6544( 8) - 07/12/96 12:06 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6544 Version: 8 Check-in Date: 12-Jul-1996 12:01:38 1.Proposal Title: Dwarf Novae in Quiescence ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: KNOX LONG SPACE TELESCOPE SCIENCE INSTITUTE CoI: Timothy R. Kallman Goddard Space Flight Center N CoI: Yuan-Kuen Ko University of Michigan N CoI: Christian Knigge Space Telescope Science Institute N CoI: Christopher Mauche Lawrence Livermore National Laboratory N ------------------------------------------------------------------------------------ 6. Abstract We propose to use the GHRS to obtain moderate (Lambda / Delta Lambda ~ 2000 ) resolution, high S/N 1160-1660 A spectra of the dwarf novae SS Cyg and WX Hyi in quiescence. We will carry out a detailed study of the resonance lines -- N V, CII, Si IV, C IV, and He II -- in these spectra to determine the surface flux of the resonance lines as a function of radius in the disk. The derived surface fluxes will allow us to determine whether X-ray photoionization of the disk explains the UV lines and the underlying continuum of these two dwarf novae (and by extension other cataclysmic variables) whose UV spectrum appears not to be dominated by the white dwarf in quiescence. We will also use the GHRS spectra to conduct a sensitive search for the narrow metal absorption lines that should reveal the hidden WD in these two dwarf novae. Finally, we will use the spectra in an attempt to constrain suggestions that absence of material in the inner accretion disk of a quiescent dwarf nova causes the delay in UV rise to outburst that is observed in dwarf nova outbursts. ------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 2] Observations Description ------------------------ We propose to obtain 3 observations of SS Cyg and of WX Hyi with the GHRS and the G140L grating in order to produce spectra with a resolution of 1750 at Lyman alpha to 2400 at C IV. Each observation will consist of two wavelength settings so that we may obtain a composite spectrum from 1160-1660 Angstrom and each observation will require two orbits to obtain a S/N of at least 70 per resolution element. This wavelength coverage is necessary so that we can study the 1s- 2p transition of N V, whose emission in the photoionization models is concentrated close to the WD, and the same transition in C IV, which should be much more extended. Another important transition Si IV will be sampled at both grating settings. In addition, the wavelength range 1160-1660 Angstrom contains a number of important absorption lines, including C III 1176, Si III 1295-1303, and Si IV 1394,1403 which would be expected if the WD temperatures are between 20,000 K and 60,000 K and N V1239,1243 and O V 1371 if the temperature is higher. The lower temperature lines were all seen in our FOS spectra of the WD in U Gem with 0.1 < EW < 2 A. We could have elected to use the FOS for these observations, but the resolution is lower, its efficiency at the shorter wavelengths is much lower, and the acquisitions, particularly for SS Cyg (because of its variability) would take longer with the FOS. We propose to space the observations out over a 9 week period for SS Cyg and over a 8 day period for WX Hyi. This will ensure that at least two of the observations are obtained when the system is in quiescence and avoid the necessity of requesting hard to schedule TOO observations. Given the duty cycle for outbursts (~20%) at least two of the three observations will be in quiescence and if the third observation occurs during outburst it will produce truly spectacular spectra of the wind-created lines (whose structure we would be pleased to analyze as well). For SS Cyg, in two orbits, each grating setting will be about 2400 s long, and will result in about 1200 counts per quarter stepped diode given the continuum flux from SS Cyg, which is about 1.2 * 10^-13 ergs/cm**2/s/A at 1300 Angstrom. Thus the S/N in the continuum in quiescence will be about 100 per two diode wide resolution element. We would observe in ACCUM mode with relatively short 2 minute increments in order to allow us to search for short-term variability in the disk, the WD, or the boundary layer. WX Hyi is a CVZ target and so the available exposure times in two orbits will be about 4200 s per grating in the first 2 orbit observation and potentially as large as 5600 s for the remaining observations. The continuum flux from WX Hyi toward the end of quiescence is 3.2*10^-14 ergs/cm**2/s/A at 1300 Angstrom. For the shorter exposures, we will obtain 575 counts per quarter-stepped diode, resulting in a S/N of 70 per resolution element. Real Time Justification ----------------------- The observations of SS Cyg should be scheduled at intervals of 3 weeks. This will ensure that two of the three observations occur in quiescence. The observations of WX Hyi should be scheduled at intervals of separated by 4 days( although this may not be possible given the limited duration of CVZ opportunities). This will ensure that two of the observations occur in quiescence. There are NO orbital phase requirements. Since we have not asked that these observations be TOO observations, there is a possiblitity that the objects will be in outburst for one of the observations. Outbursts typically last a day for WX Hyi and 7-14 days for SS Cyg. Therefore it is important that the observations not be scheduled too close together since in that case an outburst could wipe out the primary science in several visits. We have adopted therefore included special requirements to prevent subsequent observations of the same target from coming too close together. Individual 2-orbit observations of WX Hyi are long enough that they will cover an entire orbital period. SS Cyg and WX Hyi are monitored by the AAVSO. We will work closely with Janet Mattei, with whom we have an established and excellent relationship, in order to assure that we have comprehensive optical coverage of these DN both before and during the observations. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: STSCI Ship Via: Email: long@stsci.edu , ------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SS-CYG STAR,DWARF RA=21H 42M 42.56S +/- 1", J2000 F(1300)=1.6+/-0.4e-13 NOVA,ACCRETION DISK, DEC=43D 35' 9.8" +/- 1", PLATE- ID=01KD Comments: Flux listed above is in quiescence. In outburst, the flux peaks near 1e-11 at 1300 A. Position is revised position from Downes and Shara catalogue 2 WX-HYI STAR,DWARF RA=2H 09M 50.66S +/- 1", DEC=- J2000 F(1300)=2.0+/-0.4e-14 NOVA,ACCRETION 63D 18' 39.9" +/- 1", PLATE- DISK,INTERACTING ID=04CA BINARY, Comments: Flux is for low state as measured with HUT on Astro-2. High state flux is about 1.4e-12 Position is revised position from Downes and Shara catalogue 6544( 8) - 07/12/96 12:06 - [ 5] 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 SS-CYG HRS ACQ 2.0 MIRROR-N1 1 18 S ONBOARD ACQ FOR 20-30 Comments: STEP-TIME=2 (200 counts/sec) ------------------------------------------------------------------------------------------------------------------------------------ 20 SS-CYG HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 30 SS-CYG HRS ACCUM 2.0 G140L 1375-16 FP-SPLIT=NO,STEP-PATT=DEF 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 6] Visit: 02 Visit Requirements: AFTER 01 BY 16D 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 SS-CYG HRS ACQ 2.0 MIRROR-N1 1 18 S ONBOARD ACQ FOR 20-30 Comments: STEP-TIME=2 (200 counts/sec) ------------------------------------------------------------------------------------------------------------------------------------ 20 SS-CYG HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 30 SS-CYG HRS ACCUM 2.0 G140L 1375-16 FP-SPLIT=NO,STEP-PATT=DEF 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 7] Visit: 03 Visit Requirements: AFTER 02 BY 16D 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 SS-CYG HRS ACQ 2.0 MIRROR-N1 1 18 S ONBOARD ACQ FOR 20-30 Comments: STEP-TIME=2 (200 counts/sec) ------------------------------------------------------------------------------------------------------------------------------------ 20 SS-CYG HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 30 SS-CYG HRS ACCUM 2.0 G140L 1375-16 FP-SPLIT=NO,STEP-PATT=DEF 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 8] Visit: 04 Visit Requirements: CVZ 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 WX-HYI HRS ACQ 2.0 MIRROR-N1 1 54 S ONBOARD ACQ FOR 20-50 Comments: STEP-TIME=6 (35 counts/sec) ------------------------------------------------------------------------------------------------------------------------------------ 20 WX-HYI HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 30 WX-HYI HRS ACCUM 2.0 G140L 1375-16 FP-SPLIT=NO,STEP-PATT=DEF 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 40 WX-HYI HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 50 WX-HYI HRS ACCUM 2.0 G140L 1375-16 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 9] Visit: 05 Visit Requirements: CVZ AFTER 04 BY 3D 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 WX-HYI HRS ACQ 2.0 MIRROR-N1 1 54 S SEQ 10-50 NON-INT ONBOARD ACQ FOR 20-50 Comments: STEP-TIME=6 (35 counts/sec) ------------------------------------------------------------------------------------------------------------------------------------ 20 WX-HYI HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 30 WX-HYI HRS ACCUM 2.0 G140L 1375-16 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 40 WX-HYI HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 50 WX-HYI HRS ACCUM 2.0 G140L 1375-16 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 10] Visit: 06 Visit Requirements: CVZ AFTER 05 BY 3D 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 WX-HYI HRS ACQ 2.0 MIRROR-N1 1 54 S SEQ 10-50 NON-INT ONBOARD ACQ FOR 20-50 Comments: STEP-TIME=6 (35 counts/sec) ------------------------------------------------------------------------------------------------------------------------------------ 20 WX-HYI HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 30 WX-HYI HRS ACCUM 2.0 G140L 1375-16 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 40 WX-HYI HRS ACCUM 2.0 G140L 1150-14 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 36 ------------------------------------------------------------------------------------------------------------------------------------ 50 WX-HYI HRS ACCUM 2.0 G140L 1375-16 STEP-PATT=DEF,FP-SPLIT=NO 20 108.8 S 61 ------------------------------------------------------------------------------------------------------------------------------------ 6544( 8) - 07/12/96 12:06 - [ 11] Summary Form for Proposal 6544 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters STEP-PATT=DEF FP-SPLIT=NO ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 20-30 AFTER 01 BY 16D AFTER 02 BY 16D CVZ ONBOARD ACQ FOR 20-50 CVZ AFTER 04 BY 3D SEQ 10-50 NON-INT ONBOARD ACQ FOR 20-50 CVZ AFTER 05 BY 3D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N1 G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names SS-CYG WX-HYI ------------------------------------------------------------------------------------------------------------------------------------