Deciphering the bipolar planetary nebula abell 14 with 3d ionization and morphological studies

Akras, S.
Clyne, N.
Boumis, P.
Monteiro, H.
Gonçalves, D. R.
Redman, M. P.
Williams, S.
Akras, S. Clyne, N.; Boumis, P.; Monteiro, H.; Gonçalves, D. R.; Redman, M. P.; Williams, S. (2016). Deciphering the bipolar planetary nebula abell 14 with 3d ionization and morphological studies. Monthly Notices of the Royal Astronomical Society 457 (4), 3409-3419
Abell 14 is a poorly studied object despite being considered a born-again planetary nebula. We performed a detailed study of its 3D morphology and ionization structure using the SHAPE and MOCASSIN codes. We found that Abell 14 is a highly evolved, bipolar nebula with a kinematical age of similar to 19 400 yr for a distance of 4 kpc. The high He abundance, and N/O ratio indicate a progenitor of 5 M-circle dot that has experienced the third dredge-up and hot bottom burning phases. The stellar parameters of the central source reveal a star at a highly evolved stage near to the white dwarf cooling track, being inconsistent with the born-again scenario. The nebula shows unexpectedly strong [N I] lambda 5200 and [O I] lambda 6300 emission lines indicating possible shock interactions. Abell 14 appears to be a member of a small group of highly evolved, extreme type-I planetary nebulae (PNe). The members of this group lie at the lower-left corner of the PNe regime on the [NII]/H alpha versus [S II]/H alpha diagnostic diagram, where shock-excited regions/objects are also placed. The low luminosity of their central stars, in conjunction with the large physical size of the nebulae, result in a very low photoionization rate, which can make any contribution of shock interaction easily perceptible, even for small velocities.
Oxford University Press (OUP)
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Attribution-NonCommercial-NoDerivs 3.0 Ireland