11985( 3) - 27-Jan-2009 01:26:58 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11985 Version: 3 Check-in Time: 27-Jan-2009 01:26:58 STScI Edit Number: 0 Title Polarimetric WFPC2 Imaging of the Dust Torus around the Born-Again Star V605 Aquilae ------------------------------------------------------------------------------------ Type Cycle GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Geoffrey C. Clayton Louisiana State University and A & M College CoI: Dr. Howard E. Bond Space Telescope Science Institute N CoI: Dr. Olivier Chesneau Observatoire de la Cote d'Azur N CoI: Dr. Orsola De Marco American Museum of Natural History N CoI: Dr. Karl D. Gordon Space Telescope Science Institute N CoI: Dr. Florian Kerber Space Telescope - European Coordinating N Facility CoI: Dr. William B. Sparks Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract We propose the first WFPC2 polarimetric imaging of the ejecta surrounding the helium shell final flash (FF) star V605 Aql. Polarimetry is a novel, little-used capability of WFPC2, which can provide confirmation of our proposed morphology of the compact ejecta.. Evolutionary models suggest that V605 Aql is experiencing a very late and very fast thermal pulse. Its evolution from a PN central star on the white-dwarf cooling track, to a cool luminous giant, and then back again, took place in only a few decades or less. V605 Aql, central star of the large, faint, and old planetary nebula A 58, has evolved from a hot central star before the 20th century, to Teff = 5000 K in 1921, and back to 95, 000 K at the present time. A compact, but resolved, dusty nebula lies at the site of V605 Aql. In addition to an extremely hydrogen-deficient nebular emission spectrum, this knot shows stellar features, even though no star-like object is seen within the knot. Therefore, we are probably seeing light from the star scattered around the edge of a thick dust torus viewed nearly edge-on, ejected during the FF event in the early 20th century. Why a star that had already reached the top of the white-dwarf cooling track, and then expanded to become a red giant again, would be capable of such non-spherical ejection is one of the leading mysteries in late stellar evolution. We will use the high resolution of the WFPC2 PC chip to investigate the nature of the V605 Aql torus, employing filters that isolate nebular emission lines. The novel feature of our program is polarimetric imaging in the WF2 chip, using a filter that isolates scattered starlight and rejects nebular emission. If our model is correct, this scattered starlight will be very highly polarized. We will also measure the angular expansion rate of the central knot to constrain the distance. V605 Aql is a unique link between the young FF star Sakurai's Object (10 years old), and the extended FF objects A30 and A78 (few 1000 years old). ------------------------------------------------------------------------------------ 11985( 3) - 27-Jan-2009 01:26:58 - [ 2] Observations Description ------------------------ We will use WFPC2 to carry out direct and polarimetric imaging of the compact nebulosity surrounding the "born-again" star V605 Aquilae. For the direct imaging, we will place the target in the corner of the PC chip (for less degradation by CTE) and taken 2 dithered exposures each in the nebular emission lines [O III] (F502N) and [N II] (F658N). For the polarimetric imaging, we will use Strategy 2c as outlined by Biretta & Sparks in their 1995 WFPC2 ISR on WFPC2 polarimetry. The observations will be taken with the target fixed at 12.5, -12.5 in the WF2 chip (with small dithers about this position), the same telescope ORIENT throughout, and the polarizer quad at four different filter rotations. The polarizers are combined with the F547M filter, which isolates an emission line of the central star and rejects light from gas in the nebula, thus giving information on the light from the star that is scattered by dust in the nebula. We are using CLOCKS=YES throughout, since this yields significantly less time lost to overheads. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11985( 3) - 27-Jan-2009 01:26:58 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V605-AQL ISM, BIPOLAR OUTFLOW, RA=19H18M20.5700S +/- 0.1", J2000 V = 23 +/- 1 EJECTA, EMISSION LINE DEC=+01D46'58.35" +/- 0.1" NEBULA, DUST LANE, PLANETARY NEBULA Reference Frame: ICRS Comments: ------------------------------------------------------------------------------------------------------------------------------------ 11985( 3) - 27-Jan-2009 01:26:58 - [ 4] Visit: 01 Visit Requirements: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V605-AQL WFPC2 IMAGE PC1-FIX F502N ATD-GAIN=7, CR-SPLIT=NO, 1 300 S POS TARG -7, -7 CLOCKS=YES see below ------------------------------------------------------------------------------------------------------------------------------------ 2 V605-AQL WFPC2 IMAGE PC1-FIX F658N ATD-GAIN=7, CR-SPLIT=NO, 1 400 S POS TARG -7, -7 CLOCKS=YES see below ------------------------------------------------------------------------------------------------------------------------------------ 3 V605-AQL WFPC2 IMAGE PC1-FIX F658N ATD-GAIN=7, CR-SPLIT=NO, 1 400 S POS TARG -6.886075, CLOCKS=YES see below -6.886075 ------------------------------------------------------------------------------------------------------------------------------------ 4 V605-AQL WFPC2 IMAGE PC1-FIX F502N ATD-GAIN=7, CR-SPLIT=NO, 1 300 S POS TARG -6.886075, CLOCKS=YES see below -6.886075 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V605-AQL 1 WFPC2 IMAGE PC1-FIX F502N none none none none 1 400.0 S V605-AQL 2 WFPC2 IMAGE PC1-FIX F658N none none none none 1 600.0 S V605-AQL 3 WFPC2 IMAGE PC1-FIX F658N none none none none 1 600.0 S V605-AQL 4 WFPC2 IMAGE PC1-FIX F502N none none none none 1 400.0 S 11985( 3) - 27-Jan-2009 01:26:58 - [ 5] Visit: 02 Visit Requirements: 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1000 S POS TARG 12.5, -12.5 POLQP15 CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 2 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1100 S POS TARG 12.5, -12.5 POLQ CLOCKS=YES see below ------------------------------------------------------------------------------------------------------------------------------------ 3 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1000 S POS TARG 12.5, -12.5 POLQN18 CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ 4 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1100 S POS TARG 12.5, -12.5 POLQN33 CLOCKS=YES see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V605-AQL 1 WFPC2 IMAGE WF2-FIX F547M, none none none none 1 N/A POLQP15 V605-AQL 2 WFPC2 IMAGE WF2-FIX F547M, none none none none 1 1100.0 S POLQ V605-AQL 3 WFPC2 IMAGE WF2-FIX F547M, none none none none 2 N/A POLQN18 V605-AQL 4 WFPC2 IMAGE WF2-FIX F547M, none none none none 2 1100.0 S POLQN33 11985( 3) - 27-Jan-2009 01:26:58 - [ 6] Visit: 03 Visit Requirements: SAME ORIENT AS 02 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1000 S POS TARG 12.749025, POLQP15 CLOCKS=YES -12.3754875 ------------------------------------------------------------------------------------------------------------------------------------ 2 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1100 S POS TARG 12.749025, POLQ CLOCKS=YES -12.3754875 ------------------------------------------------------------------------------------------------------------------------------------ 3 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1100 S POS TARG 12.749025, POLQN18 CLOCKS=YES -12.3754875 ------------------------------------------------------------------------------------------------------------------------------------ 4 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1000 S POS TARG 12.749025, POLQN33 CLOCKS=YES -12.3754875 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V605-AQL 1 WFPC2 IMAGE WF2-FIX F547M, none none none none 1 N/A POLQP15 V605-AQL 2 WFPC2 IMAGE WF2-FIX F547M, none none none none 1 N/A POLQ V605-AQL 3 WFPC2 IMAGE WF2-FIX F547M, none none none none 2 N/A POLQN18 V605-AQL 4 WFPC2 IMAGE WF2-FIX F547M, none none none none 2 N/A POLQN33 11985( 3) - 27-Jan-2009 01:26:58 - [ 7] Visit: 04 Visit Requirements: SAME ORIENT AS 02 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1000 S POS TARG 12.1264625, POLQP15 CLOCKS=YES see below -12.8735375 ------------------------------------------------------------------------------------------------------------------------------------ 2 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1000 S POS TARG 12.1264625, POLQ CLOCKS=YES see below -12.8735375 ------------------------------------------------------------------------------------------------------------------------------------ 3 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1000 S POS TARG 12.1264625, POLQN18 CLOCKS=YES -12.8735375 ------------------------------------------------------------------------------------------------------------------------------------ 4 V605-AQL WFPC2 IMAGE WF2-FIX F547M, ATD-GAIN=7, CR-SPLIT=NO, 1 1100 S POS TARG 12.1264625, POLQN33 CLOCKS=YES -12.8735375 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ V605-AQL 1 WFPC2 IMAGE WF2-FIX F547M, none none none none 1 1100.0 S POLQP15 V605-AQL 2 WFPC2 IMAGE WF2-FIX F547M, none none none none 1 1000.0 S POLQ V605-AQL 3 WFPC2 IMAGE WF2-FIX F547M, none none none none 2 N/A POLQN18 V605-AQL 4 WFPC2 IMAGE WF2-FIX F547M, none none none none 2 N/A POLQN33 11985( 3) - 27-Jan-2009 01:26:58 - [ 8] Summary Form for Proposal 11985 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX, WF2-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN=7, CLOCKS=YES, CR-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements POS TARG -6.886075, -6.886075, POS TARG -7, -7, POS TARG 12.1264625, -12.8735375, POS TARG 12.5, -12.5, POS TARG 12.749025, -12.3754875, SAME ORIENT AS 02 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F502N, F547M, F658N, POLQ, POLQN18, POLQN33, POLQP15 ------------------------------------------------------------------------------------------------------------------------------------ Target Names V605-AQL ------------------------------------------------------------------------------------------------------------------------------------