The constrained visibility is important for minimizing potentially severe artifacts; if necessary, the constraints could be relaxed a bit, but at some cost to the scientific result. ----- Attempting Submission 1 (Fri Jul 04 03:38:21 GMT 2008) ----- Phase II Proposal 11676 (Cycle17_3068.apt) successfully submitted. ----- Attempting Submission 2 (Wed Jul 23 20:48:00 GMT 2008) ----- Assigned ID: 293 ----- Attempting Submission 1 (Fri Mar 07 08:07:57 GMT 2008) ----- Phase I Proposal 293 (3068.apt) successfully submitted. ----- Attempting Submission 2 (Fri Mar 07 21:56:19 GMT 2008) ----- A Deep ACS Study of the Spiral Outflow from the Extreme Carbon Star, CRL3068 At optical wavelengths, the extreme carbon star, AFGL3068, exhibits a remarkable spiral morphology in its dense, outflowing, circumstellar envelope, showing at least 5 windings of its externally illuminated dust shell around the invisible central star. Near-IR imaging with the Keck Telescope shows that this is a binary system with ~100 AU separation, so the spiral structure seen in the circumstellar outflow is apparently caused by the binary interaction. We propose to obtain relatively deep images of this spiral dust structure with the F475W and F606W filters in order to: 1) image more distant windings of the spiral structure, if they are present, and thereby explore the history of the mass loss rate, and 2) refine the details of the spiral density distribution of dust, for comparison with our existing dynamical & radiative transfer models of gas flow within a binary system containing a star undergoing spherical mass loss. With the proposed imaging in two filters, we will also have the color information for comparison with our models of the external illumination of the dusty envelope by Galactic starlight. Comparable dust "arcs" have been observed in a variety of other post-AGB stars, planetary and preplanetary nebulae, but none is as highly organized, as continuous, nor as clearly defined as the dust structure in AFGL3068. By understanding this favorable case, we hope to gain insights into this whole class of objects.
This observation is designed to obtain relatively deep images of a single target -- the extreme carbon star AFGL3068 -- in two filters. An integration of four orbits will be done in the F606W filter in one visit and an integration of three orbits will be done in the F475W filter in a second visit, both using the ACS with the WFC1 aperture. The mass-losing carbon star has a binary companion with a separation of 0.1 arcsec, so the circumstellar outflow forms a spiral pattern, seen earlier in snapshot observations; the goal of these observations is to follow the archimedean spiral out to a radial distance of 16 arcseconds from the binary, which corresponds to 7 or 8 windings of the spiral. A standard dither pattern will be used for the observations at both wavelengths, with cosmic ray splits taken at each position. A bright star located about 20 arcseconds from the target star projects diffraction spikes across the array, so ORIENT constraints have been set so that these spikes miss the target source area as much as possible. A large ghost from this bright star leads to additional ORIENT constraints to prevent it from landing on the source area. In addition, because the diffraction spikes from the bright star cannot be completely avoided, the two visits are grouped within 72 hours so that the spikes at the two wavelengths fall at approximately the same place. ISM AND CIRCUMSTELLAR MATTER 12 false 0.0 0.0 false false false false false SUPPORTED STAR CARBON STAR CIRCUMSTELLAR MATTER INTERACTING BINARY LONG PERIOD VARIABLE POST-AGB STAR This object was generated by the targetselector and retrieved from the SIMBAD database. CRL3068 J2000 23 19 12.3900 +17 11 35.40 J2000 ACS/WFC Imaging No No F475W ACS/WFC Imaging No No F606W POS-TARG DITHER 0.265 LINE 0.187 false false 69.05 4 20.67 ACS-WFC-DITHER-BOX 1 false Timing link suitability includes constraints ([Group (01 02) Within 3.0 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit36214.xml A bright star with prominent diffraction spikes in our snapshot image of this source lies ~20" to the Northeast of our target in position angle -24 degrees. Because the overall diameter of our target is at least 10", it is critical to minimize their effect, and that of bleeding along the Y direction of the array, by orienting the visit so that the source falls near the center (within ~ +/- 12 D) of the clear quadrants bordered by the diffraction spikes or the Y direction. Two of the four possible quadrants are discluded in order to avoid the ghost of the bright star evident in the snapshot images. The two visits are grouped together with a 72-hour timing constraint so that the diffraction spikes fall at nearly the same place at the two wavelengths being observed, thus minimizing the effects of these spikes on the ratio map. (Tic-Visit :proposal-id 11676 :visit-id "01" :proposal-version -1 :trans-version "20080624" :date "23-Jul-2008 13:43:53.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 3410688 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11676 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11676 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2922 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11676 :visit-id "01" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3060 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11676 :visit-id "01" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3060 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) true 3 0 Timing link suitability includes constraints ([Group (01 02) Within 3.0 days]) The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit36215.xml A bright star with prominent diffraction spikes in our snapshot image of this source lies ~20" to the Northeast of our target in position angle -24 degrees. Because the overall diameter of our target is at least 10", it is critical to minimize their effect, and that of bleeding along the Y direction of the array, by orienting the visit so that the source falls near the center (within ~ +/- 12 D) of the clear quadrants bordered by the diffraction spikes or the Y direction. Two of the four possible quadrants are discluded in order to avoid the ghost of the bright star evident in the snapshot images. The two visits are grouped together with a 72-hour timing constraint so that the diffraction spikes fall at nearly the same place at the two wavelengths being observed, thus minimizing the effects of these spikes on the ratio map. (Tic-Visit :proposal-id 11676 :visit-id "02" :proposal-version -1 :trans-version "20080624" :date "23-Jul-2008 13:44:20.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 4547584 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11676 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11676 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2914 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11676 :visit-id "02" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3060 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11676 :visit-id "02" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3060 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11676 :visit-id "02" :orbit-number 4 :pcs-time 195 :si-vis-utilization 3060 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) true 4 0