6700( 5) - 12/13/96 09:47 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6700 Version: 5 Check-in Date: 13-Dec-1996 09:45:15 1.Proposal Title: GHRS SPECTROSCOPY OF THE EXPOSED WHITE DWARF IN THE HIGH ACCRETION RATE DWARF NOVA RX AND ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Edward Sion VILLANOVA UNIVERSITY CoI: Dr. Paula Szkody University of Washington at Seattle N CoI: Dr. Ivan Hubeny Goddard Space Flight Center N CoI: Dr. Min Huang Villanova University N CoI: Dr. Al Holm Space Telescope Science Institute N CoI: Dr. Fuhua Cheng University of Maryland N CoI: Dr. Janet Mattei American Association of Variable Star N Observers CoI: Dr. Constanze la Dous VILSPA N CoI: Dr. Barbara Hassall Oxford University N CoI: Dr. Emmi Meyer-Hofmeister Max-Planck Institute, Garching N CoI: Dr. Fritz Myer Max-Planck Institute, Garching N ------------------------------------------------------------------------------------ 6. Abstract Out of the six dwarf novae with exposed white dwarfs studied with Hubble during quiescence, only one, U Gem, lies above the period gap where mass transfer rates are generally higher and where the white dwarfs appear to be hotter (younger?) in CV systems with quite possibly shorter evolutionary histories. RX And and its exposed white dwarf fills an absolutely critical need for another system above the gap. Orbital Phase-resolved GHRS G140L observations near the quadratures of its orbit during quiescence will deliver the following fundamental information: (1) the white dwarf rotation rate; (2) the T_eff , log g and chemical abundances of the white dwarf; (3) the orbital velocity semi-amplitudes and hence a white dwarf mass independent of disk emission line velocities; (4) delineation by profile structure, line formation regions associated with a cooler more slowly rotating white dwarf photosphere versus formation regions of higher temperature ion species associated with a boundary layer/accretion belt (or putative hot corona?) still present surrounding the white dwarf; (5) the cooling response of the white dwarf to compressional and irradiative heating by the dwarf nova event (does it explain the UV flux decline, a problem for disk instability models?); (6) tests of physical mechanisms that control the flow of accreted elements and hence abundance changes (diffusion, mixing/dilution dredgeup and ongoing accretion during quiescence). ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to obtain three observations of RX And with the GHRS G140L grating (with the added scientific benefit of high time resolution) in order to secure spectra with a resolution of 1750 at Lyman Alpha, covering the wavelength interval 1150 -1430A. The three observations will be separated by 9.5 days over a 19 day interval. For RX And the continuum flux at 1300A is 5E-14, which we expect to yield 1400 cts/diode during a 25 minute exposure. Our GHRS spectra will be carried out in the ACCUM mode. We will use the best available orbital period, determined by Kaitchuk (1989, PASP, 101, 1129) who gives the following orbital ephemeris: 2447041.932 +/- 0.2098930 E +/- 0.002. Although we emphasize white dwarf studies during dwarf nova quiescence, if RX And goes into outburst, we would welcome and most surely deliver new science by analyzing the data thoroughly and modelling it with disk, belt, white dwarf combinations (as we did with the superoutburst FOS spectrum of VW Hydri (see Huang et al. 1996) while fully characterizing the parameters of the wind outflow which very likely arises from the inner disk/boundary layer (or the metal-laden hot white dwarf atmosphere itself.) Obtaining spectra in decline or rise to outburst would allow us to model the onset or gradual spindown and cooling of the inner disk/accretion belt. Our analysis will bring to bear the effects of (1) an absorbing curtain above the disk plane (cf. Sion et al. 1995, Horne et al. 1994), the effect of the H2 quasi-molecular absorption, the effect of an accretion belt, a full steady state accretion disk, a non-steady state disk and nearly completed optically thin disk models with vertical structure, being developed by our co-I Dr. Ivan Hubeny. In addition the temperature of the white dwarf in response to the outburst will be simulated with Sion's quasi- static stellar evolution code with time variable accretion and the effects of compressional heating and boundary layer irradiation (e.g. Sion 1995). In addition we will have 1D and 2D hydrodynamic simulations with shear mixing of angular momentum of the accreted material (e.g. Sparks, Sion, Starrfield, Austin 1993) Real Time Justification ----------------------- The outbursts of RX And range from 3-10 days while its quiescence ranges from 5 to 20 days (Ritter, CV catalog). The short timing of the cycle prohibits any target of opportunity status with HST. If we define a cycle length as one outburst + one quiescence, then the shortest cycle length is 8 days and the longest cycle length is 30 days, yielding an average cycle length of 19 days. Hence, if we obtain three spectra, with the second spectrum following the first by 9.5 days and the third spectrum spaced from the second by 9.5 days, we estimate, from long term AAVSO data, that there is a 34\\% probability that the first observation will take place in outburst while there is a 66\\% probability that the first spectrum will be in quiescence. Thus any random observation has about a 66\\% chance of being in quiescence. Hence, we are confident that over any 19 day interval (the average cycle length), three equally spaced observations will yield quiescent spectra. The probability that two of the three spectra are in outburst is 34\\% while the probability that one of the three is in outburst is 34\\% and the probability that all three are in quiescence is 34\\%. Thus there is almost a 70\\% probability that at least two of our proposed spectra will be in quiescence. The three observations should each be separated by 9.5 days; the first observation should be centered at 0.25 phase, the second observaton centered at 0.25 phase, and the third observation at 0.75 phase in order to sample the quadratures for the K1 velocity semi-amplitude and hence the white dwarf mass determination. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: Dr. E.M. Sion*Department of Astronomy and Astrophysics*Villanova University*800 Lancaster Avenue*Villanova, PA 19085 Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6700( 5) - 12/13/96 09:47 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 RX-AND STAR,DWARF RA=01H 04M 35.6S +/- 0.5S, J2000 V = 14.9+/-0.1 NOVA,INTERACTING BINARY DEC=+41D 17' 58.50" +/- 0.50" B-V = +0.1+/-0.05 E(B-V) = 0.0+/-0.1 F-CONT(1400)=5.0+/-1e-14 Comments: PERIOD 5.03H AND ZERO-PHASE JD2447041.932 6700( 5) - 12/13/96 09:47 - [ 2] Visit: 01 Visit Requirements: PERIOD 5.03H AND ZERO-PHASE JD2447041.932 On Hold Comments: Additional Comments: CENTER EXPOSURE ON PHASE 0.25 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 RX-AND HRS ACQ 2.0 MIRROR-N1 BRIGHT=RETURN,SEARCH-SIZE=5 1 25 S ONBOARD ACQ FOR 2 ------------------------------------------------------------------------------------------------------------------------------------ 2 RX-AND HRS ACCUM 2.0 G140L 1290 26 54.4 S PHASE 0.20 TO 0.30 Comments: CENTER ON ORBITAL PHASE 0.25 +/- 0.05 PHASE 0.0 OCCURS AT JD2447041.932 ------------------------------------------------------------------------------------------------------------------------------------ 6700( 5) - 12/13/96 09:47 - [ 3] Visit: 02 Visit Requirements: PERIOD 5.03H AND ZERO-PHASE JD2447041.932 On Hold Comments: Additional Comments: CENTER EXPOSURE ON PHASE 0.25 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 3 RX-AND HRS ACQ 2.0 MIRROR-N1 BRIGHT=RETURN,SEARCH-SIZE=5 1 25 S ONBOARD ACQ FOR 4 ------------------------------------------------------------------------------------------------------------------------------------ 4 RX-AND HRS ACCUM 2.0 G140L 1290 21 54.4 S PHASE 0.20 TO 0.30 NON-INT Comments: CENTER ON ORBITAL PHASE 0.25 +/- 0.05 PHASE 0.0 OCCURS AT JD2444071.932 ------------------------------------------------------------------------------------------------------------------------------------ 6700( 5) - 12/13/96 09:47 - [ 4] Visit: 03 Visit Requirements: PERIOD 5.03H AND ZERO-PHASE JD2447041.932 On Hold Comments: Additional Comments: CENTER EXPOSURE ON PHASE 0.75 Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 5 RX-AND HRS ACQ 2.0 MIRROR-N1 BRIGHT=RETURN,SEARCH-SIZE=5 1 25 S ONBOARD ACQ FOR 6 ------------------------------------------------------------------------------------------------------------------------------------ 6 RX-AND HRS ACCUM 2.0 G140L 1290 21 54.4 S PHASE 0.70 TO 0.80 NON-INT Comments: CENTER ON ORBITAL PHASE 0.75 +/- 0.05 PHASE 0.0 OCCURS AT JD=2447041.932 ------------------------------------------------------------------------------------------------------------------------------------ 6700( 5) - 12/13/96 09:47 - [ 5] Summary Form for Proposal 6700 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PERIOD 5.03H AND ZERO-PHASE JD2447041.932 ONBOARD ACQ FOR 2 PHASE 0.20 TO 0.30 ONBOARD ACQ FOR 4 PHASE 0.20 TO 0.30 NON-INT ONBOARD ACQ FOR 6 PHASE 0.70 TO 0.80 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N1 G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names RX-AND ------------------------------------------------------------------------------------------------------------------------------------