! File: 4651C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:21:11:33 coverpage: title_1: THE SEAT OF STELLAR-WIND INSTABILITIES sci_cat: HOT STARS sci_subcat: MASSIVE STARS proposal_for: GO pi_fname: IAN pi_mi: D. pi_lname: HOWARTH pi_inst: UNIVERSITY COLLEGE LONDON pi_country: UK hours_pri: 1.12 num_pri: 1 hrs: Y realtime: N time_crit: Y off_fname: ROBERT off_lname: WILSON off_title: HEAD OF DEPT. off_inst: 8090 off_addr_1: DEPT. PHYSICS & ASTRONOMY off_addr_2: GOWER STREET off_city: LONDON WC1E 6BT off_country: UK ! end of coverpage abstract: line_1: IUE observations have established that variability in UV P-Cygni line_2: profiles is a fundamental property of radiatively-driven winds, and it line_3: is generally agreed that this variability is a signature of the line_4: line-driven instability. What remains unclear is whether the line_5: variability is completely intrinsic to the flow, or if it requires line_6: `seeding' from the low-velocity regime. IUE observations lack line_7: adequate signal/noise to address this problem; existing HST results line_8: are ambiguous. We propose to obtain high-quality time-series HRS line_9: spectroscopy of 68 Cygni, a star extensively observed with IUE, in line_10: order to provide an empirical answer to this question. These data line_11: will distinguish between low-velocity, mechanically-driven line_12: instabilities and intrinsic, radiatively-driven instabilities, and line_13: will define the interaction of the two regimes. The results will, line_14: in turn, have wider implications for the applicability of steady- line_15: state wind models. ! ! end of abstract general_form_proposers: lname: HOWARTH fname: IAN title: PI mi: D. inst: UNIVERSITY COLLEGE LONDON country: UNITED KINGDOM esa: Y ! lname: PRINJA fname: RAMAN mi: K. inst: UNIVERSITY COLLEGE LONDON country: UNITED KINGDOM esa: Y ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: In order to monitor short-timescale (hourly) variability in line_2: stellar-wind outflows, the P-Cygni profiles of NV (1240A), line_3: SiIV (1400A) and CIV (1550A) are to be observed in the line_4: spectrum of HD203064 once every orbit for 19 (now only 11)orbits, line_5: at high S/N, with the G160M grating. ! question: 4 section: 1 line_1: Only HST can provide the necessary high S/N in the UV resonance line_2: lines. ! question: 5 section: 1 line_1: The frequency and length of the observations is dictated by the line_2: timescales for growth and development of discrete absorption line_3: features in the profiles. At low velocities we predict that line_4: they will accelerate from 0.1v(infinity) to 0.3v(infinity) in line_5: 1.5 hours [and to 0.5v(infinity) in 3 hours]. The recurrence line_6: timescale averages approximately 20 hours, up to 25 hours. Thus line_7: observations every 1.5: hours are required for 30 hours to ensure line_8: that a low-velocity feature is caught and its early development line_9: followed. The Phase II resource estimator has shown these line_10: observations to be more `expensive' than Phase I indicated, so line_11: the number of visits has been nearly halved. There is still line_12: a good chance that the early phases of DAC development will be line_13: caught. ! !end of general form text general_form_address: lname: Howarth fname: Ian mi: D. category: PI inst: University College London addr_1: Gower Street city: London WC1E 6BT country: UNITED KINGDOM phone: (44)-71-387-7050 telex: 28722 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: HD203064 name_2: 68CYG descr_1: A,185 pos_1: RA = 21H 18M 27.19S +/- 0.01S, pos_2: DEC = +43D 56' 45.5" +/- 0.1" equinox: J2000 fluxnum_1: 1 fluxval_1: V = 5.00 +/- 0.02, TYPE=O7.5III fluxnum_2: 2 fluxval_2: B-V = -0.01 +/- 0.01 fluxnum_3: 3 fluxval_3: E(B-V) = 0.3 +/- 0.03 fluxnum_4: 4 fluxval_4: F-CONT(1240) = 6.5 +/- 0.2 E-10 fluxnum_5: 5 fluxval_5: F-CONT(1400) = 6.0 +/- 0.2 E-10 fluxnum_6: 6 fluxval_6: F-CONT(1550) = 5.0 +/- 0.2 E-10 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: HD203064 config: HRS opmode: ACQ aperture: 2.0 sp_element: MIRROR-A2 time_per_exp: 1.8S priority: 1 param_1: SEARCH-SIZE=3, param_2: BRIGHT=RETURN, param_3: LOCATE=YES req_1: ONBOARD ACQ FOR 2-4; req_2: SEQ 1-4 NO GAP; req_3: REPEAT 1-4 EVERY 90M +/- 30M req_4: FOR 10 MORE TIMES; req_5: CYCLE 3 ! linenum: 2.000 targname: HD203064 config: HRS opmode: ACCUM aperture: 2.0 sp_element: G160M wavelength: 1240 num_exp: 1 time_per_exp: 109S s_to_n: 100 fluxnum_1: 4 priority: 1 param_1: FP-SPLIT=STD, param_2: COMB=FOUR, param_3: STEP-PATT=5, param_4: DOPPLER=ON req_1: CYCLE 3 ! linenum: 3.000 targname: HD203064 config: HRS opmode: ACCUM aperture: 2.0 sp_element: G160M wavelength: 1398 num_exp: 1 time_per_exp: 109S s_to_n: 100 fluxnum_1: 5 priority: 1 param_1: FP-SPLIT=STD, param_2: COMB=FOUR, param_3: STEP-PATT=5, param_4: DOPPLER=ON req_1: CYCLE 3 ! linenum: 4.000 targname: HD203064 config: HRS opmode: ACCUM aperture: 2.0 sp_element: G160M wavelength: 1549 num_exp: 1 time_per_exp: 109S s_to_n: 100 fluxnum_1: 6 priority: 1 param_1: FP-SPLIT=STD, param_2: COMB=FOUR, param_3: STEP-PATT=5, param_4: DOPPLER=ON req_1: CYCLE 3 ! ! end of exposure logsheet ! No scan data records found