The softest Einstein AGN (Active Galactic Nuclei)
Abstract
A coarse spectral study was undertaken to find the softest sources detected with the Imaging Proportional Counter (IPC) on the Einstein Observatory. Of the nearly 7700 IPC sources, 226 have color ratios that make them candidate ultrasoft sources; of these, 83 have small enough errors that it can be said with confidence that they have a spectral component similar to those of the white dwarfs Sirius and HZ 43, nearby stars such as (alpha) Cen and Procyon, and typical polar cataclysmic variables. By means of catalog searches and ground based optical and radio observations, so far 96 of the 226 candidate soft sources were identified; 37 of them are active galactic nuclei (AGN). In the more selective subset of 83 sources, 47 were identified, 12 of them with AGN. The list of 47 identifications is given in Cordova et al. For one QSO in the sample, E0132.8--411, a fit was obtained for the pulse-height data to a power-law model and for the energy spectral index of 2.2-0.4+0.6. For the remainder of the AGN in the higher confidence sample it was infered on the basis of their x ray colors that they have a similar spectral component. Two-thirds of the AGN are detected below 0.5 KeV only, while the remainder evidence a flatter spectral component in addition to the ultra-soft component.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- 1989
- Bibcode:
- 1989STIN...9015020C
- Keywords:
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- Active Galactic Nuclei;
- Heao;
- Proportional Counters;
- Quasars;
- Stellar Spectra;
- Cosmic Rays;
- Detection;
- Energy Spectra;
- Signal To Noise Ratios;
- Stellar Color;
- X Ray Sources;
- Astrophysics