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

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SCIENTIFIC ABSTRACT
 This is the second part of a proposal on Planetary and Protoplanetary Nebulae
that  includes  spectro-imaging  and  large  scale  imaging  of  circumstellar
envelopes.   This  part  aims  mainly  to  the  study  of  the outer envelope.
Circumstellar  envelopes  of gas and dust around evolved stars can extend over
several  minutes, but become optically thin at short distance from the central
star:   using  CAM,  we  propose to map in several wide band filters the outer
part  of the envelope of a selection of a few archetypical objects through the
thermal dust emission and the scattered light:  this would give access to:  a)
the history of the mass-loss on a much larger time scale than presently known;
b)  the  structure  of  the  non-symetric  envelopes at a large distance.  The
second  part,  broad-band imaging of a selection of PNs, intends at completing
the program of spectro-imaging by tentative detection at longest wavelength of
a dusty disk and envelope around PNe and PPNe.
OBSERVATION SUMMARY
Part 1: Extended envelopes of PPNs:
 Sources:
 -  OH231.8+4.2:   an OH source with very distinctive properties:  an extended
bipolar  structure with a pronounced waist, a strong ice absorption feature at
3.05 microns, and a large terminal velocity of the outflow;
 -  IRAS  09371+1212  (Frosty Leo nebula):  the most icy envelope known today,
shows  a  disk  and  a weakly collimated very cold (T < 45K) bipolarity;
 -  CRL  2688  (egg  nebula):   the prototype of a collimated extended bipolar
nebula,  with  evidence  for a bipolar cavity, and differing from the previous
one  by  C/O  >  1;
 - CIT-6:  a prototype of close carbon star with a thick envelope.
 Proposed observations:
AOT:   General  Observation  :   Filter  LW9, LW10, SW4, SW5.  PFOV = 1.5 or 3
arcsec.   Complete integration time per filter:  15 to 30 min.  The longer the
integration  time,  the  larger  the  radial  distance  of  the probed region:
angular  radial  distance  of  typically  40  arc-sec will be reached with the
sensitivity  of  CAM.   The  elementary integration time is chosen to have the
pixel of maximum signal at the limit of saturation.
Part 2: Broad-band imaging of PNe
 Sources:
 Classical  PNe and PPNe corresponding to the previous part and to the program
of  spectro-imaging  by  P. Persi et al.:  IC 418, a classical PN; HD 44179, a
bipolar  PPN  (=  Red  Rectangle);  NGC2346,  another bipolar PPN; NGC 6302, a
bipolar PN; NGC 6720, an extended PN with ring; NGC 7027, the archetypal young
PN.   It is proposed to perform images at 15 microns to detect the presence of
a  dusty  disk  and  to  study  the distribution of cold dust.  A rather short
integration  is  sufficient  since only the bright central part is of interest
here.
 Proposed observation:
 AOT:   General  Observation,  Filter  LW9, LW10, PFOV = 1.5 arcsec


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