! File: 4449C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:12:28:07 coverpage: title_1: OCCULTATION STUDIES OF RE1149+28: AN OBJECT WITH AN EXTREME title_2: EUV/OPTICAL RATIO: CYCLE3 HIGH sci_cat: HOT STARS sci_subcat: ERUPTIVE BINARIES proposal_for: GO pi_fname: JONATHAN pi_mi: PD pi_lname: MITTAZ pi_inst: 8054 pi_country: U.K. hours_pri: 9.80 num_pri: 1 fos: Y off_fname: LEN off_lname: CULHANE off_title: LAB. DIRECTOR off_inst: 8054 off_addr_1: MULLARD SPACE SCIENCE LABORATORY off_addr_2: HOLMBURY ST. MARY off_addr_3: NR. DORKING off_city: SURREY off_country: UK off_phone: UK-483 274111 ! end of coverpage abstract: line_1: One of the fundamental and outstanding problems to be line_2: resolved in AM Her stars is the origin of the high ratio line_3: of the soft/hard X-ray flux ratio compared to the value line_4: (~ 1) predicted in the conventional shock model. The only line_5: explanation so far advanced is that of a `blobby' accretion line_6: flow which directly penetrates and heats the white dwarfs line_7: photosphere, thereby enhancing the soft X-ray flux at the line_8: expense of the hard X-ray flux. Clearly, knowledge of the line_9: state of the gas near the white dwarf is crucial in trying to line_10: understand this problem. We propose to probe the structure line_11: of the inner, UV emitting accretion stream in RE1149+28, the line_12: most extreme example of a EUV bright system. RE1149+28 has line_13: the highest EUV/optical ratio of any known AM Her, and line_14: therefore it might be expected that most of the accretion line_15: occurs via blobs. By studying the UV line emission in line_16: RE1149+28 we can gain critical information on the gas close line_17: into the WD surface, such a study being facilitated by that line_18: fact that RE1149+28 is a pole occulting system. The line_19: structure of the accretion stream can therefore be observed line_20: as it crosses the limb of the white dwarf. ! ! end of abstract general_form_proposers: lname: MITTAZ fname: JONATHAN title: PI mi: PD inst: 8054 country: UK esa: Y ! lname: ROSEN fname: SIMON mi: R inst: 8042 country: UK esa: Y ! lname: MASON fname: KEITH mi: O inst: 8054 country: UK esa: Y ! lname: HOWELL fname: STEVE mi: B inst: 3180 country: US ! lname: ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: Our investigation requires well spectrally resolved, good S/N line_2: spectra with sufficient temperal resolution to adequately sample the line_3: orbital cycle. Using the G130H grating we will cover the important line_4: lines of N V, Si IV and C IV. In order to adequately sample the line_5: critical phases when the accretion stream crosses the limb of the line_6: white dwarf (likely duration 5-10 minutes), exposure times of line_7: approximately 1 minute are required to achive sufficent time line_8: resolution as well as reasonable S/N (including the effects of line_9: phase binning). In order to maximise throughput, we are using line_10: the 4.3 arcsec aperture. To ensure that we obtain data during line_11: the limb crossing, as well as to study the orbital effects in line_12: detail, we require prefer uniform phase coverage. Unfortunately, line_13: the orbital period of RE1149+28 is nearly commensurate with that line_14: of HST, drifting by 0.06 in phase each orbit. Within the total line_15: exposure time we can not obtain uniform phase coverage using line_16: contigous orbits, but we can cover all phases. Ideally we would line_17: like to get uniform coverage, which would mean having some gaps line_18: between contiguous observations by spreading all the observations line_19: over 1.5 days. Therefore, we would like several visits if line_20: possible over a 1.5 day period, but if this is not possible line_21: contiguous orbits will cover all phases, if not uniformly. line_22: In the optical, RE1149+28 varies between 17.2 and 17.8 with a line_23: quasi-sinuosoidal lightcurve. ! question: 4 section: 1 line_1: The accretion flow within 10 stellar radii of the white dwarf line_2: should be hot (10000