interval 17–106 keV (1973)
    Springer
    Astrophysics and space science 21 (1973), S. 107-116 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The paper presents the intensity and spectral nature of the X-ray emission from Sco X-1 in the energy interval 17–106 keV based on the observations made by a balloon borne scintillation telescope system flown on November 15, 1971 from Hyderabad, India. In the 25–53 keV interval, the spectral distribution is observed to correspond to akT value of $$5.5\begin{array}{*{20}c} { + 1.5} \\ { - 1.1} \\ \end{array} \} $$ keV assuming the shape to be exponential. Over the complete energy range of observation, a power law function with the value of exponent equal to 3.6±0.5 seems to yield an adequate fit. Comparing the present data with those obtained elsewhere, the temporal characteristics of the X-ray emission from Sco X-1 are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00642196
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  • 10
    Electronic Resource
    Electronic Resource
    Low-energy gamma-rays from pulsar GX 1+4-balloon results (1987)
    Springer
    Astrophysics and space science 137 (1987), S. 233-238 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results from a search of pulsed emission in low-energy gamma-rays from GX 1+4 source observed during zenith transit in a balloon experiment in April, 1982. The observed pulsar period is 120.6±0.2 s with pulsed emission flux of (1.3±0.4)×10−5 photons cm−2 s−1 keV−1 at an average energy ∼342 keV. These pulsations, observed at gamma-ray energies perhaps for the first time from any X-ray pulsar, in conjunction with the period determined in X-rays, indicate a spin-down in contrast with the spin-up behaviour observed by others at earlier epochs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00639990
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