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arXiv:astro-ph/0209427v1 20 Sep 2002
To appear in “Winds, Bubbles and Explosions (2003)” RevMexAA(SC)
LATE HELIUM FLASH IN V605 AQL:
PNE EVOLUTION AND SHELL FORMATION IN QUICK MOTION
S. Kimeswenger1
I present recent observations of the born–
again core V605 Aql of the old planetary neb-
ula Abell 58.
The ”born-again” PNe V605 Aql (A58) and
V4344 Sgr (Sakurai) give us the rare chance to follow
shell formation and building of the winds in ”real-
time”. The high carbon abundance, and thus the
high dust formation rate, enhances the mechanisms.
Thus the timescales are shortened. My data pre-
sented here gives a quick look on the results of new
observations of V605 Aql and its old planetary neb-
ula (PN) A58 obtained at the ESO NTT (August
2002).
Remarkable changes of the spectrum relative
to that obtained by Guerrero & Manchado (1996)
in June 1994 were found. The [S II]6716+6731 and
[O I]6300+6364 lines increased compared to the [N II]
lines. He I5875 raised by 50% relative to N II5754 .
Generally all lines got stronger.
The finding of Guerrero & Manchado (1996) of
an Hαline as strong as 30% of [N II]6548 is not sup-
ported by my observations. It may originate from an
inaccurate subtraction of the line from the old neb-
ula. The absence of Hαwas found also by Pollacco
et al. (1992). I also obtained Hβimages and the
corresponding offband, obtained to remove stellar
components and continuum radiation. Those images
show the same flux of V605 AQL in the hydrogen line
and of the adjacent continuum. The flux thus stems
from the continuum. I conclude, that this object
is much more hydrogen under-abundant as given in
Guerrero & Manchado (1996). The obtained contin-
uum flux also do not match the prediction in Koller
& Kimeswenger (2001).
As Hinkle et al. (2002), using [O III] and [N II]
HST images, pointed out already, V605 Aql seems
to consist of a dense inner core and a second clump
separated from this region by about 0.5′′. This is
much smaller than the values given by Guerrero &
Manchado (1996), deconvolving ground based im-
ages. Thus a completely closed special geometry can
give only first estimates. The absence of strong blue
continuum straylight from clumps illuminated by a,
1Institut f¨ur Astrophysik der Leopold–Franzens–
Universit¨at Innsbruck, Technikerstr. 25, A-6020 Innsbruck,
Austria (Stefan.Kimeswenger@uibk.ac.at).
5700 5750 5800 5850 5900
wavelength
0
500
1000
flux
Fig. 1. The carbon line C IV5801.5+5812.1(excitation
39eV) is best fitted by two components: The vast ma-
jority of the radiation originates from a wide component
with a FWHM of 2600 km/s (FWZI of 6100 km/s), both
lines also has a narrow component, best fitted by the
same width as the neighboring lines of He Iand N II.
While the wide main component of each line fits to the
systemic velocity of the old PN A58, the narrow compo-
nent is blueshifted in the same way as the other lines of
V605 Aql. This difference in blueshift implies a model
with a optically thick dusty shell covering only a very
small outer section (Koller & Kimeswenger 2001) and a
wide optically thin hot bubble. The complete absence of
other wind lines like O IV5291 as seen in the older twin
A30 leads to the conclusion that the core of V605 Aql
has been eroded down to the pure carbon core of the
star during the 1919 event.
in line of sight hidden, central source excludes the
possibility of an open geometry. On the other hand
the strong [O III]4636 and [Ne III]3869 emission lines
cannot originate from the inner edge of an optically
thick dust shell. Those strong lines were not detected
in the 1994 spectra of Guerrero & Manchado. This
is again an indication of rapid changes in the shell.
REFERENCES
Guerrero, M.A., & Manchado, A. 1996, ApJ, 472, 711
Hinkle, K., Joyce, R., Ridgway, S., Close, L., Lebzelter,
T., & Hron, J. 2002, AAS, 199, 135.11
Koller, J., & Kimeswenger, S. 2001, ApJ, 559, 419
Pollacco, D., Lawson, W.A., Clegg, R.E.S., & Hill, P.W.
1992, MNRAS, 257, 33P
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