6422( 7) - 08/02/96 10:40 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6422 Version: 7 Check-in Date: 02-Aug-1996 11:36:32 1.Proposal Title: Spin-cycle variations of the UV emission lines of intermediate polars ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle BINARIES AND STAR FOR GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: COEL HELLIER KEELE UNIVERSITY CoI: Keith Horne University of St.Andrews N CoI: Carole Haswell University of Columbia N CoI: Phillip Martell University of Wisconsin Center N ------------------------------------------------------------------------------------ 6. Abstract The intermediate polars are a prime opportunity for observing the interaction of an accretion flow with a strong magnetic field. Yet many fundamental issues remain unresolved. For instance, it is not known whether the accretion flow passes through a partial accretion disk, as suggested by many optical studies, or whether material accretes through the direct impact of the accretion stream with the magnetosphere, as suggested by the presence of beat period modulations in intermediate polar X-ray light curves. The low energy optical emission might not trace the dominant accretion flow, but we have no velocity information in the X-ray band. Spin-cycle resolved UV spectroscopy will both give velocity information and trace the accretion flow to within 1-2 white dwarf radii of the white dwarf surface, allowing a direct link to the X- ray studies. AO Psc is a typical intermediate polar, is one of the brightest in the UV, and shows the clearest spin-cycle variations in the optical and UV emission lines -- it is thus the best target for a line profile study using HST. We propose to use the GHRS to obtain high time and spectral resolution observations of the C IV line, which is prominent in the spectrum of AO Psc. Watching how the line profile changes around the 805-s spin cycle will reveal the accretion flow as it approaches the X-ray emitting shock, settling many uncertainties regarding the flow of material from the magnetosphere onto the white dwarf. ------------------------------------------------------------------------------------ 6422( 7) - 08/02/96 10:40 - [ 2] Observations Description ------------------------ We will obtain time-resolved GHRS spectroscopy of the C IV and He II lines of the magnetic cataclysmic variable AO Psc. The 286 Angstrom range of the G140L grating covers both lines with plenty of continuum. The principal aim is to measure line profile changes through the 805-s spin cycle of AO Psc. We will use repeats of short ACCUMs to obtain a time resolution of approx 30 secs. In the analysis we will phase-add the data obtained to build up the statistics required. The phase-averaged IUE spectrum of AO Psc gives flux levels of 1.4 10^-13 and 3.0 10^-13 erg s-1 cm-2 Ang-1 at the base and peak of the C IV line respectively. Using the quoted sensitivity for our instrumental setup of 67 10^11, we obtain count rates of 0.9 & 2.0 s-1 diode-1 respectively, or 0.5 and 1.0 s-1 per resolution element. The resolution of 0.7Ang corresponds to 135 km s-1, ~17 resolution elements across the full width of the C IV line. For the first HST orbit, a guide star acquisition, a target acquisition in the LSA and an ACCUM mode readout add up to 27 mins, leaving 25 mins exposure time, from the 52-min available. On subsequent orbits the lost time (re-acquisition + readout) is 10 mins, giving 42 mins. We will use ACCUM mode with COMB=4 and STEPPATT=5 to give (with 4 sec deadtime) a readout every 31.2 secs, of which 25.6 secs is exposure. Thus we have a total of 260 mins of exposure, or ~7500 counts per resolution element in the continuum. In 20 phase bins we have a S/N of 19 in the continuum, more in the lines, which is adequate for our purposes. Real Time Justification ----------------------- No special requirements needed None required Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6422( 7) - 08/02/96 10:40 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 AO-PSC STAR,INTERMEDIATE RA = 22H 55M 17.97S +/- 0.02S, J2000 V = 13.4+/-0.3 POLAR, INTERACTING DEC = -03D 10' 40.3" +/- 0.3", B-V = 0.06 BINARY PLATE-ID = 00GY F-CONT(1520)=1.5+/-0.5e-13 F-LINE(1549)=2.4+/-0.5e-13 W-LINE(1549)=15+/-3 Comments: Coordinates are from GSC 6422( 7) - 08/02/96 10:40 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 AO-PSC HRS ACQ 2.0 MIRROR-N1 BRIGHT=RETURN,SEARCH-SIZE=3 1 45 S ONBOARD ACQ FOR 2-5 Comments: STEP-TIME=5 ------------------------------------------------------------------------------------------------------------------------------------ 2 AO-PSC HRS ACCUM 2.0 G140L 1595 FP-SPLIT=NO,COMB=FOUR, 160 27.2 S STEP-TIME=0.2,STEP-PATT=5, SPYBAL=YES Comments: NUMBER OF ITERATIONS CAN BE CHANGED TO FILL UP ORBITS, TIME PER EXPOSURE SHOULD NOT BE CHANGED. ------------------------------------------------------------------------------------------------------------------------------------ 3 AO-PSC HRS ACCUM 2.0 G140L 1595 FP-SPLIT=NO,COMB=FOUR, 160 27.2 S STEP-TIME=0.2,STEP-PATT=5, SPYBAL=YES Comments: NUMBER OF ITERATIONS CAN BE CHANGED TO FILL UP ORBITS, TIME PER EXPOSURE SHOULD NOT BE CHANGED. ------------------------------------------------------------------------------------------------------------------------------------ 4 AO-PSC HRS ACCUM 2.0 G140L 1595 FP-SPLIT=NO,COMB=FOUR, 160 27.2 S STEP-TIME=0.2,STEP-PATT=5, SPYBAL=YES Comments: NUMBER OF ITERATIONS CAN BE CHANGED TO FILL UP ORBITS, TIME PER EXPOSURE SHOULD NOT BE CHANGED. ------------------------------------------------------------------------------------------------------------------------------------ 5 AO-PSC HRS ACCUM 2.0 G140L 1595 FP-SPLIT=NO,COMB=FOUR, 160 27.2 S STEP-TIME=0.2,STEP-PATT=5, SPYBAL=YES Comments: NUMBER OF ITERATIONS CAN BE CHANGED TO FILL UP ORBITS, TIME PER EXPOSURE SHOULD NOT BE CHANGED. ------------------------------------------------------------------------------------------------------------------------------------ 6422( 7) - 08/02/96 10:40 - [ 5] Summary Form for Proposal 6422 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=3 SPYBAL=YES STEP-PATT=5 STEP-TIME=0.2 COMB=FOUR ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category BINARIES AND STAR FORMATION ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N1 G140L ------------------------------------------------------------------------------------------------------------------------------------ Target Names AO-PSC ------------------------------------------------------------------------------------------------------------------------------------