9459( 9) - 04/15/03 11:47 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9459 Version: 9 Check-in Date: 15-Apr-2003 11:46:59 1.Proposal Title: The Response of the White Dwarf in WZ Sge to the Unexpected July 2001 Superoutburst ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Edward Sion Villanova University CoI: Dr. Erik Kuulkers SRON Utrecht N CoI: Prof. Paula Szkody University of Washington N CoI: Dr. Boris Gaensicke Universitaets-Sternwarte Goettingen N CoI: Dr. Knox Long Space Telescope Science Institute N CoI: Dr. Steve Howell Planetary Sciences Institute N CoI: Prof. Sumner Starrfield Arizona State University N CoI: Dr. Bill Welsh San Diego State University N CoI: Dr. Christian Knigge Southampton University N CoI: Prof. Tom Marsh Southampton University N CoI: Dr. Danny Steeghs Southampton University N CoI: Prof. Joe Patterson Columbia University N ------------------------------------------------------------------------------------ 5. Abstract WZ Sge, the most extreme dwarf nova and one of the closest known cataclysmic variables, underwent a superoutburst in July 2001 after 22 years in quiescence. Because of the uniqueness of this event, two DD proposals were approved, one to observe the outburst itself, and another for us to observe the early decline phase. Here we propose to complete our fundamental study of the response of a dwarf nova system to an outburst by continuing our UV coverage of this most extreme outbursting system during its decline to quiescence. This decline is expected to take more than 3 yrs, with the most dramatic changes occurring in the first 2 years. The brightness of WZ Sge has made it possible for unprecedented multi-wavelength coverage with HST, Chandra, FUSE and ground-based optical. This once-in-a-lifetime chance to obtain high quality, high time (and spectral) resolution FUV data as the decline progresses into the critical transition from the disk- dominated phase to the bare white dwarf, provides an unique opportunity to study the response of the emerging white dwarf, whose chemical abundances, rotation and temperature variation with time bear the imprint of this extraordinary gigantic accretion event. ------------------------------------------------------------------------------------ 9459( 9) - 04/15/03 11:47 - [ 2] Observations Description ------------------------ Running RPS2, we will be able to obtain STIS spectra from early March, 2002 through Cycle 11 until July 2003. However, as the rate of decline begins to slow down, we will widen the spacing of our proposed FUV coverage. WZ Sge cannot be observed with HST in January and February, 2002. We propose to begin in March 2002, 8 months or 240d after the onset of the outburst. At that same point following the 1978 outburst, the decline had significantly slowed down, Therefore we request our first visit in March 2002 to include 5 orbits (needed for the mass determination), the next two visits to occur every 2 months (i.e. May, 2002 and July 2002). At this point, (~1 year post-outburst), we will widen our coverage to 3-4 month intervals (October 2002, March 2003, June 2003). All visits -- except the first one -- will consist of two consecutive HST orbits to give us adequate S/N in light of the decreasing flux. Considering the 52min visibility and the overheads for guide star acq/re-acq, target acq and STIS instrument setup, each of these two-orbit visits gives ~79 min exposure time. Using the quiescent HST/FOS spectrum of WZ Sge as input for the STIS ETC, we predict a lower limit of S/N~5 for the unbinned E140M data. Binning the spectra up by 5 provides data of least S/N~10, with a spectral resolution (~30km/s) for our scientific goals. Both high S/N and spectral resolution are absolutely essential for our scientific goals, i.e. covering the change in rotation rate, abundances, and temperature. All together, we are requesting 15 orbits for the entire project. beginfigurehtb epsscale0.5 plotonewzsge1978.ps captionThe AAVSO light curve of the 1978 outburst of WZ Sge (V-magnitude versus time in Heliocentric Julian Days). After the 1978 outburst, the UV flux continued to decline for a long time (~3 years) after the optical reached the quiescent value of V = 15.5. labelonebarrel endfigure Our setup will exclusively use the E140M grating and 0.2x0.2 aperture. Thus, we will have the same setup as we had in both of our DD programs. By changing setups, small but physically significant changes may be caused and cross- calibration problems result. While G140L could be used for the late coverage (5 visits x 1 orbit/visit reducing our total request by 5 orbits), we feel one setup for all of the observations is essential. This will permit us to make direct comparisons of detailed line profiles with the earlier DD9287/9304 E140M observations to delineate line profile shapes, different formation regions (e.g. accretion belt). For the first visit, we request orbital phase coverage to allow us to secure with STIS a high quality far-UV radial velocity curve for the white dwarf from its photospheric absorption lines throughout the binary orbit of 82 min (obtained from 5 orbits of time-resolved STIS FUV spectroscopy as the orbital phase advances by about 0.2 phase per each HST orbit). This results in each orbital phase of WZ Sge being sampled 2-3 times.This phase overlap is essential. The data will be acquired in the TIME-TAG mode because the TIME-TAGged data stream will enable us to search for the 28s periodicity and allows for an easy phase- binning. Binning by a factor of 5 in wavelength will give enough signal in the strongest lines (C I, C II, Si II) to also do line studies as a function of time during the decline while maintaining a FWHM spectral resolution of 30 km/s. The typical FWHM of the metal lines ranges between 3 and 8 Angstrom. The wavelength calibration is stable to less than 1 pixel throughout the exposure (STIS webpage). We will do regular wave-cal exposures to make certain of maintaining the wavelength scale accuracy well throughout the visits. We will cross-correlate the numerous photospheric metal lines in the white dwarf atmosphere to determine K_1. We expect K_1 < 50 km/s. There are 10-15 FUV white 9459( 9) - 04/15/03 11:47 - [ 3] dwarf metal lines due to C I, C II and Si II in the E140M wavelength range for use in the cross correlation. In addition to contemporaneous CHANDRA observations (E. Kuulkers, PI) during the decline and FUSE observations (K.Long, PI) of WZ Sge, we will have optical, ground-based observations with access to the Steward 2.3m telescope and the MMT through ASU (Co-I Starrfield). In addition, Co-I Szkody will provide APO 3.5m telescope coverage via the University of Washington, Seattle. Our detailed analysis will consist of: (A) multi-spectral component analyses of the STIS data with our full suite of codes to simultaneously model the accretion disk structure changes, the white dwarf photosphere, the accretion belt, a possible upper disk atmosphere (or accretion curtain). Codes include Tlusdisk, Tlusty 198, Synspec 45, Curtain and a newly developed code, wddiskfit, which allows us to vary the disk inclination, accretion rate and white dwarf masses, generating hundreds of composite (disk+white dwarf+accretion belt+curtain) models yielding chemical abundances, rotation rates, accretion rates, accurate Teffs, log g, accretion belt (including spin down) and the variations of all of these parameters with time; (B) searches for oscillation periodicities will led by Joe Patterson and Bill Welsh who have considerable experience in these areas (Welsh discovered the UV oscillations in WZ Sge); (C) time-variable accretion, evolutionary hydrodynamic and quasi-static simulations with spherical accretion, tangential accretion with shear mixing, and variable parameter accretion belts (see also the Sci. Just. section). vspace-0.3cm Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9459( 9) - 04/15/03 11:47 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WZSGE STAR, DWARF NOVA RA=20H 7M 36.4S +/- 0.1S, J2000 V = 8 DEC=17D 42' 15.4" +/- 0.1" Coordinate Source: Other_Source: SIMBAD 9459( 9) - 04/15/03 11:47 - [ 5] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 01-Mar-2002 AND 30-Apr-2002 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 10 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2300 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9459( 9) - 04/15/03 11:47 - [ 6] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 01-Jun-2004 AND 15-Jul-2004 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 10 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2300 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 30 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 40 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 50 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9459( 9) - 04/15/03 11:47 - [ 7] Visit: 03 Visit Priority: Visit Requirements: BETWEEN 10-May-2002 AND 10-Jun-2002 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 10 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2300 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9459( 9) - 04/15/03 11:47 - [ 8] Visit: 04 Visit Priority: Visit Requirements: BETWEEN 01-Nov-2002 AND 30-Nov-2002 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 10 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2300 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9459( 9) - 04/15/03 11:47 - [ 9] Visit: 05 Visit Priority: Visit Requirements: BETWEEN 01-Mar-2003 AND 31-Mar-2003 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 10 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2300 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9459( 9) - 04/15/03 11:47 - [ 10] Visit: 06 Visit Priority: Visit Requirements: BETWEEN 01-Aug-2002 AND 31-Aug-2002 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 10 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2300 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=300 1 2850 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9459( 9) - 04/15/03 11:47 - [ 11] Summary Form for Proposal 9459 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OII 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=300 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 01-Mar-2002 AND 30-Apr-2002 BETWEEN 01-Jun-2004 AND 15-Jul-2004 BETWEEN 10-May-2002 AND 10-Jun-2002 BETWEEN 01-Nov-2002 AND 30-Nov-2002 BETWEEN 01-Mar-2003 AND 31-Mar-2003 BETWEEN 01-Aug-2002 AND 31-Aug-2002 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names WZSGE ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------