! File: 4659C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:21:31:15 coverpage: title_1: A TIME-RESOLVED UV STUDY OF THE WIND OUTFLOW IN THE ENIGMATIC title_2: CATACLYSMIC VARIABLE, V795 HER sci_cat: HOT STARS sci_subcat: ERUPTIVE BINARIES proposal_for: GO pi_fname: SIMON pi_mi: R pi_lname: ROSEN pi_inst: UNIVERSITY OF LEICESTER pi_country: U.K. hours_pri: 2.30 num_pri: 1 fos: Y ! end of coverpage abstract: line_1: We propose to exploit the unique UV capabilities of the HST FOS to obtain the line_2: first highly time-resolved UV spectroscopy of the wind outflow in the enigmatic line_3: cataclysmic binary, V795 Her. Our previous IUE observations of this star line_4: revealed its extraordinary UV properties: whilst the continuum and most UV line_5: lines are constant, the Si IV and in particular, C IV, lines undergo dramatic line_6: variability on timescales down to the 30 minute limit imposed by the IUE line_7: sensitivity. Moreover, this behaviour, most readily associated with an line_8: outflowing wind, appears to be modulated at a period of 4.8hrs rather than the line_9: known optical periods. This line behaviour confronts present CV wind models. line_10: Using the HST FOS, we aim to 1) authenticate the tentative 4.8hr periodicity in line_11: the C IV and Si IV line fluxes to provide the foundation for more detailed line_12: study, 2) probe the shortest timescales of significant variability in the CIV line_13: line - in particular, we seek to resolve the fast evolution of the C IV line_14: absorption component to constrain the wind structure and to search for line_15: sub-structure in this feature which may reveal inhomegeneities in the wind line_16: and 3) search for radial velocity motion in the emission component of C IV as line_17: evidence of an additional line emitting, asymmetric disk source which we line_18: suspect may be the missing factor in current scenarios for V795 Her. These HST line_19: observations offer a unique opportunity to resolve the outstanding issues line_20: concerning the nature of the mass outflow in this object. ! ! end of abstract general_form_proposers: lname: ROSEN fname: SIMON title: PI mi: R inst: UNIVERSITY OF LEICESTER country: UNITED KINGDOM esa: Y ! lname: PRINJA fname: RAMAN mi: K inst: UNIVERSITY COLLEGE LONDON country: UNITED KINGDOM esa: Y ! lname: DREW fname: JANET mi: E inst: UNIVERSITY OF OXFORD country: UNITED KINGDOM esa: Y ! lname: HOWELL fname: STEVE mi: B inst: PLANETARY SCIENCES INSTITUTE country: USA esa: N ! lname: MASON fname: KEITH mi: O inst: MULLARD SPACE SCIENCE LABORATORY country: UNITED KINGDOM esa: Y ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: We propose to use the FOS (blue side) with the G130H grating to access the far line_2: UV wavelength range between 1150A and 1600A. Using the 4.3 arc second aperture line_3: (to maximise throughput) will provide data at about 1.5A resolution, a factor 4 line_4: improvement over IUE. Using 20s integrations with the FOS RAPID mode will line_5: permit us to sample the wind outflow timescales (of order 1-2 minutes) in line_6: sufficient detail to track phenomena such as opacity enhancements. We line_7: anticipate a S/N of around 10 per diode at C IV in each 20s exposure which line_8: means we can track line flux changes, for example in the C IV absorption line_9: component, to around 10%. Binning spectra to 2 minutes resolution will provide line_10: 4% accuracy per diode. These levels of accuracy should be adequate for line_11: searching for the profile changes we are interested in. In the allocated 2.3 line_12: hours of spacecraft time we can expect around 1 hour of data in two slots. This line_13: will sample 2 points within the 4.8 hour cycle and will allow us to monitor line_14: continuously, changes in the CIV line profile for intervals of about 25-30 line_15: minutes in each slot, providing much improved temporal and spectral resolution line_16: compared to our previous IUE data. line_17: *We note that the TAC recommended an allocation of 2.3 hours to be scheduled to line_18: cover the CIV absorption phase. This, however, would demand a time-critical line_19: observation. We believe a random phase sampling will provide basic initial line_20: information which will facilitate our planning of a future, more extensive line_21: observation (submitted for cycle 4) and could well, even in this short run, line_22: provide some very important clues to the :origin of the line variations. ! question: 4 section: 1 line_1: The two sets of IUE shifts we have secured in recent years revealed the line line_2: profile variability and showed evidence for periodic modulation of the CIV and line_3: SiIV line fluxes. However, it is clear that the IUE observations are unable to line_4: address the fundamental issue of the minimum timescales on which the CIV line line_5: exhibits profile changes. We know it is less than 30 minutes but currently, line_6: only HST will enable us to probe these changes at the shorter (minutes) line_7: timescales that are probably appropriate: only fast spectroscopy will permit us line_8: to observe, for example, the rapid evolution of the C IV absorption component line_9: which can convey vital information about the absorbing wind. At the same time line_10: we will be exploiting the substantial (factor 3-4) improvement in spectral line_11: resolution achievable with FOS compared to IUE. Use of the IUE high resolution line_12: mode is not viable due to the extremely low count rates expected for a 13th line_13: magnitude star in the exposure times required for our study. The combination of line_14: enhanced spectral resolution and higher achievable S/N ratios offered by the line_15: HST FOS will be crucial in pinning down the cause of the profile variability line_16: and in quantifying basic outflow properties and parameters such as the limiting line_17: wind velocity. We also stress that the wind-formed line features are only line_18: detected in the far UV band. Thus, only satellite-borne telescopes can provide line_19: the necessary observations to investigate these phenomena. ! question: 4 section: 2 line_1: To assess the feasibility of our proposed observations, we used the IUE line_2: spectrum of V795 Her (fig. 1) to appropriately scale the predicted count rates line_3: of the flat spectrum data in the HST FOS documentation. This indicates that we line_4: can expect 0.5 and 5.0 cts/s/diode at 1200A and 1550A (C IV) continuum line_5: respectively or 10 and 100 cts/diode at those points in each 20s exposure. line_6: These values are close to the extremes of count rate that we can expect in line_7: each spectrum. The resulting S/N (10/diode) at C IV will be adequate for line_8: monitoring line profile changes. Since our primary interest is in the C IV and line_9: Si IV lines, which lie around the highest region of the FOS sensitivity curve, line_10: we anticipate high quality spectra for our study, particularly when coadded line_11: into two minute time bins. ! question: 5 section: 1 line_1: No special scheduling requirements or constraints are demanded. line_2: Nevertheless, see the note (**) at the end of question 8. ! question: 6 section: 1 line_1: Routine FOS calibration data will be sufficient for our purposes. ! question: 7 section: 1 line_1: Our observational approach, i.e. time-resolved spectroscopy, is a widely used line_2: technique in CV astronomy. The many short exposures thus obtained will provide line_3: sufficient detail to establish the shortest timescales of C IV variability - we line_4: will characterise the line profiles using the techniques adopted in our IUE line_5: analyses. The spectra will be binned into larger (2-5 minute) time bins to line_6: enhance the signal/noise for any weak but persistent features. In this line_7: short allocation we will concentrate on studying the detail during the line_8: evolution of the CIV emission and absorption components (we will not be able line_9: to sample the full evolutionary timescale). Data analysis on the basically line_10: extracted spectra will be performed at the Universities of Leicester, line_11: London and Oxford where substantial computing facilities are available. ! question: 8 section: 1 line_1: Contemporaneous ground-based optical coverage will not be possible at the line_2: time of the HST observation unless it is scheduled prior to the middle line_3: of September. line_4: **We point out that we have been allocated a 20ksec ROSAT X-ray observation of line_5: V795 Her, the bulk of the observation being performed on 1993 August 12 line_6: (between 11 and 19h UT), and we are arranging contemporaneous optical line_7: coverage at that time. Efforts to secure IUE observations unfortunately line_8: failed due to the current pressure on IUE. Whilst we are not requesting the line_9: HST observations to be arranged with the ROSAT run, an HST scheduling as close line_10: to the ROSAT observation as feasible would, in the absence of IUE coverage, line_11: powerfully complement the X-ray and optical data we expect to acquire. We line_12: have also requested IR spectroscopic observations via a service programme line_13: to be performed near to the ROSAT run. If the HST observations were line_14: scheduled close to the ROSAT dates, this would maximize the scientific line_15: return on this object. ! question: 9 section: 1 line_1: GO-3578 Line eclipse mapping of an accretion disk wind line_2: GO-3579 The UV orbital lightcurve of the X-ray binary X1822-371 line_3: Neither proposal is related to the project outlined here. ! question: 10 section: 1 line_1: The analysis of our HST data will be undertaken by the PI and the line_2: Co-I's. All proposers have access to DEC Vax machines or SUN line_3: stations which are dedicated to astronomical research. ! !end of general form text general_form_address: lname: ROSEN fname: SIMON mi: R category: PI inst: University of Leicester addr_1: Dept. of Physics, addr_3: University Rd., city: Leicester country: UNITED KINGDOM phone: 0533 552077 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: V795-HER descr_1: A, 151 pos_1: PLATE-ID = 02TX, pos_2: RA=17H 12M 56.10S +/- 0.74", pos_3: DEC=33D 31' 21.45" +/- 0.74" equinox: J2000 comment_1: UV FLUXES ARE FROM IUE. S/N ~ comment_2: 10/PIXEL/BIN NEEDED PER 20S comment_3: EXPOSURE AT CIV CONTINUUM. fluxnum_1: 1 fluxval_1: V = 13.0 fluxnum_2: 2 fluxval_2: B-V = 0.6 +/- 0.1 fluxnum_3: 3 fluxval_3: E(B-V) = 0.1 +/- 0.1 fluxnum_4: 4 fluxval_4: F-CONT(1200) = 3.2 +/- 0.2 E-13 fluxnum_5: 5 fluxval_5: F-CONT(1550) = 2.8 +/- 0.2 E-13 fluxnum_6: 6 fluxval_6: F-LINE(1550) = 3.4 +/- 0.3 E-13 fluxnum_7: 7 fluxval_7: W-LINE(1550) = 10 +/- 3 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: V795-HER config: FOS/BL opmode: ACQ/PEAK aperture: 4.3 sp_element: MIRROR num_exp: 1 time_per_exp: 1S s_to_n: 10 s_to_n_time: 20S fluxnum_1: 1 fluxnum_2: 3 priority: 1 param_1: SEARCH-SIZE-X=1, param_2: SEARCH-SIZE-Y=3, param_3: SCAN-STEP-Y=1.4 req_1: ONBOARD ACQ FOR 1.5; req_2: CYCLE 3; req_3: GROUP 1-3 NO GAP; comment_1: V795 HER VARIES BY ABOUT 12% AROUND comment_2: OPTICAL MAG=13.0. THE POORLY CON- comment_3: STRAINED UV VARIATION IS <10%. comment_4: IDEALLY, TO MINIMIZE OVERHEADS, USE comment_5: CONTIGUOUS ORBITS. PLEASE ALSO SEE comment_6: NOTES AT END OF QUESTION 3* + 8**. ! linenum: 1.500 targname: V795-HER config: FOS/BL opmode: ACQ/PEAK aperture: 1.0 sp_element: MIRROR num_exp: 1 time_per_exp: 1S s_to_n: 10 s_to_n_time: 20S fluxnum_1: 1 fluxnum_2: 3 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_1: ONBOARD ACQ FOR 2-3; req_2: CYCLE 3; ! linenum: 2.000 targname: V795-HER config: FOS/BL opmode: RAPID aperture: 4.3 sp_element: G130H wavelength: 1380 num_exp: 1 time_per_exp: 30M s_to_n: 10 s_to_n_time: 20S fluxnum_1: 5 priority: 1 param_1: COMB=YES param_2: READ-TIME=20 req_1: CYCLE 3 ! linenum: 3.000 targname: V795-HER config: FOS/BL opmode: RAPID aperture: 4.3 sp_element: G130H wavelength: 1380 num_exp: 1 time_per_exp: 24M s_to_n: 10 s_to_n_time: 20S fluxnum_1: 5 priority: 1 param_1: COMB=YES param_2: READ-TIME=20 req_1: CYCLE 3 ! ! end of exposure logsheet ! No scan data records found