8130( 4) - 11/09/99 16:12 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8130 Version: 4 Check-in Date: 09-Nov-1999 16:11:23 1.Proposal Title: Solving the ``iron curtain conundrum'' ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Tim Naylor Keele University CoI: Dr. Barbara Hassall University of Central Lancashire N CoI: Dr. Koji Mukai Goddard Space Flight Center N CoI: Dr. Janet Wood Keele University N CoI: Mr. Gabriel Pratt University of Central Lancashire N ------------------------------------------------------------------------------------ 5. Abstract X-ray observations of dwarf novae in quiescence, including OY Car, show deep and unmistakable X-ray eclipses, indicating that the boundary layer is directly observable. However, quiescent UV spectra of OY Car indicate the presence of veiling material, which has been modelled at a column density that would make it impossible to observe directly the boundary layer (Horne et al. 1994). We propose to obtain phase resolved HST observations of OY Car in quiescence, simultaneous with ASCA X- ray observations, in order to resolve the apparent discrepancy between the X-ray and UV measurements of n_H. These observations will also enable us to investigate the azimuthal variation of the absorbing material. ------------------------------------------------------------------------------------ 8130( 4) - 11/09/99 16:12 - [ 2] Observations Description ------------------------ We will observe OY Car with STIS using the CCD detectors and the G230LB grating to cover 1685--3065Angstrom\ with a central wavelength of 2375Angstrom. Over this region a white dwarf spectrum is relatively flat, whilst the the `iron curtain' has many individual lines, and a large depression between 2000 and 3000Angstrom, which is over 50 percent of the flux at the column densities we are searching for. Our primary reason for using the CCD rather than the MAMA detectors is that it is possible that OY Car will go into outburst during the observations. It could reach V~ 11. Thus to avoid any possible danger to the MAMA detectors we have chosen to use the CCD. This enables us to cover the wavelength region of interest with only a small penalty in signal-to-noise. The other advantage of the CCD is the much shorter time needed between identical science exposures. Since our target is a point source a subarray of 16 pixels (0.9 arcsec) centered on the target will be used to reduce t he time between CCD exposures to 1 1 secs (9 secs overhead plus 2 secs readtime). OY Car has a continuum flux at 2300Angstrom\ of f_Lambda ~eq 5* 10^-15 ergs s^-1 cm^-2 AA^- 1. The exposure time calculator indicates that a S/N of ~eq10 per resolution element in the continuum will be obtained in a 5 minute exposure. We will therefore take a series of such exposures. These are short compared to the orbital period and therefore give good phase resolution. For the first orbit we will need approximately 7 minutes to acquire the guide stars, a further 6 minutes to acquire the target, and 5 minutes instrument overhead. The second orbit will require just 6 minutes for guide star re-acquisition. We will thus acquire around 8 exposures in the first orbit, and ten in the second, with a grand sum signal-to-noise of around 40 per resolution element in each orbit. Real Time Justification ----------------------- The observation must be simultaneous with an ASCA observation. The observations will have to be simultaneous with ASCA time. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8130( 4) - 11/09/99 16:12 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 OYCAR STAR, DWARF NOVA RA=10H 6M 22.43S +/- 0.6", DEC=- J2000 F(2000)=7e-15 70D 14' 4.9" +/- 0.6", PLATE- V = 17+/-1.5 ID=0196 8130( 4) - 11/09/99 16:12 - [ 4] Visit: 01 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Must be simultaneous with ASCA time. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 OYCAR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 10 S SEQ 10, 20 NON-INT CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 OYCAR STIS/C ACCUM 52X0.2 G230LB 2375 CR-SPLIT=2,NUM-POS=3, 1 14 M SEQ 10, 20 NON-INT MAX CD STEP-SIZE=0.5, DUR 21 M MIN DUR 9 M PATTERN-DIRECTION=PLUS, EXPAND SIZEAXIS2=100,SIZEAXIS1=1060, PATTERN=ALONG-SLIT ------------------------------------------------------------------------------------------------------------------------------------ 40 OYCAR STIS/C ACCUM 52X0.2 G230LB 2375 CR-SPLIT=3,NUM-POS=3, 1 16 M MAX DUR 24 M EXPAND MIN CD STEP-SIZE=0.5, DUR 10 M NO SPLIT PATTERN-DIRECTION=PLUS, SIZEAXIS2=100,SIZEAXIS1=1060, PATTERN=ALONG-SLIT ------------------------------------------------------------------------------------------------------------------------------------ 8130( 4) - 11/09/99 16:12 - [ 5] Summary Form for Proposal 8130 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT PATTERN=ALONG-SLIT SIZEAXIS1=1060 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements SEQ 10, 20 NON-INT SEQ 10, 20 NON-INT MAX DUR 21 M MIN DUR 9 M EXPAND MAX DUR 24 M EXPAND MIN DUR 10 M NO SPLIT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230LB ------------------------------------------------------------------------------------------------------------------------------------ Target Names OYCAR ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2375 ------------------------------------------------------------------------------------------------------------------------------------