Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5364 Report Date: 18-Jul-95:17:14 Version: ********** Check-in Date: ********** 1.Proposal Title: THE UV SPECTRAL COMPONENTS IN RE1938-461, THE BRIGHTEST ROSAT WFC DISCOVERED POLAR WITH A HIGH EUV/OPTICAL RATIO: CYCLE4 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 Simon Rosen UNIVERSITY OF LEICESTER U.K. ------------------------------------------------------------------------------------ 7. Abstract Eight new magnetic cataclysmic variables were discovered during the ROSAT WFC survey. Seven of these have been identified with polar (or AM Her) systems. A striking result that has emerged is that the new polars appear to populate a region of high EUV/optical flux ratio when compared to that measured for the previously known systems that were also detected in the WFC survey. It is highly likely that these new polars also possess large soft/hard X-ray flux ratios. In this case, the WFC result suggests that a) polars with large soft excesses are more common than previously believed and b) that the mode of accretion in these particular systems is likely to be via the direct penetration of the white dwarf's surface by blobs of accreting material rather than by the formation of a hard X-ray emitting column above the surface. The new polars will have a direct bearing on the division between the two different modes of accretion. They also provide the means to probe the detailed nature of the processes occurring in the accretion region. We are proposing low resolution HST FOS observations of the brightest of these EUV luminous polars discovered in the WFC survey to a) search for the tail of the emission component from the heated region around the accreting pole to constrain the luminosity, size and temperature of this constituent and b) to perform an initial study of the UV emission lines, measuring their flux and radial velocity motion to constrain the dynamics and physical (ionization) structure within the accretion flow. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 4.43 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5364 PI: Simon Rosen Proposal Title: THE UV SPECTRAL COMPONENTS IN RE1938-461, THE BRIGHTEST ROSAT WFC DISCOVERED POLAR WITH A HIGH EUV/OPTICAL RATIO: CYCLE4 MEDIUM. ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Simon R Rosen UNIVERSITY OF LEICESTER UNITED KING X Mike Watson UNIVERSITY OF LEICESTER UNITED KING X Julian Osborne UNIVERSITY OF LEICESTER UNITED KING X Andrew King UNIVERSITY OF LEICESTER UNITED KING X Keith Mason MULLARD SPACE SCIENCE LABORATORY UNITED KING X David Buckley UNIVERSITY OF CAPE TOWN SOUTH AFRIC ------------------------------------------------------------------------------------ 3. Description of proposed observations. We propose to obtain the first UV spectra of the recently discovered polar, RE1938-461, allowing us to measure phase- dependent variability in the UV continuum and emission lines. We will exploit the temporally resolved spectra to search for the tail of the emission from the white dwarf's heated accretion region. Potential phase differences between this component and orbitally modulated flux from the accretion flow should allow us to separate their contributions. We can then perform spectral model fits (e.g. different temperature black- body components) to constrain the temperature, luminosity and size of the emission sites. Radial velocity and flux variability in the UV emission lines will probe physical and dynamical structure in the accretion flow. We will use the FOS with the 0.9" aperture and the G160L grating to provide coverage of the 1150A-2500A\ range with a resolution of around 7A/pix. Coverage down to the shortest UV wavelengths is essential if we are to be able to search for the steep component from the heated accretion region in the far UV. We will use the FOS in RAPID mode, recording 20s exposures. This will permit us to test for any large-scale spectral changes during the transition from the faint to the bright phase. We request coverage of one orbital cycle in this initial investigation. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. The accretion flow within 10 stellar radii of the white dwarf should be hot (10000330, 590, 630, 1680 and 5400 counts/diode at the same wavelengths, permitting changes in the continuum level to be detectable at levels of less than 6% at all wavelengths in each diode. Spectra will be binned in wavelength, where necessary, to enhance the S/N. for example, by combining data over a 100 range, we might expect to improve the sensitivity to variations by a factor of 4. For this first acquisition of UV data from RE1938-461, we seek coverage of one complete orbital cycle. We request 3 hours of on-source data which will require 5 HST orbits (assuming ~32 minutes of data per HST orbit). This will provide near complete phase coverage of the orbital cycle and will yield sufficient S/N to identify and quantify the spectral components we expect to be present. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We do not request any special scheduling requirements. However, contiguous orbits will provide excellent phase coverage of the 2.33~hr orbital cycle and will maximize observing efficiency by reducing the overheads from acquisitions (i.e. we would require only one primary acquisition). ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Routine FOS calibration data will be sufficient for our purposes. Page 4 ------------------------------------------------------------------------------------ 8. Additional comments or special requests. It is extremely advantageous to acquire simultaneous multi- wavelength data for variable objects like polars since only then we can be confident that the spectra represent the same state of the system. We will be endeavouring to obtain simultaneous or near simultaneous optical spectroscopy of RE1938-461 with the HST observations in order to compare the behaviour of the UV and optical continuum and lines at the same epoch. However, we stress that we will be seeking to arrange suitable optical observations that fit in with the HST schedule, rather than requiring HST observations to be dependent on optical scheduling. One of our collaborators (DB) has been particularly successful in arranging contemporaneous optical coverage from the South African Astronomical Observatory during satellite observations of cataclysmic variables over the years. He will apply for time on the 1.9m telescope to secure simultaneous or quasi- simultaneous optical coverage of RE1938-461. We expect that such observations can be arranged at relatively short notice (1-2 months). Nevertheless, we point out that the optimum optical observing season is between July and September. ------------------------------------------------------------------------------------ 9. Description of previous HST work. GO-3578 Line eclipse mapping of an accretion disk wind. (KOM,JED). Preliminary results presented at UK National Astronomy meeting in March 1993. GO- 3579 The UV orbital lightcurve of the X-ray binary X1822-371. (KOM). Not done GO-4661 UV eclipse mapping of the Accretion flow in the eclipseing Intermediate Polar, EX Hya (SRR,KOM). Failed due to satellite/instrument problems unrelated to that observation. GO-4659 A time-resolved UV study of the wind outflow in the enigmatic cataclycmic variable, V795 Her. Supplemental time awarded. Obs not yet performed. GO-4449 Occultation studies of RE1149+28: An object with an extreme EUV/optical ratio. (KOM,SRR). Scheduled for late 93. Proposal GO-4449, whilst looking at another high EUV/optical ratio polar, is primarily aimed at searching for a UV counter- part to an occultation effect seen in the optical emission lines. Moreover, it will be using the G130H grating so that a search for the differing components that contribute to its UV continuum flux is not viable (due to the narrow range covered). RE1149+28 is also a factor of six fainter than RE1938-461. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). The analysis of our HST data will be undertaken by the PI and the Co-I's. All proposers have access to DEC Vax machines or SUN stations which are dedicated to astronomical research. ------------------------------------------------------------------------------------ 11. Address Information Name: SIMON R ROSEN Category: PI Institution: University of Leicester Address: Dept. of Physics, University Rd., City: Leicester State: Zip Code: Country: UNITED KINGDOM Telephone: 0533 552077 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 5364 [ 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 STAR-193835- A, 153 RA = 19H 38M 35.75S +/- J2000 1 V= 15.5 +/- 0.5 461256 1.0", 2 B-V = 0.0 +/- 0.3 DEC = -46D 12' 55.99" +/- 3 E(B-V) = 0.0 +/- 0.1 1.0", 4 F-CONT(1250) = 2.0 +/- 1.0 E-14 PLATE-ID = 04FS 5 F-CONT(1450) = 1.5 +/- 0.8 E-14 6 F-CONT(1750) = 1.0 +/- 0.5 E-14 7 F-CONT(2500) = 0.5 +/- 0.2 E-14 8 F-LINE(1550) = 10. +/- 5. E-14 9 W-LINE(1550) = 10 +/- 3 Comments: UV FLUXES ARE PREDICTIONS BASED ON UV DATA FROM V834 CEN, A POLAR OF SIMILAR OPTICAL MAGNITUDE. SYSTEM CAN FADE BY 2 MAGNITUDUES ON TIMESCALES OF WEEKS. TARGET POSN QUOTED TO ME AS GOOD TO 1" ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5364 [ 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 STAR-193835 FOS/BL ACQ/ 4.3 G400H SCAN-STEP- 1 10S 1 1 ONBOARD ACQ FOR -461256 PEAK Y=1.204 3 1.5 SEARCH-SIZE-X=1 CYCLE 4 SEARCH-SIZE-Y=3 Comments: STAR VARIES BY UPTO 0.5 MAGS ABOUT ITS MEAN OF V=15.5. IF IN A LOW STATE, IT COULD BE FAINTER BY 2 MAGS. OPTIMUM STRATEGY SHOULD USE ACQUISITION+CONTIGUOUS HST ORBITS ------------------------------------------------------------------------------------------------------------------------------------ 1.5 STAR-193835 FOS/BL ACQ/ 1.0 G400H SCAN-STEP- 1 10S 1 1 ONBOARD ACQ FOR -461256 PEAK X=0.602 3 1.7 SCAN-STEP- CYCLE 4 Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 1.7 STAR-193835 FOS/BL ACQ/ 0.5 G400H SCAN-STEP-X=0.3 1 10S 1 1 ONBOARD ACQ FOR 2- -461256 PEAK SCAN-STEP-Y=0.3 3 6 SEARCH-SIZE-X=3 CYCLE 4 SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 STAR-193835 FOS/BL RAPID 1.0 G160L 1830 COMB=YES 1 31.5M 25 5 1 CYCLE 4 -461256 READ-TIME=20 420S Comments: SPECTRA WILL BE PHASE FOLDED TO ACHIEVE DESIRED S/N OPTIMUM STRATEGY SHOULD USE ACQUISITION+CONTIGUOUS HST ORBITS ------------------------------------------------------------------------------------------------------------------------------------ 3 STAR-193835 FOS/BL RAPID 1.0 G160L 1830 COMB=YES 1 1880S 25 5 1 CYCLE 4 -461256 READ-TIME=20 420S ------------------------------------------------------------------------------------------------------------------------------------ 4 STAR-193835 FOS/BL RAPID 1.0 G160L 1830 COMB=YES 1 1880S 25 5 1 CYCLE 4 -461256 READ-TIME=20 420S ------------------------------------------------------------------------------------------------------------------------------------ 5 STAR-193835 FOS/BL RAPID 1.0 G160L 1830 COMB=YES 1 1880S 25 5 1 CYCLE 4 -461256 READ-TIME=20 420S ------------------------------------------------------------------------------------------------------------------------------------ 6 STAR-193835 FOS/BL RAPID 1.0 G160L 1830 COMB=YES 1 1880S 25 5 1 CYCLE 4 -461256 READ-TIME=20 420S ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5364 [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK RAPID ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=1.204 SEARCH-SIZE-X=1 SEARCH-SIZE-Y=3 SCAN-STEP-X=0.602 SCAN-STEP-Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 SCAN-STEP-X=0.3 SCAN-STEP-Y=0.3 SEARCH-SIZE-X=3 COMB=YES READ-TIME=20 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 4.43 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ERUPTIVE BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 1.5; CYCLE 4; ONBOARD ACQ FOR 1.7; ONBOARD ACQ FOR 2-6; CYCLE 4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G400H G160L ------------------------------------------------------------------------------------------------------------------------------------ Target Names STAR-193835-461256 ------------------------------------------------------------------------------------------------------------------------------------