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

¹ Copernicus Astronomical Center, Rabiańska 8, 87-100 Toruń, Poland e-mail: skg@ncac.torun.pl
² Geneva Observatory, Geneva University, 51 Chemin des Maillettes, 1290 Sauverny, Switzerland e-mail: Cristina.Chiappini@unige.ch
³ Osservatorio Astronomico di Trieste, OAT-INAF, via Tiepolo 11, Trieste, Italy
⁴ LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, Place Jules Janssen, 92190 Meudon, France e-mail: grazyna.stasinska@obspm.fr
⁵ GEMAC, Observatório do Valongo/UFRJ, Ladeira do Pedro Antônio 43, 20.080-090 Rio de Janeiro, Brazil e-mail: francois@ov.ufrj.br

Received: 21 August 2008
Accepted: 12 February 2009

Abstract

Aims. We present a homogeneous set of spectroscopic measurements secured with 4-m class telescopes for a sample of 90 planetary nebulae (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. We discuss the accuracy of these data and compare it with other recently published samples. We analyze various properties of PNe with emission-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, VL and remaining [WR] types form three, evolutionary unconnected forms of enhanced mass-loss among central stars of PNe. [WR] PNe seem to be intrinsically brighter than other PNe. Overall, we find no statistically significant evidence that the chemical composition of PNe with emission-line central stars is different from that of the remaining Galactic bulge PNe.