http://arxiv.org/abs/2106.10762
Wolf-Rayet ([WR]) and weak emission-line ($wels$) central stars of planetary nebulae (PNe) have hydrogen-deficient atmospheres, whose origins are not well understood. In the present study, we have conducted plasma diagnostics and abundance analysis of 18 Galactic PNe surrounding [WR] and $wels$ nuclei, using collisionally excited lines (CELs) and optical recombination lines (ORLs) measured with the Wide Field Spectrograph on the ANU 2.3-m telescope at the Siding Spring Observatory complemented with optical archival data. Our plasma diagnostics implies that the electron densities and temperatures derived from CELs are correlated with the intrinsic nebular H$\beta$ surface brightness and excitation class, respectively. A self-consistent method of plasma diagnostics of heavy element ORLs of N${}^{2+}$ and O${}^{2+}$ likely suggests the presence of a small fraction of cool ($\lesssim$ 7000 K), dense ($\sim$ $10^4$–$10^5$ cm$^{-3}$) materials in some objects, though with large uncertainties. Our abundance analysis indicates that the abundance discrepancy factor (ADF$\equiv$ORLs/CELs) of O${}^{2+}$ is correlated with the dichotomy between forbidden-line and He {\sc i} temperatures. Our results likely suggest the presence of a tiny fraction of cool, oxygen-rich dense clumps within the diffuse warm ionized nebulae. Moreover, our elemental abundances derived from CELs are mostly consistent with AGB models for initial masses from 1.5 to 5M$_{\odot}$. Further studies are necessary to understand better the origins of abundance discrepancies in PNe around [WR] and $wels$ stars.
A. Danehkar
Tue, 22 Jun 21
25/71
Comments: 94 pages (20+74 pages in Supplementary), 6 figures (inc. fig.set 1 (19 images), fig.set 3 (21 images)), 14 tables (inc. 7 MRT), supplementary data archived on this https URL
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