Astron. Astrophys. 356, 11-22 (2000)

Astron. Astrophys. 356, 11-22 (2000)

5. Summary and conclusions

We have presented the results of our ROSAT, ASCA and optical observations of the enigmatic soft X-ray AGN RX J0134.2-4258. We found:

RX J0134.2-4258 has shown a dramatic change in its ROSAT PSPC spectra between its RASS and a pointed PSPC observation made two years later.
Optically, RX J0134.2-4258 is a Narrow-Line Seyfert 1 galaxy with very strong FeII emission, extremely weak emission from the NLR and with a very blue optical continuum.
The slopes of the hard component of the ROSAT spectra and the ASCA spectra are consistent, and the ASCA slope is notably flat compared with other NLS1s.
It is the normalization of the hard X-ray component that varies the most and is primarily responsible for the dramatic spectral change.
RX J0134.2-4258 has been found to be one of the few NLS1s that are radio loud, and currently holds the record for radio-to-optical flux ratio in NLS1s.
Physical reasons for the strange spectral behaviour might be a variable warm absorber, the loss and regrowth of a corona above the accretion disk, or an increase in flux from a component associated with a possible jet as indicated by the radio-loudness of this source.

One important problem that applies to most transient AGN is that it is difficult to monitor their behaviour. Often years lapsed between RASS and later pointed observations. Hopefully, in the future with new survey missions it will be easier and faster to discover transients. Then they could be monitored using next-generation all sky monitor experiments such as the approved mission MAXI which will be mounted on the Japanese Experimental Module of the International Space Station, or the proposed Lobster-Eye satellite.

Online publication: March 28, 2000
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