8156( 4) - 02/03/99 10:33 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8156 Version: 4 Check-in Date: 03-Feb-1999 10:33:24 1.Proposal Title: The accretion geometry in the soft, double-pulsing intermediate polar V405 Aur ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Coel Hellier Keele University CoI: Dr William Welsh University of Texas at Austin N CoI: Dr Andrew Beardmore Keele University N ------------------------------------------------------------------------------------ 5. Abstract The intermediate polars (IPs) show several types of behavior. Some show only hard bremsstrahlung X-ray spectra, while others show an additional soft black-body component. Some show quasi- sinusoidal single-peaked pulses at the white dwarf spin period, others show double-peaked pulse profiles. We have suggested that both dichotomies are related to the area of the accretion footprint on the white dwarf, and hence to the process by which the magnetic field disrupts the accretion disk. In order to confirm or refute our hypothesis we aim to observe V405 Aur, the only IP showing both a soft X-ray component and a double-peaked pulse profile. We will use UV STIS spectra to measure the temperature of the pulsation, and hence deduce its emitting area (one of the most useful pieces of information to obtain, since it can be immediately compared to the white dwarf area to tell us where the pulse originates). We will further compare the UV pulse profile to the optical and X-ray pulse profiles and model all three with our simulation code to deduce their origin. Additionally, the analysis of the UV line profiles will give us velocity information from near the white dwarf for the first time. By putting all this information together we can deduce the accretion geometry, and thus, by tracing field lines back to the point where the field disrupts the disk, obtain constraints on the (largely unknown) physics of the transition region. ------------------------------------------------------------------------------------ 8156( 4) - 02/03/99 10:33 - [ 2] Observations Description ------------------------ We will obtain time-resolved STIS spectroscopy of the far-UV spectrum of the magnetic cataclysmic variable V405 Aur. The E140M echelle will cover the 1150- 1700 Ang range, covering lines such as the C iv 1550 doublet and He ii 1640. The principal aim is to measure line profile changes through the 545-s spin cycle of V405 Aur. We will use TIME-TAG mode for adequate time resolution. In the analysis we will phase-add the data obtained to build up the statistics required. We have no current UV spectrum of V405 Aur but we can predict it accurately using the UV spectra of the very similar and well studied intermediate polars such as AO Psc (V=14.0) and FO Aqr (V=13.5). Scaling their UV spectra by the magnitude of V405 Aur (V=14.5) we predict flux levels of gives flux levels of 0.9*10^-13 and 1.9*10^-13 erg s^-1 cm^-2 AA^-1 at the base and peak of the C iv line respectively. For the first HST orbit of the visit, a guide star acquisition, a target acquisition and a peakup will be followed by whatever TIME-TAG exposure fills the orbit. For subsequent orbits a guide star re-acquisition is followed by TIME-TAG exposure to fill the orbit. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: NO Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8156( 4) - 02/03/99 10:33 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V405-AUR STAR, INTERMEDIATE RA=05H 57M 59.29S +/- 0.5", J2000 V = 14.6+/-0.3 POLAR DEC=+53D 53' 44.9" +/- 0.5", B-V = 0.06 PLATE-ID=00VN F-CONT(1520)=0.9+/-0.5e-13 F-LINE(1549)=1.6+/-0.5e-13 W-LINE(1549)=15+/-3 8156( 4) - 02/03/99 10:33 - [ 4] Visit: 01 Visit Priority: 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 V405-AUR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.5 S ONBOARD ACQ FOR 2-5 CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 V405-AUR STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=500 1 2350 S UV-MAM G A Comments: Exposure time estimated to fill the orbit - can be adjusted to fit. Buffer-time is conservative due to source variability by factors of 2-3 on ~3 min timescales. ------------------------------------------------------------------------------------------------------------------------------------ 3 V405-AUR STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=500 1 2750 S UV-MAM G A Comments: Exposure time estimated to fill the orbit - can be adjusted to fit. ------------------------------------------------------------------------------------------------------------------------------------ 4 V405-AUR STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=500 1 2890 S UV-MAM G A Comments: Exposure time estimated to fill the orbit - can be adjusted to fit. ------------------------------------------------------------------------------------------------------------------------------------ 5 V405-AUR STIS/F TIME-TA 0.2X0.2 E140M 1425 BUFFER-TIME=500 1 2350 S UV-MAM G A Comments: Exposure time estimated to fill the orbit - can be adjusted to fit. ------------------------------------------------------------------------------------------------------------------------------------ 8156( 4) - 02/03/99 10:33 - [ 5] Summary Form for Proposal 8156 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT BUFFER-TIME=500 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2-5 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names V405-AUR ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 ------------------------------------------------------------------------------------------------------------------------------------