Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 2446c Report Date: 09-May-96:17:07 Version: ********** Check-in Date: ********** 1.Proposal Title: TIME-RESOLVED SPECTROPHOTOMETRY OF ECLIPSING CATACLYSMIC VARIABLES ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS GO Sub Category ERUPTIVE BINARIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr. Keith Horne STSCI USA 301-338-4964 DR. ------------------------------------------------------------------------------------ 7. Abstract We will use the Faint Object Spectrograph to acquire time-resolved ultraviolet spectrophotometry of 8 eclipsing cataclysmic variables covering the full range of binary periods (1.5 to 8h) and accretion disk morphologies for these systems. Light- curve synthesis and maximum entropy mapping techniques will be used to interpret the eclipse data to determine the masses, radii and temperatures of the component stars, the physical conditions in the accretion disk and boundary layer between the accretion disk and its central white dwarf, and the rates of mass transfer. The ultraviolet spectra and ultraviolet eclipse light curves are crucial because they probe the hot inner regions of the accretion disk and the boundary layer between the accretion disk and the white dwarf. The results will test theories of the structure of accretion disks and theories of the structure and evolution of close binaries in the late stages of their evolution. ------------------------------------------------------------------------------------ 8. Scientific Key Words: WHITE DWARF, ECLIPSING BINARY, INTERACTING BINARY, DWARF NOVA, ACCRETTION ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 38.60 par: 0 10. Num targs pri: 8 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 2446c PI: Dr. Keith Horne Proposal Title: TIME-RESOLVED SPECTROPHOTOMETRY OF ECLIPSING CATACLYSMIC VARIABLES ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Dr. R. S. Polidan ARIZONA, UNIVERSITY OF USA Dr. E. L. Robinson TEXAS, UNIVERSITY OF USA Dr. Allen W. Shafter TEXAS, UNIVERSITY OF USA Dr. Paula Szkody WASHINGTON, UNIVERSITY OF USA Dr. R. A. Wade ARIZONA, UNIVERSITY OF USA Dr. J. H. Wood TEXAS, UNIVERSITY OF USA Dr. Er H. Zhang TEXAS, UNIVERSITY OF USA Dr. J. Patterson COLUMBIA UNIVERSITY USA Dr. John C. Raymond CFA USA P.I. Keith Horne STSCI USA Dr. Tom Marsh STSCI USA Page 3 ------------------------------------------------------------------------------------ 3. Description of proposed observations. PHASE I PROPOSAL: We will obtain time-resolved spectrophotometry of the eclipses of selected cataclysmic variables using the Faint Object Spectrograph. The eclipses last from roughly 10 min in HT Cas to 1.5 hr in V363 Aur, and during the eclipses the systems vary on timescales as short as a few seconds. We will use the FOS in the ``RAPID READOUT'' mode to resolve these variations. Including observations just before and after the eclipses (needed to establish baselines and measure out-of-eclipse variations), the individual observations will take between 58 min and 140 min, depending on the target. We will observe several eclipses for each system to distinguish systematic eclipse features from the random ``flickering'' variations characteristic of cataclysmic variables. In three cases we will observe during out-of-eclipse phases to determine what ultraviolet variations are associated with the large large orbital ``hump'' that is seen in the optical. For each system the observations should be obtained as close together in time as possible in order to reduce the effect of secular variations on the properties of the eclipses. We are interested primarily in the continuum and its variations, and in emission line fluxes rather than line profiles, and will therefore use low dispersions to obtain broad wavelength coverage. For half the eclipses we will use the G160L disperser and the blue Digicon, giving spectral coverage from 1150 to 2500 Angstroms. For the other half we will use the PRISM disperser and the red Digicon, covering 1850 to 7000 Angstroms. The longer wavelengths are essential to (1) tie FOS to ground-based observations and (2) provide maximum sensitivity to optically thin radiation. Our faintest target (HT Cas) has visual magnitude 16.4 outside of eclipse, and an energy distribution that is approximately flat in F_nu. We estimate that using G160L we will detect about 340 photons in 10 seconds in a 100 Angstrom bandpass centered at 2000 Angstroms, for a signal-to-noise ratio of 20. We expect flickering variations to be present at about this same level in all objects. With three eclipses, this should be adequate to separate the white dwarf from the boundary layer using their contributions to the shape of ingress and egress, which last about 60 seconds. We expect that the time-critical nature of the observations and the need for uninterrupted long exposures (Section 5) will make scheduling difficult. We therefore request long-term status (two years), to ensure that all the observations can be made. During the first year we request that 10.5 hours observing time be allocated for observations of our two top priority targets. The remaining time should be allocated for the second year. PHASE II PROPOSAL: Given a Cycle 1 allocation of 4.0 hours supplemental priority time, our strategy is to concentrate on eclipses of HT Cas. HT Cas is in the continuous viewing zone, and it has eclipses every 106 minutes that will be covered with 25 minutes on-target exposure time. Thus the time-critical nature of the experiment should not be too restrictive even given its supplemental priority. We plan 10 sec time-resolution coverage of 5 eclipses, 3 eclipses with FOS,BLUE,G160L, and 2 with FOS,RED,PRISM. The G160L order-zero spectrum records a broad-band optical flux simultaneously with each first order UV spectra. A short FOS,BLUE,PRISM exposure is taken just after each blue eclipse. The 5 eclipses should be scheduled as close together in time as possible to minimize any long- term secular variations. Page 4 ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. We request time-critical observations for two reasons. First, the observations must cover specific orbital phases, usually phases centered on eclipse but in other cases phases that include two successive eclipses. Second, we must observe three (or four) eclipses of each star so we can identify features in the light curves caused by flickering variations as opposed to eclipses. The cataclysmic variables vary secularly, and as the time interval between the eclipses increases, the size of secular changes in the systems will increase. All observations of a given target should, if possible, be obtained within a period of one or two weeks to minimize the effect of these secular variations. The cataclysmic variables vary secularly, so it is difficult to construct eclipse light curves by joining parts of many different eclipses. Whole eclipses must be observed whenever possible. To observe whole eclipse light curves, it is necessary to have uninterrupted long exposures. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. The proposed HST observations are self contained: the eclipse analyses will yield new and significant information even if no other data are available. We feel strongly, however, that the scientific results of the eclipse analyses will be greater if the spectrophotometry from HST is complemented by photometry or spectrophotometry at other wavelengths. We will therefore attempt to obtain contemporaneous or even simultaneous observations at other wavelengths. We have access to ground-based telescopes at the McDonald, La Palma, Manastash Ridge, Mount Hopkins, Kitt Peak and Cerro Tololo observatories, and we will request observing time on these telescopes for supporting eclipse observations at visual and near-infrared wavelengths. We also have access to the Voyager spacecraft and a far UV spectral imaging telescope that will fly as an attached Shuttle payload (Hitch-hiker) and as a Spartan mission. The Voyagers and at least the Hitch-hiker should be operating during the proposed observing period. We will attempt with these instruments to acquire simultaneous far-ultraviolet photometry for the high priority targets. ------------------------------------------------------------------------------------ 11. Address Information Name: KEITH HORNE Category: PI Institution: SPACE TELESCOPE SCIENCE INSTITUTE Address: 3700 SAN MARTIN DRIVE City: BALTIMORE State: MD Zip Code: 21218 Country: USA Telephone: Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 2446c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 HT-CAS STAR; ECLIPSING BINARY; RA = 01H 10M 13.1S +/- 2000 1 V = 14.5 +/- 2.0, E(B-V) = 0.0 DWARF NOVA 0.5", 2 F(1500) = 5 +/- 3 E-15 VARIABLE; INTERACTING DEC = +60D 04' 36.0" +/- 3 F(2500) = 3 +/- 2 E-15 BINARY 0.5", PLATE-ID=01MU Comments: VARIABLE STAR. V MAGNITUDE GIVEN CORRESPONDS TO FULL RANGE FROM QUIESCENCE TO OUTBURST AWAY FROM THE ECLIPSE. UV FLUXES SPECIFIED FOR QUIESCENCE ONLY. STAR VANISHES DURING ECLIPSE. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2446c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DEFINE HT-CAS FOS/BL ACQ/ 4.3 MIRROR FAINT=3300 1 10S 1 ONBOARD ACQ FOR 2- HTBECL BINARY BRIGHT=330000 3 Comments: BRIGHT AND FAINT SET VERY WIDE BECAUSE FIELD SIMPLE BUT OBJECT IS VARIABLE. EXPECT 3300 COUNTS /SECOND IF QUIESCENT UP TO MAYBE 50 TIMES MORE IN OUTBURST. ALSO FLICKERS BY 30 PERCENT IN 10 SEC. ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE HT-CAS FOS/BL RAPID 1.0 G160L 1150- READ-TIME=10 1 22M 1 SEQ 2-3 NON-INT HTBECL 2524 ZERO-PHASE JD2443727.93721 +/ - 1S PERIOD 0.0736472039D +/- 0.0000000005D Comments: THE EXPOSURE TIME IS DETERMINED PHASE 0.91 +/- BY PHASE COVERAGE, NOT SIGNAL- 0.02 TO-NOISE. CENTER THIS EXPOSURE ON PHASE 0.01. BINARY PERIOD IS 106M. ------------------------------------------------------------------------------------------------------------------------------------ 3 DEFINE HT-CAS FOS/BL RAPID 1.0 PRISM 1800- READ-TIME=10 1 2M 2 PHASE 0.2 +/- 0.1 HTBECL 5500 OF REF 2 Comments: BLUE PRISM EXPOSURE IMMEDIATELY AFTER ECLIPSE. ------------------------------------------------------------------------------------------------------------------------------------ 4 DEFINE HT-CAS FOS/RD ACQ/ 4.3 MIRROR FAINT=3300 1 10S 1 ONBOARD ACQ FOR 5 HTRECL BINARY BRIGHT=330000 Comments: BRIGHT AND FAINT SET VERY WIDE BECAUSE FIELD SIMPLE BUT OBJECT IS VARIABLE. EXPECT 5600 COUNTS /SECOND IF QUIESCENT UP TO MAYBE 50 TIMES MORE IN OUTBURST. ALSO FLICKERS BY 30 PERCENT IN 10 SEC. ------------------------------------------------------------------------------------------------------------------------------------ 5 DEFINE HT-CAS FOS/RD RAPID 1.0 PRISM 1800- READ-TIME=10 1 24M 1 NON-INT HTRECL 8000 PHASE 0.90 +/- 0.03 OF REF 2 Comments: THE EXPOSURE TIME IS DETERMINED BY PHASE COVERAGE, NOT SIGNAL- TO-NOISE. CENTER THIS EXPOSURE ON PHASE 0.01. BINARY PERIOD IS 106M. ------------------------------------------------------------------------------------------------------------------------------------ 7 USE HTBECL ------------------------------------------------------------------------------------------------------------------------------------ 8 USE HTRECL ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 2446c [ 7] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 9 USE HTBECL ------------------------------------------------------------------------------------------------------------------------------------ 10 USE HTRECL ------------------------------------------------------------------------------------------------------------------------------------ 11 USE HTBECL ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 2446c [ 8] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/BINARY RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FAINT=3300 BRIGHT=330000 READ-TIME=10 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 38.60 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ERUPTIVE BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-3 SEQ 2-3 NON-INT; ZERO-PHASE JD2443727.93721 +/- 1S ; PERIOD 0.0736472039D +/- 0.0000000005D ; PHASE 0.91 +/- 0.02 PHASE 0.2 +/- 0.1 OF REF 2 ONBOARD ACQ FOR 5 NON-INT ; PHASE 0.90 +/- 0.03 OF REF 2 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G160L PRISM ------------------------------------------------------------------------------------------------------------------------------------ Target Names HT-CAS ------------------------------------------------------------------------------------------------------------------------------------