Bibcode
DOI
Guerrero, M. A.; Manchado, A.
Referencia bibliográfica
The Astrophysical Journal, Volume 508, Issue 1, pp. 262-267.
Fecha de publicación:
11
1998
Revista
Número de citas
37
Número de citas referidas
33
Descripción
We present high-quality (subarcsecond) optical narrowband CCD images of
the planetary nebula NGC 6881, which reveal a highly collimated bipolar
structure. A careful examination of the [N II] image and of the [N
II]/[O III] and [N II]/Hα ratio images shows that NGC 6881 is a
quadrupolar planetary nebula, that is, a twice bipolar planetary nebula,
each pair of lobes having a different symmetry axis. In addition, a
striking knotty, looplike structure has been discovered in the southeast
extreme of the nebula. Its appearance strongly suggests a precessing
jetlike structure. Kinematical information of the different
morphological features confirms the proposed nature of this nebula. The
bright core is a ring that is collimating the bipolar lobes, while the
looplike structure turns out to be a precessing jet. Assuming a simple
ballistic model, an age of 7400d yr (d is the distance in kpc) is worked
out, which can be compared with the computed age of the inner lobes of
400d yr. The precession period is 3800d yr. An upper limit of the
ionized mass ejected (1.8 x 10^-5d^5/2 M_&sun;) in the precessing jet
has also been calculated.