Bibcode
Rodríguez, M.; Corradi, R. L. M.; Mampaso, A.
Bibliographical reference
Astronomy and Astrophysics, v.377, p.1042-1055 (2001)
Advertised on:
10
2001
Journal
Citations
43
Refereed citations
36
Description
We present low and high resolution long-slit spectra of three bipolar
planetary nebulae (PNe) with bright central cores: A
79, He 2-428 and M 1-91.
He 2-428 and M 1-91 have high
density (from 103.3 to 106.5 cm-3)
unresolved nebular cores that indicate that strong mass loss/exchange
phenomena are occurring close to their central stars. An F0 star is
found at the centre of symmetry of A 79; its
reddening and distance are consistent with the association of the star
with the nebula. The spectrum of the core of He 2-428
shows indications of the presence of a hot star with red excess
emission, probably arising in a late-type companion. A
79 is one of the richest PNe in element{N} and element{He},
the abundances of M 1-91 are at the lower end of the
range spanned by bipolar PNe, and He 2-428 shows very
low abundances, similar to those measured for halo PNe. The extended
nebulae of A 79 and He 2-428 have
inclined equatorial rings expanding at a velocity of ~ 15 km
s-1, with kinematical ages >=104 yrs. The
association of these aged, extended nebulae with a dense nebular core
(He 2-428) or a relatively late type star (A 79) is interpreted as
evidence for the binarity of their nuclei. Based on observations made
with the 2.5 m INT and the 2.6 m NOT telescopes operated on the island
of La Palma by the ING and the NOTSA, respectively, in the Spanish
Observatorio del Roque de Los Muchachos (ORM) of the Instituto de
Astrofísica de Canarias.