ROSAT Observations of Four Unidentified EMSS Sources
Abstract
We present an analysis of four unidentified Einstein Observatory Extended Medium Sensitivity Survey sources detected in two pointed ROSAT/PSPC observations. One source (MS0420.0-3838) is resolved in two sources denoted with N (North) and S (South) in the ROSAT image. Only for one source (MS0420.6-3839) we have enough counts to allow a spectral analysis. For the other sources we have limited ourselves to the calculation of the x-ray hardness ratio and then, assuming a galactic value for the hydrogen column density, we have derived an energy index α_E_. We find a wide range of α_E_ (1 <= α_E_ <= 3). Thanks to a significantly improved x-ray positional accuracy, generally only one or two objects down to ~22 mag are present in the error circle. We have spectroscopically identified three sources with AGN: two are radio-quiet QSO at z = 0.831 and z = 0.482, the third one is a Narrow Emission Line Galaxy at z = 0.572. For the remaining sources no optical spectroscopy is available, however the values of α_ox_ and α_ro_ show that also these sources are probably AGN.
- Publication:
-
The Astronomical Journal
- Pub Date:
- September 1994
- DOI:
- 10.1086/117126
- Bibcode:
- 1994AJ....108..970C
- Keywords:
-
- Galaxies;
- Rosat Mission;
- Spectrum Analysis;
- X Ray Astronomy;
- X Ray Sources;
- Astronomical Spectroscopy;
- Color;
- Graphs (Charts);
- Identifying;
- Proportional Counters;
- Ratios;
- Stellar Magnitude;
- Tables (Data);
- X Ray Spectra;
- X Ray Telescopes;
- Astronomy;
- X-RAYS: INTERSTELLAR;
- GALAXIES: ACTIVE