Contents of: VI/111/./abstract/MMEIXNER_PPNAFS.abs

The following document lists the file abstract/MMEIXNER_PPNAFS.abs from catalogue VI/111.
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==> In this proposal, more time is being requested for MMEIXNER.PROP_AFS.
==> This proposal requests an upgrade from Priority 3 for MMEIXNER.PROP_AFS.
During the last stages of its evolution, low mass stars (<8 Msol) loose about
1 Msol in the form of a cool, low velocity (10 km/s) molecular wind on
the Asymptotic Giant Branch (AGB). This phase is thought to end with a burst
of increasing mass loss rate (the "superwind") which largely exhausts the
star.  The star then moves to the left in the HR diagram (the proto-
planetary nebula phase, PPN). Once the central star becomes hot enough, the
still expanding AGB wind will be ionized. At some point during its evolution,
the central star will start losing mass in a fast (100-1000 km/s) but low
density wind. This fast wind will drive fast shocks into the AGB wind.
The interaction of these winds and the hardening of the UV radiation field
will shape the resulting planetary nebula.  Understanding this mass loss
process and its evolution during the AGB, PPN and PN phases is a key problem
within astrophysics because most of interstellar gas and dust originates
from these stellar sources.
Here, we propose high resolution spectroscopy  of far-infrared atomic
fine structure lines in  IRAS 22272+5435 (PPN), Hb 12 (PN), and BD
30+3639 (PN).   IRAS 22272+5435 has  been detected in the [CII] 158
um line in the central programme and our proposed observations follow
up on this important discovery.  Hb 12  is the classical example of a
PNe with a photodissociation region.  BD 30+3639 has unusually high
velocity molecular gas out flow suggestive of shocks.  In all three
cases,  our proposed observations of the far-infrared atomic fine
structure lines will provide information on the relative importance of
photodissociation and shocks in these objects.

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