Diffuse Cosmic X-ray Research Articles

The Isotropy of the Diffuse Cosmic X-Rays Determined by Oso-Iii

Diffuse cosmic X rays observation by telescope aboard OSO 3 satellite, determining isotropy

Effect of scattered photons on the spectrum of diffuse X-rays observed at balloon altitude

Effect of the scattering of cosmic diffuse X-rays in the atmosphere on the observed spectrum at balloon altitude is examined. It is shown that the contribution of the scattered X-rays cannot be eliminated by the usual method of extrapolating the growth curve and that the atmospheric absorption of the primary X-rays has been overcorrected thus far by 25–40%.

Observational results on diffuse cosmic X-rays: (Invited discourse)

The present status of observations of the diffuse cosmic X-rays is discussed. The energy spectrum in the energy range 1–100 keV has been well established. The flux around 0.25 keV appears to be rather high. The basis of the classical argument that the integration of normal galaxies in the universe is not sufficient to explain the diffuse X-ray flux is re-examined. Recent observations around 0.25 keV are discussed and results are compiled.

Observations on diffuse cosmic X-rays in the energy range 20–120 keV

In this paper we present observations of the diffuse background X-rays in the energy range 20–120 keV, based on two balloon experiments carried out from Hyderabad (latitude 17.6°N, longitude 78.5°E), India. The flights were made on April 28, 1968 and December 22, 1968. The detector used was a NaI(Tl) crystal of effective area 97.3 cm2and thickness 4 mm. The crystal was surrounded both by active and passive collimators. The passive collimator was a cylindrical graded shield of lead, tin, and copper, and the active collimator was a plastic scintillator surrounding the shield. The FWHM of the telescope was 18.6° and the geometrical factor for isotropic radiation 13.2 cm2sr. The pulses from the NaI crystal were sorted into ten contiguous channels extending from 17 to 124 keV. An Am241source came into the field of view of the telescope periodically and provided in-flight calibration of the detector. All the information was recorded on photographic film.

The Diffuse Cosmic X-Ray Background from 20 TO 220 keV

view Abstract Citations (53) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Diffuse Cosmic X-Ray Background from 20 TO 220 keV Bleeker, J. A. M. ; Deerenberg, A. J. M. Abstract Balloon experiments wfth identical X-ray detectors, carried out from three different geomagnetic latitudes (A = 20 , 40 , and 50 ) resulted in an accurate determination of the energy spectrum of the diffuse cosmic X-ray background between 20 and 220 keV. The spectrum closely fits a single power law: I(E)dE = 195E-2'45+- photons keV ' Thus we conclude that the flattening of the spectrum observed at lower energies occurs below 20 keV, with a change in spectral index of one power. Extrapolation of the present results to the -ray region above 100 MeV yields a flux which is 1 order of magnitude lower than the isotropic flux of -rays observed by Clark, Garmire, and Kraushaar in OSO-IlI. This suggests different mechanisms of origin for the isotropic flux of %-rays above 100 MeV and the background of cosmic X-rays. Publication: The Astrophysical Journal Pub Date: January 1970 DOI: 10.1086/150304 Bibcode: 1970ApJ...159..215B full text sources ADS |

A Measurement of the Diffuse Cosmic X-Ray Background from 17 to 167 keV

This paper presents a measurement of the diffuse cosmic X-ray background made during the balloon flight described in preceding papers and elsewhere. The data used for this paper were obtained with the actively shielded and collimated detector previously described. The geometric factor of the detector was 1.17 cm2 sterad.

Observations of cosmic X-ray sources in the 10–250 keV range

Observations of cosmic X-ray sources have been made from high-altitude balloons over Palestine, Texas, using actively collimated detectors. In this technique, a thin NaI central counter 10 to 50 cm2 in area is surrounded by a CsI well crystal shield several centimeters thick. The aperture, about 8° to 20° FWHM, is determined by either the well opening or an active honeycomb collimator. The background is determined mainly by diffuse cosmic and atmospheric X-rays entering the forward aperture. The detector is usually either servo-controlled to track the source or operated as a meridian device. Data are telemetered over the 20–250 keV range in a digital format from a 128-channel pulse-height analyzer. Several strong sources in the northern hemispheric sky have been observed. The Crab nebula has a power-law differential number spectrum with an index of –1.9 ± 0.1 and an intensity of about 10−2 photons/cm2-s-keV at 20 keV. Two observations in September 1965 and September 1966 on this object give the same flux and spectral index within about 5% over the 20–100 keV range. The source Cygnus XR-1 also has a power-law shape, very similar in slope and intensity to the Crab, which extends above background to at least 180 keV. These measurements are in general agreement with those of other workers. The power-law spectrum of the Crab and Cygnus XR-1 may be contrasted with that of SCO XR-1, which has an exponential spectrum, typical of a hot gas at 50 × 106 °K.

Diffuse Cosmic X-Ray Background Between 4 and 40 KEV

view Abstract Citations (52) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Diffuse Cosmic X-Ray Background Between 4 and 40 KEV Seward, F. ; Chodil, G. ; Mark, Hans ; Swift, C. ; Toor, A. Abstract Diffuse X-ray background fluxes have been observed in many of the rocket flights made to study discrete X-ray sources. The X-ray background spectrum observed in two recent (September 20 and September 22, 1966) flights from Johnston Island is presented. Observations were made of backgrounds perpendicular to and in the galactic plane. The X-ray flux was found to be roughly isotropic. It follows a power law spectrum having N(E) 1 6 The total radiated energy observed between 4 and 40 keV is 9 X 10-8 ergs sterad-1. Publication: The Astrophysical Journal Pub Date: December 1967 DOI: 10.1086/149387 Bibcode: 1967ApJ...150..845S full text sources ADS |