! File: 4606C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:19:27:06 coverpage: title_1: SPECTROPOLARIMETRY OF HD197770, A SEARCH FOR A GRAPHITE title_2: SIGNATURE IN THE INTERSTELLAR POLARIZATION sci_cat: INTERSTELLAR MEDIUM sci_subcat: DUST proposal_for: GO cont_id: 4606 pi_title: DR. pi_fname: CHRISTOPHER pi_mi: M pi_lname: ANDERSON pi_inst: UNIVERSITY OF WISCONSIN pi_country: USA pi_phone: 608-262-0492 hours_pri: 1.35 num_pri: 1 fos: Y funds_amount: 34138 funds_length: 12 funds_date: JAN-94 pi_position: PROFESSOR off_fname: CHERYL off_mi: E off_lname: GEST off_title: ADMIN. OFFICER off_inst: 3884 off_addr_1: 750 UNIVERSITY AVENUE off_city: MADISON off_state: WI off_zip: 53706 off_country: USA off_phone: 608-262-4880 ! end of coverpage abstract: line_1: The wavelength dependence of the ultraviolet interstellar linear line_2: polarization for 8 stars with substantial interstellar extinction was line_3: observed by the Wisconsin Ultraviolet Photo Polarimeter Experiment line_4: (WUPPE) during the 1990 December Astro-1 mission. One star, HD197770 line_5: shows a very distinct polarization feature which coincides with the line_6: well known 2175 A extinction bump. Most models of the interstellar line_7: grains invoke graphite to explain the extinction bump. Computations line_8: by Draine (1988) based on the discrete dipole approximation show that line_9: a very good match to the bump can be produced by small (typical size of line_10: order 100A) graphite disks (axial ratios of order 1.5). Draine's line_11: model also suggests that these grains will produce a feature in the line_12: linear polarization like that observed by WUPPE. The birefringence of line_13: graphite also introduces circular polarization with a zero crossing at line_14: the feature, but its level is too small to be measured in practical line_15: exposure times. Thus we propose to utilize the HST FOS to measure line_16: linear polarization in the vicinity of 2175 A and thereby confirm line_17: the WUPPE result, further substantiate the presence or absence line_18: of a small, aligned graphite component of the interstellar medium line_19: along this line of sight and test the Draine models. line_20: THIS OBSERVATION WILL NOT BE POSSIBLE AFTER HST REFURBISHMENT ! ! end of abstract general_form_proposers: lname: ANDERSON fname: CHRISTOPHER title: PI mi: M inst: UNIVERSITY OF WISCONSIN country: USA ! ! end of general_form_proposers block general_form_text: question: 2 section: 1 line_1: See Phase I Submission ! question: 3 section: 1 line_1: We propose to use the Faint Object Spectrograph in its line_2: polarimetric mode to observe this one star. Since the 2175 A line_3: extinction feature which is the subject of the investigation is near line_4: the wavelength at which the sensitivities of the two grating systems line_5: cross over, it is necessary to make observations with both gratings in line_6: order fully to cover the ultraviolet polarization curve. Since only line_7: linear polarization is to be measured, only a 8 filter position line_8: polscan is required and superior signal to noise can be achieved line_9: in the allotted time. ! question: 4 section: 1 line_1: The observations needed to attempt to detect the line_2: polarization signature of graphite are in the ultraviolet so that line_3: ground-based observations cannot serve this purpose. The Wisconsin line_4: Ultraviolet Photo Polarimeter Experiment (WUPPE) which made the line_5: observations which motivate this proposal was used only in its linear line_6: mode on Astro-1. WUPPE will attempt to observe circular polarization line_7: in HD197770 on Astro-2, but the confirmation of the Astro-1 result line_8: by a completely different insturment is simply good scientific line_9: practice. The HST FOS is the only other existing spacecraft which line_10: could make such observations. ! question: 5 section: 1 line_1: No special scheduling requirements apply to this observation, however line_2: it should be noted that it this object can be quite close to the line_3: continuous viewing zone of the spacecraft. It is thus possible that line_4: by proper scheduling a better spacecraft usage efficiency than that line_5: predicted by the resource estimator might be achieved. ! question: 6 section: 1 line_1: NONE ! question: 7 section: 1 line_1: It is expected that the standard data reduction routines of the Institute line_2: will suffice for the data reduction. We include funds for a one week visit line_3: to the Institute for this purpose. For analysis purposes a wide variety of line_4: interstellar dust modeling programs are available at the PI's institution line_5: and will be used. In particular should the signature be found, a diverse line_6: population of discrete dipole approximation computations will be done and line_7: mixed to explore the fitting parameters of the signature. ! question: 8 section: 1 line_1: NONE ! question: 9 section: 1 line_1: NONE ! question: 10 section: 1 line_1: The University of Wisconsin will provide the computer facilities of the line_2: Midwestern Astronomical Data Reduction and Analysis Facility (MADRAF) for line_3: the analyis work on this project. ! !end of general form text general_form_address: lname: ANDERSON fname: CHRISTOPHER mi: M title: PROF category: PI inst: UNIVERSITY OF WISCONSIN addr_1: DEPARTMENT OF ASTRONOMY addr_2: 475 NORTH CHARTER STREET city: MADISON state: WI zip: 53706 country: USA phone: 608-262-0492 telex: 265452 UOFSISC MDS ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: HD197770 descr_1: A,111, pos_1: RA = 20H 41M 57.95S +/- 0.02S, pos_2: DEC = +56D 55' 58.2" +/- 0.2", equinox: 1950 pm_or_par: N fluxnum_1: 1 fluxval_1: V=6.32+/-0.02, TYPE=B2III, fluxval_2: E(B-V)=+0.33 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 0.100 targname: HD197770 config: FOS/BL opmode: ACQ/PEAK aperture: 4.3 sp_element: G190H num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: SEARCH-SIZE-X=1, param_2: SEARCH-SIZE-Y=3, param_3: SCAN-STEP-Y=1.4 req_1: CYCLE 3 / 0.1-2; req_2: ONBOARD ACQ FOR 0.2; ! linenum: 0.200 targname: HD197770 config: FOS/BL opmode: ACQ/PEAK aperture: 1.0 sp_element: G190H num_exp: 1 time_per_exp: 1S fluxnum_1: 1 priority: 1 param_1: SEARCH-SIZE-X=6, param_2: SEARCH-SIZE-Y=2, param_3: SCAN-STEP-Y=0.7, param_4: SCAN-STEP-X=0.7 req_2: ONBOARD ACQ FOR 1-2; ! linenum: 1.000 targname: HD197770 config: FOS/BL opmode: ACCUM aperture: 1.0 sp_element: G190H,POL0-B wavelength: 1954 num_exp: 1 time_per_exp: 2299.0S s_to_n: 1000 fluxnum_1: 1 priority: 1 param_1: POLSCAN=8B ! linenum: 2.000 targname: HD197770 config: FOS/BL opmode: ACCUM aperture: 1.0 sp_element: G270H,POL0-B wavelength: 2820 num_exp: 1 time_per_exp: 1294.0S s_to_n: 1000 fluxnum_1: 1 priority: 1 param_1: POLSCAN=8B ! ! end of exposure logsheet ! No scan data records found