Universitat de - Departament d'Astronomia i Meteorologia ...

172 General conclusions
particular, runaway microquasars could be connected with some of the uniden-
tified faint, variable, and soft γ-ray EGRET sources above/below the galactic
plane.
Part II:
1. We have presented a cross-identification method to search for REXBs, which
are potential microquasar sources. The obtained results give confidence to
the proposed method, since the output list of objects included all but one
known persistent HMXB microquasars within |b| < 5 ◦ . The obtained list
after removing previously known sources contains 13 new radio emitting X-
ray sources, of which 8 have been classified as high priority objects.
2. We have studied 6 of these 8 sources, and found optical counterparts to all of
them. We have obtained accurate positions at both radio and optical wave-
lengths, perfectly compatible between them. We also have obtained radio
spectra and optical magnitudes of the sources.
3. We have presented EVN and MERLIN observations of these six sources. Five
of the six objects have been detected and imaged, presenting different mor-
phologies: one source has a two-sided jet, three sources have one-sided jets,
and one source is compact.
4. After our observations we conclude that the sources 1RXS J001442.2+580201
and 1RXS J013106.4+612035 are promising microquasar candidates in the
Galaxy. 1RXS J042201.0+485610 is probably of thermal nature due to its
highly inverted spectrum at high radio frequencies, and we note its extended
appearance at optical wavelengths. 1RXS J062148.1+174736 is probably ex-
tragalactic due to the extended optical counterpart. 1RXS J072259.5−073131
displays a bent one-sided jet, which is a common property in blazars. Finally,
the source 1RXS J072418.3−071508 is an already identified quasar.
5. Work in progress. Optical spectroscopic observations of the first five sources
are in progress for autumn 2002, to clearly unveil their galactic or extragalactic
nature. On the other hand, the remaining sources in the list will be eventually
studied in the future.