Monthly Notices of the Royal Astronomical Society 439: 3605-3615 (2014)
doi: 10.1093/mnras/stu203

Observations and three-dimensional photoionization modeling of the Wolf-Rayet planetary nebula Abell 48¹

A. Danehkar,$^{\,1}$ ² H. Todt,$^{\,2}$ B. Ercolano$^{\,3,4}$ and A.Y. Kniazev $^{\,5,6,7}$
$^{1}$ Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109, Australia
$^{2}$ Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str.24/25, 14476 Potsdam, Germany
$^{3}$ Universitäts-Sternwarte München, Ludwig-Maxmilians Universität München, Scheinerstr.1, D-81679 München, Germany
$^{4}$ Exzellenzcluster Universe, Technische Universität München, Boltzmannstr.2, D-85748 Garching, Germany
$^{5}$ South African Astronomical Observatory, PO Box 9, 7935 Observatory, Cape Town, South Africa
$^{6}$ Southern African Large Telescope Foundation, PO Box 9, 7935 Observatory, Cape Town, South Africa
$^{7}$ Sternberg Astronomical Institute, Lomonosov Moscow State University, Moscow, Russia

Date: Accepted 2014 January 28. Received 2014 January 28; in original form 2013 September 10

Abstract:

Recent observations reveal that the central star of the planetary nebula Abell 48 exhibits spectral features similar to massive nitrogen-rich Wolf-Rayet (WN) stars. This raises a pertinent question, whether it is still a planetary nebula or rather a ring nebula of a massive star. In this study, we have constructed a three-dimensional photoionization model of Abell 48, constrained by our new optical integral field spectroscopy. An analysis of the spatially resolved velocity distributions allowed us to constrain the geometry of Abell 48. We used the collisionally excited lines (CELs) to obtain the nebular physical conditions and ionic abundances of nitrogen, oxygen, neon, sulfur and argon, relative to hydrogen. We also determined helium temperatures and ionic abundances of helium and carbon from the optical recombination lines (ORLs). We obtained a good fit to the observations for most of the emission-line fluxes in our photoionization model. The ionic abundances deduced from our model are in decent agreement with those derived by the empirical analysis. However, we notice obvious discrepancies between helium temperatures derived from the model and the empirical analysis, as overestimated by our model. This could be due to the presence of a small fraction of cold metal-rich structures, which were not included in our model. It is found that the observed nebular line fluxes were best reproduced by using a hydrogen-deficient expanding model atmosphere as the ionizing source with an effective temperature of $T_{\rm eff}$  = 70kK and a stellar luminosity of $L_{\rm\star}$  = 5500L $_{\bigodot}$ , which corresponds to a relatively low-mass progenitor star ($\sim3$  M $_{\bigodot}$ ) rather than a massive Pop I star.

Key words: ISM: abundances - planetary nebulae: individual: Abell48 - stars: Wolf-Rayet

Footnotes

... Abell 48¹

Based on observations made with the Australian National University (ANU) Telescope at the Siding Spring Observatory, and the Southern African Large Telescope (SALT) under programs 2010-3-RSA_OTH-002.

...²

E-mail: ashkbiz . danehkar @ students . mq . edu . au