6474( 6) - 03/15/96 09:37 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6474 Version: 6 Check-in Date: 15-Mar-1996 09:33:02 1.Proposal Title: UV-SPECTROSCOPY OF A PECULIAR HIGHLY MAGNETIC WHITE DWARF ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle HOT STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Stefan Jordan Institut fuer Astronomie und Astrophysik der Universitaet Kiel CoI: Detlev Koester Institut fuer Astronomie und Astrophysik N der Universitaet Kiel ------------------------------------------------------------------------------------ 6. Abstract HE 1211-1707 was discovered in the Hamburg-ESO Quasar Survey as a blue object, showing a very peculiar spectrum during optical follow-up spectroscopy with EFOSC at the 3.6 m Telescope at ESO in March 1993. Subsequent observations in January 1994 and March 1995 showed very strong spectral variations within 20 min. We interpret this variability as being due to a magnetic field on the surface of a rotating white dwarf, having a relatively uniform magnetic field on one hemisphere and a much larger spread of field strengths visible during other phases of the rotational period. Unfortunately, all efforts have failed to determine approximate magnetic field strengths by comparison with sophisticated model calculations for hydrogen rich atmospheres and field strengths below 1000 MG. Therefore, either helium is the dominating absorber or the object possesses the highest magnetic field ever measured on the surface of a white dwarf. A UV spectrum would considerably help to set constraints to the range of possible field strengths by measuring the position of the blue shifted Lyman Alpha Sigma component, if hydrogen is present in the atmosphere. Although HE 1211-1707 is one of the hottest magnetic white dwarfs the relative faintness of the star did not allow such an analysis with two UV spectra taken with the IUE satellite, and an observation with the HST is needed to understand this unique and mysterious object. ------------------------------------------------------------------------------------ 6474( 6) - 03/15/96 09:37 - [ 2] Observations Description ------------------------ We plan to use the 4.3 aperture and acquire the target with ACQ/BIN followed by ACQ/PEAK (total pattern: Z+E2) for a centering accuracy of aobut 0.08 arcsec. The remainder of the first orbit plus a second orbit (after re-acquisition) will be used to obtain spectra of the 1250 to 2520 Angstrom region in ACCUM mode. From the IUE spectra we estimate the flux at 1500 Angstrom to be 1.8 erg cm^-1 sec^-1 AA^-1, leading to a S/N of about 25 in 10 min. We will thus bin the accumulated spectra in about 10 min exposures for a search of variability. For the total integrated spectra (about 75 minutes) we will achieve a S/N >~ 50, which should clearly show the Lyman alpha components, if H is present in this star. Real Time Justification ----------------------- None. None. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6474( 6) - 03/15/96 09:37 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HE1211-1707 STAR,DA, RA=12H 14M 08.3S +/- 0.3S,DEC=- J2000 V = 16.9+/-0.1 17D 24' 39.6" +/- 0.3",PLATE- F(1300)=20.e-15 ID=03YG F(1550)=20.e-15 F(1900)=12.e-15 6474( 6) - 03/15/96 09:37 - [ 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 HE1211-1707 FOS/BL ACQ/BIN 4.3 MIRROR 1 9.0S ONBOARD ACQ FOR 2 ARY ------------------------------------------------------------------------------------------------------------------------------------ 2 HE1211-1707 FOS/BL ACQ/PEA 0.25- MIRROR SCAN-STEP- 1 5S ONBOARD ACQ FOR 3 K PAIR-A Y=0.11,SCAN- STEP- X=0.11,SEARCH- SIZE-Y=4,SEARCH Comments: critical Peak-up -SIZE-X=4 ------------------------------------------------------------------------------------------------------------------------------------ 3 HE1211-1707 FOS/BL ACCUM 1.0- G160L STEP- 1 8.5M PAIR-A PATT=SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 4 HE1211-1707 FOS/BL ACCUM 1.0- G160L STEP- 1 40.0M PAIR-A PATT=SINGLE ------------------------------------------------------------------------------------------------------------------------------------ 6474( 6) - 03/15/96 09:37 - [ 5] Summary Form for Proposal 6474 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=0.11 SCAN-STEP-X=0.11 SEARCH-SIZE-Y=4 SEARCH-SIZE-X=4 STEP-PATT=SINGLE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G160L ------------------------------------------------------------------------------------------------------------------------------------ Target Names HE1211-1707 ------------------------------------------------------------------------------------------------------------------------------------