Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5500 Report Date: 18-Jul-95:17:32 Version: ********** Check-in Date: ********** 1.Proposal Title: ENERGY BALANCE AND EMISSION LINES IN DQ HERCULIS STARS CYCLE 4 - MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category ERUPTIVE BINARIES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Joseph Patterson COLUMBIA UNIVERSITY USA ------------------------------------------------------------------------------------ 7. Abstract The accretion flows onto the magnetic white dwarfs in DQ Herculis stars are only dimly understood. Rapid rotation of the white dwarfs is signified by the presence of pulsations, but the flux in the observed pulses is small compared to that of the disk light, contrary to theory. We propose to use the continuum channels in the FOS to look for large-amplitude pulses in the UV light of YY Dra, and thereby constrain the flux and temperature associated with the accretion bright spot (presumably beneath the radial accretion shock.) We also propose to look for a wavelength- dependent phase shift across the strong UV emission lines, which would be indicative of an ionizing searchlight beam sweeping in azimuth around the disk. This would conclusively certify a photoionization origin for the UV lines, and the phase would decide between origin in an accretion column or a disk. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 6.00 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5500 PI: Joseph Patterson Proposal Title: ENERGY BALANCE AND EMISSION LINES IN DQ HERCULIS STARS CYCLE 4 - MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Joseph Patterson COLUMBIA UNIVERSITY USA Carole A Haswell STSCI USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. We propose 6 hours of FOS observations with the G130H grating. This will yield ~0.3 ct/s/diode in the continuum, and we will have ~200 diodes in the continuum from 1350 to 1606 A. Thus a count rate of ~300 per 6.18s can be achieved, yielding a S/N ~20 for the summed continuum for each 6.18s data packet. The dominant optical period is 275 s, suggesting a readout time of 6.18s will resolve the pulse well. Most of the emission-line information is likely to come from the C IV line, which is ~40 A wide, and therefore can yield ~25 resolution elements. The count rate at line peak (saturated in the IUE exposure) will be at least 5 ct/s/diode, or 7.5 ct/s/resolution element. A S/N~12 can be obtained for each line peak spectral resolution element with a time resolution of 20s. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. A measurement of the pulsed flux at UV wavelengths is needed to ascertain if the "missing flux" is in the UV/EUV. Only HST offers the time resolution in the UV. We have been studying the target stars for ten years at optical, ultra-violet (IUE), and X-ray (HEAO-1, 2) wavelengths. We are increasing the density of our optical coverage, in order to derive unique long-term ephemerides. We have learned the pulsed fluxes in the intervals 1-100 A and 3500-7000 A; now we wish to push into the forbidden region by another factor of 3. For the emission-line study, it is also the time-resolution (and sensitivity) of HST/FOS which is needed. A few similar studies of other stars have been carried out using hydrogen lines; but these lines tend to come from EVERYWHERE in the binary, principally the outer disk which does not carry information about the inner accretion flows (and certainly not about the radiation field required to power the UV emission lines We need at least one binary orbit (4.0 hrs) of FOS data. This is principally in order to distinguish the two candidate periods of 530 s and 550 s, which go out of phase by 360 degrees in 1 orbit. We are requesting some over-sampling (to 7.1 hrs) in order to protect against an unfavorable distribution in orbital phase, which would certainly clobber the experiment if these two periods could not be distinguished. We calculated the expected count rate using the IUE spectrum in quiescence and the XCAL package at STScI. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. No special scheduling requests. We will take responsibility for obtaining ground-based photometry which is sufficiently "contemporaneous" to assure correctly phased comparison of the UV and optical light curves. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. N/A ------------------------------------------------------------------------------------ 8. Additional comments or special requests. ------------------------------------------------------------------------------------ 9. Description of previous HST work. No previous data/observing time received. Page 3 ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). 1.The analysis of the UV time series will use a battle-tested set of software written over the last 15 years for optical photometry. These run on any computer; no special features are needed. 2. We have official "long-term status" at Cerro Tololo, and also access to Lick Observatory, which we will use to insure knowledge of the optical pulse ephemerides. 3. We hope to use EUVE to detect or set bounds to these stars at shorter wavelengths. 4. One graduate student at Columbia will be supported full time on this project. ------------------------------------------------------------------------------------ 11. Address Information Name: Joseph Patterson Category: PI Institution: Columbia University Address: Dept. of Astronomy Columbia University 538 West 120th Street City: New York State: NY Zip Code: 10027 Country: USA Telephone: 212 854 3276 Telex (or e-mail): 220094 COLU UR ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5500 [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 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 YY-DRA PG- A,149,154,906 PLATE-ID = 01L3, J2000.0 1 V = 15.65 +/- 0.55 1140+72 DO- RA = 11H 43M 38.364S +/- 2 B-V = 0.5 DRA 1.0", 3 E(B-V) = 0.05 +/- 0.05 DEC = +71D 41' 20.18" +/- 4 F-LINE(1549) = 29 +/- 9 E-13 1.0" 4 W-LINE(1549) = 16 +/- 2 5 F-CONT(1300) = 2 +/- 0.6 E-14 5 F-CONT(1650) = 1.5 +/- 0.5 E-14 5 F-CONT(1950) = 1.0 +/- 0.3 E-14 Comments: IN QUIESCENCE INCLUDES M DWARF MASS DONOR. (B-V)=-0.1 FOR HOT COMPONENT. ERROR DUE TO IUE SATURATION ERROR INC INTRINSIC VARNS OBJECT UNDERGOES RARE DWARF NOVA OUTBURSTS: 3WKS PER 10 YEARS. IN OUTBURST OBJECT BRIGHTENS BY 5 MAGNITUDES. T(HOT)~40000K ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5500 [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 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 YY-DRA FOS/BL ACQ/ 4.3 MIRROR SEARCH-SIZE-X=1 1 9S 5 1 ONBOARD ACQ FOR 2 YYDRA PEAK SEARCH-SIZE-Y=3 SCAN-STEP- Y=1.204 Comments: VARIABLE STAR EXPECT 30% VARNS IN FLUX EXP FOR ~10000 COUNTS ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE YY-DRA FOS/BL ACQ/ 1.0 MIRROR SEARCH-SIZE-X=6 1 15S 5 1 ONBOARD ACQ FOR YYDRA PEAK SEARCH-SIZE-Y=2 2.5 SCAN-STEP- X=.602 SCAN-STEP- Y=.602 Comments: VARIABLE STAR EXPECT 30% VARNS IN FLUX EXP FOR ~10000 COUNTS ------------------------------------------------------------------------------------------------------------------------------------ 2.5 DEFINE YY-DRA FOS/BL ACQ/ 0.3 MIRROR SEARCH-SIZE-X=5 1 15S 5 1 ONBOARD ACQ FOR 3 YYDRA PEAK SEARCH-SIZE-Y=5 SCAN-STEP- X=.172 SCAN-STEP- Y=.172 Comments: VARIABLE STAR EXPECT 30% VARNS IN FLUX EXP FOR ~10000 COUNTS ------------------------------------------------------------------------------------------------------------------------------------ 3 DEFINE YY-DRA FOS/BL RAPID 4.3 G130H 1150- READ-TIME=6.18 1 387.898 1 YYDRA 1606 Comments: PLEASE CHECK WE USE SHORTEST READ-TIME ALLOWED FOR 32KHZ DATA RATE. TONY KEYES CONFIRMED FOS MANUAL PRESCRIPTION INCORRECT NO S/N CALC WE OPTIMISE TIME-RES PLS INCREASE EXP-TIME TO FILL ORBIT. ------------------------------------------------------------------------------------------------------------------------------------ 4 USE CYCLE 4 / 1-4 YYDRA Comments: TO PERMIT COORDINATED OBSERVATIONS, PLEASE NOTIFY P.I. WHEN DATES ARE SCHEDULED OR CHANGED. RELAX TIMING CONSTRAINT IF REQUIRED FOR SCHEDULING. ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5500 [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-Y=1.204 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 SCAN-STEP-X=.602 SCAN-STEP-Y=.602 SEARCH-SIZE-X=5 SEARCH-SIZE-Y=5 SCAN-STEP-X=.172 SCAN-STEP-Y=.172 READ-TIME=6.18 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 6.00 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ERUPTIVE BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 2.5 ONBOARD ACQ FOR 3 CYCLE 4 / 1-4 ; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G130H ------------------------------------------------------------------------------------------------------------------------------------ Target Names YY-DRA PG-1140+72 DO-DRA ------------------------------------------------------------------------------------------------------------------------------------