9082( 2) - 01/29/01 13:08 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9082 Version: 2 Check-in Date: 29-Jan-2001 13:08:21 1.Proposal Title: Expansion distances to the symbiotic Miras He 2-104 and He 2-147 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Romano Corradi Isaac Newton Group, Observatorio del Roque de los Muchachos CoI: Prof. Ulisse Munari Padova and Asiago Astronomical N Observatories CoI: Dr. Francesca R. Boffi Space Telescope Science Institute N CoI: Dr. Mario Livio Space Telescope Science Institute N ------------------------------------------------------------------------------------ 5. Abstract We propose to measure the expansion parallax of the nebulae around the binary symbiotic Miras He 2-104 (the Southern Crab) and He 2-147 by means of high resolution WFPC2/F658N images to be taken at two different epochs. Given the large outward velocities of these nebulae inferred from ground-based spectroscopy, their apparent expansion can be measured by HST imaging over timescales of only 2-3 years. For He 2-104 we have already obtained ``Epoch 1'' HST images (cf. STScI-PRC- PR99- 32). Combining the angular and radial velocity expansions will straightforwardly yield the distance to the proposed targets. Knowledge of the distance to these nebulae will provide a solid contribution to a variety of research fields such as (a) the energetics of nuclear burning in symbiotic binaries containing a Mira, (b) the pulsation mode of binary Miras, and (c) the viability of Mira symbiotics as supersoft X-ray sources and potential progenitors of Type Ia supernovae. HST high resolution imaging of the nebulae combined with ground-based spectroscopy will also address the still debated issue of the formation of bipolar nebulae by collimated outflows from evolved stars. ------------------------------------------------------------------------------------ 9082( 2) - 01/29/01 13:08 - [ 2] Observations Description ------------------------ We propose to observe He 2-104 and He 2-147 in the light of N II 6583 Angstrom with the WFPC2 camera. Observing in the N II line has the following advantages: i) N II6583 is the brightest line in the extended nebulae of all symbiotic Miras in the range 350-1200 nm; ii) the contrast in luminosity between the central source and the much fainter extended nebula is strongly reduced as compared, for instance, to H-alpha, limiting the oversaturation of the unresolved central source. Excellent results have been already obtained with HST NII imaging for He 2-104 on May 1999. We plan now to take `Epoch 2' images during cycle 11 (>=3 yr later) with exactly the same instrumental configuration and orientation of the nebula in the WFPC2 CCDs. As for He 2-147, according to our ground-based spectra the N II luminosity of the unresolved central source is of 3E-13 erg cm-2 sec-1. From ground-based images the surface brightness of the ring nebula is estimated to be 1E-14 erg cm-2 sec-1 arcsec-2. To record the nebula with a good S/N ratio while avoiding strong oversaturation of the central source, a total exposure of about 3800 sec split into 8 exposures of 400 sec each, and 4 exposures of 140 sec each, is planned. The long exposures will allow us to reach a S/N>=6 per PC pixel (gain 15) in the ring. The short ones will allow us to have the central source well exposed without saturation. Dithering will be performed to improve spatial resolution. Including overheads for the exposures, dithering, guide star acquisition and re-acquisition, clock synchronization, and filter positioning, it makes 2 spacecraft orbits. Standard calibration files are required. Epoch 1 observations for He 2-147 (2 orbits, see above) are expected to be performed as early as possible during Cycle 10, and Epoch 2 observations (another 2 orbits) during Cycle 12 at least 2 years later. To allow for precise comparison of images in different epochs, the same centering on the PC camera, ORIENT parameter, and exposure times will be used. Real Time Justification ----------------------- It woould be important to schedule the `Epoch 1' images of He2-147 as early as possible in Cycle 10, or even better in the slots of visibility at the end of cycle 9 (March 4 - May 3, and May 13-24, 2001), to allow for a large enough gap (>2 yr) before the `Epoch 2' observations to be obtained during cycle 12. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9082( 2) - 01/29/01 13:08 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PK327-04D1 STAR, SYMBIOTIC STAR, RA=16H 14M 1.0S +/- 0.1S, DEC=- J2000 V = -30 V = 15+/-2 EMISSION LINE NEBULA, 56D 59' 26.8" +/- 0.5", PLATE- F-LINE(6583)=3+/-2e-13 EJECTA, AGB STAR, NOVA- ID=06PU SURF-LINE(6583)=1e-14 LIKE Coordinate Source: GSC_SURVEY_PLATE 9082( 2) - 01/29/01 13:08 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFPC2-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.559017 Coordinate_Frame POS-TARG Pattern_Orient 26.565051 Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 9082( 2) - 01/29/01 13:08 - [ 5] Visit: 01 Visit Priority: Visit Requirements: ORIENT 120D TO 153D ORIENT 300D TO 330D On Hold Comments: Additional Comments: The two ranges indicated for the ORIENT parameter (about 180 deg from each other) are equally good. It would be highly desirable to schedule the visit as early as possible in Cycle 10, or even better in the slots of visibility at the end of cycle 9 (March 4 - May 3, and May 13-24, 2001), to allow for a large enough gap before the `Epoch 2' observations to be obtained during Cycle 12. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 PK327-04D1 WFPC2 IMAGE PC1-FIX F658N ATD-GAIN=15 1 140 S PATTERN 1 10-20 ------------------------------------------------------------------------------------------------------------------------------------ 20 PK327-04D1 WFPC2 IMAGE PC1-FIX F658N ATD-GAIN=15 2 400 S ------------------------------------------------------------------------------------------------------------------------------------ 9082( 2) - 01/29/01 13:08 - [ 6] Summary Form for Proposal 9082 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PC1-FIX ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ATD-GAIN=15 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 120D TO 153D ORIENT 300D TO 330D PATTERN 1 10-20 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F658N ------------------------------------------------------------------------------------------------------------------------------------ Target Names PK327-04D1 ------------------------------------------------------------------------------------------------------------------------------------