! File: 4305C.PROP ! Database: PEPDB ! Date: 20-FEB-1994:21:06:19 coverpage: title_1: A CRITICAL EXTENSION OF THE INTERSTELLAR POLARIZATION CURVE: title_2: CYCLE3HIGH sci_cat: INTERSTELLAR MEDIUM sci_subcat: DUST proposal_for: GO pi_fname: GEOFFREY pi_mi: C. pi_lname: CLAYTON pi_inst: U.COLORADO CASA pi_country: USA hours_pri: 3.00 num_pri: 1 fos: Y funds_length: 12 off_fname: LAURENCE off_mi: D. off_lname: NELSON off_title: DIRECTOR off_inst: UNIVERSITY OF COLORADO off_addr_1: OFFICE OF CONTRACT AND GRANTS off_addr_2: CAMPUS BOX B-19 off_city: BOULDER off_state: CO off_zip: 80309 off_country: USA off_phone: 303-492-2695 ! end of coverpage abstract: line_1: WUPPE obtained the first ultraviolet spectropolarimetric observations line_2: which provided data on the wavelength dependence of interstellar line_3: polarization along 8 lines of sight. The data reveal three distinct UV line_4: wavelength dependences: Serkowski, super-Serkowski, and a bump at line_5: 2175 A. The behavior of the UV polarization seems to be correlated to line_6: Lambda-max. Wolff et al. (1993) use the WUPPE data to re-examine four grain line_7: models used to fit the extinction and polarization in the visible and IR. line_8: Stringent constraints are placed upon models by the necessity of line_9: reproducing both Serkowski and super-Serkowski behavior. In fact, the line_10: UV polarimetry allowed Wolff et al. to identify non-physical aspects of line_11: several grain models, and to obtain information about grain morphology line_12: and environments. However, the observed sample suffers from selection line_13: bias. All but one of the objects fall into a narrow band of Lambda-max, line_14: critically under sampling the observed range. We propose to add an line_15: extreme Lambda-max sightline to the existing sample. This will provide line_16: a double impact: 1) verification of the Lambda-max/UV behavior trend line_17: and 2) key insight into the physical nature of grains and their line_18: environments. HST is uniquely suited to provide these data and Cycle 3 is the line_19: last opportunity to do polarimetry with HST. One consequence of the installation line_20: of COSTAR will be the permanent loss of HST's polarimetric capabilities. ! ! end of abstract general_form_proposers: lname: CLAYTON fname: GEOFFREY title: PI mi: C. inst: U.COLORADO CASA country: USA ! lname: WOLFF fname: MICHAEL mi: J. inst: UNIVERSITY OF WISCONSIN country: USA ! ! end of general_form_proposers block general_form_text: question: 2 section: 1 line_1: 2. Scientific Justification line_3: ==> Not required for Phase II <== ! question: 3 section: 1 line_1: 3. Short Description of Proposed Observations line_3: We plan to use the Faint Object Spectrograph in its polarimetric mode, line_4: which will no longer be useful after Cycle 3, to observe HD 204827 line_5: which is characterized by an extreme value of lambda-max. Because of the 2175 A line_6: Bump and the fact that the deviations from the Serkowski Curve occur line_7: primarily below 2500 A, both of which are near the wavelength at which line_8: the sensitivities of the two grating systems cross over, it is necessary to line_9: make observations with both the G190H and G270H gratings in order fully line_10: to cover the ultraviolet polarization curve. Eight waveplate positions line_11: will be used. ! question: 4 section: 1 line_1: 4. Need for HST line_3: The observations obtained by WUPPE clearly demonstrate the complexity line_4: of UV polarization. The modeling efforts of Wolff et al. (1993) have line_5: clearly delineated the immense potential of these observations to place line_6: constraints on the physical characteristics of the interstellar dust grains. line_7: Unfortunately, their work was limited by the range of lambda-max values line_8: available. It is crucial that the range of lambda-max be properly sampled. line_9: The inability of ground-based instrumentation to access UV regime line_10: necessitates the use of a space-based facility. Further use of WUPPE is line_11: problematic at best and, in any case, will be able to provide only a small line_12: number of interstellar objects. The only other spacecraft capable of making line_13: these observations in the foreseeable future is the HST. Although a line_14: proposal to study interstellar UV polarization has been accepted for Cycle line_15: 1 (Somerville et al.), its targets (HD7252, HD 98965, HD161056) have line_16: values of lambda-max already sampled by WUPPE (5100, 5900, and 5700 A, line_17: respectively). Given the critical nature of extending the UV interstellar line_18: polarimetry database and the future loss of FOS's polarimetric capability, line_19: Cycle 3 represents the last best opportunity to observe extreme lambda-max line_20: objects. ! question: 5 section: 1 line_1: 5. Justification of Exposure Times line_2: The fact that the super-Serkowski behavior is most obvious below 2500 A line_3: necessitates the use of both the G190H and G270H gratings. In order to be able line_4: to unambiguously characterize the UV polarimetry behavior, we required that the line_5: deviation be at least 3 sigma in a 100 A bin around 1900 A and 2400 A line_6: (using about 3 A per diode which accounts for the loss of resolution due to the line_7: aberration). line_8: An example calculation for HD204827 (Pmax=5.6%, lambda-max=4600 A) is line_9: included below to demonstrate the feasibility of this project. line_10: The second column gives the counts per diode taking all correction factors line_11: into consideration. The 3rd and 4th columns indicate the 1 sigma polarimetric line_12: error, for a 100 A and a 200 A bin centered around the given wavelength. line_13: The right-hand column gives the extrapolation of the Serkowski line_14: relationship into the UV. The "deviation" line_15: indicated is the difference in the Serkowski extrapolation line_16: and the amount of polarization expected if HD204827 has a super-Serkowski line_17: behavior similar to that of HD25443. line_18: l (A) cts/diode 100 A bin 200 A bin Serkowski P(%) line_19: 1700 3800 0.23 0.16 2.60 line_20: 1900 2800 0.27 0.19 3.06 ("deviation" is 1.1%) line_21: 2100 1100 0.42 0.30 3.48 line_22: 2300 1600 0.35 -- 3.86 line_23: 2500 23000 0.16 -- 4.20 ("deviation" is 0.8%) ! question: 6 section: 1 line_1: 6. a. Justification of special scheduling requests line_2: ==> none <== ! question: 6 section: 2 line_1: 6. b. Special calibration requirements line_2: ==> none <== ! question: 7 section: 1 line_1: 7. Data Reduction and Analysis line_2: It is expected that the standard data reduction routines of the Institute will line_3: suffice for the data reduction. We include funds for a one week visit to the line_4: Institute for this purpose. Data analysis will initially be an extension of line_5: the grain modeling approach and methods employed by Wolff et al. line_6: (1993). This will entail the use of several grain morphologies and computational line_7: techniques. Analytical formulae are available for both the homogeneous and the line_8: concentric (core-mantle) infinite cylinders as well as homogeneous spheroids. line_9: These shapes have been successful in reproducing the general shape of the line_10: interstellar polarization curve. However, actual line_11: dust grains are likely to have irregular shapes for which exact analytical line_12: solutions do not exit. Thus, we will also utilize the Discrete-Dipole line_13: Approximation (DDA) which represents a grain as a collection of spherical line_14: dipoles. The utility of this method has been significantly advanced in the past line_15: three years through major improvements in theory, application of efficient line_16: numerical algorithms, and faster computers. As recent advances in the study of line_17: dust have provided motivation for line_18: the existence of composite grains, our analysis work will consider several grain line_19: possibilities. Unfortunately, no exact methods exist for the theoretical line_20: determination of bulk optical constants for a mixture of materials. Effective line_21: medium theory, with neglects the subparticle interactions, may be used to line_22: approximate such constants. In addition, we will again utilize the DDA which line_23: dispenses with the previous approximation. ! question: 8 section: 1 line_1: 8. Special Comments line_2: ==> none <== ! question: 9 section: 1 line_1: 9. Previous HST observing Time line_2: ==> none <== ! question: 10 section: 1 line_1: 10. Resources to be Supplied by Institution(s) line_2: The Pine Bluff Observatory (University of Wisconsin) will provide (near-) line_3: simultaneous spectropolarimetry for the target as line_4: well as variability studies in order to maximize the utility of the FOS line_5: observations. Computer facilities at the CASA and at the Midwestern line_6: Astronomical Data Reduction and Analysis Facility (MADRAF) will be available line_7: for the analysis work on this project. CASA provides six months of support line_8: for G. Clayton. ! !end of general form text general_form_address: lname: CLAYTON fname: GEOFFREY mi: C. category: PI inst: U.Colorado CASA addr_1: CAMPUS BOX 389 city: BOULDER state: CO zip: 80309 country: USA phone: 303-492-4057 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: HD204827 name_2: GSC03977-00961 descr_1: A,110 pos_1: RA=322.24040D +/- 0.3", pos_2: DEC=58.74001D +/-0.3", pos_3: PLATE-ID=00C6 equinox: 2000 pm_or_par: N fluxnum_1: 1 fluxval_1: V=7.95 +/- 0.01, TYPE=B0V fluxnum_2: 2 fluxval_2: B-V=0.80 +/- 0.01 fluxnum_3: 3 fluxval_3: E(B-V)=1.10 +/- 0.05 fluxnum_4: 4 fluxval_4: F-CONT(3200)=12 +/- 1E-13 fluxnum_5: 5 fluxval_5: F-CONT(2400)=2 +/- 0.1E-13 fluxnum_6: 6 fluxval_6: F-CONT(2000)=1 +/- 0.1E-13 fluxnum_7: 7 fluxval_7: F-CONT(1600)=1 +/- 0.1E-13 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: HD204827 config: FOS/BL opmode: ACQ/PEAK aperture: 4.3 sp_element: G190H wavelength: 1900 num_exp: 1 time_per_exp: 0.7S s_to_n: 70 fluxnum_1: 1 priority: 1 req_1: ONBOARD ACQ FOR 2; req_2: SPATIAL SCAN; req_3: CYCLE 3/1-4; req_4: SEQ 1-4 NO GAP comment_1: PEAKUP ACQUISITION FOR BRIGHT comment_2: STAR. ! linenum: 2.000 targname: HD204827 config: FOS/BL opmode: ACQ/PEAK aperture: 1.0 sp_element: G190H wavelength: 1900 num_exp: 1 time_per_exp: 1S s_to_n: 70 fluxnum_1: 1 priority: 1 req_1: ONBOARD ACQ FOR 3-4; req_2: SPATIAL SCAN comment_1: PEAKUP IN 1 ARCSEC APERTURE. ! linenum: 3.000 targname: HD204827 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G190H wavelength: 1900 num_exp: 1 time_per_exp: 2182.5S s_to_n: 77 s_to_n_time: 4365S fluxnum_1: 6 priority: 1 param_1: POLSCAN=4B ! linenum: 3.100 targname: HD204827 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G190H wavelength: 1900 num_exp: 1 time_per_exp: 2182.5S s_to_n: 77 s_to_n_time: 4365S fluxnum_1: 6 priority: 1 param_1: POLSCAN=4B ! linenum: 4.000 targname: HD204827 config: FOS/BL opmode: ACCUM aperture: 4.3 sp_element: G270H wavelength: 2700 num_exp: 1 time_per_exp: 500S s_to_n: 130 s_to_n_time: 500S fluxnum_1: 4 priority: 1 param_1: POLSCAN=8B ! ! end of exposure logsheet scan_data: line_list: 1 fgs_scan: N cont_dwell: D dwell_pnts: 3 dwell_secs: 1.00 scan_width: 0.0000 scan_length: 2.8000 sides_angle: 90.0000 number_lines: 1 scan_rate: 0.0000 first_line_pa: 0.0000 scan_frame: S/C len_offset: 1.4 wid_offset: 0.0 ! line_list: 2 fgs_scan: N cont_dwell: D dwell_pnts: 6 dwell_secs: 1.00 scan_width: 0.7000 scan_length: 3.5000 sides_angle: 90.0000 number_lines: 2 scan_rate: 0.0000 first_line_pa: 90.0000 scan_frame: S/C len_offset: 1.75 wid_offset: 0.35 ! ! end of scan data