Up: High X-ray-to-optical flux ratio
This is a rather small sample compared with 18811 entries in RASS-BSC.
However it gives us a view into what kind of objects occupy the highest
X-ray-to-optical flux ratio regime. We can draw following conclusion from
the sample identification results:
- 1.
- Finding BL Lac objects by identifying X-ray sources with very
high X-ray-to-optical flux ratio is proved to be fruitful.
- 2.
- Those X-ray parameters listed in RASS-BSC can give a clue to the
optical counterparts of X-ray sources. Pre-identification can be achieved
if the combination properties in X-ray band (count-rate, hardness ratio and
extent) and optical band (visual magnitude and morphology) are concerned.
- 3.
- The peculiar HR1 distribution of AGN predicts that there is a soft
X-ray excess over the flat hard X-ray continuum of AGN in the sample.
Acknowledgements
We thank an anonymous referee for valuable comments and suggestions.
Dr. D.-W. Xu, X.-J. Jiang and Dr. Z.-H. Zhu give us much help in preparing the
manuscript. This work is partly supported by the Pandeng Project of the
Chinese Scientific Committee and the Chinese National Natural Science
Foundation.
Up: High X-ray-to-optical flux ratio
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