8254( 7) - 04/12/00 11:52 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8254 Version: 7 Check-in Date: 12-Apr-2000 11:51:27 1.Proposal Title: A Unique Calibration of Asteroseismology: the DBV GD358 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Donald Winget University of Texas at Austin CoI: Prof. S.O. Kepler Universidade Federal do Rio Grande do Sul N CoI: Atsuko Nitta University of Texas at Austin N CoI: Dr. Antonio Kanaan Universidade Federal do Rio Grande do Sul N ------------------------------------------------------------------------------------ 5. Abstract An improved understanding of the white dwarf stars has a great potential in both physics and astronomy. Determination of the basic physical parameters of the white dwarf stars will help us realize that potential; asteroseismology is the key. We can use asteroseismology to constrain the stellar structure and evolution, including the stellar mass and even the stellar distance if we can determine the pulsation indices (k, \ell, m) of the non-radial g-mode light variations observed in compact pulsators. We made tentative identifications for GD 358 using a method based on the frequency distribution of consecutive radial overtone g-modes. A comparison of the amplitude of the pulsation between the optical and the UV proves to be another independent method to identify the pulsation indices. Our project is to apply both methods to GD358. We will measure the optical amplitude with ground-based time series photometry. By observing the DBV star GD 358 with the HST, we have a unique op portunity to cross-calibrate the t wo methods -- essential if we are to have confidence in the conclusions drawn from either method. The future of asteroseismology of white dwarf stars hinges on these observations. We attempted this science previously with HST. The observations were successful, but GD358 had other ideas (See Justify Duplications section). This exciting data set only adds to the importance of the proposed calibration observation. ------------------------------------------------------------------------------------ 8254( 7) - 04/12/00 11:52 - [ 2] Observations Description ------------------------ According to the STIS exposure time calculator, the local peak count rate is 3.862 counts/sec/pix. After acquiring data, we will co-add the data in 50 Angstrom and 20 sec bins to get lightcurves with a sampling rate that will give1 us S/N sufficient to determine the amplitude of the pulsation modes if present, and find out their \ell value. We choose the G140L grating because the amplitude of pulsation with different \ell is specially sensitive to the spectral region allowed by this grating. We will use 52 * 0.5 slit to get as much light as possible from the star without the complication arising from the flat fielding. The flat fielding done by illuminating the entire slit will not be appropriate for the star which is a point source if we used a larger slit. The 52 * 0.5 slit will avoid this problem without loosing too much light from the target. This aperture will require on-board acquisition. Since the pulsation modes can go through beating, we request three visits, two three- orbit observations and one four-orbit observation, to make sure we can resolve the pulsation modes. In order to apply M2 successfully, the HST observation must be accompanied with ground base observation. In order to coordinate this, we ask all visits to be scheduled within 2 weeks of each other Real Time Justification ----------------------- This project is a Time-Critical observation as we must obtain the data in UV and optical simultaneously. We will coordinate the ground observation with the HST observation by using the BETWEEN constraints once we know the telescope time allocated on the ground. We will have a coordinated ground observation with selected sites of the Whole Earth Telescope collaboration to ensure simultaneous observation with the HST. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: YES Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8254( 7) - 04/12/00 11:52 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 GD358 STAR, DB, PULSATING RA=16H 47M 18.64S +/- 0.3", J2000 V = 13.65 VARIABLE DEC=32D 28' 32.32" +/- 0.3", B = 13.54 PLATE-ID=0380 B-V = -0.11 U-B = -1.04 F(2646)=9.95e-14 Coordinate Source: Comments: Parallax and Proper motion from "The General Catalogue of Trigonometric Stellar Parallaxes", forth Edition, 1995, van Altena, Lee, and Hoffleit, Yale University Observatory. Flux from Bica et al., 1996, AAS, 119, 211 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) B1983.292 -0.01156 0.039 0.0273 8254( 7) - 04/12/00 11:52 - [ 4] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 31-May-2000:22:00:00.0 AND 05-Jun-2000:03:30:00.0 On Hold Comments: Additional Comments: The HST observation must be accompanied by the ground-based observation. BETWEEN requirements enforce this. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 GD358 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S SEQ 10-20 NON-INT CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 35 M UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 30 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 43 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 40 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 42 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8254( 7) - 04/12/00 11:52 - [ 5] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 31-May-2000:22:00:00.0 AND 05-Jun-2000:03:30:00.0 On Hold Comments: Additional Comments: The HST observation must be accompanied by the ground-based observation. BETWEEN requirements enforce this. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 GD358 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S SEQ 10-20 NON-INT CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 35 M UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 30 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 43 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 40 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 42 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8254( 7) - 04/12/00 11:52 - [ 6] Visit: 03 Visit Priority: Visit Requirements: BETWEEN 31-May-2000:22:00:00.0 AND 05-Jun-2000:02:00:00.0 On Hold Comments: Additional Comments: The HST observation must be accompanied by the ground-based observation. BETWEEN requirements enforce this. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 GD358 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.0 S SEQ 10-20 NON-INT CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 35 M UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 30 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 43 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 40 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 43 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 50 GD358 STIS/F TIME-TA 52X0.5 G140L 1425 BUFFER-TIME=150 1 43 M NO SPLIT UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 8254( 7) - 04/12/00 11:52 - [ 7] Summary Form for Proposal 8254 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT BUFFER-TIME=150 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 31-May-2000 22 00 00.0 AND 05-Jun-2000 03 30 00.0 SEQ 10-20 NON-INT NO SPLIT BETWEEN 31-May-2000 22 00 00.0 AND 05-Jun-2000 03 30 00.0 BETWEEN 31-May-2000 22 00 00.0 AND 05-Jun-2000 02 00 00.0 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names GD358 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------