9893( 6) - 05/11/04 15:46 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9893 Version: 6 Check-in Date: 11-May-2004 19:42:46 1.Proposal Title: The field structure of the most strongly magnetized white dwarf PG1031+234 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance GO 12 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Stefan Jordan Universitat Tubingen, Institut fur Astronomie & Astrophysik CoI: Dr. Boris T. Gaensicke University of Southampton N CoI: Dr. Gary D. Schmidt University of Arizona N ------------------------------------------------------------------------------------ 6. Abstract With a maximum field strength of 1 GG PG1031+234 has the strongest magnetic field found in any white dwarf. Since magnetic fields generated on earth are limited to a few MG, this star is an important cosmic laboratory to test the atomic data calculated for field strengths which are similar to those in recyled millisecond pulsars. Our aim is to take phase resolved FUV spectra covering the rotational (spin) period of 204 minutes. The variation of the position and shape of the Lyman alpha components is very important for a detailed mapping of magnetic field topology, which is believed - according to an analysis of the optical data - to consist of a general dipole field with a polar field strength of 500 MG and a magnetic spot with a field reaching 1 GG. Moreover, we will search for the forbidden 1s0 -> 2s0 transition of hydrogen which would indicate the additional presence of an electric field, and, for quasi-molecular features of hydrogen which would provide constraints on the detailed temperature structure of the atmosphere. It is also important to redetermine the effective temperature with time resolved UV data, since an inconsistency between the analysis of IUE spectrum (Teff approx. 25000 K), integrated over one full rotational period, and the optical spectrum (15000 K) exists which is also reflected in a large uncertainty of the mass determination. ------------------------------------------------------------------------------------ 9893( 6) - 05/11/04 15:46 - [ 2] Observations Description ------------------------ Our scientific goals require time-resolved FUV spectroscopy covering an entire 204 min spin cycle of PG 1031+234. Given its declination, the target is visible for 53 min. Accounting for the overhead times - first guide star acq. 6 min, guide star re-acq. 5 min, target acq. 6 min, instrument overhead 8 min - we request 6 HST orbits. Because of the beat between HST's orbit and the spin phase of PG 1031+234, the observations have to be scheduled in two separate visits (1+2) of three orbits each, separated by a 6-orbit gap. The instrument setup to be used is the G140L grating and the 52x0.2 arc second aperture, providing a spectral resolution of R approx. 1000, fully sufficient to resolve the Lyman-alpha components. The observations will be be carried out in the TIME-TAG mode, allowing for an arbitrary binning in time. We expect to achieve a signal-to-noise ratio of more than 20 over the entire observed wavelength range in about 15 min. This superb spin phase resolution (Delta phi=0.075) will permit to reconstruct the magnetic feld topology in PG 1031+234 by use of our Zeeman tomography. During the second half of the last HST orbit (12) of visit 2, we will switch to the STIS/CCD channel and obtain two single 3 min exposure with the G430L (2900-5700A) and the G750L (5236-10266 A) gratings. The total time spent in the STIS/CCD configuration are 2x(3min exposure + 5 min overhead)=16 min. These optical spectra with S/N> 20 over most of the covered wavelength range are necessary to identify from the Balmer line positions the optical spin phase corresponding to our FUV observations. This strategy is essential for the successful modelling of the field topology model for PG 1031+234. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9893( 6) - 05/11/04 15:46 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PG1031+234 STAR, DA RA=10H33M49.27S +/- 0.3", J2000 V = 15.1+/-0.5 DEC=+23D09'16.26" +/- 0.3", F(1500)=5.0+/-0.5e-14 PLATE-ID=0259 Coordinate Source: GSC_SURVEY_PLATE Comments: Magnetic DA White Dwarf Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1983.037 -0.0039 0.0226 0.0 9893( 6) - 05/11/04 15:46 - [ 4] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 30% On Hold Comments: Additional Comments: First part of three exposures (1, 2, 3) Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PG1031+234 STIS/CCD ACQ F28X50LP MIRROR 1 2 S Comments: ACQ for PG1031+234 first visit ------------------------------------------------------------------------------------------------------------------------------------ 2 PG1031+234 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2285 S -MAMA G Comments: Exposure als long as possible to fill the orbit ------------------------------------------------------------------------------------------------------------------------------------ 3 PG1031+234 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2879 S -MAMA G Comments: Exposure als long as possible to fill the orbit ------------------------------------------------------------------------------------------------------------------------------------ 4 PG1031+234 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2879 S -MAMA G Comments: Exposure als long as possible to fill the orbit ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 01 1 none none none none 1 tbd 01 2 none none none none 1 tbd 01 3 none none none none 2 tbd 01 4 none none none none 3 tbd 9893( 6) - 05/11/04 15:46 - [ 5] Visit: 02 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 30%; AFTER 01 BY 9.9 Orbits TO 10.1 Orbits On Hold Comments: Additional Comments: Second part of three exposures (4, 5, 6) after 6 orbit gap (10th, 11th, 12th) orbit PC changed link to after by 9.9 to 10.6 orbits. 9 would represent the above, but infeasable due to SAA. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PG1031+234 STIS/CCD ACQ F28X50LP MIRROR 1 2 S Comments: ACQ for PG1031+234 second visit ------------------------------------------------------------------------------------------------------------------------------------ 2 PG1031+234 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2285 S -MAMA G Comments: Exposure als long as possible to fill the orbit ------------------------------------------------------------------------------------------------------------------------------------ 3 PG1031+234 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 2879 S -MAMA G Comments: Exposure als long as possible to fill the orbit ------------------------------------------------------------------------------------------------------------------------------------ 4 PG1031+234 STIS/FUV TIME-TA 52X0.2 G140L 1425 BUFFER-TIME=300 1 1756 S -MAMA G Comments: Exposure als long as possible to fill the orbit ------------------------------------------------------------------------------------------------------------------------------------ 5 PG1031+234 STIS/CCD ACCUM 52X0.2 G430L 4300 1 180 S Comments: First of two optical (2900-5700A) CCD exposures for phase synchronization ------------------------------------------------------------------------------------------------------------------------------------ 6 PG1031+234 STIS/CCD ACCUM 52X0.2 G750L 7751 1 180 S Comments: Second of two optical (5236-10266A) CCD exposures for phase synchronization ------------------------------------------------------------------------------------------------------------------------------------ 7 CCDFLAT STIS/CCD ACCUM 52X0.2 G750L 7751 2 DEF Comments: Flatfield to correct for fringes in the red/infrared. Default Time suggested by support astronomer Alison Vick ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 02 1 none none none none 1 tbd 02 2 none none none none 1 tbd 9893( 6) - 05/11/04 15:46 - [ 6] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Visit Id| Exp Id |Primary |Secondary |Iteration |CR-SPLIT |Orbit Num |Duration | |Pattern Pos |Pattern Pos |Num |Num | | ------------------------------------------------------------------------------------------------------------------------------------ 02 3 none none none none 2 tbd 02 4 none none none none 3 tbd 02 5 none none none 1 3 tbd 02 5 none none none 2 3 tbd 02 6 none none none 1 3 tbd 02 6 none none none 2 3 tbd 02 7 none none 1 none 3 tbd 02 7 none none 2 none 3 tbd 9893( 6) - 05/11/04 15:46 - [ 7] Summary Form for Proposal 9893 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=300 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE; SCHED 30% PCS MODE FINE; SCHED 30%; AFTER 01 BY 9.9 Orbits TO 10.1 Orbits ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L G430L G750L ------------------------------------------------------------------------------------------------------------------------------------ Target Names PG1031+234 CCDFLAT ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 4300 7751 ------------------------------------------------------------------------------------------------------------------------------------