! File: 4401C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:10:20:52 coverpage: title_1: ULTRAVIOLET SPECTROPOLARIMETRY OF GD229: CYCLE3 HIGH sci_cat: HOT STARS sci_subcat: WHITE DWARFS proposal_for: GO pi_fname: GARY pi_mi: D. pi_lname: SCHMIDT pi_inst: STEWARD OBSERVATORY pi_country: USA hours_pri: 4.04 num_pri: 1 fos: Y funds_length: 12 off_fname: CHARLES off_mi: A. off_lname: GEOFFRION off_title: ASSOC. V.P. RESEARCH off_inst: 1210 off_addr_1: ADMINISTRATION 601 off_addr_2: UNIVERSITY OF ARIZONA off_city: TUCSON off_state: AZ off_zip: 85721 off_country: USA off_phone: (602) 621-3513 ! end of coverpage abstract: line_1: We propose to obtain spectropolarimetric observations of the unique magnetic line_2: white dwarf GD229, which exhibits numerous, strong unidentified features in the line_3: ultraviolet and optical spectrum. It has a very high but unknown magnetic line_4: field strength and an unknown atmospheric composition. Accurate UV spectro- line_5: polarimetry is critical to determining the parameters of this star for several line_6: reasons: (1) It should yield a rough estimate of the field strength based on line_7: the behavior of the ratio of circular to linear polarization at the shorter line_8: wavelengths. (2) We will search for the well-defined Lyman alpha sigma plus line_9: component, from a possible trace hydrogen abundance, which could also reveal line_10: the field strength and geometry. (3) The high quality spectrum will yield a line_11: wealth of detailed UV features subject to future analysis using calculations line_12: of Zeeman splitting of heavier ions in the presence of the order 10^9 gauss line_13: magnetic fields. This observation may not be possible after installation of line_14: the COSTAR optics. ! ! end of abstract general_form_proposers: lname: SCHMIDT fname: GARY title: PI mi: D. inst: STEWARD OBSERVATORY country: USA ! lname: ALLEN fname: RICHARD mi: G. inst: STEWARD OBSERVATORY country: USA ! lname: LIEBERT fname: JAMES mi: W. inst: STEWARD OBSERVATORY country: USA ! lname: SMITH fname: PAUL mi: S. inst: STEWARD OBSERVATORY country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: FOS/BL spectropolarimetric observations of the magnetic white dwarf GD229 will line_2: be obtained using the G130H, G190H, and G270H gratings, 4.3 arcsec aperture, and line_3: B waveplate. None of the UV spectral features of GD229 have been identified and line_4: our observations are intended to cover the entire UV window accessible to line_5: polarimetry with HST. It is especially important that polarization measurements line_6: be made as far into the ultraviolet as possible. Given the brightness of the line_7: object in the UV, and the relatively poor transmission of the polarimeter line_8: optics below 1600A, three 36-minute polarization measurements will be made with line_9: G130H. These observations will allow measurement of both circular and linear line_10: polarization down to 1280A. In addition, three 32.8-minute measurements will be line_11: made using G190H. A 36-minute observation of GD229 with the G270H grating will line_12: be made to bridge the gap in wavelength between G160L and ground-based optical line_13: measurements. Also, the G270H observations provide polarimetry of the extremely line_14: sharp spectral feature observed at 3200A. These observations MUST take place line_15: before COSTAR is installed in the telescope. ! question: 4 section: 1 line_1: Of course there is no other spacecraft existing or planned with spectro- line_2: polarimetric capability at wavelengths below 3000A. Furthermore, it is our line_3: understanding that, after the implementation of the COSTAR optics, the off-axis line_4: reflections of the two magnesium-fluoride-coated mirrors will cause a line_5: significant instrumental polarization, a mixing of Stokes parameters due to line_6: retardation of the light paths, for a target object. Since this cannot be line_7: calibrated on the ground, it would be problematic at best and perhaps impossible line_8: to achieve an adequate calibration of FOS spectropolarimetry using targets in line_9: space. (A similar problem has prevented accurate optical spectropolarimetry on line_10: our largest telescope in Arizona, the Multiple Mirror Telescope.) Hence, if line_11: these observations are to be obtained ever with the HST they should be obtained line_12: before the additional optics are implemented. ! question: 4 section: 2 line_1: Seven spectropolarimetric observations will be made of GD229 (3 each using G130H line_2: and G190H, and 1 using G270H). Each observation will consist of exposures at 8 line_3: position angles of the B waveplate. Total exposure times will be 108 minutes for line_4: G130H, 98.4 minutes for G190H, and 36 minutes for G270H. All observations will line_5: be made with FOS/BL and 4.3x4.3 arcsecond aperture. Because of the importance of line_6: polarimetry at wavelengths shorter than 1600A for this project, the FOS/BL line_7: detector must be used to yield information on both linear and circular line_8: polarization as well as flux. We will also use FOS/BL for the G270H observation line_9: because the instrument overhead times involved in changing the detector and line_10: reacquiring the target will basically cancel the efficiency gained from using line_11: the FOS/RD detector. ! question: 5 section: 1 line_1: Polarimetric and flux calibration of the G130H, G190H, and G270H gratings are line_2: necessary with FOS/BL, 4.3 arcsec aperture, and B waveplate. ! question: 7 section: 1 line_1: As discussed in question 2, the approximate field strength of the star may be line_2: estimated from the respective behavior of the amplitudes of circular vs. linear line_3: polarization. This is the first and simplest analysis. line_4: Secondly, if a Ly-alpha sigma+ component is identified, its profile will be line_5: modeled using the techniques of D.T. Wichramasinghe, who kindly ported his line_6: software to Steward Observatory during his 1990 sabbatical. This code produces line_7: synthetic absorption spectra of magnetic stars by solving in detail the line_8: radiative transfer for each Stokes parameter over the entire surface of the line_9: star, and includes magnetic opacities in determining the temperature structure. line_10: For GD229, however, we expect based on analysis of optical spectropolarimetry line_11: that hydrogen will be at best a trace element. As pointed out previously, line_12: calculations of Zeeman shifts for helium and heavier elements at very high field line_13: strengths have not been carried out. Particularly if GD229 exhibits a rich UV line_14: spectrum of absorption and polarimetric features, we can use our HST data as a line_15: spur to theorists to carry out the appropriate calculations. This may require line_16: years of time, but the data may only be obtained now. ! !end of general form text general_form_address: lname: SCHMIDT fname: GARY mi: D. category: PI inst: Steward Observatory addr_1: STEWARD OBSERVATORY addr_2: UNIVERSITY OF ARIZONA city: TUCSON state: AZ zip: 85721 country: USA phone: (602) 621-6534 telex: 467175 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: GD229 descr_1: A,119 pos_1: RA=20H 12M 22.24S +/- 1", pos_2: DEC=31D 13' 47.3" +/- 1", pos_3: PLATE-ID=02UC equinox: 2000 pm_or_par: Y pos_epoch_bj: J pos_epoch_yr: 1984.50 ra_pm_val: 0.002495 dec_pm_val: 0.0970 plate_req: N fluxnum_1: 1 fluxval_1: V=14.90 +/- 0.3 fluxnum_2: 1 fluxval_2: B-V=0.50 +/- 0.3 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 10.000 targname: GD229 config: FOS/BL opmode: ACQ/BINARY aperture: 4.3 sp_element: MIRROR num_exp: 1 time_per_exp: 3.0S priority: 1 param_1: BRIGHT=720000 req_1: CYCLE 3 / 10-12.1; req_2: SEQ 10-12.1 NO GAP; req_3: ONBOARD ACQ FOR 11-12.1 ! linenum: 11.000 targname: GD229 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G130H wavelength: 1150-1606 num_exp: 1 time_per_exp: 2160S priority: 1 param_1: POLSCAN=8B ! linenum: 11.100 targname: GD229 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G130H wavelength: 1150-1606 num_exp: 1 time_per_exp: 2160S priority: 1 param_1: POLSCAN=8B ! linenum: 11.200 targname: GD229 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G130H wavelength: 1150-1606 num_exp: 1 time_per_exp: 2160S priority: 1 param_1: POLSCAN=8B ! linenum: 11.250 targname: GD229 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G130H wavelength: 1150-1606 num_exp: 1 time_per_exp: 2160S priority: 1 param_1: POLSCAN=8B ! linenum: 11.300 targname: GD229 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G190H wavelength: 1600-2330 num_exp: 1 time_per_exp: 1968S priority: 1 param_1: POLSCAN=8B ! linenum: 11.400 targname: GD229 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G190H wavelength: 1600-2330 num_exp: 1 time_per_exp: 1968S priority: 1 param_1: POLSCAN=8B ! linenum: 11.500 targname: GD229 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G190H wavelength: 1600-2330 num_exp: 1 time_per_exp: 1968S priority: 1 param_1: POLSCAN=8B ! linenum: 12.100 targname: GD229 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G270H wavelength: 2227-3301 num_exp: 1 time_per_exp: 30M priority: 1 param_1: POLSCAN=8B ! ! end of exposure logsheet ! No scan data records found