The UU Her-type stars: Possible tracers of recent star formation at high galactic latitudes

A general review of the group of UU Her-type stars proposed recently as a possible new type of variables is given. The available observations (spectra and photometry) reveal them as luminous Population I F-type supergiants of normal composition. This fact contradicts their great distances above the galactic plane. As there is no reason so far to distrust the results from the spectroscopic analyses and photometry, the galactic plane should be excluded as a possible birthplace of the UU Her-stars. In this respect they might probably indicate that recent star formation (though occasional) from already enriched material was possible at high galactic latitudes. Moreover, normal Main-Sequence B-stars seem now also to be found there.Much attention is paid to the specific semiregular variability of the UU Her-stars. The type of pulsations remains conjectural, but simple radial pulsations should obviously be ruled out.