9092( 2) - 02/13/01 11:15 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9092 Version: 2 Check-in Date: 13-Feb-2001 11:14:55 1.Proposal Title: V605 Aql: Sakurai's older brother ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Kenneth Hinkle National Optical Astronomy Observatories, AURA CoI: Dr. Thomas Lebzelter University of Vienna N CoI: Dr. Richard Joyce NOAO N CoI: Ms. Abigail Hedden Carleton College N ------------------------------------------------------------------------------------ 5. Abstract Post-AGB stars can undergo a final episode of helium shell burning after the star has ejected a planetary nebula and has started on the white dwarf track. Starting in 1996 Sakurai's star has been observed to undergo a final helium shell flash. The same series of events occurred in V605 Aql 91 years ago. These stars both ejected a shell of gas first seen as a pseudo-photosphere and then as a thick dust envelope. The shells are expanding at about 100 km s-1 and in the case of V605 Aql the shell now appears about 1" across. We propose to image this shell with WFPC2. The shell contains ionized material as well as dust. By combining WFPC2 and Gemini high spatial resolution infrared images we will discriminate between bipolar and lumpy models of the circumstellar shell. Since the precursor to the final flash was a white dwarf, as opposed to an AGB star with a complex structure and complex circumstellar environment, the observations will provide a test of the origins of structure in circumstellar shells and planetary nebulae. Comparison with a decade old FOC image may yield the luminosity of V605 Aql. ------------------------------------------------------------------------------------ 9092( 2) - 02/13/01 11:15 - [ 2] Observations Description ------------------------ We will observe the expanding central knot of the planetary nebula A58. This central knot is synonymous with the precursor central star V605 Aql. In ground based observations V605 Aql is marginally resolved indicating a diameter between 0.5 and 1.4 arcsecond. Thus the 0.1 arcsecond pixels of WFC will provide adequate spatial resolution to study the geometry the central knot. Fluxes in the [O III] and [N II] lines have been estimated with the help of a spectrum of this object from the HST archive. Observations will be done in two standard WFPC2 filters centered on these emission lines, namely F502N and F658N. The integration time in each filter will be divided to allow removal of cosmic ray hits. We plan to achieve a S/N ratio of at least 3 per pixel in each filter. A HST pre-COSTAR [O III] image of V605 Aql exists in the archive. V605 Aql is a rapidly expanding shell and so has changed since this image was taken. Also in the new image [O III] V605 Aql will be better resolved to allow us to study the geometry. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9092( 2) - 02/13/01 11:15 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PK037-05D1 STAR, PLANETARY NEBULA RA=19H 18M 20.56S +/- 0.169S, J2000 V = 22 CENTRAL STAR, POST-AGB DEC=1D 46' 58.81" +/- 0.279" STAR, EMISSION LINE NEBULA Coordinate Source: IMAGE_TIED_TO_GSC_FRAME 9092( 2) - 02/13/01 11:15 - [ 4] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 PK037-05D1 WFPC2 IMAGE WF3 F502N 3 350 S ------------------------------------------------------------------------------------------------------------------------------------ 20 PK037-05D1 WFPC2 IMAGE WF3 F658N 2 230 S ------------------------------------------------------------------------------------------------------------------------------------ 9092( 2) - 02/13/01 11:15 - [ 5] Summary Form for Proposal 9092 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures WF3 ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F502N F658N ------------------------------------------------------------------------------------------------------------------------------------ Target Names PK037-05D1 ------------------------------------------------------------------------------------------------------------------------------------