6049( 8) - 11/18/96 13:44 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6049 Version: 8 Check-in Date: 18-Nov-1996 13:41:27 1.Proposal Title: Monitoring the size and shape of Mira-- type stars throughout their pulsation cycles ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Cool Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: MARIO LATTANZI OSSERVATORIO ASTRONOMICO DI TORINO CoI: M.W. Feast University of Cape Town N CoI: U. Munari Osservatorio Astronomico di Padova N CoI: P.A. Whitelock South African Astronomical Observatory N ------------------------------------------------------------------------------------ 6. Abstract We propose to utilize the unmatched angular resolution in the visual of the astrometer FGS, in an attempt to measure SIZES and SHAPES of Miras variables and their variations with the pulsation phase. In particular, it would be possible, for the first time, to cover the full 4\div6 (average) magnitude range of a pulsation cycle with the same instrument and with a fairly high signal--to--noise throughout. The scientific return is potentially very rewarding. Mapping the variations of Mira diameters is of key importance for the detailed understanding of their pulsation mechanism, and ultimately, for the use of Miras as galactic and extragalactic distance indicators. Also, confirmation of elliptical projected disks would set constraints on the existence and relevance of non- radial pulsations. The programme is particularly suited for the FGS, the only orbiting interferometer. It requires, together, all of those outstanding characteristics, high angular resolution, large dynamical range, and faint (for an interferometer) magnitude limit, which make this wide--band visual interferometer unique compared to ground based facilities. ------------------------------------------------------------------------------------ Observations Description ------------------------ To achieve the scientific goals set forth earlier, the science exposures proposed all use the TRANS mode of the astrometer FGS (FGS 3). As described in the FGS Instrument Handbook (Version 4.0), and in recently published papers (Bernacca, Lattanzi et al. 1993, Lattanzi et al. 1994) this mode samples the interference fringe produced by the Koester's prism interferometer, the "heart" of the Fine Guidance Sensor. There are two Koester's prism interferometers in each FGS. These are fed by a beam-- splitter to give sensitivity in two orthogonal directions, usually referred to as X and Y axes. When a TRANS mode observation is executed, the FGS istantaneous field-of-view scans across the target at a fixed 45^degrees angle to the X and Y axes. Therefore, each FGS3 TRANS scan produces two fringes which can then be independently analyzed for signatures other than those characteristic of the FGS3 standard single star UP69. Indeed, deviations from the single star fringes is what is used to measure projected angular diameters (Figs. 1 and 2). Possible asymmetry of the measured X and Y projected diameters are easily oriented on the sky utilizing HST attitude data and the measurements themselves. Although the circumstances for the detectability of any deviation from spherical symmetry are several, the chance is statistically reasonable. Assuming an axially symmetric shape (oblate spheroid), we stand fairly good chances to observe some ellipticity of such shape when projected on the sky (worst case being zero inclination of the axis of symmetry to the observer). The probability is further reduced by the necessity that the semi--major axis of the ellipse be aligned as closely as possible to the FGS axes for maximum effect on the projected fringes. Neverthless, visual interpolation among the simulated fringes in Figs. 1 and 2 shows that it should not be difficult to measure accurately differences of 20\\ in the projected diameters as derived from the X-- and Y- - fringes. Figs. 1 and 2 show also that the FGS should be able to measure variations of 6\\div10 mas in angular diameters larger than 20\\div25 mas. To maximize the accuracy of these measurements, it is necessary to achieve maximum S/N and proper sampling of the interferometric fringe. We than propose to execute 30 TRANS scans per visit (per target). The required on--sky length/scan is 2."1 (1".5 per FGS axis). Each scan is sampled every 0".008, i.e., pixels of 0".006 per FGS axis. Following the Cycle 5 Phase I Proposal Instructions volume, each visit comprises a guide star acquisition (12 min), the set--up time (including the selected filter) for TRANS mode (3 min), then the science exposure. Given that each science exposure consists of 30 TRANS scans of the kind defined above, and that each sample along the scan takes a fixed 0.025 sec, the 30 scans take 31.3 min, for a total of 12+3+31.3 = 46.3 min per visit. This is less than the visibility period per orbit. Therefore, we request one orbit per visit per target. Recent observations (Lattanzi et al. 1994 and references therein) show that scans with the same pixel size and same filter element (PUPIL) give optimal resolution with minimum scan time. Multiple, consecutive scans are required for three reasons. First, spacecraft jitter can corrupt fringes. With multiple scans one can identify jitter--corrupted fringes and reject them. Second, multiple scans are the only reliable way to check on the repeatibility of a detection. Finally, multiple scans are co- -added to increase the signal-- to--noise ratio (S/N). This is crucial for best resolution during the reductions and to allow for star variability (our targets have quite large magnitude variations). Successful exposures should yield co-- added fringes with typical S/N > 60. We request 7 visits per target. All of the visits on R Car and R Leo are in Cycle 5. Two visits of R Cas and one visit of R Hya are left for Cycle 6 in order to complete the coverage of their pulsation cycles. Seven visits per target allow to derive an angular diameter value at any time along the pulsation cycle with an error comparable to that of the measured values (~ sqrt3/7 mas for a perfect cosine model). This is assuming the diameter variations are modelled as a simple cosine function of time with three parameters and a 1--mas error for each of the seven measured diameters. All of our targets will be too bright during part of their pulsation cycles to be observed with the PUPIL element and the 5--mag neutral density filter will then be required. It is necessary to have F5ND fringes of the FGS single star standard UP69. Routine TRANS mode calibration observations on UP69 run by the STScI provide reference data for the PUPIL element but not for the F5ND filter. We have therefore added two F5ND calibration orbits on UP69 in Cycle 5 and we foresee 1 for Cycle 6. Length, pixel size, and number of scans in the calibration visits are the same as for the science observations. The two Cycle 5 calibrations visits will be placed as close in time as possible to the F5ND science observations. Should the STScI Cycle 5 calibration plan for TRANS mode include the F5ND filter , the calibrations orbits requested would not be necessary. Real Time Justification ----------------------- None. We plan to perform coordinated ground-based observations of the proposed targets with the telescopes in Sutherland (RSA) and Asiago (Italy) to which we have regular access as resident astronomers: beginitemize em UBVRI and JHKL photometry to derive bolometric light curves and colours; em high resolution spectroscopy to map the motion of the star atmosphere during the pulsation cycle and to study the profile evolution of emission lines at the head of the Balmer series. enditemize As said earlier, the programme stars are in the HIPPARCOS programme and satisfactory trigonometric parallaxes will therefore become available the beginning of 1996. Angular diameters could then be easily transformed into linear dimensions and, when combined with the photometric and spectroscopic ground-based observations, improve current understanding of the pulsation mechanism in Miras stars. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 STAR, Pulsating RA = 09H 47M 33.465S +/- 0.01S, 2000 V = 8.6+/-0.5 Variable DEC = +11D 25' 43.44" +/- 0.1" Comments: variable color, brightest magnitude V=5.5, faintest V=10.2, Sp=M6 III Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0006 -0.047 0.012 2 HD120285 STAR, Pulsating RA = 13H 49M 02.09S +/- 0.023S , 2000 V = 8.8+/-0.5 Variable DEC = -28D 22' 03.2" +/- 0.3" Comments: variable color, brightest magnitude V=5.8, faintest V=9.7, Sp=M7 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.0029 -0.060 0.0 6049( 8) - 11/18/96 13:44 - [ 2] Visit: 01 Visit Requirements: PCS MODE F BETWEEN 05-NOV-95 AND 14-NOV-95 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 FGS TRANS 3 PUPIL STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 3] Visit: 02 Visit Requirements: PCS MODE F BETWEEN 29-DEC-95 AND 11-JAN-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 4] Visit: 03 Visit Requirements: PCS MODE F BETWEEN 28-JAN-96 AND 10-FEB-96 On Hold Comments: Additional Comments: Pulsating Variable at its MAX brightness Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 5] Visit: 04 Visit Requirements: PCS MODE F BETWEEN 26-FEB-96 AND 11-MAR-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 6] Visit: 05 Visit Requirements: PCS MODE F BETWEEN 27-APR-96 AND 10-MAY-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 FGS TRANS 3 PUPIL STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 7] Visit: 06 Visit Requirements: PCS MODE F BETWEEN 01-JUN-96 AND 14-JUN-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 FGS TRANS 3 PUPIL STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 8] Visit: 07 Visit Requirements: PCS MODE F BETWEEN 20-JUN-96 AND 28-JUN-96 On Hold Comments: Additional Comments: Pulsating Variable at its MIN brightness Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 FGS TRANS 3 PUPIL STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 9] Visit: 08 Visit Requirements: PCS MODE F BETWEEN 7-OCT-96 AND 14-OCT-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD84748 FGS TRANS 3 PUPIL STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 10] Visit: 09 Visit Requirements: PCS MODE F BEFORE 13-FEB-1997 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD120285 FGS TRANS 3 PUPIL STEP-SIZE=0.6,SCANS=15 1 937.0 S SEQ 1-2 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 HD120285 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=15 1 937.0 S ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 11] Visit: 10 Visit Requirements: PCS MODE F BETWEEN 16-DEC-95 AND 25-DEC-95 On Hold Comments: Additional Comments: Pulsating Variable at its MIN brightness Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD120285 FGS TRANS 3 PUPIL STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 12] Visit: 11 Visit Requirements: PCS MODE F BETWEEN 13-JAN-96 AND 26-JAN-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD120285 FGS TRANS 3 PUPIL STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 13] Visit: 12 Visit Requirements: PCS MODE F BETWEEN 08-MAR-96 AND 21-MAR-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD120285 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 14] Visit: 13 Visit Requirements: PCS MODE F BETWEEN 02-MAY-96 AND 15-MAY-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD120285 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 15] Visit: 14 Visit Requirements: PCS MODE F BETWEEN 06-JUN-96 AND 19-JUN-96 On Hold Comments: Additional Comments: Pulsating Variable is at its MAX brightness Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD120285 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 16] Visit: 15 Visit Requirements: PCS MODE F BETWEEN 16-JUL-96 AND 29-JUL-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD120285 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 17] Visit: 16 Visit Requirements: PCS MODE F BETWEEN 09-SEP-96 AND 22-SEP-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 HD120285 FGS TRANS 3 F5ND STEP-SIZE=0.6,SCANS=30 1 1875.0 ------------------------------------------------------------------------------------------------------------------------------------ 6049( 8) - 11/18/96 13:44 - [ 18] Summary Form for Proposal 6049 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TRANS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters STEP-SIZE=0.6 SCANS=30 SCANS=15 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Cool Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F BETWEEN 05-NOV-95 AND 14-NOV-95 PCS MODE F BETWEEN 29-DEC-95 AND 11-JAN-96 PCS MODE F BETWEEN 28-JAN-96 AND 10-FEB-96 PCS MODE F BETWEEN 26-FEB-96 AND 11-MAR-96 PCS MODE F BETWEEN 27-APR-96 AND 10-MAY-96 PCS MODE F BETWEEN 01-JUN-96 AND 14-JUN-96 PCS MODE F BETWEEN 20-JUN-96 AND 28-JUN-96 PCS MODE F BETWEEN 7-OCT-96 AND 14-OCT-96 PCS MODE F BEFORE 13-FEB-1997 SEQ 1-2 NON-INT PCS MODE F BETWEEN 16-DEC-95 AND 25-DEC-95 PCS MODE F BETWEEN 13-JAN-96 AND 26-JAN-96 PCS MODE F BETWEEN 08-MAR-96 AND 21-MAR-96 PCS MODE F BETWEEN 02-MAY-96 AND 15-MAY-96 PCS MODE F BETWEEN 06-JUN-96 AND 19-JUN-96 PCS MODE F BETWEEN 16-JUL-96 AND 29-JUL-96 PCS MODE F BETWEEN 09-SEP-96 AND 22-SEP-96 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements PUPIL F5ND ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD84748 HD120285 ------------------------------------------------------------------------------------------------------------------------------------