14802( 2) - 21-Jul-2016 13:23:17 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14802 Version: 2 Check-in Time: 21-Jul-2016 13:23:17 STScI Edit Number: 0 Title Synoptic Imaging Polarimetry Observations of CRL 2688: What's Whipping the Egg? ------------------------------------------------------------------------------------ Type Cycle GO 24 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Dean C. Hines Space Telescope Science Institute Y CoI: Dr. Joel H. Kastner Rochester Institute of Technology N CoI: Dr. Bruce Balick University of Washington N CoI: Dr. Ruobing Dong University of California - Berkeley N CoI: Dr. Ori Dosovitz Fox Space Telescope Science Institute N CoI: Dr. Stacey N Bright Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract We propose to obtain new imaging polarimetry of the archetypical pre-planetary nebula, CRL 2688 (The Egg Nebula) with the ACS/WFC in the F606W and F775W filters. Pre-planetary nebulae are objects caught in the short-lived, rapidly changing transition phase between the AGB and planetary nebula (PN) stages of stellar evolution. Their morphology bridges the gap between the spherical mass-loss of AGB stars and the surprisingly non-spherical morphologies observed in PN. The mechanism(s) that drives this departure from sphericity is highly debated, and has many implications for stellar and galactic evolution. CRL 2688 is the nearest (to Earth) pre-planetary nebula. Its complex morphology exhibiting lobes, rings, "search light beams, " and a dust lane -- all of which shine in highly polarized light -- make it an ideal specimen for detailed investigation with the high spatial resolution and exquisite polarimetric precision and accuracy provided by HST/ACS. Our proposed observations will be compared with previous ACS imaging polarimetry obtained in 2002 (providing a ~14 year baseline) to: 1) look for secular changes in properties of the scattering particles and scattering geometries within the lobes, rings, SLBs and dust lane; 2) form perpendiculars to the polarization position angles to pinpoint the location of the central illuminating source -- comparison between epochs will place constraints on changes in that source; 3) precisely measure proper motions in the lobes, SLBs, and rings. Our results will provide new insights into the processes that transform the spherical envelopes of a dying low mass stars into the often highly aspherical structures witnessed in planetary nebulae. ------------------------------------------------------------------------------------ Observations Description ------------------------ We will observe CRL 2688 with the WFC on ACS using two broad-band filters (F606W & F775W) combined with the POLV polarizers to obtain imaging polarimetry from 0.48-0.85|um. We use POLV polarizers, as they are most polarimetrically efficient at the desired wavelengths. We chose the F606W to match the observations obtained in 2002; therefore this is a duplicate, but the source structures have changed since then, which is the reason for obtaining new observations. We also include F775W observations to determine the wavelength dependence of the polarization, which in turn places strong constraints on the 14802( 2) - 21-Jul-2016 13:23:17 - [ 2] scattering particles and their scattering geometry. To minimize any systematics caused by residual field distortions in our images relative to the 2002 observations, we constrain the new observations to have a spacecraft orientation (roll) that is within a few degrees of the previous 2002 observations. We use a 4 point box dither to mitigate cosmic rays. We also include a postfash to mitigate CTE effects. ------------------------------------------------------------------------------------ 14802( 2) - 21-Jul-2016 13:23:17 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V-V1610-CYG EXT-STAR, POST-AGB STAR RA=21H02M18.8400S, J2000 V = 17 DEC=+36D41'41.10" Reference Frame: Other: SIMBAD Extended: YES Comments: Highly polarized (30%-70%) preplanetary nebula. The magnitue is an average surface brightness in V-mag/sq. arcsec ------------------------------------------------------------------------------------------------------------------------------------ 14802( 2) - 21-Jul-2016 13:23:17 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.262 Line_Spacing 0.192 Coordinate_Frame POS-TARG Pattern_Orient 18.39 Angle_Between_Sides 68.14 Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 14802( 2) - 21-Jul-2016 13:23:17 - [ 5] Visit: 01 (CRL 2688 POL*V/F606W) Visit Requirements: BETWEEN 08-OCT-2016:00:00:00 AND 22-OCT-2016:00:00:00 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V-V1610-CYG ACS/WFC ACCUM WFC F606W, 1 554 S PATTERN 1 1-3 POL0V (2216 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 V-V1610-CYG ACS/WFC ACCUM WFC F606W, 1 554 S POL60V (2216 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 V-V1610-CYG ACS/WFC ACCUM WFC F606W, 1 554 S POL120V (2216 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ V-V1610-CYG 1 ACS/WFC ACCUM WFC F606W, 1 none none none 1 N/A POL0V V-V1610-CYG 1 ACS/WFC ACCUM WFC F606W, 2 none none none 1 N/A POL0V V-V1610-CYG 1 ACS/WFC ACCUM WFC F606W, 3 none none none 2 N/A POL0V V-V1610-CYG 1 ACS/WFC ACCUM WFC F606W, 4 none none none 3 N/A POL0V V-V1610-CYG 2 ACS/WFC ACCUM WFC F606W, 1 none none none 1 N/A POL60V V-V1610-CYG 2 ACS/WFC ACCUM WFC F606W, 2 none none none 2 N/A POL60V V-V1610-CYG 2 ACS/WFC ACCUM WFC F606W, 3 none none none 2 N/A POL60V V-V1610-CYG 2 ACS/WFC ACCUM WFC F606W, 4 none none none 3 N/A POL60V V-V1610-CYG 3 ACS/WFC ACCUM WFC F606W, 1 none none none 1 N/A POL120V V-V1610-CYG 3 ACS/WFC ACCUM WFC F606W, 2 none none none 2 N/A POL120V V-V1610-CYG 3 ACS/WFC ACCUM WFC F606W, 3 none none none 3 N/A POL120V V-V1610-CYG 3 ACS/WFC ACCUM WFC F606W, 4 none none none 3 N/A POL120V 14802( 2) - 21-Jul-2016 13:23:17 - [ 6] Visit: 02 (CRL 2688 POL*V/F775W) Visit Requirements: SAME ORIENT AS 01; BETWEEN 08-OCT-2016:00:00:00 AND 22-OCT-2016:00:00:00; SEQ 01, 02 WITHIN 4 Orbits On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V-V1610-CYG ACS/WFC ACCUM WFC F775W, 1 554 S PATTERN 1 1-3 POL0V (2216 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 V-V1610-CYG ACS/WFC ACCUM WFC F775W, 1 554 S POL60V (2216 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 V-V1610-CYG ACS/WFC ACCUM WFC F775W, 1 554 S POL120V (2216 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ V-V1610-CYG 1 ACS/WFC ACCUM WFC F775W, 1 none none none 1 N/A POL0V V-V1610-CYG 1 ACS/WFC ACCUM WFC F775W, 2 none none none 1 N/A POL0V V-V1610-CYG 1 ACS/WFC ACCUM WFC F775W, 3 none none none 2 N/A POL0V V-V1610-CYG 1 ACS/WFC ACCUM WFC F775W, 4 none none none 3 N/A POL0V V-V1610-CYG 2 ACS/WFC ACCUM WFC F775W, 1 none none none 1 N/A POL60V V-V1610-CYG 2 ACS/WFC ACCUM WFC F775W, 2 none none none 2 N/A POL60V V-V1610-CYG 2 ACS/WFC ACCUM WFC F775W, 3 none none none 2 N/A POL60V V-V1610-CYG 2 ACS/WFC ACCUM WFC F775W, 4 none none none 3 N/A POL60V V-V1610-CYG 3 ACS/WFC ACCUM WFC F775W, 1 none none none 1 N/A POL120V V-V1610-CYG 3 ACS/WFC ACCUM WFC F775W, 2 none none none 2 N/A POL120V V-V1610-CYG 3 ACS/WFC ACCUM WFC F775W, 3 none none none 3 N/A POL120V V-V1610-CYG 3 ACS/WFC ACCUM WFC F775W, 4 none none none 3 N/A POL120V 14802( 2) - 21-Jul-2016 13:23:17 - [ 7] Summary Form for Proposal 14802 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WFC ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 08-OCT-2016:00:00:00 AND 22-OCT-2016:00:00:00, PATTERN 1 1-3, SAME ORIENT AS 01, SEQ 01, 02 WITHIN 4 Orbits ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F606W, F775W, POL0V, POL120V, POL60V ------------------------------------------------------------------------------------------------------------------------------------ Target Names V-V1610-CYG ------------------------------------------------------------------------------------------------------------------------------------