Planetary nebulae in the direction of the Galactic bulge:on nebulae with emission-line central stars

摘要

Aims. We present a homogeneous set of spectroscopic measurements secured with 4-m class telescopes for a sample of 90 planetarynebulae (PNe) located in the direction of the Galactic bulge.Methods. We derive their plasma parameters and chemical abundances. For half of the objects this is done for the first time. Wediscuss the accuracy of these data and compare it with other recently published samples. We analyze various properties of PNe withemission-line central stars in the Galactic bulge.Results. Investigating the spectra we found that 7 of those PNe are ionized by Wolf-Rayet (WR) type stars of the very late (VL)spectral class WC 11 and 8 by weak emission-line (WEL) stars. From the analysis we conclude that the PN central stars of WEL, VLand remaining WR types form three, evolutionary unconnected forms of enhanced mass-loss among central stars of PNe. WR PNeseem to be intrinsically brighter than other PNe. Overall, we find no statistically significant evidence that the chemical compositionof PNe with emission-line central stars is different from that of the remaining Galactic bulge PNe.