! Proposal 6474, submission 1 ! PI: Stefan Jordan ! Received Wed Feb 14 11:50:05 EST 1996 ! From: supas027@astrophysik.uni-kiel.d400.de ! +====================+ ! | PED OUTPUT PRODUCT | ! +====================+ ! ! /astrotmp_week/supas058/hst/6474.prop ! Generated by PREPROCESSOR, version 6.0e ! Date: Wed Feb 14 11:21:54 MET 1996 Proposal_Information Title: UV-SPECTROSCOPY OF A PECULIAR HIGHLY MAGNETIC WHITE DWARF Proposal_Category: GO Scientific_Category: HOT STARS Cycle: 6 Investigators PI_Name: Stefan Jordan PI_Institution: Institut fuer Astronomie und Astrophysik der Universitaet Kiel CoI_Name: Detlev Koester CoI_Institution: Institut fuer Astronomie und Astrophysik der Universitaet Kiel Contact: 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. Questions Observing_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: Fixed_Targets Target_Number: 1 Target_Name: HE1211-1707 Alternate_Names: Description: STAR,DA, Position: RA=12H 14M 08.3S +/- 0.3S,DEC=-17D 24' 39.6" +/- 0.3",PLATE-ID=03YG Equinox: J2000 RV_or_Z: RA_PM: Dec_PM: Epoch: Annual_Parallax: Flux: V = 16.9+/-0.1 F(1300)=20.e-15 F(1550)=20.e-15 F(1900)=12.e-15 Comments: Solar_System_Targets Generic_Targets Scan_Data Visits Visit_Number: 01 Visit_Requirements: On_Hold_Comments: Visit_Comments: Exposure_Number: 1 Target_Name: HE1211-1707 Config: FOS/BL Opmode: ACQ/BINARY Aperture: 4.3 Sp_Element: MIRROR Wavelength: Optional_Parameters: Number_of_Iterations: 1 Time_Per_Exposure: 9.0S Special_Requirements: ONBOARD ACQ FOR 2 Comments: Exposure_Number: 2 Target_Name: HE1211-1707 Config: FOS/BL Opmode: ACQ/PEAK Aperture: 0.25-PAIR-A Sp_Element: MIRROR Wavelength: Optional_Parameters: SCAN-STEP-Y=0.11,SCAN-STEP-X=0.11,SEARCH-SIZE-Y=4,SEARCH-SIZE-X=4 Number_of_Iterations: 1 Time_Per_Exposure: 5S Special_Requirements: ONBOARD ACQ FOR 3 Comments: critical Peak-up Exposure_Number: 3 Target_Name: HE1211-1707 Config: FOS/BL Opmode: ACCUM Aperture: 1.0-PAIR-A Sp_Element: G160L Wavelength: Optional_Parameters: STEP-PATT=SINGLE Number_of_Iterations: 1 Time_Per_Exposure: 8.5M Special_Requirements: Comments: Exposure_Number: 4 Target_Name: HE1211-1707 Config: FOS/BL Opmode: ACCUM Aperture: 1.0-PAIR-A Sp_Element: G160L Wavelength: Optional_Parameters: STEP-PATT=SINGLE Number_of_Iterations: 1 Time_Per_Exposure: 40.0M Special_Requirements: Comments: Data_Distribution ! Defaults indicated; change if desired Medium: 8MM Blocking_Factor: 10 Ship_To: PI_Address Ship_Via: UPS Recipient_Email: ! Let us know what you think of this template and software! ! Please send a list of your likes and dislikes to your Program Coordinator