7755( 6) - 10/17/97 10:18 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7755 Version: 6 Check-in Date: 17-Oct-1997 10:17:26 1.Proposal Title: Fundamental Parameters of White Dwarfs in Close Binaries with Late-Type Stars ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO/CAR 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: STEPHANE VENNES UC BERKELEY CoI: Prof. John R. Thorstensen Dartmouth College, Department of Physics N and Astronomy CoI: Elisha Polomski University of Florida, Astronomy N Department ------------------------------------------------------------------------------------ 5. Abstract White dwarfs in close binaries, in a degenerate pair or with a main sequence companion, emerge from a common envelope phase, concomitant with the passage of the most evolved component through the asymptotic giant branch. The properties of the present-day binary are dictated by the efficiency of the momentum transfer leading to orbital shrinkage and mass ejection from the system (PN). Little is known of this process. Three new close binaries similar to the prototypical system Feige 24 (P=4.2d) consisting of a hot white dwarf star and a late-type companion (dM) have been identified in extreme ultraviolet all-sky surveys (EUVE J0720-317, EUVE J1016- 053, EUVE J2013+400); these objects may represent a dominant phase of white dwarf evolution. We have completed accurate radial velocity studies of the main sequence companion in the three new systems using echelle spectroscopy at Lick Observatory from which we derived accurate orbital ephemerides and mass functions. Extreme Ultraviolet Explorer spectroscopy of the system EUVE J1016-053 also revealed a peculiar abundance pattern in the white dwarf atmosphere, possibly the signature of intense accretion from the close mass-losing companion. We show that GHRS observations will solve the question of the peculiar surface abundance of the accreting white dwarf and also accurately solve the mass function of the system and constrain models of close binary evolution. ------------------------------------------------------------------------------------ 7755( 6) - 10/17/97 10:18 - [ 2] Observations Description ------------------------ We propose to make spectroscopic observations at wavelengths between 1150 and 1750 Angstroms of Feige 24, a white dwarf binary system, and to measure orbital velocities at 2 different orbital phases. Because the binary orbital periods are on the order of a few hours, the observations must be constrained to within one, or at the most two orbits to minimize the effects of blurring in velocity. This also limits the S/N to about 20 (in the following Table, 1st orbital phase refers to phi=0.75 and 2nd orbital phase to phi=0.25). Wavelength calibrations are needed to determine the wavelength zero point accurately and subsequently calculate velocities. A WAVECAL is performed for each new exposure. A WAVECAL allows wavelength zero points to be determined more accurately. In order to minimize blurring in velocity, as a Special Requirement each WAVECAL must follow the ACCUM exposure to which it applies and must not be split from its group of ACCUM exposures. For the E140M grating, this allows wavelengths to be determined to a greater accuracy than 0.5 pixel. Object Name Wavelength Flux Exposure S/N Orbits (angstroms) (erg cm-2 s-1 angs-1) (min) Feige 24(1st phase) 1300 5.6e-12 20 34 1 Feige 24(2nd phase) 1300 5.6e-12 20 34 1 An example of a typical exposure calculation follows: Feige 24 has a flux at 1300 angstroms (from IUE) of 5.6e-12 erg cm-2 s-1 angstroms-1. Neither scattered light nor dark count are important for our purposes. Using the "Exposure Time Calculator" we determined that an exposure of 20 minutes result in a signal-to-noise ratio of 34 (per resolution element). Real Time Justification ----------------------- To maximize the relative accuracy of the measurement of the primary orbital velocity amplitude, we suggest to conduct the observations near binary orbital quadratures. The ephemeris of each system is known to sufficient accuracy to provide accurate scheduling in the forecoming decade. However, it is sufficient to schedule each visit using the spacecraft orbit nearest to the desired binary phase. With orbital periods ranging from 17 hours to 4 days, scheduling opportunities arise regularly on corresponding intervals of time. Accurate ephemeris and orbital motion for the secondary have been determined prior to the proposed HST observations. Calibration Justification ------------------------- Wavelength calibrations are needed to determine the wavelength zero point accurately and subsequently calculate velocities. A WAVECAL is performed for each new exposure. A WAVECAL allows wavelength zero points to be determined more accurately. In order to minimize blurring in velocity, as a Special Requirement each WAVECAL must follow the ACCUM exposure to which it applies and must not be split from its group of ACCUM exposures. Additional Comments ------------------- ------------------------------------------------------------------------------------ 7755( 6) - 10/17/97 10:18 - [ 3] Data Distribution Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7755( 6) - 10/17/97 10:18 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WD0232+035 STAR,DA RA=02H 35M 07.51S +/-0.02S, J2000 V = 12.42+/-0.01 DEC=+03D 43' 56.6" +/-0.3", TYPE=DA PLATE-ID=002M B-V = -0.24+/-0.01 F(1300)=56+/-5.6e-13 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1982.882 0.0057 0.0086 0.0 7755( 6) - 10/17/97 10:18 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PERIOD 4.23160D AND ZERO-PHASE JD2448578.397 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WD0232+035 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S PHASE 0.23 TO 0.25 CD P ONBOARD ACQuisition FOR 2-3 SEQ 1-3 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 WD0232+035 STIS/F ACCUM 0.2X0.2 E140M 1425 1 30 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7755( 6) - 10/17/97 10:18 - [ 6] Visit: 02 Visit Priority: Visit Requirements: PERIOD 4.23160D AND ZERO-PHASE JD2448578.397 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WD0232+035 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S PHASE 0.73 TO 0.75 CD P ONBOARD ACQuisition FOR 2-3 SEQ 1-3 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 WD0232+035 STIS/F ACCUM 0.2X0.2 E140M 1425 1 28 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 WAVE STIS/F ACCUM 0.2X0.2 E140M 1425 1 DEF UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7755( 6) - 10/17/97 10:18 - [ 7] Summary Form for Proposal 7755 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/CAR ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PERIOD 4.23160D AND ZERO-PHASE JD2448578.397 PHASE 0.23 TO 0.25 ONBOARD ACQuisition FOR 2-3 SEQ 1-3 NON-INT PHASE 0.73 TO 0.75 ONBOARD ACQuisition FOR 2-3 SEQ 1-3 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names WD0232+035 WAVE ------------------------------------------------------------------------------------------------------------------------------------