9179( 4) - 01/11/02 10:53 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9179 Version: 4 Check-in Date: 11-Jan-2002 10:52:18 1.Proposal Title: Calibrating convection efficiency with quasi-molecular features in magnetic white dwarfs ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Stefan Jordan Universitat Kiel CoI: Prof. Dr. Detlev Koester Universitaet Kiel, ITAP N CoI: Dr. Boris T. Gaensicke Universitaetssternwarte Goettingen N CoI: Dr. Peter Schmelcher Institut fuer Physikalische Chemie, N Universitaet Heidelberg CoI: Dr. Nicole F. Allard Observatoire de Paris-Meudon, Departement N Atomes et Molecules en Astrophysique CoI: Dr. Burkhard Wolff Universitaet Kiel, ITAP N CoI: Dr. Susanne Friedrich Universitaet Kiel, ITAP N ------------------------------------------------------------------------------------ 5. Abstract We have discovered quasi-molecular absorption features of Lyman Alpha (at ~ 1400 and 1600 Angstrom) in UV spectra of magnetic white dwarfs taken with IUE; hitherto such features have only been known in non-magnetic objects where they offered a very accurate determination of the atmospheric parameters. With high quality HST/STIS UV spectra of five white dwarfs we will for the first time be able to study the molecular potential of H_2 and H_2^+ under the influence of a magnetic field and to compare the results to theoretical calculations. Besides the relevance for atomic and molecular physics, the HST observations will be a tool to precisely determine effective temperatures and gravities (and thereby age and mass). Even more important is the possibility to test the efficiency of convection under the influence of a strong magnetic field and to find out how strongly the degree of ionization equilibrium is modified by the magnetic field. Convection is a completely free parameter in the computation of the model atmospheres and the analyses of all magnetic white dwarfs with effective temperatures between 10000 K and about 17000 K suffer from this uncertainty. Finally, one of our target stars is within an close binary (AM Her-type), and provides us with the possibility to test how the quasi- molecular features change due to the enrichment of the hydrogen atmosphere with heavy elements from the secondary star. ------------------------------------------------------------------------------------ 9179( 4) - 01/11/02 10:53 - [ 2] Observations Description ------------------------ We propose to observe our program stars with the G140L grating and the 52*0.2 aperture, giving approximately 1Angstrom \ resolution. In order to detect significant deviations from zero-magnetic field profiles for the quasi- molecular features a S/N ratio between about 20 (for KUV23162 and GD90 with very strong quasi-molecular features detected or predicted) and about 60 (for the object with weaker absorption features) is necessary. Subtracting the guide star acquisition (6min), the target acquisition (6min), and the STIS/\-MAMA overhead (8min), leaves 32-36 min on-target time for the exposure. For all stars but GD 90 one orbit is sufficient (see table for the S/N ratio estimated with the STIS Exposure Time Calculater); in the case of GD 90 three orbits are needed. The overhead (1 min) and acquisition time (5 min) for the second and third orbit is reduced and results in 2* 48 min of exposure time (in total: 130 min). Orbits and resulting S/N ratios Object &Alt. Name &Orbits &Exp. time / min &S/N RX J1313-32 & &1 &33 &39 WD 1017+366 &GD 116 &1 &34 &57 WD 1743-521 &BPM 25114 &1 &36 &43 WD 2316+123 &KUV 23162 &1 &32 &22 WD 0816+376 &GD 90 &3 &130 &21 Real Time Justification ----------------------- The accretion state of RX J1313-32 will be monitored through collaborations with CTIO and SAAO. The observation of RX J1313-32 will be put ON-HOLD until a low state is confirmed by ground-based photometry. As the system is characterized by long lasting low states (>=6 months; Thomas et al. 1999), the STIS visit can easily be fed into the normal HST schedule after notification of the low state. For the single white dwarfs no such constraints exist. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9179( 4) - 01/11/02 10:53 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WD0816+376 STAR, DA RA=08H 19M 46.64S +/- 0.03S, J2000 V = 15.6+/-0.1 DEC=37D 31' 29.06" +/- 0.3", B-V = 0.22+/-0.1 PLATE-ID=02D5 F(1300)=0.3+/-0.3e-15 F(1500)=3.6+/-0.5e-15 F(1700)=6.9+/-0.5e-15 Coordinate Source: GSC_SURVEY_PLATE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.3132 -0.0113 -0.0891 0.0 2 WD1017+366 STAR, DA RA=10H 20M 54.21S +/- 0.03S, J2000 V = 15.96+/-0.1 DEC=36D 26' 49.21" +/- 0.3", B-V = 0.0+/-0.1 PLATE-ID=01R3 F(1300)=2.8+/-0.5e-14 F(1500)=2.8+/-0.5e-14 F(1700)=2.0+/-0.5e-14 Coordinate Source: GSC_SURVEY_PLATE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.1320 -0.0027 -0.1322 0.0 3 WD1743-521 STAR, DA RA=17H 47M 46.74S +/- 0.03S, J2000 V = 15.74+/-0.1 DEC=-52D 7' 8.81" +/- 0.2", B-V = 0.09+/-0.1 PLATE-ID=0689 F(1300)=1.4+/-0.5e-14 F(1500)=3.2+/-0.5e-14 F(1700)=2.5+/-0.3e-14 Coordinate Source: GSC_SURVEY_PLATE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1987.6970 0.00697 -0.09498 0.0 4 WD2316+123 STAR, DA RA=23H 18M 44.99S +/- 0.03S, J2000 V = 15.53+/-0.15 DEC=12D 36' 2.99" +/- 0.5", B-V = 0.08+/-0.08 PLATE-ID=00JE F(1300)=0.2+/-0.2e-14 F(1500)=1.2+/-0.3e-14 F(1700)=1.5+/-0.2e-14 Coordinate Source: GSC_SURVEY_PLATE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982.7939 0.0092 -0.0418 0.0 5 RXJ1313.2- STAR, Polar RA=13H 13M 17.12S +/- 0.02S, J2000 V = 16.0+/-0.5 3259 DEC=-32D 59' 12.24" +/- 0.3", F(1300)=1.4+/-0.2e-14 PLATE-ID=03DS F(1500)=1.4+/-0.3e-14 F(1700)=0.8+/-0.2e-14 Coordinate Source: GSC_SURVEY_PLATE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1975.4094 0.0 0.0184 0.0 9179( 4) - 01/11/02 10:53 - [ 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 WD0816+376 STIS/C ACQ F28X50L MIRROR 1 2 S CD P Comments: ACQ for 20-40 ------------------------------------------------------------------------------------------------------------------------------------ 20 WD0816+376 STIS/F ACCUM 52X0.2 G140L 1425 1 2449 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 WD0816+376 STIS/F ACCUM 52X0.2 G140L 1425 1 2979 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 WD0816+376 STIS/F ACCUM 52X0.2 G140L 1425 1 2979 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9179( 4) - 01/11/02 10:53 - [ 5] Visit: 02 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 WD1017+366 STIS/C ACQ F28X50L MIRROR 1 2 S CD P Comments: ACQ for 20 ------------------------------------------------------------------------------------------------------------------------------------ 20 WD1017+366 STIS/F ACCUM 52X0.2 G140L 1425 1 2469 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9179( 4) - 01/11/02 10:53 - [ 6] Visit: 03 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 WD1743-521 STIS/C ACQ F28X50L MIRROR 1 2 S CD P Comments: ACQ for 20 ------------------------------------------------------------------------------------------------------------------------------------ 20 WD1743-521 STIS/F ACCUM 52X0.2 G140L 1425 1 2592 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9179( 4) - 01/11/02 10:53 - [ 7] Visit: 04 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 WD2316+123 STIS/C ACQ F28X50L MIRROR 1 2 S CD P Comments: ACQ for 20 ------------------------------------------------------------------------------------------------------------------------------------ 20 WD2316+123 STIS/F ACCUM 52X0.2 G140L 1425 1 2391 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9179( 4) - 01/11/02 10:53 - [ 8] Visit: 05 Visit Priority: Visit Requirements: ON HOLD On Hold Comments: the visit will be executed after that ground-based CCD photometry confirms that RXJ1313 is in a state of low accretion. 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 RXJ1313.2-3 STIS/C ACQ F28X50L MIRROR 1 3 S 259 CD P Comments: ACQ for 20 ------------------------------------------------------------------------------------------------------------------------------------ 20 RXJ1313.2-3 STIS/F TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2320 S 259 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9179( 4) - 01/11/02 10:53 - [ 9] Visit: 1A 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 WD0816+376 STIS/C ACQ F28X50L MIRROR 1 2 S CD P Comments: ACQ for 20-40 ------------------------------------------------------------------------------------------------------------------------------------ 20 WD0816+376 STIS/F TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2399 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 30 WD0816+376 STIS/F TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2979 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 40 WD0816+376 STIS/F TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2979 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9179( 4) - 01/11/02 10:53 - [ 10] Summary Form for Proposal 9179 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=300 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ON HOLD ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names WD0816+376 WD1017+366 WD1743-521 WD2316+123 RXJ1313.2-3259 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------