SIMBAD references

A photoelectric monitoring program has been applied, during the last four years, to five central stars of planetary nebulae (PNNs) with strong OVI λ3811-34 A emission. NGC6905 and, marginally, NGC2452, show intrinsic luminosity variations, while NGC7026, IC2003 and NGC1501 have constant luminosity within a few mmag. Photometric data have been analyzed with the best available packages for power-spectra reductions. Both pulsators have periods and physical characteristics well encompassed by the theoretical pulsational models relative to these stars.