7734( 3) - 09/12/97 09:29 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7734 Version: 3 Check-in Date: 12-Sep-1997 09:28:25 1.Proposal Title: UV Eclipse Spectroscopy of Accretion Disk Winds ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARY STARS GO/CAR 7 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: KEITH MASON MULLARD SPACE SCIENCE LABORATORY CoI: J.E. Drew Oxford University N CoI: C. Knigge Oxford University N ------------------------------------------------------------------------------------ 6. Abstract We shall monitor wind-formed UV lines in the highly inclined disk-accreting CV, UX UMa as they are eclipsed by the companion star. By measuring the way in which lines from several different ionic species change in shape and strength as the wind is progressively covered, we will probe its ionisation structure as well as its geometry and kinematics. The data will be compared with the results of Monte Carlo simulation of the line profiles to provide quantitative constraints on outflow collimation, acceleration, and mass- loss rate. Our goal is to build a full and self consistent model for the wind and to determine where in the system the wind originates (e.g. white dwarf, boundary layer, or disk). We will then be in a position to investigate what drives the wind and the effect it has on the underlying accretion disk structure. The proposal builds on highly successful observations of UX UMa begun by us in Cycle 2 in a restricted wavelength range. Repairs to the GHRS now permit its full potential for such a study to be realised. This is a carryover of part of GHRS proposal 6079 modified to use STIS. ------------------------------------------------------------------------------------ 7734( 3) - 09/12/97 09:29 - [ 2] Observations Description ------------------------ Our scientific objectives call for time sequences of spectra which follow the target through eclipse by the companion star. Thus the length of observation is determined by the duration of eclipse rather than by signal to noise considerations. We plan to use the G140L grating on side 1 of the GHRS which gives the optimum balance between spectral resolution and wavelength coverage for this application. The combination will yield 0.7Angstrom per pixel, sufficient to resolve, and derive separate eclipse light curves for, all the major features of the lines (for example the FWHM of the narrow absorption features seen in CIV is about 2Angstrom). The lines to be observed range from CIII 1175Angstrom at the shortward extreme to HeII 1640Angstrom at the longward extreme. This can be covered with two grating settings, centered at about 1293Angstrom and 1523Angstrom. The continuum eclipse of UX UMa lasts for about 20 minutes, the eclipse of the lines for about 30-40 minutes. This can be contained within one spacecraft orbit. To guard against variability unrelated to the binary motion, we propose to observe two eclipses at each grating setting. To maximise coverage of the eclipse, we would in some cases acquire the target in the previous spacecraft orbit. The remainder of the acquisition orbit would be used to obtain an unambiguous out- of-eclipse spectrum for comparison with the spectrum during eclipse. This is an essential reference. Our previous work has demonstrated the existance of orbital-phase related changes in the line profiles outside of eclipse. These are presently unexplained, but may have important consequences for the modelling of the wind and the changes during eclipse. We therefore plan one contiguous series of 4 spacecraft orbits where we monitor the eclipse in the first and fourth orbits (the orbital period of UX UMa is very close to an exact number (three) of HST orbits) and the more general orbital changes in between. Allowing for coverage of four eclipses, and for acquisition and out-of- eclipse spectra, we require a total of 8 spacecraft orbits to observe UX UMa. Though the exposure time is determined by phase coverage rather than the source flux, it is important to note that UX UMa is one of the brightest high inclination nova-like CV. The continuum near 1500Angstrom\\\\\\\\ should yield a flux of 2* 10^-13 erg cm^- 2s^-1AA^-1 (based on the IUE ULDA). This translates to a S/N of 10 per diode in about 1.5 minutes (0.005 in phase). This is adequate for our purposes as demonstrated by our cycle 2 observations of UX UMa (made with the G160M grating on side 2 of GHRS prior to the COSTAR repair mission). The peak flux in the CIV emission line (the brightest of the wind-formed resonance lines) is about twice that of the continuum. Real Time Justification ----------------------- The observations must occur at a specific phase in the orbital cycle of the binary in order to sample the eclipse. The binary period of UX UMa is 0.196671278 days, and observations of the eclipse should start at about phase 0.93+/-0.02. The eclipse should be centered in the spacecraft viewing window as well as possible. Supporting ground based photometry may be arranged, but is not essential and should not influence the HST scheduling. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7734( 3) - 09/12/97 09:29 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7734( 3) - 09/12/97 09:29 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 UXUMA STAR,Nova- RA=13H 36M 40.97S +/- J2000 V = 12.7+/-0.3 like,Interacting Binary 0.02S,DEC=51D 54' 50.2" +/- B-V = 0.0 0.3",PLATE-ID=00XN F-LINE(1549)=5+/-1e-13 W-LINE(1549)=15+/-5 F-CONT(1549)=2+/-0.3e-13 F-LINE(1640)=2+/-0.2e-13 W-LINE(1640)=10+/-3 F-CONT(1640)=2+/-0.3e-13 A(V) = 0.06+/-0.06 Comments: Eclipsing variable star - mid-eclipse V=14.1 7734( 3) - 09/12/97 09:29 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PERIOD 0.196671278 D AND ZERO-PHASE JD2443904.878720 On Hold Comments: Additional Comments: Exact timings adjustable in consultation with PI to accomodate actual HST orbit schedule most efficiently. Exposure times dictated by time coverage, not S/N Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 UXUMA STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S ONBOARD ACQ FOR 2-3 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 UXUMA STIS/F TIME-TA 52X2 G140M 1550 BUFFER-TIME=3200 1 26 M UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 3 UXUMA STIS/F TIME-TA 52X2 G140M 1550 BUFFER-TIME=3200 1 40 M PHASE 0.91 TO 0.95 UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 7734( 3) - 09/12/97 09:29 - [ 6] Summary Form for Proposal 7734 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT BUFFER-TIME=3200 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/CAR ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARY STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PERIOD 0.196671278 D AND ZERO-PHASE JD2443904.878720 ONBOARD ACQ FOR 2-3 PHASE 0.91 TO 0.95 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names UXUMA ------------------------------------------------------------------------------------------------------------------------------------