RWT 152 is one of the few known planetary nebulae with an sdO central star. We present subarcsecond red tunable filter Hα imaging and intermediate-resolution, long-slit spectroscopy of RWT 152 obtained with OSIRIS/GTC (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy/Gran Telescopio Canarias) with the goal of analysing its properties. The Hα image reveals a bipolar nebula with a bright equatorial region and multiple bubbles in the main lobes. A faint circular halo surrounds the main nebula. The nebular spectra reveal a very low excitation nebula with weak emission lines from H+, He+ and double-ionized metals, and absence of emission lines from neutral and single-ionized metals, except for an extremely faint [N II] λ6584 emission line. These spectra may be explained if RWT 152 is a density-bounded planetary nebula. Low nebular chemical abundances of S, O, Ar, N and Ne are obtained in RWT 152, which, together with the derived high peculiar velocity (~ 92-131 km s-1), indicate that this object is a halo planetary nebula. The available data are consistent with RWT 152 evolving from a low-mass progenitor (~1 M⊙) formed in a metal-poor environment.
Bibliographical noteFunding Information:
This paper is based on observations made with the Gran Telescopio Canarias (GTC), installed at the Spanish Observatorio de El Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma. This paper has been partially supported by grant AYA 2011-24052 (AA, ES), AYA 2011-30228-C3-01 (LFM), ESP2014-55996-C2-2-R (AU) and AYA2014-57369-C3-3-P (LFM) of the Spanish MINECO (all them co-funded by FEDER funds). We also acknowledge support from grant INCITE09 312191PR (AU, LFM, AA) of Xunta de Galicia, partially funded by FEDER funds, from grant PRX15/00511 (AU) of the Spanish MECD, and from grant 12VI20 (AU, LFM, AA) of the University of Vigo. AA also acknowledges support from FONDECYT through postdoctoral grant 3160364. We are very grateful to the staff on the El Roque de los Muchachos Observatory and specially to Antonio Cabrera for helping us to plan and reduce the observations successfully. We also thank Irene Pintos for her detailed explanations about the tunable filters. We acknowledge support from the Faculty of the European Space Astronomy Centre (ESAC). This research has made use of the SIMBAD data base, operated at the CDS, Strasbourg (France), Aladin, NASA's Astrophysics Data System Bibliographic Services and the SpanishVirtual Observatory supported from the Spanish MINECO through grant AYA2011-24052.
© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
- ISM: abundances
- Planetary nebulae: individual: RWT 152