! $Id: 6422,v 7.1 1996/08/02 14:36:29 pepsa Exp $ Proposal_Information ! Section 4 Title: Spin-cycle variations of the UV emission lines of intermediate polars Proposal_Category: GO Scientific_Category: BINARIES AND STAR FORMATION Cycle: 6 Investigators PI_name: Coel Hellier PI_Institution: Keele University CoI_Name: Keith Horne CoI_Institution: University of St.Andrews Contact: ! Y or N (designate at most one contact) CoI_Name: Carole Haswell CoI_Institution: University of Columbia Contact: ! Y or N (designate at most one contact) CoI_Name: Phillip Martell CoI_Institution: University of Wisconsin Center Contact: ! Y or N (designate at most one contact) 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. Questions ! Free format text (please update) Observing_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: Fixed_Targets Target_Number: 1 Target_Name: AO-PSC Alternate_Names: GSC5238-0223 Description: STAR,INTERMEDIATE POLAR, INTERACTING BINARY Position: RA = 22H 55M 17.97S +/- 0.02S, DEC = -03D 10' 40.3" +/- 0.3", PLATE-ID = 00GY Equinox: J2000 Flux: V=13.4 +/- 0.3, B-V=0.06, F-CONT(1520) = 1.5 +/- 0.5 E-13, F-LINE(1549) = 2.4 +/- 0.5 E-13, W-LINE(1549) = 15 +/- 3 Comments: Coordinates are from GSC Visits Visit_Number: 1 Visit_Requirements: Exposure_Number: 1 Target_Name: AO-PSC Config: HRS Opmode: ACQ Aperture: 2.0 Sp_Element: MIRROR-N1 Wavelength: Optional_Parameters: BRIGHT=RETURN, SEARCH-SIZE=3 Number_of_Iterations: 1 Time_Per_Exposure: 45S Special_Requirements: ONBOARD ACQ FOR 2-5 Comments: STEP-TIME=5 Exposure_Number: 2 Target_Name: AO-PSC Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1595 Optional_Parameters: FP-SPLIT=NO,COMB=FOUR,STEP-TIME=0.2,STEP-PATT=5,SPYBAL=YES Number_of_Iterations: 160 Time_Per_Exposure: 27.2S Special_Requirements: Comments: NUMBER OF ITERATIONS CAN BE CHANGED TO FILL UP ORBITS, TIME PER EXPOSURE SHOULD NOT BE CHANGED. Exposure_Number: 3 Target_Name: AO-PSC Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1595 Optional_Parameters: FP-SPLIT=NO,COMB=FOUR,STEP-TIME=0.2,STEP-PATT=5,SPYBAL=YES Number_of_Iterations: 160 Time_Per_Exposure: 27.2S Special_Requirements: Comments: NUMBER OF ITERATIONS CAN BE CHANGED TO FILL UP ORBITS, TIME PER EXPOSURE SHOULD NOT BE CHANGED. Exposure_Number: 4 Target_Name: AO-PSC Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1595 Optional_Parameters: FP-SPLIT=NO,COMB=FOUR,STEP-TIME=0.2,STEP-PATT=5,SPYBAL=YES Number_of_Iterations: 160 Time_Per_Exposure: 27.2S Special_Requirements: Comments: NUMBER OF ITERATIONS CAN BE CHANGED TO FILL UP ORBITS, TIME PER EXPOSURE SHOULD NOT BE CHANGED. Exposure_Number: 5 Target_Name: AO-PSC Config: HRS Opmode: ACCUM Aperture: 2.0 Sp_Element: G140L Wavelength: 1595 Optional_Parameters: FP-SPLIT=NO,COMB=FOUR,STEP-TIME=0.2,STEP-PATT=5,SPYBAL=YES Number_of_Iterations: 160 Time_Per_Exposure: 27.2S Special_Requirements: Comments: NUMBER OF ITERATIONS CAN BE CHANGED TO FILL UP ORBITS, TIME PER EXPOSURE SHOULD NOT BE CHANGED. Data_Distribution ! Defaults indicated; change if desired Medium: 8MM ! 8MM or 6250BPI or 1600BPI Blocking_Factor: 10 ! 10 or 1 ! Only astronomers with very old 9- ! track tape drives should consider ! a blocking factor of 1 Ship_To: PI_Address ! STSCI or PI_Address or ! PI Address from Phase I is: ! ! Department of Physics ! Keele ! Staffordshire ! ST5 5BG ! ! Ship_Via: UPS ! UPS (2-day) or OVERNIGHT ! Overnight shipping done at PI expense Recipient_Email: ! Needed if Ship_To: is not PI_Address !