TY  - JOUR
A1  - Toalá, Jesús Alberto
A1  - Ramos-Larios, Gerardo
A1  - Guerrero, Martin A.
A1  - Todt, Helge Tobias
T1  - Hidden IR structures in NGC40
BT  - Signpost of an ancient born-again event
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present the analysis of infrared (IR) observations of the planetary nebula NGC40 together with spectral analysis of its [WC]-type central starHD826. Spitzer IRS observations were used to produce spectral maps centred at polycyclic aromatic hydrocarbons (PAH) bands and ionic transitions to compare their spatial distribution. The ionic lines show a clumpy distribution of material around the main cavity of NGC40, with the emission from [Ar II] being the most extended, whilst the PAHs show a rather smooth spatial distribution. Analysis of ratio maps shows the presence of a toroidal structure mainly seen in PAH emission, but also detected in a Herschel PACS 70 mu m image. We argue that the toroidal structure absorbs the UV flux from HD826, preventing the nebula to exhibit lines of high-excitation levels as suggested by previous authors. We discuss the origin of this structure and the results from the spectral analysis of HD826 under the scenario of a late thermal pulse.
KW  - stars: carbon
KW  - stars: evolution
KW  - stars: winds, outflows
KW  - ISM: molecules
KW  - planetary nebulae: individual: NGC40
KW  - infrared: ISM
Y1  - 2019
U6  - https://doi.org/10.1093/mnras/stz624
SN  - 0035-8711
SN  - 1365-2966
VL  - 485
IS  - 3
SP  - 3360
EP  - 3369
PB  - Oxford Univ. Press
CY  - Oxford
ER  -