Hidden IR structures in NGC 40: signpost of an ancient born-again event

DOI: 
10.1093/mnras/stz624
Publication date: 
01/03/2019
Main author: 
Toalá, J. A.
IAA authors: 
Guerrero, M. A.
Authors: 
Toalá, J. A.;Ramos-Larios, G.;Guerrero, M. A.;Todt, H.
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Pages: 
3360-3369
Abstract: 
We present the analysis of infrared (IR) observations of the planetary nebula NGC 40 together with spectral analysis of its [WC]-type central star HD 826. 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 NGC 40, 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 μm image. We argue that the toroidal structure absorbs the UV flux from HD 826, 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 HD 826 under the scenario of a late thermal pulse.
Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85066985310&doi=10.1093%2fmnras%2fstz624&partnerID=40&md5=07032f45dded4d52412aba72dd336c93
ADS Bibcode: 
2019MNRAS.485.3360T
Keywords: 
stars: evolution;stars: winds;outflows;stars: carbon;infrared: ISM;ISM: molecules;planetary nebulae: individual: NGC 40;Astrophysics - Solar and Stellar Astrophysics;Astrophysics - Astrophysics of Galaxies