Direct evidence for a two component spectrum of the soft X-ray background.
Abstract
Two pointed ROSAT observations of neutral hydrogen clouds located at very different distances in the general direction of the Draco nebula are presented. These observations offer a unique possibility to study the temperature distribution of the soft X-ray background (SXRB) in detail. The observed anticorrelation of the Hi column densities and the soft X-ray count rates is in quantitative agreement with the theoretical absorption cross section of the interstellar matter. Furthermore, soft X-ray spectra give direct evidence for the existence of a two component spectrum of the SXRB. Fits to the X-ray spectra are in agreement with a model consisting of a cooler (T_local_=~10^5.85+/-0.1^K) local X-ray emitting plasma in addition to a hotter (T_distant_=~10^6.3+/-0.1^K) plasma located beyond the galactic HI layer. The emission measure of the distant plasma is 4-5 times higher than of the local plasma. Therefore this distant plasma contributes significantly to the (1)/(4)keV and (3)/(4)keV diffuse background emission.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1994
- Bibcode:
- 1994A&A...289..597K
- Keywords:
-
- Background Radiation;
- Diffuse Radiation;
- Hydrogen Clouds;
- Interstellar Matter;
- X Ray Astronomy;
- X Ray Spectra;
- Absorption Cross Sections;
- Cosmic Plasma;
- Emissivity;
- H I Regions;
- Rosat Mission;
- Temperature Distribution;
- Astronomy;
- ISM: INDIVIDUAL OBJECTS: DRACO CLOUDS;
- ISM: STRUCTURE;
- X-RAYS: GENERAL;
- X-RAYS: INTERSTELLAR;
- DIFFUSE RADIATION