6489( 12) - 05/06/96 08:57 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6489 Version: 12 Check-in Date: 06-May-1996 08:54:44 1.Proposal Title: The Identification and Cooling of the White Dwarf in the WZ Sge-Like System AL Com ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Binaries and Star For GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Paula Szkody University of Washington CoI: Dr. Ed Sion Villanova N CoI: Steve Howell Planetary Science Institute N CoI: Dr.Warren Sparks Los Alamos National Lab N ------------------------------------------------------------------------------------ 6. Abstract We propose to obtain 3 FOS observations (one in 1996 Feb, one in April and one in June) in order to identify and measure the cooling of the white dwarf in the WZ Sge- like system AL Com, which underwent a long outburst in April-June 1995. Unlike most dwarf novae systems, which undergo outbursts on timescales of weeks to months and which last only days to 2 weeks at most, the recurrence for AL Com is 20 yrs and its outburst lasted 2 months. This is very similar to the system WZ Sge (recurrence of 33 yrs and outburst length of 4 months). The UV cooling of WZ Sge lasted for more than 3 yrs and enabled the determination of the heating and cooling properties of its highly unusual DAQZ white dwarf. Obtaining the cooling curve of AL Com in the 1150-2500Angstrom region will finally allow further tests of accretion heating in the regime of extremely low viscosity and mass transfer rate that exists in these very long timescale systems. In addition, we will be able to determine the temperature and type of white dwarf in comparison to the highly unusual one in WZ Sge. We have waited 17 yrs (since the 1978 outburst of WZ Sge) to find another comparable system. ------------------------------------------------------------------------------------ 6489( 12) - 05/06/96 08:57 - [ 2] Observations Description ------------------------ We will make 3 observations over the Feb-June interval. The first 2 will take place in Feb and April and will use 2 orbits of dark-time, and the third will take place in June and use 4 orbits of dark-time. Each will use the FOS/BL with G160L to obtain low resolution (4.6-10A) spectra from 1150-2510A. We used the known UV flux of WZ Sge at quiescence (2.5E-14 at 1500A) and scaled by the difference in optical magnitudes between WZ Sge and AL Com (4.5 mag = factor of 63) to estimate the quiescent flux of AL Com at 1500A will be about 4E-16. Using the value of S (at 1500A) and T (for 1 arcsec aperture) with this flux gives a count rate of 0.019 c/s/diode. With a correction factor of 1.37 for a count rate close to dark count yields a time of 97 min to reach a signal-to- noise of 9. This is the equivalent of 4 orbits of dark time (25 min/orbit). The first observation is expected to have a higher flux (by a factor of 4) and the second (by a factor of 2-3) so we will use 50 min (2 orbits) of integration. Real Time Justification ----------------------- We need 3 observations separated by about half a year and before the object returns to UV quiescence. To fit these in before the sun constraints prevent observations (the end of July), we need the first observation in the beginning of Feb, the second in April and the third in June. In order to eliminate the effects of geocoronal Lyman alpha, we need to use the dark-time (shadow) portions for fitting. Calibration Justification ------------------------- Additional Comments ------------------- Program will begin earlier than normal Cycle 6 programs in order to catch AL Com during its cooling following its April 95 outburst. ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6489( 12) - 05/06/96 08:57 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 AL-COM STAR, DWARF NOVA RA=12H 32M 25.86S +/- 0.02S, J2000.0 V = 20.0+/-0.5 DEC=14D 20' 42.7" +/- 0.2", B-V = 0.1+/-0.2 PLATE-ID=00G0 F-CONT(1500)=8+/-4e-16 6489( 12) - 05/06/96 08:57 - [ 4] Visit: 01 Visit Requirements: BETWEEN 1-FEB-96 AND 29-FEB-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 AL-COM FOS/BL ACQ/BIN 4.3 MIRROR 1 250S ONBOARD ACQ FOR 11 ARY ------------------------------------------------------------------------------------------------------------------------------------ 11 AL-COM FOS/BL RAPID 1.0-PAI G160L 1150-25 READ-TIME=60 1 66.0M R-A 10 ------------------------------------------------------------------------------------------------------------------------------------ 6489( 12) - 05/06/96 08:57 - [ 5] Visit: 02 Visit Requirements: BETWEEN 1-APR-96 AND 30-APR-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 AL-COM FOS/BL ACQ/BIN 4.3 MIRROR 1 370S ONBOARD ACQ FOR 21 ARY ------------------------------------------------------------------------------------------------------------------------------------ 21 AL-COM FOS/BL RAPID 1.0-PAI G160L READ-TIME=60,STEP-PATT=SINGLE 1 66.0M R-A ------------------------------------------------------------------------------------------------------------------------------------ 6489( 12) - 05/06/96 08:57 - [ 6] Visit: 03 Visit Requirements: BETWEEN 1-JUN-96 AND 30-JUN-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 30 AL-COM FOS/BL ACQ/BIN 4.3 MIRROR 1 370S ONBOARD ACQ FOR 31 ARY ------------------------------------------------------------------------------------------------------------------------------------ 31 AL-COM FOS/BL RAPID 1.0-PAI G160L READ-TIME=60,STEP-PATT=SINGLE 1 155.0M EXPAND R-A ------------------------------------------------------------------------------------------------------------------------------------ 6489( 12) - 05/06/96 08:57 - [ 7] Visit: 04 Visit Requirements: BETWEEN 1-FEB-96 AND 29-FEB-96 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 AL-COM FOS/BL ACQ/BIN 4.3 MIRROR 1 250S ONBOARD ACQ FOR 11 ARY ------------------------------------------------------------------------------------------------------------------------------------ 11 AL-COM FOS/BL RAPID 1.0-PAI G160L 1150-25 STEP-PATT=SINGLE,READ-TIME=60 1 66.0M R-A 10 ------------------------------------------------------------------------------------------------------------------------------------ 6489( 12) - 05/06/96 08:57 - [ 8] Summary Form for Proposal 6489 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters READ-TIME=60 STEP-PATT=SINGLE ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Binaries and Star Formation ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 1-FEB-96 AND 29-FEB-96 ONBOARD ACQ FOR 11 BETWEEN 1-APR-96 AND 30-APR-96 ONBOARD ACQ FOR 21 BETWEEN 1-JUN-96 AND 30-JUN-96 ONBOARD ACQ FOR 31 EXPAND ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G160L ------------------------------------------------------------------------------------------------------------------------------------ Target Names AL-COM ------------------------------------------------------------------------------------------------------------------------------------