6421( 4) - 03/08/96 09:25 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6421 Version: 4 Check-in Date: 08-Mar-1996 09:22:54 1.Proposal Title: Resolving the Unique Magnetic/Non- Magnetic Double-Degenerate Binary LB 11146 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Gary Schmidt University of Arizona CoI: James Liebert University of Arizona N CoI: Paul Smith University of Arizona Y ------------------------------------------------------------------------------------ 6. Abstract LB 11146 is an unresolved binary of unknown period consisting of a nonmagnetic (B_e < 30 kG) white dwarf plus a component with one of the strongest magnetic fields yet found on a white dwarf (B_e ~ 700 MG). The magnetic star also possesses a different atmospheric composition than its hydrogen-dominated companion, as it exhibits several broad spectral features that cannot be attributed to hydrogen in the presence of a strong magnetic field. Finally, the binary is the only known double- degenerate system where the total mass exceeds the Chandrasekhar limit. Knowledge of the current component separation is critical for understanding whether the peculiar end-state of this binary is a result of differences in the star-formation process or of a peculiar mass-transfer or common-envelope effect. Radial velocity studies appear to preclude short periods (a \lta 0.1 AU), while ground-based images are unresolved at the limit of ~20 AU. We propose to investigate the important region 2- 20 AU ("s0.05-"s0.5) through FOC imaging. Frames obtained at two different wavelengths and covering just one HST orbit will distinguish between the two components and at the same time test a model of LB 11146 based on a spectroscopic decomposition of the binary. ------------------------------------------------------------------------------------ 6421( 4) - 03/08/96 09:25 - [ 2] Observations Description ------------------------ Simulations based on the known combined spectral flux of the two components and of the point-spread function of HST+FOC have demonstrated that the goals of this project can be reached with just two FOC/96 (512*512) images; one a 1200 s exposure using the F307M+F6ND filters; the other of 600 s duration using F550M+F2ND. These filter combinations ensure that the count rate will be linear even if the binary is not resolved. The exposure time has been set so that a signal-to- noise-ratio of at least 40 is reached for each component assuming the fluxes derived in the Liebert et al. (1993) model. ``FOCSIM'' calculations estimate ~340 counts in the central pixel for each star in the F550M+F2ND observation. For F307M+F6ND in 1200 s, we expect ~180 cts and ~360 cts in the central pixel for the nonmagnetic and magnetic components, respectively. In both exposures the background is <=sssim1 count. The target will be acquired using the ``Blind Pointing'' procedure (Mode III target acquisition). The images will only require 1 orbit to acquire. No special calibrations will be needed. begintabularlll Cycle 6 & Primary Orbits:1 & Exposures:2, endtabular Real Time Justification ----------------------- None. None. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6421( 4) - 03/08/96 09:25 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LB11146 STAR, Composite RA=09H 48M 46.74S +/- 1.0", J2000 V = 14.4+/-0.1 Spectral Type DEC=24D 21' 27.46" +/- 1.0", B-V = -0.15 PLATE-ID=01X3 6421( 4) - 03/08/96 09:25 - [ 4] Visit: 01 Visit Requirements: 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 LB11146 FOC/96 IMAGE 512X512 F550M,F2N5460 1 700S D ------------------------------------------------------------------------------------------------------------------------------------ 2 LB11146 FOC/96 IMAGE 512X512 F307M,F6N3080 1 1400S D ------------------------------------------------------------------------------------------------------------------------------------ 6421( 4) - 03/08/96 09:25 - [ 5] Summary Form for Proposal 6421 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOC/96 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F550M,F2ND F307M,F6ND ------------------------------------------------------------------------------------------------------------------------------------ Target Names LB11146 ------------------------------------------------------------------------------------------------------------------------------------