A survey of hard spectrum ROSAT sources - I. X-ray source catalogue
Abstract
We present a catalogue of 147 serendipitous X-ray sources selected to have hard spectra (α<0.5) from a survey of 188 ROSAT fields. Such sources must be the dominant contributors to the X-ray background at faint fluxes. We have used Monte Carlo simulations to verify that our technique is very efficient at selecting hard sources: the survey has >=10 times as much effective area for hard sources as it has for soft sources above a 0.5-2keV flux level of 10-14ergcm-2s-1. The distribution of best-fitting spectral slopes of the hard sources suggests that a typical ROSAT hard source in our survey has a spectral slope α~0. The hard sources have a steep number flux relation (dN/dS~S-γ with a best-fitting value of γ=2.72+/-0.12) and make up about 15per cent of all 0.5-2keV sources with S>10-14ergcm-2s-1. If their N(S) continues to fainter fluxes, the hard sources will comprise ~40per cent of sources with 5×10-15<S<10-14ergcm- 2s-1. The population of hard sources can therefore account for the harder average spectra of ROSAT sources with S<10-14ergcm-2s-1. They probably make a strong contribution to the X-ray background at faint fluxes and could be the solution to the X-ray background spectral paradox.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 2000
- DOI:
- 10.1046/j.1365-8711.2000.03735.x
- arXiv:
- arXiv:astro-ph/0006347
- Bibcode:
- 2000MNRAS.318.1073P
- Keywords:
-
- CATALOGUES;
- SURVEYS;
- X-RAYS: GENERAL;
- Astrophysics
- E-Print:
- 13 pages, 6 figures, Accepted for publication in MNRAS