6022( 5) - 12/08/95 10:03 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6022 Version: 5 Check-in Date: ********** 1.Proposal Title: THE ZZ CETI INSTABILITY STRIP AND STELLAR CONVECTION ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Hot Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Detlev Koester Universitaet Kiel, Kiel CoI: Nicole Allard Observatoire de Paris-Meudon, Meudon N CoI: Gerard Vauclair Observatoire Midi-Pyrenees, Toulouse N ------------------------------------------------------------------------------------ 6. Abstract ZZ Ceti stars are variable white dwarfs of spectral type DA. The theoretically predicted instability strip depends on several uncertain assumptions, most importantly the efficiency of convective energy transport. Empirical determinations from optical spectra are not as accurate as desirable, because the Balmer lines reach maximum strengths within the instability strip and vary only little with temperature. The UV spectrum is much better suited since we have recently improved the quantitative description of the quasi-molecular satellite features, that vary strongly with temperature. The analysis of G117-B15A (in several studies defining the hot edge of the instability strip), which was observed by us in Cycle 2 confirms that an accuracy of 200 K or better can be achieved. It also shows that convection must be more efficient than normally assumed, and that the temperature of G117-B15A is 1000 K lower than determined previously, raising the question that perhaps GD165, the last remaining hot edge candidate with relatively uncertain temperature determination, defines the blue edge. ------------------------------------------------------------------------------------ 6022( 5) - 12/08/95 10:03 - [ 2] Observations Description ------------------------ We want to obtain spectral coverage (time averaged) of the range dominated by the Lyman Alpha red wing satellites, i.e. 1250 - 2500 Angstrom, for the variable white dwarf GD165. With FOS/BL and the G160L grating we will achieve a S/N ranging from 30 around 1400 Angstrom\ (H^+ satellite) to 60 at 1600 Angstrom\ (H satellite), and close to 100 in the continuum longward of the satellites in a single orbit. This project would a few years ago have been marginally feasible with IUE. However, our experience on two occasions in 1993 with combined ESA/NASA shifts has convinced us, that in the present state of the IUE satellite it is not possible. A major reason is that we do not simply want to determine effective temperatures from models with well established input physics, but also determine the effect of different assumptions about convection theory through a detailed study of the line profile between 1250 and 1800 Angstrom. For that we need a good signal to noise ratio, especially in the wing of Lyman Alpha, which cannot at present be obtained with IUE. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6022( 5) - 12/08/95 10:03 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1422+095 STAR, ZZ CETI STAR RA=14H 24M 39.42S +/- 0.3", 2000 F-CONT(1700) = 6 +/-2 E-14 DEC=09D 17' 17.4" +/- 0.3", V=14.32+/-0.2 PLATE-ID=03QS B-V=0.14+/-0.1 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982.3 -0.01475 -0.126 0.0 6022( 5) - 12/08/95 10:03 - [ 4] Visit: 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1422+095 FOS/BL ACQ/BIN 4.3 MIRROR 1 5S ONBOARD ACQ FOR 2 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1422+095 FOS/BL ACCUM 1.0 G160L 1600 1 1290S ------------------------------------------------------------------------------------------------------------------------------------ 6022( 5) - 12/08/95 10:03 - [ 5] Visit: 02 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1422+095 FOS/BL ACQ/BIN 4.3 MIRROR 1 5S ONBOARD ACQ FOR 2 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1422+095 FOS/BL ACCUM 1.0- G160L 1600 1 1290S PAIR-A ------------------------------------------------------------------------------------------------------------------------------------ 6022( 5) - 12/08/95 10:03 - [ 6] Summary Form for Proposal 6022 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Hot Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G160L ------------------------------------------------------------------------------------------------------------------------------------ Target Names WD1422+095 ------------------------------------------------------------------------------------------------------------------------------------