! $Id: 5314,v 8.1 1994/11/07 14:25:50 pepsa Exp $ coverpage: title_1: THE RED EDGE OF THE ZZ CETI INSTABILITY STRIP sci_cat: COOL STARS sci_subcat: PULSATING STARS proposal_for: GO pi_fname: GERARD pi_lname: VAUCLAIR pi_inst: OBSERVATOIRE MIDI PYRENEES pi_country: FRANCE pi_phone: 33-61-332953 hours_pri: 1.00 num_pri: 1 fos: Y off_fname: MICHEL off_lname: BLANC off_title: DIRECTOR off_inst: 5474 off_addr_1: 14 AV. E. BELIN off_city: 31400 TOULOUSE off_country: FRANCE ! end of coverpage abstract: line_1: ZZ Ceti stars are variable white dwarfs of spectral type DA. The line_2: theoretically predicted instability strip depends on several line_3: uncertain assumptions, most importantly the efficiency of line_4: convective energy transport and the detailed structure of the line_5: outer stellar layers. Empirical determinations from optical line_6: spectra are not as accurate as desirable, because the Balmer line_7: lines reach maximum strengths within the instability strip and line_8: vary only little with temperature. The UV spectrum is much line_9: better suited since we have recently improved the quantitative line_10: description of the quasi-molecular satellite features, that vary line_11: strongly with temperature and should ultimately allow an line_12: accuracy of 200 K. Observations for G117-B15A (defining the hot line_13: edge of the instability strip) have been obtained in Nov. 92. line_14: In this project, we propose to observe BPM30551, one of the line_15: coolest ZZ Ceti stars. ! ! end of abstract general_form_proposers: lname: ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We want to obtain spectral coverage of the range dominated by the line_2: Lyman alpha red wing satellites, i.e. 1300 - 2500 A, for the line_3: variable white dwarf BPM30551. With FOS and the G160L grating we line_4: will achieve a S/N of >15 for BPM30551 around 1500 A, where a line_5: secondary flux maximum between the 1400 and 1600 A satellites is line_6: extremely temperature sensitive. For lambda > 1650 A the flux line_7: rises steeply in the star, and the expected S/N ranges from 30 to line_8: 80. We will use the ACCUM mode for this object. ! question: 3 section: 2 line_1: ! question: 4 section: 1 line_1: Numerous attempts to determine the boundaries of the instability line_2: strip have been performed with optical or IUE data, among others line_3: also by one of the current CO-PI's (Weidemann and Koester 1984, line_4: Astron.Astrophys. 132, 195). A recent summary of these studies line_5: is given in Wesemael et al. 1991 (White Dwarfs, Nato ASI Series line_6: C, Vol.336, p.159). line_8: The red edge of the instability strip is unfortunately defined by line_9: 4 different stars in 4 studies, the coolest ones being BPM30551 line_10: and G255-2 around 10000 K (with large uncertainties), while the line_11: next coolest stars do only appear above 11000 K, thus precluding line_12: any firm conclusions from a comparison with observations. line_14: With V = 15.3 and a very steeply declining flux shortward of 1650 line_15: A BPM30551 is too faint to give a useful spectrum with the IUE line_16: satellite. For an accurate temperature determination and line_17: possibly also a determination of the surface gravity (and thus line_18: mass) from the relative strength of the Lyman alpha satellites we line_19: will need an average S/N of about 20 in the UV. ! question: 5 section: 1 line_1: ! question: 6 section: 1 line_1: ! ! question: 8 section: 1 line_1: ! question: 9 section: 1 line_1: The first observations (in the White Dwarf Consortium Project) line_2: were obtained in June 1992. D.Koester and N.Allard are line_3: currently working on the analysis of spectra for L745-46A, line_4: together with N.Feautrier (Meudon). This project is not related to line_5: the current proposal. line_7: Related to the present project, G117-B15A has been observed and line_8: the data are being analyzed. G255-2 might be observed during line_9: Cycle 3, but the program received Medium priority. ! question: 10 section: 1 line_1: Observatoire Midi-Pyrenees provides computing facilities and line_2: basic support for G. Vauclair. line_4: The Observatoire de Meudon provides computing facilities and line_5: basic support (secretarial, technical programming etc.) for line_6: N. Allard. line_8: The computing facilities of the Institut fuer Theoretische Physik line_9: und Sternwarte (University of Kiel) will also be available for line_10: this project free of charge. ! !end of general form text general_form_address: lname: VAUCLAIR fname: GERARD category: PI inst: 5474 addr_1: OBSERVATOIRE MIDI PYRENEES addr_2: LABORATOIRE D'ASTROPHYSIQUE DE TOULOUSE addr_3: 14, AV. E. BELIN, F-31400 TOULOUSE city: TOULOUSE country: FRANCE phone: 33-61-332953 ! lname: category: CON ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: WD0104-464 name_2: BPM30551 descr_1: A, descr_2: 120, descr_3: 177 pos_1: RA = 01H06M53.241S +/- 0.3", pos_2: DEC = -46D8'55.29" +/- 0.3", pos_3: PLATE-ID = 04FI equinox: 2000 pm_or_par: Y pos_epoch_bj: B pos_epoch_yr: 1979.70 ra_pm_val: 0.021300 dec_pm_val: 0.0800 comment_1: RA_PM_VAL IS IN TIME-SEC/YR comment_2: AS DEMANDED IN THE HANDBOOK fluxnum_1: 1 fluxval_1: V = 15.26 +/- 0.05 fluxnum_2: 2 fluxval_2: F-CONT(1700) = 8.00 +/- 0.5 E-15 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: WD0104-464 config: FOS/BL opmode: ACQ/BINARY aperture: 4.3 sp_element: MIRROR num_exp: 1 time_per_exp: 10.0S fluxnum_1: 1 priority: 1 param_1: NTHSTAR=1 req_1: CYCLE 4 / 1.0-3.0; req_2: ONBOARD ACQ FOR 2.0; ! linenum: 2.000 targname: WD0104-464 config: FOS/BL opmode: ACQ/PEAK aperture: 0.3 sp_element: MIRROR num_exp: 1 time_per_exp: 2.0S fluxnum_1: 1 priority: 1 param_1: TYPE=UP param_2: SEARCH-SIZE-X=5 param_3: SEARCH-SIZE-Y=5 param_4: SCAN-STEP-X=.172 param_5: SCAN-STEP-Y=.172 req_1: ONBOARD ACQ FOR 3.0 ! linenum: 3.000 targname: WD0104-464 config: FOS/BL opmode: ACCUM aperture: 0.3 sp_element: G160L wavelength: 1600 num_exp: 1 time_per_exp: 38.3M fluxnum_1: 2 priority: 1 ! ! end of exposure logsheet ! No scan data records found