Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4651c Report Date: 09-May-96:19:45 Version: ********** Check-in Date: ********** 1.Proposal Title: THE SEAT OF STELLAR-WIND INSTABILITIES ------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------ 7. Abstract IUE observations have established that variability in UV P-Cygni profiles is a fundamental property of radiatively-driven winds, and it is generally agreed that this variability is a signature of the line-driven instability. What remains unclear is whether the variability is completely intrinsic to the flow, or if it requires `seeding' 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. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 1.12 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 4651c PI: Ian D. Howarth Proposal Title: THE SEAT OF STELLAR-WIND INSTABILITIES ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Ian D. Howarth UNIVERSITY COLLEGE LONDON UNITED KING X Raman K. Prinja UNIVERSITY COLLEGE LONDON UNITED KING X ------------------------------------------------------------------------------------ 3. Description of proposed observations. In order to monitor short-timescale (hourly) 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 (now only 11)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. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The frequency and length of the observations is dictated by the timescales for growth and development of discrete absorption features in the profiles. At low velocities we predict that they will accelerate from 0.1v(infinity) to 0.3v(infinity) in 1.5 hours [and to 0.5v(infinity) in 3 hours]. The recurrence timescale averages approximately 20 hours, up to 25 hours. Thus observations every 1.5: hours are required for 30 hours to ensure that a low-velocity feature is caught and its early development followed. The Phase II resource estimator has shown these observations to be more `expensive' than Phase I indicated, so the number of visits has been nearly halved. There is still a good chance that the early phases of DAC development will be caught. ------------------------------------------------------------------------------------ 11. Address Information Name: Ian D. Howarth Category: PI Institution: University College London Address: Gower Street City: London WC1E 6BT State: Zip Code: Country: UNITED KINGDOM Telephone: (44)-71-387-7050 Telex (or e-mail): 28722 ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4651c [ 3] ------------------------------------------------------------------------------------------------------------------------------------ 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 HD203064 A,185 RA = 21H 18M 27.19S +/- J2000 1 V = 5.00 +/- 0.02, TYPE=O7.5III 68CYG 0.01S, 2 B-V = -0.01 +/- 0.01 DEC = +43D 56' 45.5" +/- 3 E(B-V) = 0.3 +/- 0.03 0.1" 4 F-CONT(1240) = 6.5 +/- 0.2 E-10 5 F-CONT(1400) = 6.0 +/- 0.2 E-10 6 F-CONT(1550) = 5.0 +/- 0.2 E-10 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4651c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 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 HD203064 HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=3 1.8S 1 ONBOARD ACQ FOR 2- BRIGHT=RETURN 4 LOCATE=YES SEQ 1-4 NO GAP REPEAT 1-4 EVERY 90M +/- 30M FOR 10 MORE TIMES CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD203064 HRS ACCUM 2.0 G160M 1240 FP-SPLIT=STD 1 109S 100 4 1 CYCLE 3 COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 3 HD203064 HRS ACCUM 2.0 G160M 1398 FP-SPLIT=STD 1 109S 100 5 1 CYCLE 3 COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ 4 HD203064 HRS ACCUM 2.0 G160M 1549 FP-SPLIT=STD 1 109S 100 6 1 CYCLE 3 COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4651c [ 5] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN LOCATE=YES FP-SPLIT=STD COMB=FOUR STEP-PATT=5 DOPPLER=ON ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 1.12 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category MASSIVE STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-4; SEQ 1-4 NO GAP; REPEAT 1-4 EVERY 90M +/- 30M FOR 10 MORE TIMES; CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-A2 G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD203064 68CYG ------------------------------------------------------------------------------------------------------------------------------------