Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 3683c Report Date: 09-May-96:18:47 Version: ********** Check-in Date: ********** 1.Proposal Title: ACCRETION DISK MAPPING IN ECLIPSING CATACLYSMIC VARIABLES ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID STELLAR ASTROPHYSICS GO Target of Oppt. Sub Category ERUPTIVE BINARIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Dr Keith D Horne STSCI USA 301-338-4964 DR ------------------------------------------------------------------------------------ 7. Abstract We will use the FOS in RAPID readout mode to obtain time-resolved ultraviolet spectrophotometry of accretion disk eclipses in two long-period cataclysmic variables, the nova-like variable UX UMa and the dwarf nova IP Peg in outburst and quiescence. From the eclipse data in the UV lines and continuum, we will map the structure of the hot inner accretion disk, boundary layer, and stream-disk interaction region using a combination of light-curve synthesis and maximum entropy mapping techniques. The principle goal of this experiment is to study the structure of accretion disks in order to test accretion disk models that are applied widely throughout astrophysics, e,g, in models of protostars and active galactic nuclei. The observations will also permit a study of the geometry of winds in these systems, and more accurate determinations of the masses, radii, and temperatures of the primary and secondary stars, which will contribute to our understanding of the evolution of close binary systems. NOTE: TAC has cut the UX UMa observations from this proposal. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 10.32 par: 0 10. Num targs pri: 2 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 3683c PI: Dr Keith D Horne Proposal Title: ACCRETION DISK MAPPING IN ECLIPSING CATACLYSMIC VARIABLES ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Keith D Horne STSCI USA Heinz Barwig UNIVERSITY OF MUNICH GERMANY X Knox Long STSCI USA Karl-Heinz Mantel UNIVERSITY OF MUNICH GERMANY X Thomas R Marsh OXFORD UNIVERSITY UK X Ronald S Polidan NASA/GSFC USA John C Raymond CENTER FOR ASTROPHYSICS USA Edward L Robinson UNIVERSITY OF TEXAS USA Rene Rutten STERRENKUNDIG INSTITUUT "ANTON NETHERLANDS X PANNEKOEK", AMSTERDAM Allen W Shafter SAN DIEGO STATE UNIVERSITY USA Paula Szkody UNIVERSITY OF WASHINGTON USA Richard A Wade PENN STATE UNIVERITY USA Janet H Wood UNIVERSITY OF KEELE UNITED KING X Er-Ho Zhang UNIVERSITY OF TEXAS AT AUSTIN USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We will observe 3 eclipses of IP Peg in quiescence, and 4 eclipses of IP Peg near the peak and on the decline from an outburst. We will rely upon the AAVSO to inform us when an outburst of IP Peg begins, and the HST observations of IP Peg declining from outburst should begin within 2-4 days later. For each eclipse, binary phases -0.15 thru +0.15 should ideally be covered to include the eclipse of the disk with enough baseline on either side to establish the out-of- eclipse spectrum. This would require 68 minutes for IP Peg (Porbit=228m). We settle here for ~49min exposures covering phases -0.10 to +0.11. IP Peg 's binary period is approximately 2.38 HST orbit periods, thus an opportunity to observe an eclipse may occur every 5 HST orbits. Observing a minimum of three eclipses will help us to distinguish systematic eclipse features from random flickering variations that are characteristic of cataclysmic variables. The mean of the three eclipses will be used to study the disk structure, while the residuals after subtracting the mean eclipse will inform us about the variability properties of different parts of the disk. For IP Peg in quiescence, the 3 eclipses should be obtained as close together in time as possible in order to minimize the effect of secular variations in the disk structure. For IP Peg in outburst we wish to obtain 4 eclipses spaced by about 1 day in order to follow the propogation of cooling fronts as the disk declines from outburst. We will use the Blue Digicon with G160L disperser, which gives spectral coverage at 6.5A/pixel from 1150 to 2300A, and the Red Digicon with PRISM disperser, which covers 1700 to 9000A with variable resolution. These low dispersions provide the broadest possible wavelength coverage with sufficient resolution to isolate the strong but widely-spaced emission lines from the continuum. Our interest lies primarily in eclipses of continuum and emission line fluxes rather than in velocity profiles of the lines. The zero-order spectrum available with the G160L grating will provide a simultaneous optical light curve. For IP Peg in quiescence we will observe the first and third eclipses with FOS,BLUE,G160L and the second with FOS,RED,PRISM. The red spectra covering the MgII emission line and the Balmer continuum and line emission will help to constrain optically-thin regions such as the disk chromosphere. Both the red and blue configurations cover the 1700-2300A region, from which we will construct the best mean UV continuum light curve. For IP Peg in outburst we use FOS,BLUE,G160L for all 4 eclipses. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The following capabilities unique to HST are needed: (1) sensitivity at space- ultraviolet wavelengths. (2) large aperture and efficient instruments. Other space instruments (IUE, Astro, Voyager, etc.) have collecting areas too small to achieve the necessary signal-to-noise ratios during the rapid eclipses, or cannot provide adequate time-resolution of the eclipses. Our team has extensive experience in observations and theoretical modelling of the spectra and eclipses of cataclysmic variables. We have observed eclipses with ground-based telescopes and have published analyses for a half-dozen systems. We have analyzed ultraviolet spectrophotometry of cataclysmic variables with IUE, Voyager and HUT and have published results for several dozen systems. We have measured radial velocity curves for about two dozen cataclysmic variables. We have studied the theoretical and observational properties of boundary layers between accretion disks and white dwarfs. These efforts have established the framework for interpreting the HST observations of eclipses in the ultraviolet, which provide crucial information about the the white dwarf, the inner regions of the disk and the boundary layer between them. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We request time-critical observations for two reasons. First, the observations must cover specific orbital phases centered on eclipse. Second, we must observe three 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 secular variations also make it 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. We request target of opportunity status for part of the observations intended to catch eclipses of IP Peg in outburst. The recurrence time for IP Peg is about 60- 100 days; the probability of occurrence is high, but our understanding of the outbursts is too primitive to predict in advance when outbursts will occur. We will arrange for the AAVSO to monitor IP Peg and alert us when an outburst occurs. The decline from outburst generally begins 3-5 days after the rise, so a 2-3-d response should make it possible for the eclipses to occur near the peak or early decline of the outburst. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Instrument Mode Special Calibration Requirement __________ _______ ________________________________ FOS/BL G160L Observe a flux standard that does not saturate the zero-order spec Page 4 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. Initial data reduction and calibration will use the standard pipelined software at STScI. We will display the data as trailed spectrograms, and probably do some hand editing to eliminate noise bursts and other special problems. Calibrated data will then be distributed to co-investigators for analysis at their home institutions. We will extract eclipse light curves in selected continuum passbands and the emission lines. The three eclipses will be averaged together to form mean light curves, and the mean will be subtracted from the individual eclipses to examine the residuals due to flickering variations. Power-spectrum analysis will be performed to search for coherent or quasiperiodic oscillations which are sometimes seen in the optical light from cataclysmic variables. Some immediate qualitative interpretations will be made by direct inspection of the light curves. Ground-based and/or Voyager data obtained around the times of the HST observations will be brought together for interpretation along with the HST results. We will then proceed to fit detailed models to the data, using the light -curve synthesis and eclipse mapping techniques we have developed for ground- based data (see Horne 1985, Zhang, Robinson and Nather 1986). These analyses will yield geometries of the components, temperature and luminosity distributions for the disk, and the properties of the boundary layers. For the IP Peg observations in outburst a time-dependent disk model will be compared with the data to derive disk instability parameters. Improvements in the disk model codes will probably be needed to fit the high-quality HST observations. Results of these investigations will be presented at meetings and written up for publication in major refereed journals. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. The proposed HST observations form a self contained experiment: 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 enhanced 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. For this purpose we have access to ground-based telescopes at the McDonald, La Palma, Mt. Laguna, Mt. Wendelstein, Manastash Ridge, Mount Hopkins, and Kitt Peak 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 with which we will attempt to obtain far-UV coverage of UX UMa eclipses. Our team has experience from several previous experiments involving simultaneous ground- and satellite-based observations. (NOTE: TAC has cut the UX UMa observations from this proposal.) ------------------------------------------------------------------------------------ 9. Description of previous HST work. GO-2243 "The Shock-Wave Structure of Herbig Haro Objects" Schwartz, Bohm, Cohen, Dopita, Hartman, Jones, Mundt, Raymond. GO-2356 "Identification of SNRs in M83 and other Spiral Galaxies" Long, Blari, Winkler, Kirshner, Raymond. GO-2380 "Instabilities in Accretion Disks and the Outbursts of Dwarf Novae" Horne and Marsh. GO-2334 "Ultraviolet Spectroscopy of the Black Hole A0620-00" McClintock, Remillard, and Horne. GO-3232 "Observations of X-Ray Nova Muscae 1991" Panagia, Lund, Gilmozzi, Horne, Paresce, Valle, and Schrader. Robinson has GTO time on the HSP. The first science data from the HSP will not be obtained before August 1991 according to the present HST schedule. GO-2380 may obtain eclipse observations of the short-period dwarf nova OY Car to test the prediction of disk instability models that the disk's UV flux should increase during quiescence. The present proposal will observe two systems with Porbit near 4h, the nova-like variable UX UMa, and the dwarf nova IP Peg. This will begin to sample the dependence of disk structure over the (Porbit-Mdot) parameter space. Page 5 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Salary and basic computer facilities are being provided for the P.I and many of the Co-Is. ------------------------------------------------------------------------------------ 11. Address Information Name: KEITH HORNE Category: PI Institution: STSCI Address: 3700 SAN MARTIN DRIVE City: BALTIMORE State: MD Zip Code: 21218 Country: USA Telephone: 410-338-4964 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 3683c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 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 IP-PEG A,149,161 PLATE-ID = 02BB, J2000 1 V = 15 +/- 1 RA = 23H 23M 8.61S +/- 0.5", 1 B-V = 0.2 DEC = +18D 24' 59.5" +/- 1 F-CONT(1500) = 1 +/- 1 E-14 0.5" 2 V = 11 +/- 1 2 B-V = 0.0 2 F-CONT(1500) = 1 +/- 1 E-13 Comments: DWARF NOVA V=11 IN OUTBURST, V=14-16 IN QUIESCENCE. ECLIPSING STAR, V=18 IN ECLIPSE. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3683c [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 DEFINE IP-PEG FOS/BL ACQ/ 4.3 G160L 1 15S 1 1 GROUP 1-2 NO GAP B PEAK ONBOARD ACQ FOR 1.5 SPATIAL SCAN ------------------------------------------------------------------------------------------------------------------------------------ 1.5 DEFINE IP-PEG FOS/BL ACQ/ 1.0 G160L 1 15S 1 1 ONBOARD ACQ FOR 2 B PEAK SPATIAL SCAN ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE IP-PEG FOS/BL RAPID 4.3 G160L 1500 READ-TIME=6.18 1 40.75M 1 NON-INT B PERIOD 0.15820613D +/- 0.00000004D ZERO-PHASE JD2445615.4224 +/- 0.001D Comments: TRY TO CENTER EXPOSURE ON PHASE PHASE 0.90 +/- 0.005, MUST COVER PHASES -0.09 0.02 TO +0.10. BINARY PERIOD IS NEAR 2.36 HST ORBITS, THUS ECLIPSE WINDOW OCCURS EVERY 5TH HST ORBIT. ------------------------------------------------------------------------------------------------------------------------------------ 4 DEFINE IP-PEG FOS/RD ACQ/ 4.3 G160L 1 15S 1 1 GROUP 4-5 NO GAP R PEAK ONBOARD ACQ FOR 4.5 SPATIAL SCAN ------------------------------------------------------------------------------------------------------------------------------------ 4.5 DEFINE IP-PEG FOS/RD ACQ/ 1.0 G160L 1 15S 1 1 GROUP 4-5 NO GAP R PEAK ONBOARD ACQ FOR 5 SPATIAL SCAN ------------------------------------------------------------------------------------------------------------------------------------ 5 DEFINE IP-PEG FOS/RD RAPID 4.3 PRISM READ-TIME=6.18 1 39.5M 1 NON-INT R PHASE 0.90 +/- 0.02 OF REF 2 Comments: TRY TO CENTER EXPOSURE ON PHASE 0.005, MUST COVER PHASES -0.09 TO +0.10. BINARY PERIOD IS NEAR 2.36 HST ORBITS, THUS ECLIPSE WINDOW OCCURS EVERY 5TH HST ORBIT. ------------------------------------------------------------------------------------------------------------------------------------ 7 USE B AT 30-SEP-92 +/- 90D SEQ 7-9 WITHIN 7 D Comments: PI IS PLANNING COORDINATED OBSERVATIONS. ------------------------------------------------------------------------------------------------------------------------------------ 8 USE R AFTER 7 Comments: AS SOON AS POSSIBLE AFTER 7 ------------------------------------------------------------------------------------------------------------------------------------ 9 USE B AFTER 8 Comments: AS SOON AS POSSIBLE AFTER 8 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 3683c [ 8] ------------------------------------------------------------------------------------------------------------------------------------ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 USE B TARG OF OPP / 10- 13 SEQ 10-13 WITHIN 7 D Comments: EXECUTE AS SOON AS POSSIBLE AFTER PI REQUEST TO ACTIVATE THESE TARG OF OPP EXPOSURES. ------------------------------------------------------------------------------------------------------------------------------------ 11 USE B AFTER 10 BY 1D +/- 1 D Comments: IDEALLY 15 HRS AFTER 10 ------------------------------------------------------------------------------------------------------------------------------------ 12 USE B AFTER 11 BY 1D +/- 1 D Comments: IDEALLY 15 HRS AFTER 11 ------------------------------------------------------------------------------------------------------------------------------------ 13 USE B AFTER 12 BY 1D +/- 1 D CYCLE 2 / 1-13 Comments: IDEALLY 15 HRS AFTER 12 ------------------------------------------------------------------------------------------------------------------------------------ Scan Paramters Form Proposal ID: 3683c [ 9] ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 1 Exposure Logsheet lines: 1,4 FGS Scan: DWELL Dwell Only: dwell points/line: 3 Seconds per dwell: 1.00 Scan width (arc-secs): 0.0000 Scan length (arc-secs): 2.8000 Angle between sides (degrees) 90.00 Number of lines: 1 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 0.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 1.4000 Width Offset (arc-sec): 0.0 ------------------------------------------------------------------------------------------------------------------------------------ Data ID: 2 Exposure Logsheet lines: 1.5,4.5 FGS Scan: DWELL Dwell Only: dwell points/line: 6 Seconds per dwell: 1.00 Scan width (arc-secs): 0.7000 Scan length (arc-secs): 3.5000 Angle between sides (degrees) 90.00 Number of lines: 2 Scan rate (arc-sec/sec): 0.0000 PA of first scan line (degrees) 90.000 Scan frame (CEL or S/C): S/C Length Offset (arc-sec): 1.7500 Width Offset (arc-sec): 0.3500 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 3683c [ 10] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL FOS/RD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters READ-TIME=6.18 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 10.32 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR ASTROPHYSICS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ERUPTIVE BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 1-2 NO GAP; ONBOARD ACQ FOR 1.5; SPATIAL SCAN; ONBOARD ACQ FOR 2; NON-INT ; PERIOD 0.15820613D +/- 0.00000004D ; ZERO-PHASE JD2445615.4224 +/- 0.001D ; PHASE 0.90 +/- 0.02 ; GROUP 4-5 NO GAP; ONBOARD ACQ FOR 4.5; ONBOARD ACQ FOR 5; NON-INT; PHASE 0.90 +/- 0.02 OF REF 2; AT 30-SEP-92 +/- 90D ; SEQ 7-9 WITHIN 7 D ; AFTER 7 ; AFTER 8 ; TARG OF OPP / 10-13 ; SEQ 10-13 WITHIN 7 D ; AFTER 10 BY 1D +/- 1 D ; AFTER 11 BY 1D +/- 1 D ; AFTER 12 BY 1D +/- 1 D ; CYCLE 2 / 1-13 ; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G160L PRISM ------------------------------------------------------------------------------------------------------------------------------------ Target Names IP-PEG ------------------------------------------------------------------------------------------------------------------------------------