Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 5362 Report Date: 18-Jul-95:17:14 Version: ********** Check-in Date: ********** 1.Proposal Title: A TIME_RESOLVED, HIGH_RESOLUTION UV STUDY OF THE WIND OUTFLOW IN THE EXCEPTIONAL CATACLYSMIC VARIABLE, V795 HER: 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 We propose to exploit the unique UV capabilities of the HST FOS to obtain the first time-resolved, high-resolution UV spectroscopy of the wind outflow in the enigmatic cataclysmic binary, V795 Her. Our previous IUE observations of this star have revealed extraordinary UV properties. Specifically, the SiIV and CIV line profiles change markedly on timescales at least as fast as the 30 minute exposure limit imposed by the sensitivity of IUE. Moreover, repeat observations over several allocation rounds have confirmed a coherent modulation on a period of 4.86hrs rather than at the known optical periods. It is well-established that many disk-accreting CVs show periodic UV line profile variation, but V795 Her breaks the mould in varying on a period that appears not to be the orbital period. A plausible origin for the usual orbital variation is wind shadowing of asymmetric disk structure induced by the mass transfer stream. However, it remains to be established whether such a model can be applied to the peculiar case of V795 Her. Indeed, it is unlikely that the intrinsic wind properties hold the key to the periodic UV line behaviour since the natural timescale of the wind source, believed to be seated in the inner disk, is of order minutes. The primary objectives are 1) to investigate and quantify radial velocity motion in the CIV emission component, 2) to define the nature and shortest timescales of variation in both the SiIV and CIV line profiles, 3) to measure any correlated continuum flux changes. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 13.85 par: 0 10. Num targs pri: 1 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: FOS ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 5362 PI: Simon Rosen Proposal Title: A TIME_RESOLVED, HIGH_RESOLUTION UV STUDY OF THE WIND OUTFLOW IN THE EXCEPTIONAL CATACLYSMIC VARIABLE, V795 HER: CYCLE4 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Simon R Rosen UNIVERSITY OF LEICESTER UNITED KING X Raman Prinja UNIVERSITY COLLEGE LONDON UNITED KING X Janet Drew UNIVERSITY OF OXFORD UNITED KING X Steve Howell PLANETARY SCIENCES INSTITUTE USA Edward Robinson UNIVERSITY OF TEXAS USA Allen Shafter CALIFORNIA STATE UNIVERSITY,SAN USA DIEGO Keith Mason MULLARD SPACE SCIENCE LABORATORY UNITED KING X ------------------------------------------------------------------------------------ 3. Description of proposed observations. We will use the FOS (blue side digicon detector) with the G130H grating to access the far UV wavelength range between 1150A and 1600A. Using the 0.9 arc second aperture should provide data at about 1A resolution, a factor 5-6 improvement over our IUE data. Spectra will be recorded using 20s integrations with FOS RAPID mode to probe the fastest changes in the wind, enabling us to search for features within the CIV and SiIV absorption profiles that might be associated with clumping in the wind or other phenomena reflecting the inner disk rotation timescales. We anticipate a S/N of >10 per diode at the CIV continuum per 20s exposure. Co-adding spectra into 2-3 minute time bins will enhance the S/N for longer timescale studies (we can expect a S/N level ~30 per diode at the CIV continuum). This will permit close monitoring of the development of the absorption and emission components of the CIV line and for tracking inherent radial velocity motion (we can expect perhaps 40 time bins through the entire absorption event ($\sim$90 mins - 0.3 in phase). We will cover two 4.8hr cycles in a our requested 9.9hr exposure. Mildly time-critical observations are requested (see section 5) to ensure that we sample all phases of the 4.86 hr variation. We request three blocks of observations, each of six contiguous spacecraft orbits, with the blocks being separated by about 27 spacecraft orbits. Page 3 ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Our 3 IUE observations of V795 Her revealed the 4.8hr periodic variability in its CIV and SiIV lines. However these obser- vations, the best that can be realistically achieved with IUE, can not address the rapid timescales of CIV line profile variability which is less than the minimum time between any of our IUE exposures (30 minutes). Only HST can probe the faster (minutes) timescales that are probably appropriate, e.g. the rapid evolution of the C IV absorption component which can convey vital information about the absorbing wind. Equally, we will exploit the factor ~6 improvement in spectral resolution of the HST FOS over IUE. Use of the high resolution IUE mode is not practicable due to the very low expected count rates and long exposure therefore needed to secure adequate S/N. Moreover, the poor IUE wavelength calibration (~ +/- 4A = +/-800 km/s) severely restricts any unambiguous search for motion of the emission component(s): we are searching for motion at this or smaller velocities The combination of enhanced spectral resolution and higher achievable S/N ratios offered by the HST FOS will be crucial in pinning down the cause of the profile variability and in quantifying basic outflow properties and parameters such as the limiting wind velocity. A further important advantage of FOS over IUE is the relative internal flux calibration between spectra. We need an accuracy of about 2% (over a 50A range) to constrain models but could only achieve ~10% with IUE, the limit imposed by internal IUE calibration uncertainties. Our feasibility estimates are based on scaling our observed IUE spectra by the sensitivity curves of the flat spectrum presented in the HST FOS documentation. We expect about 3.5, 6.6 and 8.0 cts/s/diode at the NV (1240) continuum, CIV continuum and the CIV (1550) line peak respectively or 70, 130 and 160 cts/diode respectively in each 20s exposure, resulting in a S/N >11/diode at C IV. To monitor longer timescale periodic changes, we will coadd the spectra into 2-3 minute bins yielding ~900 counts at the C IV continuum per bin. Since our primary interest is in the C IV and Si IV lines, which lie around the highest region of the FOS sensitivity curve, we anticipate high quality (S/N~20-30 per diode per 2-3 min spectrum) spectra for our study. In each 2-3 minute spectrum, we can expect to secure around 50000 counts in a 50A wide range at the CIV continuum, permitting us to readily achieve the objective of monitoring continuum flux changes to around 1-2% accuracy averaged over such a range. We seek a total of 9.9 hours on-source time to effectively sample two 4.8hr cycles (see section 5), allowing us to check for cycle-to-cycle variability. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. We are requesting (mildly) time-critical observations because the 4.86hr (292 minute) period of the UV lines differs by only 4 minutes from 3 times the HST Earth-orbital period. Thus, if we used contiguous orbits, we would sample only a limited range of phases, leaving large gaps in the phase coverage. To overcome this, we request that the observation be split into three blocks, each of six contiguous HST orbits (slots). This will provide eighteen ~30 minute slots of data (assuming an on-source window per HST orbit of about 30 mins) covering an effective interval of two 4.8hr periods. We further request that the blocks are spaced apart by around 27 HST orbits (1.8 days). Although we have declared this request as time-critical, it does not demand any specific start epoch, merely that the three blocks be spaced apart by a certain amount and that 6 contiguous HST orbits be used within each block. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. Routine FOS calibration data will be sufficient for our purposes. Page 4 ------------------------------------------------------------------------------------ 8. Additional comments or special requests. We will endeavour to obtain simultaneous or near simultaneous optical spectroscopy of V795 Her with the HST observations in order to search, in detail, for correlated optical emission line behaviour. Despite the substantial amounts of IUE data now taken, such simultaneous optical observations have yet to be secured. 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. This should not be a problem since several members of this collaboration (SBH, ELR, AS) have access to suitable telescopes at the Lowell and McDonald Observatories for which time can be gained at relatively short notice. Nevertheless, the best time for ground- based observations of V795 Her is between April and August with June as the optimum choice. ------------------------------------------------------------------------------------ 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 93. GO- 3579 The UV orbital lightcurve of the X-ray binary X1822-371. (KOM) - not done. GO-3600 Oscillations, flaring and tomography of AE Aqr. (ELR). GO-3683 Accretion disk mapping in eclipsing cataclysmic variables. (ELR) GO-4661 Ultra -violet eclipse mapping of the accretion flow in the eclipsing Intermediate Polar, EX Hya. (SRR,KOM,RKP). This programme failed due to satellite/instrument problems unrelated to this observation. Could not be rescheduled. GO-4449 Occultation studies of RE1149+28: An object with an extreme EUV/optical ratio. (KOM,SRR). Scheduled for cycle 3 GO-4659 A time-resolved UV study of the wind outflow in the enigmatic cataclycmic variable, V795 Her. Supplemental time awarded but for only 2.3 hours. Obs not yet performed. The proposal GO-4659 was the initial request of this proposal but was awarded only 2.3 hrs of supplemental time. It will not by itself resolve the issues. No other programmes are related to this one. Papers: The Crab pulsar in the visible and UV with 10 micro- second time resolution: J.W. Percival, J.D. Biggs, J.F. Dolan, E.L. Robinson, et al, Ap.J., 407, 276, 1993. Several other GTO papers involving ELR have been submitted or are in preparation. ------------------------------------------------------------------------------------ 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 = 5362 [ 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 V795-HER A, 151 RA = 17H 12M 56.10S +/- J2000 1 B = 13.0 +/- 0.2 0.74", 2 B-V = 0.6 +/- 0.1 DEC = +33D 31' 21.45" +/- 3 E(B-V) = 0.1 +/- 0.1 0.74", 4 F-CONT(1200) = 3.2 +/- 0.4 E-13 PLATE-ID = 02TX 5 F-CONT(1550) = 2.8 +/- 0.3 E-13 6 F-LINE(1550) = 3.4 +/- 1.0 E-13 7 W-LINE(1550) = 10 +/- 3 Comments: UV FLUXES ARE FROM IUE. S/N ~10/PIXEL/BIN NEEDED PER 20S EXPOSURE AT CIV CONTINUUM CIV LINE VARIES BETWEEN ABSORPTION AND EMISSION. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5362 [ 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 V795-HER FOS/BL ACQ/ 4.3 G130H SCAN-STEP- 1 1S 1 1 ONBOARD ACQ FOR PEAK Y=1.204 3 1.5 SEARCH-SIZE-X=1 CYCLE 4 / 1-27 SEARCH-SIZE-Y=3 Comments: STAR VARIES BY ABOUT 0.2 MAGS ABOUT ITS MEAN OF B=13.0. ------------------------------------------------------------------------------------------------------------------------------------ 1.5 V795-HER FOS/BL ACQ/ 1.0 G130H SCAN-STEP- 1 1S 1 1 ONBOARD ACQ FOR PEAK X=0.602 3 1.7 SCAN-STEP- Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 1.7 V795-HER FOS/BL ACQ/ 0.5 G130H SCAN-STEP-X=0.3 1 1S 1 1 ONBOARD ACQ FOR 2- PEAK SCAN-STEP-Y=0.3 3 7 SEARCH-SIZE-X=3 SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 2 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S Comments: USE 3 BLOCKS, EACH CONSISTING OF ACQUISITION + 6 CONTIGUOUS HST ORBITS. BLOCKS SHOULD IDEALLY BE ABOUT 27 HST ORBITS APART. START EPOCH OF 1ST BLOCK IS ARBITRARY. ------------------------------------------------------------------------------------------------------------------------------------ 3 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 4 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 5 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 6 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 7 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 11 V795-HER FOS/BL ACQ/ 4.3 G130H SCAN-STEP- 1 1S 1 1 ONBOARD ACQ FOR PEAK Y=1.204 3 11.5 SEARCH-SIZE-X=1 AFTER 1 BY 1.8D +/ SEARCH-SIZE-Y=3 - .3D Comments: STAR VARIES BY ABOUT 0.2 MAGS ABOUT ITS MEAN OF B=13.0. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5362 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 11.5 V795-HER FOS/BL ACQ/ 1.0 G130H SCAN-STEP- 1 1S 1 1 ONBOARD ACQ FOR PEAK X=0.602 3 11.7 SCAN-STEP- Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ 11.7 V795-HER FOS/BL ACQ/ 0.5 G130H SCAN-STEP-X=0.3 1 1S 1 1 ONBOARD ACQ FOR 12 PEAK SCAN-STEP-Y=0.3 3 -17 SEARCH-SIZE-X=3 SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 12 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S Comments: USE 3 BLOCKS, EACH CONSISTING OF ACQUISITION + 6 CONTIGUOUS HST ORBITS. BLOCKS SHOULD IDEALLY BE ABOUT 27 HST ORBITS APART. START EPOCH OF 1ST BLOCK IS ARBITRARY. ------------------------------------------------------------------------------------------------------------------------------------ 13 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 14 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 15 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 16 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 17 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 21 V795-HER FOS/BL ACQ/ 4.3 G130H SCAN-STEP- 1 1S 1 1 ONBOARD ACQ FOR PEAK Y=1.204 3 21.5 SEARCH-SIZE-X=1 AFTER 1 BY 3.6D +/ SEARCH-SIZE-Y=3 - .3D Comments: STAR VARIES BY ABOUT 0.2 MAGS ABOUT ITS MEAN OF B=13.0. ------------------------------------------------------------------------------------------------------------------------------------ 21.5 V795-HER FOS/BL ACQ/ 1.0 G130H SCAN-STEP- 1 1S 1 1 ONBOARD ACQ FOR PEAK X=0.602 3 21.7 SCAN-STEP- Y=0.602 SEARCH-SIZE-X=6 SEARCH-SIZE-Y=2 ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 5362 [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 21.7 V795-HER FOS/BL ACQ/ 0.5 G130H SCAN-STEP-X=0.3 1 1S 1 1 ONBOARD ACQ FOR 22 PEAK SCAN-STEP-Y=0.3 3 -27 SEARCH-SIZE-X=3 SEARCH-SIZE-Y=3 ------------------------------------------------------------------------------------------------------------------------------------ 22 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S Comments: USE 3 BLOCKS, EACH CONSISTING OF ACQUISITION + 6 CONTIGUOUS HST ORBITS. BLOCKS SHOULD IDEALLY BE ABOUT 27 HST ORBITS APART. START EPOCH OF 1ST BLOCK IS ARBITRARY. ------------------------------------------------------------------------------------------------------------------------------------ 23 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 24 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 25 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 26 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ 27 V795-HER FOS/BL RAPID 1.0 G130H 1380 COMB=YES 1 27M 10 5 1 READ-TIME=20 20S ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 5362 [ 9] 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 13.85 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category ERUPTIVE BINARIES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 1.5; CYCLE 4 / 1-27 ONBOARD ACQ FOR 1.7 ONBOARD ACQ FOR 2-7 ONBOARD ACQ FOR 11.5; AFTER 1 BY 1.8D +/- .3D ONBOARD ACQ FOR 11.7 ONBOARD ACQ FOR 12-17 ONBOARD ACQ FOR 21.5; AFTER 1 BY 3.6D +/- .3D ONBOARD ACQ FOR 21.7 ONBOARD ACQ FOR 22-27 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130H ------------------------------------------------------------------------------------------------------------------------------------ Target Names V795-HER ------------------------------------------------------------------------------------------------------------------------------------