Towards an improvement in the spectral description of central stars of planetary nebulae

Abstract

Context. There are more than 3000 known Galactic planetary nebulae (PNe), but only 492 central stars of Galactic planetary nebulae (CSPN) have known spectral types. It is vital to increase this number in order to have reliable statistics, which will lead to an increase of our understanding of these amazing objects. Aims. We aim to contribute to the knowledge of central stars of planetary nebulae and stellar evolution. Methods. This observational study is based on Gemini Multi-Object Spectrographs (GMOS) and with the Intermediate Dispersion Spectrograph (IDS) at the Isaac Newton Telescope (INT) spectra of 78 CSPN. The objects were selected because they did not have any previous classification, or the present classification is ambiguous. These new high quality spectra allowed us to identify the key stellar lines for determining spectral classification in the Morgan-Keenan (MK) system. Results. We have acquired optical spectra of a large sample of CSPN. From the observed targets, 50 are classified here for the first time while for 28 the existing classifications have been improved. In seven objects we have identified a P-Cygni profile at the He i lines. Six of these CSPN are late O-type. The vast majority of the stars in the sample exhibit an absorption-type spectrum, and in one case we have found wide emission lines typical of [WR] stars. We give a complementary, and preliminary, classification criterion to obtain the sub-type of the O(H)-type CSPN. Finally, we give a more realistic value of the proportion of CSPN that are rich or poor in hydrogen.

Catalogue of the central stars of planetary nebulae

“…The spectral type VL was implemented by Górny et al (2009), which is in fact consistent with a late [WC]. -O(H): Although these objects follow the classification criteria for massive O-type stars, in Weidmann et al (2018) some characteristics of the O-type stars that are CSPNe are described. In this type of stars it is possible to improve the spectral classification with qualifiers (Sota et al 2011(Sota et al , 2014Maíz Apellániz et al 2016).…”

“…It has proven to be a useful tool for the astronomical community. However, ever the last nine years there has been an increase in the number of CSPNe with new determined spectral types (or improved through spectra with better quality and resolution, such as in Weidmann et al 2018), an upgrade of that catalogue becomes necessary. In addition, during these years many new developments have been published concerning the CSPNe.…”

Hunting Young White Dwarfs at the Center of Planetary Nebulae

“…The integration times for spectroscopy on source are given in Table 2. Using IRAF 4 tasks, the spectra were reduced following standard procedures: overscan and combined bias subtraction, dome flat-fields, and cosmic ray removal. The technique employed to remove the nebular contribution is described in Weidmann et al (2018). Finally, the three spectra per target were averaged.…”

“…c Measurements on good-quality spectra of early O-type stars and WDs presented by Weidmann et al (2018). d Measurements on spectra published by Drilling et al (2013), considering only the hottest subtypes.…”

Post-common envelope binary systems experiencing helium-shell driven stable mass transfer

“…Other possible examples of CE events are planetary nebulae (PNe) with a close binary at their centre (Bond et al 1978;Jones & Boffin 2017). A recent observational study of optical spectra of a large sample of Galactic planetary nebulae by Weidmann et al (2018) shows features such as hydrogen-deficiency or stellar lines that are shifted with respect to the nebular ones for example, which suggest a binary core in several systems. The connection between duplicity and the observed nebular structure has been proposed on theoretical and observational grounds.…”