9304( 2) - 08/27/01 08:59 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9304 Version: 2 Check-in Date: 27-Aug-2001 08:58:18 1.Proposal Title: Ultraviolet Spectroscopy of the Unexpected Outburst of WZ Sagittae ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Edward Sion Villanova University CoI: Boris Gaensicke Georg-August Universitat Goettingen N CoI: Paula Szkody University of Washington N CoI: Knox Long STScI N CoI: Sumner Starrfield Arizona State University N CoI: Warren Sparks LANL N CoI: Steve Howell Planetary Sciences Institute N CoI: Erik Kuulkers SRON Utrecht N CoI: R. Mark Wagner Univ. of Arizona N CoI: Christian Knigge Southampton N CoI: Tom Marsh Southampton N ------------------------------------------------------------------------------------ 5. Abstract Unexpectedly, the extreme dwarf nova WZ Sge went into outburst on July 23, 2001, ten years earlier than anticipated. This event offers the chance to obtain high-quality, time-resolved far-UV spectra with STIS, as the outburst continues through its peak into decline. we propose to monitor spectroscopic changes with STIS once a month for 4 months as the system transitions from a brightening disk-dominated system to a white dwarf-dominated system. Our modeling of the luminous disk-dominated phase with combinations of model accretion disks (with vertical structure) and high gravity photospheres will reveal changes in the accretion rate as accretion proceeds during the outburst, spectroscopic changes in the white dwarf (cooling rate in response to heating we will model hydrodynamically), changes in chemical abundances brought about by accretion, diffusion and mixing, and changes in the rotation rate of the white dwarf and its accretion belt, if present. The outburst coverage will monitor spectroscopic profile shape and velocity signatures of outflow, external circumbinary ring formation, and signs of infall due to possible re-accretion of previously ejected matter (cf.Leibowitz and Mazeh, 1981, ApJ and references therein). We are coordinating extensive multi-wavelength coverage. ------------------------------------------------------------------------------------ 9304( 2) - 08/27/01 08:59 - [ 2] Observations Description ------------------------ We will observe WZ Sge 4 times, for a total of 4 HST orbits allocated to this DD program. Each of the four 1 orbit HST visits will be used to obtain high time-and spectral resolution FUV data, using the STIS/FUV-MAMA/E140M set-up in TIME-TAG mode. For all exposures, we will use the 0.2x0.2 arcsecond slit. Our first HST observation should be scheduled to be as close as possible to either 8 September, 2001 or 22 September, 2001, which are the dates of the Fuse observations. Our observing strategy is to use all of the time available for scientific exposures to obtain successive 3000 s (or shorter) TIME-TAGged FUV exposures. Real Time Justification ----------------------- WZ Sagittae is the nearest and brightest member of the class of WZ Sge-type cataclysmic variables. These systems have extremely rare and large outbursts, separated by intervals of decades. WZ Sge itself had outbursts in 1913, 1946, and 1978, suggesting a 33-year periodicity and that the next outburst would occur only in 2011, after the demise of the HST and its UV capabilities. Unexpectedly, however, WZ Sge went into outburst on July 23, 2001, ten years earlier than anticipated. This event offers the once-in-a-lifetime chance to obtain high-quality, time-resolved far-UV spectra with STIS, as the outburst continues through its peak and into decline. Since we lacked the foresight to submit a Target of Opportunity proposal for Cycle 10, we herewith propose a Director's Discretionary program to exploit this surprising opportunity. These observations are a once in a "Hubble" lifetime chance to obtain a data set that will provide a legacy for an entire generation of researchers working on accretion physics. Accordingly, we will waive ANY proprietary period. The data will be non-proprietary immediately. We propose to monitor the spectroscopic changes with STIS once a month for 4 months as the system transitions from a brightening disk-dominated system to a white dwarf-dominated system. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9304( 2) - 08/27/01 08:59 - [ 3] 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 = 13 DEC=17D 42' 15.4" +/- 0.1" Coordinate Source: OTHER_SOURCE 9304( 2) - 08/27/01 08:59 - [ 4] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 10-Sep-2001 AND 20-Sep-2001 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=99 1 2330 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9304( 2) - 08/27/01 08:59 - [ 5] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 10-Oct-2001 AND 20-Oct-2001 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=99 1 2330 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9304( 2) - 08/27/01 08:59 - [ 6] Visit: 03 Visit Priority: Visit Requirements: BETWEEN 10-Nov-2001 AND 20-Nov-2001 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=99 1 2330 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9304( 2) - 08/27/01 08:59 - [ 7] Visit: 04 Visit Priority: Visit Requirements: BETWEEN 10-Dec-2001 AND 20-Dec-2001 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 WZSGE STIS/C ACQ F28X50O MIRROR 1 1.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 20 WZSGE STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=99 1 2330 S UV-MAM G A ------------------------------------------------------------------------------------------------------------------------------------ 9304( 2) - 08/27/01 08:59 - [ 8] Summary Form for Proposal 9304 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OII 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=99 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 10-Sep-2001 AND 20-Sep-2001 BETWEEN 10-Oct-2001 AND 20-Oct-2001 BETWEEN 10-Nov-2001 AND 20-Nov-2001 BETWEEN 10-Dec-2001 AND 20-Dec-2001 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names WZSGE ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------