Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5315 Report Date: 18-Jul-95:17:08 Version: ********** Check-in Date: ********** 1.Proposal Title: THE SEAT OF STELLAR-WIND INSTABILITIES: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category MASSIVE STARS ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Ian D. Howarth UNIVERSITY COLLEGE LONDON UK 01044-71-387-7 ------------------------------------------------------------------------------------ 7. Abstract IUE observations have established that high-velocity variability in UV P-Cygni profiles is a fundamental property of radiatively-driven winds, and that this variability is a signature of the line-driven instability. It is unclear, however, whether the variability is completely intrinsic to the flow, or if it requires a perturbing `seed' from the low-velocity regime. IUE observations lack adequate signal/noise to address this problem; existing HST results are ambiguous. We propose to obtain high-quality time-series HRS spectroscopy of 68 Cygni, a star extensively observed with IUE, in order to provide an empirical answer to this question. These data will distinguish between low-velocity, mechanically-driven instabilities and intrinsic, radiatively-driven instabilities, and will define the interaction of the two regimes. The results will, in turn, have wider implications for the applicability of steady-state wind models, and will provide basic constraints on our radiation hydro code. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 2.17 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5315 PI: Ian D. Howarth Proposal Title: THE SEAT OF STELLAR-WIND INSTABILITIES: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Ian D. Howarth 8090 UK X Stan P. Owocki 1845 USA Raman K. Prinja 8090 UK X ------------------------------------------------------------------------------------ 3. Description of proposed observations. In order to monitor short-timescale (hour) variability in stellar-wind outflows, the P-Cygni profiles of NV (1240A), SiIV (1400A) and CIV (1550A) are to be observed in the spectrum of HD203064 once every orbit for 19 orbits, at high S/N, with the G160M grating. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Only HST can provide the necessary high S/N in the UV resonance lines of interest. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The prime driver for this programme is to obtain adequately sampled time-series spectra over the maximum likely development time for a `discrete absorption component' in the stellar wind. "Adequately sampled" implies an absolute minimum frequency of once per orbit, while the maximum recurrence time is about 25 hours. The observations should therefore be scheduled to take place once per orbit for 19 consecutive orbits, a bare minimum sampling rate for a length of time certain to catch at least one event. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. None ------------------------------------------------------------------------------------ 8. Additional comments or special requests. Advance notification of scheduling will allow co-ordinated ground- based spectroscopy to be arranged. ------------------------------------------------------------------------------------ 9. Description of previous HST work. We have used data from the science verification phase, in combination with IUE spectra, to study variability in P-Cygni profiles of Zeta Oph. Those data show no discrete features at velocities of less than about 1100 km/s, supporting a purely intrinsic origin for wind variability. However, this behaviour appears to be different to that seen in Xi Per, which is more closely similar to 68 Cyg. Xi Per and Zeta Oph are the only two stars for which HST data suited to the study of low-velocity variable features are available to us. In neither case is the time sampling adequate, and there are no time series observations with suitable sampling in the archive. Page 3 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Extensive interactive data-analysis capabilities through the major Starlink node sited at UCL (both Unix and VMS machines), plus usual `well-founded laboratory' facilities. The UCL O-star group currently consists of one staff member (IDH), one research fellow (RKP), two research assistants, and two postgrad students. Manpower at about this level is expected to be maintained for the foreseeable future, and will be drawn on as necessary for the analysis of the HST data. The group at Bartol includes one associate professor (SPO), two research scientists (Alex Fullerton and Ken Gayley), and two graduate students (Glenn Cooper and Steven Cranmer). Owocki has worked extensively on the theory of the wind instabilty, and developed the radiation hydrodynamics code to simulate its nonlinear evolution. This code is run on remote Crays accessed via Internet to Bartol's local VMS/VAX cluster. Fullerton has done extensive observations of optical line variability in O stars, and Gayley works on theory of line transfer in hot-star winds. Cooper is currently completing a Ph.D thesis on X-ray emission from instability-driven shocks, and Cranmer is beginning a thesis aimed at exploring the effect of rotation on the formation of unstable wind structure. ------------------------------------------------------------------------------------ 11. Address Information Name: IAN D. HOWARTH Category: PI Institution: 8090 Address: DEPT. PHYSICS AND ASTRONOMY UNIVERSITY COLLEGE LONDON GOWER STREET City: LONDON State: Zip Code: WC1E 6BT Country: UK Telephone: 01044-71-387-7050 Telex (or e-mail): (SPAN) 19752::IDH ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5315 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD210839 A,105 RA = 22H 11M 30.6S +/- J2000 1 V = 5.04 +/- 0.02, TYPE=O6I LAMBACEP 0.01S, 1 B-V = +0.25 +/- 0.01 DEC = +59D 24' 52.1" +/- 2 E(B-V) = 0.55 +/- 0.03 0.1" 3 F-CONT(1240) = 1.0 +/- 0.2 E-10 4 F-CONT(1400) = 1.2 +/- 0.2 E-10 5 F-CONT(1550) = 1.5 +/- 0.2 E-10 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5315 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD210839 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=3 4.5S 1 CYCLE 4 BRIGHT=RETURN ONBOARD ACQ for 9- LOCATE=YES 11 GROUP 9-22 WITHIN 4D ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE # HRS ACCUM # G160M 1398 FP-SPLIT=FOUR 1 545S 100 4 1 CYCLE 4 ORBIT COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 3 DEFINE # HRS ACCUM # G160M 1240 FP-SPLIT=FOUR 1 545S 100 3 1 CYCLE 4 ORBIT COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 4 DEFINE # HRS ACCUM # G160M 1398 FP-SPLIT=FOUR 1 545S 100 4 1 CYCLE 4 ORBIT COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 5 DEFINE # HRS ACCUM # G160M 1549 FP-SPLIT=FOUR 1 436S 100 5 1 CYCLE 4 ORBIT COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 6 DEFINE # HRS ACCUM # G160M 1398 FP-SPLIT=FOUR 1 545S 100 4 1 CYCLE 4 ORBIT COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 7 DEFINE # HRS ACCUM # G160M 1240 FP-SPLIT=FOUR 1 545S 100 3 1 CYCLE 4 ORBIT COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 8 DEFINE # HRS ACCUM # G160M 1398 FP-SPLIT=FOUR 1 545S 100 4 1 CYCLE 4 ORBIT COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 9 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 10 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 11 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5315 [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 12.5 HD210839 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=3 4.5S 1 CYCLE 4 BRIGHT=RETURN ONBOARD ACQ for 13 LOCATE=YES -15 AFTER 11 by 8H ------------------------------------------------------------------------------------------------------------------------------------ 13 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 14 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 15 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 16.5 HD210839 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=3 4.5S 1 CYCLE 4 BRIGHT=RETURN ONBOARD ACQ for 17 LOCATE=YES -19 AFTER 15 by 8H ------------------------------------------------------------------------------------------------------------------------------------ 17 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 18 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 19 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 20.5 HD210839 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=3 4.5S 1 CYCLE 4 BRIGHT=RETURN ONBOARD ACQ for 21 LOCATE=YES -22 AFTER 19 by 8H ------------------------------------------------------------------------------------------------------------------------------------ 21 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ 22 USE HD210839 2.0 ORBIT ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5315 [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN LOCATE=YES FP-SPLIT=FOUR COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 2.17 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category MASSIVE STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 4; ONBOARD ACQ for 9-11; GROUP 9-22 WITHIN 4D; ONBOARD ACQ for 13-15; AFTER 11 by 8H; ONBOARD ACQ for 17-19; AFTER 15 by 8H; ONBOARD ACQ for 21-22; AFTER 19 by 8H; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-A2 G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD210839 LAMBACEP ------------------------------------------------------------------------------------------------------------------------------------