Ultrasoft x-rays from the southern galactic hemisphere
We have observed the x-ray background radiation at ultrasoft energies (90--280 eV; 140--44 A) in selected portions of the southern galactic hemisphere. Our results indicate the following: (i) The regions observed are generally less intense than those previously observed in the northern galactic hemisphere. (ii) Portions of the sky south of b/sup I I/ = -60/sup 0/ are enhanced up to 50% in intensity. (iii) A 9% upper limit is set on the intrinsic fluctuations of the 90--150 eV background within the detector beamwidth of 0.01 sr. A significant lower limit to the source density (> or approx. = 0.2 pc/sup -3/), in a discrete-source model of the background, can be established because the energy of these x-rays is lower than the energy sampled in most other studies (approx. 220 eV). (iv) The spectrum is extremely soft, being characterized in thermal models with kT < 100 eV. (v) The spectra toward the galactic pole and the galactic plane do not differ greatly. The data are consistent with an origin of the radiation in a hot interstellar plasma with T approx. 600,000 K and n/sub e/ approx. 0.007 cm/sup -3/. Under the assumptions of this model the measured count rate corresponds to a flux of 8 x 10/sup -9/ ergs cm/sup -2/ sr/sup -1/ s/sup -1/ in the band 90--150 eV. (AIP)
- Research Organization:
- Physics Department and Center for Space Research, Massachusetts Institute of Technology
- OSTI ID:
- 7323801
- Journal Information:
- Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 211:1; ISSN ASJOA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
640105 -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC GASES
COSMIC PHOTONS
COSMIC RADIATION
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ENERGY RANGE
EV RANGE
EV RANGE 10-100
EV RANGE 100-1000
FLUIDS
GALAXIES
GASES
INTERSTELLAR SPACE
IONIZING RADIATIONS
MASSLESS PARTICLES
MILKY WAY
PHOTONS
PLASMA
RADIATIONS
SOFT X RADIATION
SPACE
SPECTRA
VARIATIONS
X RADIATION
X-RAY SPECTRA