Abstracts of Cycle 1 FUSE Guest Investigator Programs The following abstracts are presented as submitted to NASA in the Phase 1 FUSE proposals in May 1998. In the peer review process some proposals may have been reduced in scope or targets. Such changes are not reflected in these abstracts. PGMID: A001 PI: Werner, Klaus Institution: Institut fur Astronomie und Astrophysik, Universitat Tubingen, Germany Title: Ultra-hot winds from DO white dwarfs We propose to study the two prototypes of a new class of hot white dwarfs (WD). The optical spectra reveal absorption lines from ultra-high ionized metals (e.g.\ O\,VIII), a phenomenon never observed before in any astronomical object. The occurrence of such features requires temperatures in the order of 10$^6$\,K, far in excess of the stellar T$_{\rm eff}$. The asymmetric profile shapes suggest formation in a rapidly accelerating high-speed wind (10\,000~km/s). These stars represent the most convincing proof for on-going mass-loss from WDs. We have demonstrated that a large fraction of hot WDs shows this phenomenon, concluding that perhaps {\it all} WD go through this evolutionary stage. We will study the wind properties and possible consequences for WD evolution on hand of detailed NLTE modelling. Recently obtained medium-resolution UV (HST) and FUV (ORFEUS) spectra pose new problems. In particular, the FUV region contains many inter-/circumstellar features which contaminate the photospheric spectrum. Hence we ask for high-resolution high-S/N FUV spectra for a deeper insight into this mysterious phenomenon. ------------------------------------------------------------------------------ PGMID: A002 PI: Combes, Francoise Institution: DEMIRM, Observatoire de Paris, France Title: Cold H2 in the outer galactic disk The cold molecular hydrogen gas (below 10\,K) does not radiate, and it is an open question to know in which quantity it is present in galaxies and in particular in the Milky Way. Within the optical disk, the metallicity is significant enough that the cold H$_2$ is traced by molecules such as CO (with large uncertainties however, in particular for very cold H$_2$). But at the border of the optical disk (basically at the solar radius) and beyond, the amount of H$_2$ is unknown. We have recently developped the case for the presence of large masses of cold molecular hydrogen in the outer disks of spiral galaxies and in dwarf irregulars. The bulk of the H$_2$ gas would be located in small clumpuscules, the smallest fragments of the hierarchical fractal structure of the gaseous interstellar medium. Because they are cold, only absorption in front of external sources can reveal them. Since we want to sample the outer disk, suitable sources are not stars, but remote QSO's almost in the plane of the disk ($b < 10^\circ$). In regions with no or very little dust, it is possible to probe larger column densities than for normal clouds, up to the limit where the H$_2$ itself absorbs most of the UV-light of the QSO. In the solar neighbourhood, we can also probe high-latitude molecular clouds, in front of high-latitude QSO's. Since at this radius, there exists still some CO tracer, these observations will determine the conversion ratio H$_2$/CO, which remains an open problem for high-latitude clouds. ------------------------------------------------------------------------------ PGMID: A003 PI: Hutchings, John Institution: Dominion Astrophysical Observatory, HIA, NRC of Canada, Canada Title: Phase-resolved investigation of supersoft X-ray binaries We propose to obtain phase-resolved $FUSE$ spectra of three supersoft X-ray binaries, achieving S/N of $\sim$20 over 0.5--1.0\AA\ in orbital phase bins of $\leq$0.1P. The emission line features in the $FUSE$ wavelength range cover a wide range of ionization giving a unique dataset for determination of the binary parameters, component masses, and disk structures which cannot be provided by optical and $HST$ data. We will also use the combined data for each system to detect and measure high-velocity lines from bi-polar jets which are seen in the optical spectra of all three systems. High-ionization lines from these jets are of particular interest since they are formed in the innermost region where the jets are undergoing their collimation and acceleration. An improved understanding of jets has wide astrophysical implications. ------------------------------------------------------------------------------ PGMID: A004 PI: Schmid, Hans Martin Institution: Landessternwarte Heidelberg, Germany Title: O VI raman scattering and the geometric structure of symbiotic stars We propose FUSE observations of the O~VI 1032, 1038 emission line structures in symbiotic systems in order to compare them with spectroscopic and spectropolarimetric observations of the Raman scattered counterparts in the red spectral region. From this we can derive the Doppler shift and polarization induced in the H$^0$ Raman scattering process. This allows to deduce information on the geometric and dynamic structure of the red giant's wind region in these interacting binary systems. In particular, our analysis should clarify the geometry of the ionization front between the cool giant and the hot component, which depends in a very sensitive way on hydrodynamical and radiative interaction processes. ------------------------------------------------------------------------------ PGMID: A010 PI: Ferrario, Lilia Institution: Astrophysical Theory Centre, Australian National University, AUS Title: The magnetic field structure of the 450 MG ultramassive white dwarf EUVE J0317-855 We have recently identified the dominant features in the optical spectra of the rapidly rotating (725\fs5) magnetic white dwarf EUVE~~J0317--855 with $H{\alpha}$ 2s0 - 3p-1, 2s0 - 3p0 and $H{\beta}$ 2s0 - 4f-1 in a magnetic field of 100-300 MG, but some features remain unidentified. IUE data show Ly$\alpha$ ${\sigma^+}$ at 1300\AA, and an unidentified feature near 1330 \AA. Models using centred and off-centred dipole field structures provide a reasonable fit to the averaged spectra for a dipole strength of $B_d=450$ MG displaced from the centre of the star by 35\% $R_*$ and viewed at a mean angle of $30 -60\gradi$ to the dipole axis. The nature of the observed spectral variations and of the unidentified lines remains unknown. We propose to carry out phase-dependent FUSE observations of the Lyman line series in order to resolve the field structure responsible for the observed photometric and spectroscopic variations. Based on a single TTAG data set we will reconstruct five seperate high-SN spectra, each at a specific rotational phase. ------------------------------------------------------------------------------ PGMID: A013 PI: Dreizler, Stefan Institution: Institut fur Astronomie und Astrophysik, Universitat Tubingen, Germany Title: Trace elements and radiative levitation in hot helium-rich white dwarfs We propose to observe three helium-rich (DO) white dwarfs in order to determine their photospheric abundances of trace elements (e.g. C, N, O, H, Fe, Ni,...). FUSE spectroscopy is ideal for this purpose since the FUV allows to explore a large variety of line transitions of various elements which are not detectable in existing optical or UV spectra of the targets. The data will be analyzed with non-LTE metal line blanketed model atmospheres. The results will be compared to predictions from newly developed, self-consistent diffusion/radiative levitation calculations under non-LTE conditions. The observed metal abundances will serve as bench-marks for such kind of new calculations. As a basis for this work we have obtained high-S/N optical spectra of almost all known DO white dwarfs within the last five years as well as HST GHRS spectra of selected DO white dwarfs. A comprehensive analysis of the atmospheric parameters is now available. For the present proposal we have selected three targets which -- together with calibration and PI targets-- represent the non-DA white dwarf cooling sequence from the hot end down to the DB gap. ------------------------------------------------------------------------------ PGMID: A019 PI: Gladstone, Randy Institution: Southwest Research Institute, USA Title: A FUSE observation of argon on Titan The origin of Titan's thick nitrogen and methane atmosphere is a compelling enigma. One key and still missing observable concerns the abundances of noble gases in general, and argon in particular. Detection of argon would indicate that the N$_2$ and CO now found in the atmosphere probably came in with ice during Titan's accretion. Alternatively, if there is very little argon, then we have to turn to models starting with frozen ammonia, methane and water ice, indicating a more important role for the Saturn sub-nebula, and requiring subsequent modification by photochemistry. Current estimates on the fraction of argon in Titan's atmosphere are crude, and based only on indirect evidence, and range from 0--25\%. We have modeled Titan's expected photoelectron-generated EUV emissions with argon as an added constituent. The bright resonance line of argon at 1048\ang\ is predicted to be present at a level of 7--12~R, for assumed argon abundances of 5--25\% in the lower atmosphere of Titan. At a brightness of 7~R, an 80~ks integration time by FUSE would provide a $>\!5\sigma$ detection of argon in the atmosphere of Titan (a 30~ks integration would provide a $>\!3\sigma$ detection). An accurate determination of the abundance of argon on Titan would be useful in preparing for the arrival of the {\it Cassini} orbiter and {\it Huygens} probe at the Saturn system. ------------------------------------------------------------------------------ PGMID: A022 PI: Fisher, George Institution: Space Sciences Laboratory, University of California-Berkeley, USA Title: Coronal heating during stellar flares and the search for proton beams We will obtain high resolution FUSE spectra of the dMe star AD Leo during periods of quiescence and during flares to study the physics of atmospheric heating in flare stars. We will also obtain coordinated ground based observations including multicolor photometry and high resolution optical spectroscopy. Light curves obtained during flares will allow us to determine the coronal loop length and flare coverage area on the stellar surface. The FUSE spectra will also allow us to determine the structure and evolution of temperature and density in the corona, transition region, and chromosphere, allowing us to test detailed models of flare evolution. The unprecedented sensitivity and resolution of FUSE will strongly constrain current models. Finally, we will search for significant red-shifted emission in the Lyman series lines of hydrogen during the rise phase of flares, possibly indicating the presence of energetic proton beams. The existence and role of proton beams in both solar and stellar flares is currently a subject of great debate. ------------------------------------------------------------------------------ PGMID: A023 PI: Buat, Veronique Institution: Laboratoire d'Astronomie Spatiale, CNRS, Marseille, France Title: The FUV spectral energy distribution of star-forming galaxies We propose to observe several bright star-forming galaxies with FUSE. These galaxies are selected to have been already observed in the near UV, visible and far-infrared. The analysis of the entire spectral energy distribution longward the Lyman break will allow us to study the star formation history, the initial mass function and the effects of dust extinction in these objects. These galaxies will constitute needful templates for the study of high redshift actively star-forming galaxies. Under reasonable assumptions for intrinsically bright galaxies, the UV continuum (912-1200$\AA$) is rather insensitive to the star formation history and the initial mass function. Any departure from the expected flat spectrum in our sample of intrinsically bright galaxies may be attributed to the effects of internal dust and will be used to deduce an empirical attenuation curve down to the Lyman break. The analysis of the stellar absorption lines in the far and near UV complemented with the interstellar emission lines in the optical and the overall shape of the spectral energy distribution of the galaxies will give us constraints about the recent star formation history, the initial mass function of the more massive stars and the contribution of an older underlying stellar population. ------------------------------------------------------------------------------ PGMID: A024 PI: Mouchet, Martine Institution: DAEC, Observatoire de Paris-Meudon, France Title: The origin of peculiar UV line ratios in magnetic cataclysmic variables Magnetic Cataclysmic Variables (MCV) typically show UV emission line intensity ratios broadly compatible with photo-ionization by thermal radiation of ~20-50 eV, arising from accretion onto highly magnetized white dwarfs. However, four systems display peculiar UV line ratios not compatible with any modelling, suggesting a very peculiar ionization/ excitation process or surprising abnormal abundances which might be signs of a recent nova explosion or reflect the non-solar composition of the companion's atmosphere. We propose to observe the two Polars, BY Cam (H0538+608) and V1309 Ori (RX J0515.6+0105) which both show a strong deficiency in CIV correlated with a large excess in NV. The unprecedented sensitivity of FUSE in the 905-1195\AA{} region will allow the measurement of the expected strong OVI doublet as well as several crucial C and N lines, all of which are essential to discriminate between models for the origin of the C, N emission line anomaly. The program requests a total of {\bf 16} orbits (including 2 orbits for acquisition) and a total on-source exposure time of {\bf 28 ksec} for the two sources to obtain spectra with a spectral resolution of 0.3\AA{} and a S/N ratio above 5 in the continuum allowing a detailed multi-component line profile study over several orbital phases. ------------------------------------------------------------------------------ PGMID: A026 PI: Heber, Ulrich Institution: Astronomisches Institut, Universitat Erlangen-Nurnberg, Germany Title: Abundances of the pop II sdO stars LS IV-12.1 and ROB 162 LS IV-12.1 and ROB 162 are rare, hot (\Teff=50 -- 60\,000K) subdwarf O stars of population II, evolving from the asymptotic giant branch to the white dwarf domain. FUSE spectra are proposed to determine the abundances of C,N,Si,P,S and Fe by means of NLTE model atmospheres. In the case of \ls\, its high radial velocity allows the photospheric resonance lines to be separated from interstellar components. The results of the abundance analysis will shed light on PAGB evolution in population II stars and will allow physical processes such as dredge-up of nuclearly processed matter and/or gas-dust fractionation in the AGB progenitor stars envelope to be investigated. The [S/Fe] ratio is a sensitive tracer of the latter process. The crucial sulphur abundance can most reliably be derived from the \ion{S}{4} and \ion{S}{6} lines in the FUV. ------------------------------------------------------------------------------ PGMID: A034 PI: Barstow, Martin Institution: Department of Physics and Astronomy, University of Leicester, UK Title: White dwarf evolution: heavy element abundances and the DA temperature scale We propose FUSE observations of a sample of the hottest known DA white dwarfs to study their evolution and the link between them and their CSPN progenitors. Analysis of the H Lyman lines provides a unique determination of $T_{eff}$ and log g for each star, taking into account the heavy element abundances, which are known to affect the temperature determination, which we will determine from measurements of line strengths in the high resolution FUSE spectra. Importantly, FUSE gives us access to absorption lines of several species which cannot be studied in any other wavelength range. From this work, combined with observations of cooler PI/calibration white dwarf targets, when they appear in the public archive, we will reestablish the hot DA white dwarf temperature scale. In addition, with significantly improved accuracy in the temperature determination we will be able to track the evolution of stellar photospheric abundance with cooling age for the first time. ------------------------------------------------------------------------------ PGMID: A035 PI: Mulchaey, John Institution: Carnegie Institution of Washington, USA Title: The warm intragroup medium in spiral-rich groups of galaxies Recent ROSAT observations indicate that $\sim$ 20\% of nearby groups of galaxies contain a low-density, X-ray emitting intragroup medium. If present in all groups of galaxies, the intragroup medium would be the dominant baryonic component in the local universe. However, the ROSAT observations indicate that X-ray emission is almost exclusively restricted to groups that are dominated by elliptical and S0 galaxies. The much more common spiral-dominated groups, such as the Local Group, are not X-ray detected. The most likely explanation for the non-X-ray detection of spiral-rich groups is that the intragroup medium in these systems is too cool to produce detectable X-ray emission. The intragroup medium in spiral-rich groups is expected, however, to produce detectable absorption features in the spectra of background quasars. We propose to observe with FUSE three AGN situated behind low redshift spiral-rich groups to search for the O VI doublet in absorption, as expected from a warm intragroup medium. The detection of O VI absorption from these groups would verify that an intragroup medium exists in all groups and is the dominant baryonic component in the local universe. The S/N of our proposed FUSE observations are such that the failure to detect O VI in absorption would put strict limits on the presence of an intragroup medium in spiral-rich groups. Furthermore, this limit would suggest that our current estimate for the amount of baryonic material in groups is overestimated by at least a factor of ten. ------------------------------------------------------------------------------ PGMID: A036 PI: Thuan, Trinh Xuan Institution: Astronomy Department, University of Virginia, USA Title: Far-ultraviolet studies of metal-deficient blue compact dwarf galaxies How galaxies form is one of the most fundamental questions in astrophysics. Much effort has gone into the search for primeval galaxies at high redshifts. But these galaxies are faint and small, making their study very difficult even with the largest telescopes. We propose here an alternative approach, the study of nearby blue compact dwarf (BCD) galaxies that are chemically young. Our sample consists of 4 BCDs, two of which are among the most metal-deficient galaxies known, and which appear to be truly young, not containing stars older than $\sim$100 Myr, SBS 0335--052 ($Z_\odot$/41) and UGC 4483 ($Z_\odot$/21). The two other BCDs, MKN 59 ($Z_\odot$/8) and MKN 71 ($Z_\odot$/10), have larger metallicities and ages, and allow us to explore the far-UV properties of BCDs over a wider range of sub-solar metallicities. The proposed FUSE observations will allow us to investigate: 1) the H$_2$ content of BCDs. This will directly constrain models of galaxy formation as H$_2$ is an important cooling agent in the primordial gas; and 2) the evolutionary history and stellar winds in BCDs by detecting the P Cygni profiles of high ionization lines not observed at longer wavelengths such as S VI and O VI. The proposed observations will give us the opportunity to explore new spectroscopic techniques in the far-UV that can be later applied to the study of the star formation history in high-redshift primeval star-forming galaxies, where the far-UV is shifted to the near-UV or the optical. ------------------------------------------------------------------------------ PGMID: A041 PI: Simon, Theodore Institution: Institute for Astronomy, University of Hawaii, USA Title: Finding the onset of convection in main sequence stars Main sequence A stars have both a small convective core as well as a thin convective layer just below the visible surface. While neither of these two regions is directly observable, convection clearly plays a key role in many aspects of A star behavior. One of the most notable of these is the formation of a high temperature chromosphere or corona. Using FUSE, we propose to observe the far UV spectra of a sample of 8 normal A-type stars, which cover a broad range in $T_{\rm eff}$ and color index. Our goal is to use the diagnostically important lines of O VI, which form at 300,000 K, and the density-sensitive lines of C III, which form at 60,000 K, to find the locus for the onset of convection zones, coronae, and chromospheres along the main sequence, thereby testing the predictions of stellar structure models as well as chromospheric/coronal heating models. Such observations are best made below \lya, where A--star photospheres appear much darker and offer less of a hindrance than at near UV and optical wavelengths ------------------------------------------------------------------------------ PGMID: A044 PI: Boroson, Bram Institution: High Energy Astrophysics Division, Smithsonian Astrophysical Observatory, USA Title: Wind ionization in high mass X-ray binaries We propose to observe three High Mass X-ray Binaries with FUSE; one LMC source (LMC X-4), one SMC source (SMC X-1) and one galactic source (Vela X-1). We will observe the \ion{O}{6}$\lambda\lambda1031,1037$ P~Cygni line variations over the binary orbit. The orbital variations result from X-ray photoionization of the wind, and allow us to model the wind structure to determine its density and velocity field. We will look for pulsations in the UV lines and continuum. Lyman series absorption lines from the primary star will help us model the wind lines, and can measure the rotation and orbit of the primary. We will also look for ellipsoidal variations in the continuum light curves. ------------------------------------------------------------------------------ PGMID: A046 PI: Heckman, Timothy Institution: Center for Astrophysical Sciences, Johns Hopkins University, USA Title: The FUV spectra of starbursts Starbursts are a significant component of the present-day universe, and offer unique laboratories for both studying the processes that have regulated the formation and evolution of galaxies, and for testing models of high-mass stellar evolution. We propose to exploit the unique strengths of FUSE to obtain full-resolution ($\sim 10$ km s$^{-1}$) high quality (S/N $\geq$ 15) spectra of the six UV-brightest starbursts. These starbursts span ranges of 20 in metallicity (1/8 to 2.5 solar) and $\sim$ 10$^2$ in luminosity. The spectra will be used to study: 1) the coronal-phase gas that may dominate the energetics of starburst-driven `superwinds' 2) the H$_2$ that probably dominates the ISM mass and regulates the star-formation 3) the starburst dust-attenuation law in the unexplored FUV window 4) the stellar content of the starburst (thereby probing the IMF and burst history). These will be the finest UV spectra obtained to-date for starbursts. In particular, the FUSE MDRS aperture allows us to obtain high-resolution spectra of nearly the entire starburst (rather than small pieces, as with HST and STIS). ------------------------------------------------------------------------------ PGMID: A048 PI: Hartigan, Patrick Institution: Dept. of Space Physics and Astronomy, Rice University, USA Title: FUV observations of low and high-excitation Herbig-Haro shocks We propose to test our understanding of radiative cooling behind shocks by comparing the fluxes of far-UV emission lines in stellar jets with predictions from shock models. Our targets include the brightest examples of three distinct types of shock waves in these objects -- high-excitation, low-excitation/molecular, and preionized. Spectra of the high-excitation bow shock HH~1F should have detectable O~VI $\lambda$1035 emission if existing models are accurate. The lack of such emission would suggest that magnetic fields play an important role in the dynamics of this object. The unique combination of detectable H$_2$ fluorescent lines and low reddening in the low-excitation object HH~47A will allow us to measure the relative importance of molecular and atomic cooling in low-velocity shocks, and to assess the degree to which pumping by postshock Lyman $\alpha$ and Lyman $\beta$ photons heats the H$_2$. A FUSE spectrum of the preionized low-excitation bow shock HH~47D will clarify how the ambient UV radiation affects emission line ratios between 900\AA\ and 1200\AA . ------------------------------------------------------------------------------ PGMID: A049 PI: Wakker, Bart Institution: Department of Astronomy, University of Wisconsin-Madison, USA Title: 10^5 K gas in the halo of the Large Magellanic Cloud One of the stated major scientific goals of the FUSE PI programs is a survey of the amount and distribution of the \OVI\ ion in the Milky Way disk and halo and in the Magellanic Clouds, in order to understand how matter and energy are transferred between the disk and halo. In particular, the halo program allows to understand how plumes generated by OB associations spread out. A study of \OVI\ in the halo must avoid sightlines through active regions. This is the case for about 100 Milky Way sightlines on the reserved-target list, but only for 3 stars selected in the Large Magellanic Cloud (LMC). Since we recently used \CIV\ absorption data to show that the LMC indeed has \dex5\,K halo gas, we request time with FUSE to study the global distribution of the \OVI\ absorption in the LMC. With these data we will asses the relationship between the \dex6\,K X-ray emitting gas, the \dex4\,K \Ha\ maps, and the \dex5\,K gas. ------------------------------------------------------------------------------ PGMID: A051 PI: Federman, Steven Institution: Univ. Toledo USA Title: Molecular hydrogen excitation in photodissociation regions We propose to study photodissociation regions through observations of absorption from rotational levels in the vibrational ground state of H$_2$. These transitions occur below 1150 \AA. Photodissociation regions are found around newly-formed B stars and beyond the H~{\small II} regions surrounding newly-formed O stars because their ultraviolet flux is sufficient to convert molecular species into atoms. H$_2$ is destroyed by a two step process: absorption into excited electronic states followed by radiative decay into the continuum of the ground electronic state. This occurs with an efficiency of $\sim$ 10\%; the remaining decays to excited vibrational states then lead to infrared emission that returns the molecule to the vibrational ground state, but with a non-thermal distribution for the populations of high-lying rotational levels. We will extract the gas temperature from the relative amounts in the lowest rotational levels and the flux of ultraviolet radiation permeating the gas from the amount in excited rotational levels. The estimates for temperature and flux will lead to refined models of photodissociation regions previously based solely on infrared emission. ------------------------------------------------------------------------------ PGMID: A052 PI: Deharveng, Jean-Michel Institution: Laboratoire d'Astronomie Spatiale CNRS, Marseille, France Title: The Lyman continuum radiation from galaxies The amount of ionizing radiation released into the intergalactic medium by star formation is a poorly known but crucial parameter. It would tell how the galaxies can complement the contribution of quasars for ionizing the IGM, especially at the epoch of re-ionization when the number density of quasars is apparently low. Direct measurements are difficult and scarce. Indirect evaluations using stellar population synthesis are plagued by the uncertainties on the Lyman continuum (\Lyc) escape fraction. We would like to take advantage of the sensitivity of FUSE down to 900 \AA~ to detect (or set significant upper limit on) the \Lyc\ radiation of nearby star-forming galaxies. We have selected two galaxy candidates with a redshift large enough to get rid of the residual galactic opacity resulting from the accumulation of the Lyman series absorption lines. ------------------------------------------------------------------------------ PGMID: A053 PI: Reimers, Dieter Institution: Hamburger Sternwarte, Universitat Hamburg, Germany Title: Intergalactic ionized helium absorption toward 15 new bright quasars We propose to probe the far-UV continuum fluxes of 15 new bright ($V<17$) $2.4 < z < 2.9$ quasars from the Hamburg Bright Quasar Survey by means of single-orbit snapshot exposures, with the aim of identifying one or more suitably bright objects for detailed studies of intergalactic HeII absorption over this redshift range. We also propose to carry out a $4 \cdot 10^{4}$~s exposure of the newly discovered quasar HS1549+1919 ($z=2.83$, $V\simeq 15.6$) -- an object that promises to reach a flux of $F_\lambda \sim 6 \times 10^{-15}$ erg~s$^{-1}$~cm$^{-2}$\thinspace{\AA}$^{-1}$ at redshifted HeII~$\lambda304$. If confirmed by its snapshot exposure, this object would be the brightest ``clear'' high redshift quasar discovered so far. Since the detailed study of HeII absorption lies at the limit of the capabilities of {\it FUSE}, a $\simeq5$ and $\simeq 2$ times boost in signal over the two other Hamburg quasars and {\it FUSE} targets HS1700$+$6416 and HE2347$-$4342 will dramatically increase the amount and quality of information on the physical state of the intergalactic medium that can be extracted from {\it FUSE} observations of intervening HeII absorption. ------------------------------------------------------------------------------ PGMID: A054 PI: Burleigh, Matthew Institution: Dept. of Physics and Astronomy, University of Leicester, UK Title: The fundamental parameters of white dwarfs in Sirius-type binaries We will use {\it FUSE} to accurately determine the fundamental parameters (T$_{eff}$, log g, radius and mass) of a recently discovered sample of unresolved, optically invisible white dwarfs in Sirius-type binary systems. Far-ultraviolet spectroscopy of the H Lyman series is the {\em only} means available to achieve this goal. We will then use the mass determinations to investigate the initial-to-final mass relation for white dwarf stars. In addition, {\it Hipparcos} provides us with well constrained parallaxes for ten of the primaries in this sample. We will use this data, together with the parameters determined with {\it FUSE}, to retrieve the stellar masses and hence test the empirical mass-radius relation, comparing it with that for isolated stars. Finally, we will search for evidence of elements heavier than He in these hot stars' photospheres and in the circumstellar environment, and determine their abundances. ------------------------------------------------------------------------------ PGMID: A058 PI: Miller, Eric Institution: Department of Astronomy, University of Michigan, USA Title: H2 as the primary gas component at large galactic radius Molecular absorption line studies and X-ray absorption observations toward extragalactic sight lines indicate that molecular gas is as abundant as neutral atomic gas in the Solar vicinity. At larger Galactic radii, H$_{2}$ exceeds HI in some locations, and if this is generally true, it implies a dramatic revision in the picture of neutral gas in disk galaxies. To determine if H$_{2}$ dominates the ISM at large radii, we propose to measure the H$_{2}$ column toward AGNs projected behind the outer parts of two external disk galaxies with measured HI columns. ------------------------------------------------------------------------------ PGMID: A060 PI: Koratkar, Anuradha Institution: Space Telescope Science Institute, USA Title: The FUV spectral energy distribution of quasars A well known feature of Active Galactic Nuclei (AGN) is the Big Blue Bump (BBB) continuum component which extends from 1 \micron\ to soft X-rays, containing more than half the bolometric emission of an unobscured AGN. Its origin is directly related to the main energy production mechanism. Theoretical arguments based on accretion disk models and on photoionization models suggested that the BBB peaks in the EUV. However, recent UV observations by Zheng et al. and soft X-ray observations by Laor et al. suggest the FUV turns over just below 1000~\AA\ and extends as a single power-law to $\sim$1~keV. This very surprising spectral shape has important implications for both accretion disk and photoionization models. Since there is no overlap between the high $z\simeq 1$ UV and low $z\simeq 0.2$ soft X-ray samples, it is not clear whether the implied SED in fact holds for any individual quasar. We propose here to obtain complete FUV coverage of a sample of 23 low $z$ PG quasars, for which high quality soft X-ray spectra are available. The combined {\em ROSAT PSPC+FUSE} spectra will allow us to set the most accurate constraints on the ionizing SED of quasars from both sides of the Galactic opacity barrier (at 912~\AA-0.15~keV). This will allow us to test directly, and in each object, whether the FUV indeed turns over below 1000~\AA\ into a single power-law which matches the 0.15-1~keV power-law. This sample was studied extensively and systematically in nearly all spectral bands, and highly significant correlations were found among the optical, UV and soft X-ray emission properties, providing important hints for the physical processes which shape AGN emission properties. The {\em FUSE} data will allow us to explore the expected correlations with FUV emission lines. A few of the objects in this sample show UV and soft X-ray absorption. Higher spectral resolution observations proposed for some of these objects will provide important clues on the nature and possible association between the X-ray and UV absorbers. ------------------------------------------------------------------------------ PGMID: A061 PI: Hutchings, John Institution: Dominion Astrophysical Observatory, HIA, NRC of Canada, Canada Title: The hottest stars in M31 and M33 We propose FUSE observations of the brightest OB stars in the local group galaxies M31 and M33. The stars are faint but their UV fluxes are known from HST and UIT data. This will extend the stellar wind and interstellar studies currently under way with HST and ground-based telescopes, with similar resolution (1000) and S/N. The program will expand our comparison of stellar winds, evolution, and the ISM among the major galaxies of the local group. ------------------------------------------------------------------------------ PGMID: A063 PI: Witt, Adolf Institution: Department of Physics & Astronomy, The University of Toledo, USA Title: Dust scattering propereties in reflection nebulae We propose to observe the three reflection nebulae NGC 2023, NGC 7023, and IC 435 and their illuminating stars with the aim to derive the dust scattering properties in three systems with widely differing far-UV extinction curves. The wavelength dependence of extinction in the 90-120 nm range in these three nebulae will be determined by the pair method, employing the far-UV SEDs of four lightly reddened comparison stars of appropriate spectral types, also to be observed as part of this project. Dust scattering properties in the form of wavelength-dependent values for the albedo and the phase function asymmetry will be derived with the use of Monte-Carlo multiple scattering models and with substantial reference to earlier analyses of these objects carried out at longer UV, visible, and near-IR wavelengths by the PI and his collaborators. The results will aid in the identification of the nature of the grains responsible for the steep far-UV rise in the interstellar extinction curve, and they will provide essential input parameters for models of the far-UV diffuse galactic light and for models treating the radiative transfer in dusty galaxies. ------------------------------------------------------------------------------ PGMID: A065 PI: Raymond, John Institution: Smithsonian Astrophysical Observatory, USA Title: H2 in HH2: fluorescence or collisions? Herbig-Haro object shock waves are visible in Balmer lines and forbidden lines in the optical and in $\rm H_2$ ro-vibrational transitions in the infrared. A few HH objects are seen in $\rm H_2$ Lyman and Werner bands in the UV. HUT observations of HH2 have raised the question of the excitation mechanism of this UV emission, and the answer bears directly upon the physics of the shocks themselves. FUSE has the spectral resolution to determine whether the 1050 $\rm \AA$ and 1100 $\rm \AA$ features result from fluorescence of Ly$\alpha$ photons or from collisional excitation by electrons. The line widths, which may be as large as 125 km/s, will be a valuable constraint on the models, and the observation will detect lines of C III and O VI if they are present at 1/3 the upper limits from HUT. ------------------------------------------------------------------------------ PGMID: A066 PI: Raymond, John Institution: Smithsonian Astrophysical Observatory, USA Title: Non-radiative shocks in the Cygnus Loop FUSE measurements of the O VI doublet in non-radiative shock waves provide unique diagnostics for the physics of collisionless shock waves (ion-ion and electron-ion equilibration) as well as a means to observe the onset of radiative cooling. It is necessary to understand these processes in order to derive the physical parameters and the evolutionary states of supernova remnants and other astrophysical shocks. We propose to observe two filaments in the Cygnus Loop. One is a 300 km/s pure non-radiative shock. The other is a crisp filament seen in the light of [Ne V] which marks the encounter between the main supernova remnant blast wave and a large, dense cloud. ------------------------------------------------------------------------------ PGMID: A068 PI: Bregman, Joel Institution: Department of Astronomy, University of Michigan, USA Title: Do elliptical galaxy cooling flows actually cool? The fundamental prediction of the cooling flow model for hot gas in elliptical galaxies is that the hot gas loses its thermal energy and becomes cool gas, typically at a rate of 1 $M_{\odot}$ yr$^{-1}$ for X-ray bright ellipticals. The most powerful test of this model would be the detection of cooling gas at $\sim10^{5.5}$ K, when it has lost more than 90\% of it thermal energy. OVI emitting gas is produced in this temperature range and the predicted luminosity is high enough that this gas should be easily observable by FUSE with the LWRS aperture. Measurements of OVI emission for our five galaxies of different $\dot M$ permit two important tests of the cooling flow picture, while non-detections will lead to severe limits, $\dot M < 0.04 M_{\odot}$ yr$^{-1}$, and a dismissal of the model. ------------------------------------------------------------------------------ PGMID: A070 PI: Boisse, Patrick Institution: Laboratoire de Radioastronomie, Ecole Normale Superieure, Paris, France Title: Probing the very small scale structure (l~10 AU) in the ISM We propose to investigate the very small scale structure (l $\simeq$ 5 - 10 AU) in the molecular, atomic and ionized phases of the interstellar medium by repeatedly observing a bright runaway O star located behind a translucent molecular cloud. The selected star, HD 34078 (AE Aur) moves at a transverse velocity of 103 km/s and the spectra taken during cycle 1 at three distinct epochs separated by 3-4 months will allow to sample adjacent lines of sight distant by $\simeq$ 5 AU at the cloud distance. The spectral range covered by FUSE is very well suited to conduct a coordinated search for small amplitude fluctuations of the column density for molecules (H$_2$, $^{12}$CO, $^{13}$CO, ...), atoms (CI, SI, ...) and ions (SiII, CII, FeII, ...). By performing a detailed comparison of the absorption lines detected in the three successive spectra, we expect to significantly improve the characterization of the ubiquitous AU-scale structure in the ISM and better understand its nature and origin. The properties of the proposed source as well as those of the interstellar gas along the line of sight are well characterized by previous observations (IUE, high resolution optical spectroscopy), which makes HD 34078 an ideal target for this project. Depending on the results obtained from cycle 1 observations, we will propose to extend the monitoring of the absorption lines during cycle 2 and/or 3, especially in order to investigate the variability on larger scales (l $\simeq$ 30 - 50 AU). If no variations are detected among cycle 1 spectra, the observations proposed will at least permit a detailed study of a well documented line of sight. ------------------------------------------------------------------------------ PGMID: A075 PI: Morse, Jon Institution: Center for Astrophysics and Space Astronomy, University of Colorado, USA Title: Abundances in O-rich SNRs: observational tests of nucleosynthesis We propose to obtain \fuse\ far-UV spectroscopic observations of the oxygen-rich supernova remnants N132D in the LMC and E0102.2--7219 in the SMC. The \fuse\ spectra will be coupled with our existing \hst\ FOS spectra and scheduled \axaf\ GTO spectra of the uncontaminated SN debris to provide complete, unprecedented sensitivity and wavelength coverage of the emission from the X-rays to the near-IR. We will compare the observed line ratios to predictions made by theoretical models in order to determine the excitation mechanisms and to derive reliable elemental abundances. Of primary importance is to measure the O~VI $\lambda\lambda1032$ emission from these objects with \fuse, which is key to determining the relative importance of collisional ionization and photoionization for producing the observed emission. N132D and E0102.2--7219 are the only O-rich SNRs that can be spatially resolved {\it and} studied effectively at UV wavelengths. The combined \fuse\ + \hst\ + \axaf\ data will provide important tests for theories of nucleosynthesis in massive stars as well as improve our understanding of the dynamics of supernova explosions and mixing in the ejecta. ------------------------------------------------------------------------------ PGMID: A083 PI: Guinan, Edward Institution: Dept. of Astronomy, Villanova University, USA Title: Solar physics with FUSE: FUV studies of solar analogs and twins We propose to use FUSE for an in-depth study of the evolution of the transition region and low corona of a solar-mass star throughout its main-sequence lifetime. This program is part of a comprehensive study of the ``Sun in Time'' across the electromagnetic spectrum. We have defined a homogeneous sample of single G0-5~V stars with well-known rotation periods that are proxies of the Sun at different ages. We intend to study dynamics of the lower layers of the stellar atmospheres by investigating line shifts, line asymmetries, and line broadenings that we presume are related to chromospheric evaporation by high-energy processes identified in the overlying corona. Emission measure and temperature analysis will allow us to obtain a complete 3-D atmospheric model of active regions that we will link to the previously obtained coronal X-ray data. We will infer transition region pressures through the powerful density-sensitive ratio of the C~III 977\AA/1176\AA\ lines; this important diagnostic will be adequate to identify and model the relevant magnetic structures based on the solar analogy, and, together with our coronal X-ray (ROSAT, ASCA, SAX), EUV (EUVE), and TR (IUE/HST) data, to infer the importance of coronal energy releases. Our FUSE investigation is central to the understanding of the evolution of magneto-dynamic atmospheric phenomena, and the associated high-energy emissions in the Sun and in solar-type stars. It also bears on the question of the young Sun's influence on the developing planetary system. The FUSE observations will further be used to estimate the important D/H ratio along the sightlines to the stars, and to search for the presence of stellar analogs to the solar wind. Coordinated /contemporaneous observations (with XMM, ROSAT, HST, optical photometers, partly from guaranteed time programs) are planned and will be organized. ------------------------------------------------------------------------------ PGMID: A084 PI: Mauche, Christopher Institution: Astrophysics Group, Lawrence Livermore National Laboratory, USA Title: High resolution FUV spectroscopy of EX Hydrae We propose to obtain high spectral resolution orbit- and spin-phase resolved FUV spectra of the intermediate polar EX~Hya. These spectra will be used to (1) resolve the FUV emission lines into their various components to constrain the location of, and the physical conditions in, the line-emitting gas, (2) measure the strength and phasing of the narrow absorption features to determine the column density through, and the ionization state of, the bulge on the edge of the accretion disk, and (3) measure the continuum flux distribution in the FUV and its variation on the spin and binary phases to constrain the effective temperature and area of the hot spot on the surface of the white dwarf and the effective temperature of the truncated inner disk. ------------------------------------------------------------------------------ PGMID: A085 PI: Dinerstein, Harriet Institution: Astronomy Department, University of Texas at Austin, USA Title: Far-UV absorption-line spectroscopy of the neutral envelopes of planetary nebulae In the last few years has it become clear that planetary nebulae (PNe) are not quite what they seem to be at first glance: they are {\it not} simply fully ionized circumstellar nebulae. Instead, for most PNe the ionized gas is merely the innermost zone of a massive, mostly neutral, circumstellar envelope. These neutral/molecular envelopes have been studied by the PI and her collaborators via fluorescently-pumped near-infrared H$_2$ emission lines, far-infrared emission lines such as [O I] 63 $\mu$m, and, most recently, optical Na I absorption lines. We propose to use FUSE to obtain high-resolution spectra of the central stars, using their continua as backdrops for observing UV absorption lines of key neutral and molecular species, in order to determine excitation temperatures, column densities, and other properties of these envelopes. This study will connect tightly to existing and future optical and infrared observations, as well as to previous GRHS and upcoming STIS programs. The FUSE observations are particularly important because {\it only} with FUSE will it be possible to directly observe the H$_2$ Lyman and Werner bands, the very lines that pump the cascade that produces the infrared H$_2$ lines. With their high-surface-brightness infrared line emission, PNe provide a remarkable opportunity for tying together the absorption and emission components of the H$_2$ fluorescence process, now known to be widespread in the ISM. FUSE will also enable us to measure the populations of the fine-structure levels of the $^3$P ground state of O I and connect these to far-infrared line observations by the PI of [O I] 63 $\mu$m, the primary coolant for the warm atomic gas in PNe, and [O I] 145 $\mu$m. In addition, FUSE will sample lines of other species such as C I and Cl I, as well as revealing new spectral features from the central stars. From this study we will learn about both the physics of UV-illuminated nebulae (``PDRs" or ``photodissociation regions") and about this enigmatic phase of stellar evolution, during which most of the stellar envelope is removed. ------------------------------------------------------------------------------ PGMID: A086 PI: Keel, William Institution: Dept. of Physics and Astronomy, Univ. of Alabama-Tuscaloosa, USA Title: Nearby galaxies in the FUV: toward comparison with high-redshift galaxies We propose a program of FUSE spectroscopy of star-forming regions in local galaxies to complement planned observations with the STARLITE far-UV shuttle hitch-hiker payload (which offers excelent diffuse-source sensitivity and spatial resolution at the expense of point-source performance and spectral resolution). The two datasets would complement each other uniquely for understanding the overall far-UV spatial and spectral morphology of these galaxies, an important first step toward being able to interpret this passband as seen optically in high-redshift galaxies. We concentrate on M33, whose combination of proximity and star-forming rate makes it especially amenable for this comparison. The S/N requirements are designed to allow separation of the lines in the Lyman $\beta$/O VI/C II blend which are diagnostic of the massive-star mix (particularly unevolved versus evolved stars), which has proven very difficult to unravel at longer wavelengths. Comparing the two data sets will tell whether the brightest star-forming regions are representative of the overall FUV-emitting population, and will be used to search for scattering effects. These data will enable us to interpret observations of high-redshift galaxies (higher every month now) in a more realistic context than yet possible. ------------------------------------------------------------------------------ PGMID: A088 PI: Brown, Thomas Institution: Lab. for Astronomy and Solar Physics, NASA/GSFC, USA Title: Hot populations in nearby elliptical galaxies Because they are composed of old, passively evolving populations, elliptical galaxies offer great promise for tracing the evolution of the Universe. Their apparent simplicity makes them the first beachhead in the quest to understand galactic evolution, and if they evolve slowly enough, they can be calibrated as standard candles at great distances. The hot stars responsible for the ``UV upturn'' phenomenon are key indicators of age and abundance in ellipticals. These stars are well isolated in the {\it FUSE} wavelength range from the cooler main sequence stars that complicate interpretation at wavelengths longer than 2000~\AA. We propose to observe three ellipticals through the {\it FUSE} $30 \times 30^{\prime\prime}$ aperture: NGC~221, NGC~4649, and NGC~1399. Although NGC~221 is a fundamental testing ground for theories of stellar and galactic evolution, its spectrum has never been measured below Lyman $\alpha$. NGC~4649 and NGC~1399 were observed by {\it HUT}, but at considerably lower signal-to-noise and resolution than possible with {\it FUSE}. With {\it FUSE} data, the absorption lines of C, N, and Si prevalent in the far-UV will provide invaluable composition diagnostics for the hot stellar populations in ellipticals. Furthermore, {\it FUSE} is uniquely qualified to measure the Lyman series, an important diagnostic of effective temperature and surface gravity. {\it FUSE} presents the opportunity to finally and unequivocally characterize the population responsible for the UV upturn. ------------------------------------------------------------------------------ PGMID: A090 PI: Krasnopolsky, Vladimir Institution: Department of Physics, Catholic University of America, USA Title: Search for H2 in Mars' atmosphere We propose to detect H$_2$ on Mars by observing its spectrum with FUSE in the beginning of June 1999 with integration time of 18 ks. This observation will also allow studying the far UV spectrum of Mars with an unprecendented quality. H$_2$ is probably the most abundant species which has not been observed on Mars. Photochemical models predict its mixing ratio from 7 to 50 ppm. The upper limit to the H$_2$ density of $1.1\times 10^5$ cm$^{-3}$ at the altitude of 560 km was established using the Mariner 9 ultraviolet spectrometer observations. This limit is very close to the value which is required to explain the densities of atomic hydrogen observed with Mariner 6, 7, and 9. A spectrum of Mars observed with the Hopkins Ultraviolet Telescope does not show H$_2$ emissions. This may raise a problem of a H$_2$ deficit on Mars, and a possible detection with FUSE may be of crucial importance. The most sensitive method for spectroscopic detection of H$_2$ is observations of the P1 (6-v'') lines of the H$_2$ Lyman band system. These lines are much stronger than other H$_2$ lines due to their excitation by the solar Lyman-beta line, the effect discovered by one of us (PDF) twenty five years ago. However, the expected intensities are low, a few tenths of rayleigh, even for these lines. The unique sensitivity and resolution of FUSE will allow detection of H$_2$ in the upper atmosphere of Mars. Extrapolation of the measured abundance to the lower atmosphere will result in the H$_2$ mixing ratio with an uncertainty of 30\%. Thus, H$_2$ can be measured for the first time on Mars, and FUSE can provide a key measurement which was impossible for the numerous spacecraft that visited Mars. ------------------------------------------------------------------------------ PGMID: A093 PI: Shore, Steven Institution: Dept. of Physics and Astronomy, Indiana University South Bend, USA Title: FUSE observations of galactic and LMC novae in outburst We propose target of opportunity observations of classical novae in the Galaxy and the Large Magellanic Cloud in the early stages of outburst. The FUV represents the final frontier in the study of the early history of the expansion of nova ejecta, when the overlying optically thick metallic line absorption spectrum (called the ``iron curtain'') lifts and it is possible to see through the ejected shell to the deepest layers of the still optically thick ejecta. During the period following the explosion, the central source illuminates the ejecta. To date, only three novae have been observed in the region from 900 - 1200\AA, V1974 Cyg 1992 (Voyager UVS, ORFEUS), Cir 1995 (HUT), and Aql 1995 (HUT). The 1995 novae were observed only at relatively low resolution with HUT during the ASTRO-2 mission and within one month of outburst, while V1974 Cyg was observed nearly 4 years after maximum and only with limited S/N. The ability to correctly model the outburst, determine the abundances in the ejecta, and obtain a comprehensive picture of the energetics of the outburst can only be achieved through multiwavelength observations. The FUV plays a vital part in these studies. ------------------------------------------------------------------------------ PGMID: A094 PI: Benjamin, Robert Institution: Dept. of Physics, University of Wisconsin, USA Title: Observational constraints for the Galactic fountain We propose to simultaneously search for diffuse \OVI~ emission and \OVI~ absorption in the same direction for which Martin \& Bowyer (MB) detected \CIV~ 1549 \AA~ emission: $l=155$, $b=58$. This is also the direction of the ``Lockman window''. For \OVI~ absorption, we will use the compact UV bright galaxy Mk 153 as a background source. Measurement of Galactic \OVI~ absorption and emission along the same line of sight will determine the density and pressure of the hot gas. Our results will be combined with MB's \CIV~ 1549 \AA~ and \OIII] 1662 \AA~ detections, as well as optical $H \alpha$, [S II], and [O III] emission from the Wisconsin $H \alpha$ Mapper, and $\onequarter {\rm -keV}$ X-ray shadowing studies of this region. Comparison with calculations of nonequilibrium cooling flows will be used to constrain models for the origin of this hot gas and determine whether the gas pressure is high enough to drive a ``galactic fountain'' flow. ------------------------------------------------------------------------------ PGMID: A099 PI: Leighly, Karen Institution: Columbia Astrophysics Laboratory, Columbia University, USA Title: FUV spectroscopy of narrow-line Seyfert 1 galaxy RE 1034+39 It has long been thought that the shape of the ionizing continuum of an Active Galactic Nucleus (AGN) should have an effect on its emission-line ratios. This is important since the line ratios then potentially provide a way to infer shape of the continuum in the unobservable EUV wavelength range. It was suspected that the ratio of \ion{O}{6} to Ly$\alpha$ should be especially sensitive to this shape: \ion{O}{6} should be strong when the continuum in the optical--UV--soft X-ray range is hard. Among the recently presented observational evidence lending support for this idea are the {\it HUT} spectra showing that some Seyfert 1 galaxies with strong X-ray soft excesses have also strong \ion{O}{6} lines. The Seyfert 1 galaxy RE~1034+38 has a remarkable spectral energy distribution. Its optical and UV spectra are very red, but there is no evidence for absorption. Its soft X-rays are very strong, with a steep spectrum. Such a hard ionizing continuum should produce a huge \ion{O}{6} line. We propose a 50~ks {\it FUSE} observation of RE~1034+39 to test the extreme limits of the trend for strong \ion{O}{6} to accompany a hard ionizing continuum. This observation will enhance our understanding of the influence of the continuum shape on the production of the strong broad emission lines in AGN. The signal to noise in the resulting spectrum should be good enough that we can resolve the line, and measure strong deviations of the continuum from a power law. Coordinated {\it ASCA} and optical spectroscopic observations are planned as well as accretion disk and photoionization modeling. ------------------------------------------------------------------------------ PGMID: A100 PI: Harper, Graham Institution: CASA, University of Colorado, USA Title: FUV spectra of evolved late-K and M stars: mass loss revisited The FUV radiation field of evolved late-K and M stars, which is dominated by H Lyman emission lines, controls the ionization balance of key atomic and ionic species, the dissociation equilibrium of molecular H$_2$ and CO, and provides crucial information on the excitation of hydrogen. FUSE observations of the FUV flux below $1044$\AA{ } will allow us to constrain the Ca~II/Ca~III balance and remove a key uncertainty in previous studies on stellar mass-loss rates. The FUV photoionization flux was previously {\it unknown}, but FUSE spectra can unlock the wealth of information from early optical studies of Ca~II. We propose to construct detailed radiative transfer models from the H Lyman $\beta$ and $\gamma$ line profiles. These models will provide constraints on the hydrogen ionization, the dominant source of electrons in chromospheres, and the formation of the Lyman continuum which is not directly observable. FUSE will also allow us to observe wind induced line profile asymmetries and to constrain with great sensitivity the volume of $\sim 3\times 10^5$~K plasma which traditional ``non-coronal'' stars are now thought to possess. We propose deep exposures of the brightest K bright giant ($\alpha$~TrA K3~II), the brightest K supergiant ($\lambda$~Vel K4~Ib), and two of the brightest M giants ($\gamma$~Cru M3~III, $\beta$~Gru M5~III). These stars have been studied extensively in the UV and optical, and we have recently obtained the first radio detections for all these targets. We will incorporate the knowledge gathered from the FUV into our unified chromospheric/wind models for these stars. These spectra will provide a valuable complement to the spectral-types and evolutionary phases of the GTO targets. FUV spectra of the M stars will provide crucial input physics for circumstellar photochemistry. ------------------------------------------------------------------------------ PGMID: A106 PI: Bohm-Vitense, Erika Institution: Astronomy Department, University of Washington, USA Title: O VI emission lines in Hyades F stars We propose to obtain additional empirical constraints on the atmospheric heating mechanisms operating in stellar transition regions (TR) and coronae. In particular, we will address the question of whether different heating mechanisms may be working in different layers of a given star and whether the relative importance of the mechanisms changes from star to star. The heating mechanisms may depend on T$_{eff}$, gravity, rotation, magnetic fields, age, chemical composition, and, possibly, binarity. In order to identify the heating mechanisms, we need to disentangle the dependences on all these parameters. We propose to do this by observing the 1032 \& 1038~\AA\ O~VI emission lines in a large sample of main sequence Hyades F stars. These stars are chosen since they are the brightest cluster stars with strong TR-emission and because marked changes in the heating mechanisms apparently occur around spectral type F5, leading to easily-observable effects on our spectral diagnostics. In addition, the age, chemical composition, and surface gravity of these stars are essentially the same, removing dependences on 3 of the stellar parameters. Relations between the lower-TR and upper-TR emissions, together with their relationships to the coronal X-ray emission will tell us the relationship between heating mechanisms in the different layers. We already have reliable lower-TR emission line (e.g. C~IV) measurements for 15 Hyades F stars observed by IUE and will be obtaining such for 17 additional Hyades F stars in an approved Cycle 7 HST program. FUSE will provide the critically needed flux measurements of upper-TR lines (O~VI), as well as of an additional lower-TR line, C~III. ------------------------------------------------------------------------------ PGMID: A107 PI: Flynn, Brian Institution: Center for EUV Astrophysics, University of California-Berkeley, USA Title: Distribution of Argon in the dayside lunar atmosphere The lunar atmosphere was first detected by Apollo instruments over 25 years ago. Both neutral Ar and He were detected, with peak nighttime number densities of $\sim$10$^3$~cm$^{-3}$ (Hodges et al.\ 1974). However only nighttime surface densities could be measured due to daytime outgassing from spacecraft hardware. Furthermore, due to the nature of the Apollo measurements, the spatial distribution of the most abundant known atmospheric species, Ar and He, could not be measured. In December 1996, the 1048 \AA\ resonance scattering line of Ar was detected at the 3$\sigma$ level above the lunar dayside for the first time using the ORFEUS SPAS II satellite (Flynn 1998). Due to the faintness of the Ar signal, and due to the insensitivity (relative to FUSE) of ORFEUS, no spatial information could be extracted from the data. Modeling the atmosphere as an optically thin 400~K barometric distribution indicates an Ar abundance surprisingly $\sim500\times$ greater than the theoretical daytime value (Hodges et al.\ 1974), which may indicate that the atmosphere is actually optically thick. A measurement of the radial distribution of the 1048 \AA\ emission would not only provide valuable information on the Ar source but also indicate whether or not the atmosphere is optically thick. We propose to use the greater sensitivity of FUSE to confirm the ORFEUS dayside Ar detection, and to measure the spatial brightness distribution for the first time. ------------------------------------------------------------------------------ PGMID: A108 PI: Dixon, Van Institution: Space Sciences Laboratory, The University of California, Berkeley, USA Title: FUSE spectroscopy of hot post-AGB stars in globular clusters We propose to obtain \fuse\ spectra of four hot post-asymptotic giant branch (PAGB) stars in globular clusters: ROB 162 in NGC 6397, ZNG 1 in NGC 5904 (M5), ROA 5342 in NGC 5139 ($\omega$ Cen), and III-60 in NGC 6723. These stars have temperatures greater than 40,000 K and are located in globular clusters with well-known distances, metallicities, and ages. Despite their short ($\sim 10^5$ yr) lifetimes, hot PAGB stars may contribute significantly to the enrichment of the interstellar medium, the photoionization of the halo, and the integrated ultraviolet flux of old stellar populations. We will model the \fuse\ spectra with non-LTE line-blanketed stellar atmospheres in order to derive the stars' effective temperatures and surface gravities and the abundances of important species such as carbon, nitrogen, and silicon. These parameters will be used to set constraints on processes such as mass-loss and dredge-up on the AGB, superwinds at the AGB turnoff, and the white dwarf mass in globular clusters. ------------------------------------------------------------------------------ PGMID: A109 PI: Walter, Frederick Institution: Department of Physics and Astronomy, State University of New York, USA Title: Werner bands of H2 in CS environments of selected classical T Tau stars The circumstellar disks of young stellar objects are likely to be dominated by hydrogen molecules (H$_{2}$). Using the HST/GHRS, we detected strong permitted H$_2$ Lyman band emission from a sample of classical T~Tauri stars. These bands arise either through fluorescent pumping by strong stellar emission lines or by shock heating. We propose FUSE observations of the H$_2$ Werner bands. These could be fluoresced by stellar O~VI emission, by shock heating, or by thermal processes at 1000~K. Measurement of these fluxes will greatly assist our study of the gaseous circumstellar environments of pre-main sequence stars. ------------------------------------------------------------------------------ PGMID: A111 PI: Chu, You-Hua Institution: Department of Astronomy, University of Illinois, USA Title: Interfaces in N51D We are studying the interfaces between hot (\dex6\,K) and warm (\dex4\,K) gas in the superbubble N\,51\,D in the Large Magellanic Cloud. N\,51\,D provides a well defined closed environment with known distance, size, kinetic and thermal energy. We have X-ray, radio and optical data and have been allocated time to obtain HST-STIS spectra for 4 lines of sight. The STIS spectra include lines of \NV, \CIV, \SiIV, and lower ionization species, and the four probe stars sample different projected distances from the center of the superbubble. We propose to use FUSE spectra of these four stars. Two are already on the reserved-target list, we request time for the other two. The integration times will be $\sim$10\,ks in three cases, so that we can obtain the O\,VI emission as well as the \OVI\ absorption. The FUSE spectra will yield information on \CI, \CIII, \NI, \NII\ and \NIII, so that we will have spectra for four ionization stages of C and N. Taken together, these data will allow a determination of the density, pressure and ionization of \dex2\,K, \dex4\,K, \dex5\,K and \dex6\,K gas in N\,51\,D. ------------------------------------------------------------------------------ PGMID: A117 PI: Lieu, Richard Institution: Dept of Physics, University of Alabama-Huntsville, USA Title: Search for UV emission lines from the warm intracluster medium A new component of diffuse soft X-ray and EUV emission has been found in all of the five clusters hitherto observed. In some clusters the soft excess is as luminous as that of the well-known intracluster X-rays. A thermal origin involves large quantities of warm gas, but was predicted by Cen and Ostriker whose cold dark matter model puts 55 \% of the present day baryons in this gas. Several authors also suggested a non-thermal (inverse-Compton) interpretation. Both scenarios have their pros and cons, and only further observations by better techniques can lead to a verdict. This proposal concerns a very effective means of gathering independent evidence for the thermal model. If warm gas is indeed present in such vast amounts one will expect prominent O VI emission lines. Previous missions failed to detect them, but their upper limits were not particularly constraining. With the much improved sensitivity of FUSE, one can now make definitive statements about the existence or otherwise of intracluster gas at the temperatures inferred from the soft excess measurements. We suggest observations at various radii of the three brightest soft excess clusters, to measure the spatial distribution of warm gas. ------------------------------------------------------------------------------ PGMID: A118 PI: Wolff, Michael Institution: Space Science Institute USA Title: FUV extinction: unique insights into the nature and role of small dust grains Understanding interstellar dust and its role in the universe is very important. Virtually all observations of astrophysical objects and their physical processes are affected by the presence of dust either within the system being studied or along its line of sight. We propose a research program that will significantly improve our knowledge of dust properties, specifically those of small grains. Such an advance has not been possible prior to the advent of FUSE and its unique capabilities: the high far ultraviolet (FUV) throughput and the ability to resolve H$_2$ lines, combined with a well-characterized instrumental calibration. We will derive FUV extinction curves for several types of sightlines which possess distinct signatures associated with the small grain population and whose mid-UV extinction curves reveal vastly differing amounts of intermediate-sized particles. In addition to a variety of important Galactic sightlines (\ie\ extreme values of $R_V$, polarized 2175~\AA\ feature), we include objects in each of the Magellanic Clouds where very non-Galactic mid-ultraviolet extinction properties are seen. These data will be used to probe and constrain the properties of the small dust grains, such as abundance and size, and their connection to the very different environments observed. ------------------------------------------------------------------------------ PGMID: A120 PI: Wannier, Peter Institution: Jet Propulsion Laboratory, California Institute of Technology, USA Title: The atomic-to-molecular transition in the halos of dense IS clouds FUSE observations of interstellar H$_2$ will enable a breakthrough study of the cool atomic and molecular gas (CAMM) associated with dense molecular clouds. We propose to initiate such a systematic study of the extended halos around four nearby clouds, which have been well characterized using radio and infrared techniques. The H$_2$ absorption-line spectra toward hot background stars will yield (1) direct H$_2$ column densities, (2) gas kinetic temperatures and (3) the diffuse UV radiative intensity. From the information in the atomic Lyman series and HD absorption lines, we will estimate (1) the atomic column density, yielding information about the space density, and (2) the cosmic ray ionization rate. In addition to the proposed FUSE observations, we plan an independently-funded observational program which will provide vitally-needed information about the cloud kinematics. For the FUSE sightlines, we will obtain optical spectra of CH and other species, using ultra-high spectral resolution, which will reduce uncertainties in the analysis caused by systematic variations in excitation with radial velocity. ------------------------------------------------------------------------------ PGMID: A121 PI: Gibson, Brad Institution: Mount Stromlo & Siding Spring Observatories, Australian National University Title: High velocity clouds: origin and environment High-velocity clouds (HVCs) are an important, but poorly understood component of the Galactic halo. Our missing knowledge of their metallicities has been a major impediment in unlocking the mystery of their origin. With FUSE a metallicity determination will be possible by observing \NI. At the same time, the properties of \OVI\ absorption associated with the HVCs tell us about the relation between hot and neutral halo gas. Since few bright AGNs are projected on a HVC, the FUSE PI program will sample just two HVCs, which are not representative of the general population and thus the results may lead to a biased interpretation. We therefore propose to study metallicities and hot gas in the other HVC populations. Since the FUV flux is not known for any of the possible probes, we will first undertake a limited pilot survey of sightlines through several key HVCs which are not yet sampled. We will follow the identical strategy adopted by the D/H and Milky Way \OVI\ PI programs and acquire 2 ksec exposure snapshots of 11 AGN, to verify our estimated FUV fluxes, from which the 3 highest quality candidates will be identified for subsequent high signal-to-noise (60\,ksec) observations. ------------------------------------------------------------------------------ PGMID: A123 PI: St-Louis, Nicole Institution: Departement de physique, Universite de Montreal, Canada Title: Colliding winds in hot, massive binaries We propose to secure a time sequence of ultraviolet (UV) spectra for a WR+O binary system to study the physical parameters and the structure of the bow shock zone formed when the winds of the two hot stars collide. Of particular importance in the {\sl FUSE} UV range is the presence of a broad spread of emission lines with different ionization levels, ranging from O\thinspace VI to C\thinspace III. These lines are expected to arise in the bow shock zone at progressively larger distances from the X-ray heated bow head, as the compressed plasma flows outward along the shock cone and cools. The study of how these lines vary with orbital phase in the 14.9-day WC4+O5-6 LMC binary Br~22 will allow us to map out the structure and kinematics of the bow shock. This in turn will provide useful constraints on the basic parameters of the winds as well as the collision process itself. Br~22 is a particularly good example of a system in which wind-wind collision effects are known to be strong. ------------------------------------------------------------------------------ PGMID: A126 PI: Long, Knox Institution: Space Telescope Science Institute, USA Title: The evolution of disks and winds in dwarf nova outbursts SS Cyg and U Gem are the ``prototypical'' dwarf novae. However, EUV and FUV spectra of the two systems in outburst are very different, probably due to the fact that the boundary layer luminosity of SS Cyg is much less than in U Gem. We propose to exploit these differences to isolate the wind and disk signatures in dwarf novae. By using FUSE to obtain multiple high S/N spectra of both systems through outburst, we will (1) probe the ionization and kinematic structure of the wind as a function of system brightness, (2) isolate the contributions of the disk to the FUV spectra, and (3) examine physical conditions and abundances of material just being accreted onto the disk from the secondary. FUSE studies of dwarf novae, coupled with detailed model comparisons, are crucial to a better understanding of disks and winds in non-magnetic cataclysmic variables. ------------------------------------------------------------------------------ PGMID: A129 PI: Nichols, Joy Institution: IPAC, California Institute of Technology, USA Title: Shocks in dense clouds in the Vela supernova remnant We propose high resolution FUSE spectra to study a recently identified interaction of the Vela supernova remnant with a dense cloud region along its western edge. The goal is to quantify the temperature, ionization, density, and abundance characteristics associated with this shock/dense cloud interface. Our detection of high-velocity absorption line C~I at +90 to +130 km/s with IUE toward a narrow region interior to the Vela SNR strongly suggests the Vela supernova remnant is interacting with a dense ISM or molecular cloud. The shock/dense cloud interface is suggested by (1) the rarity of detection of high-velocity C~I seen in IUE spectra, (2) its very limited spatial distribution in the remnant, and (3) a marked decrease in X-ray emission in the region immediately west of the position of these stars where one also finds a 100 micron emission ridge in IRAS images. We would like to investigate the shock physics and general properties of this interaction region through a focussed UV absorption line study using FUSE spectra. FUSE is the only instrument that can obtain data that covers the tremendous range in density, temperature, and ionization that are expected. We propose to study the supernova remnant/cloud interaction using O VI coupled with IUE data, as well as several density and temperature line diagnostics in the FUSE range. H$_2$ absorption is also especially important to evaluate the molecular formation and abundances near the interface of the dense cloud. ------------------------------------------------------------------------------ PGMID: A130 PI: Rice, John Institution: Department of Physics and Astronomy, Brandon University, Canada Title: Phase resolved studies of the magnetic A-star 17 Com (HD 108662) We propose to make multiple phase resolved observations of the variable magnetic chemically peculiar star 17~Com~A to improve our understanding its far-UV continuum and line opacity. The fluxes at FUSE wavelengths are expected to be quite sensitive to abundance and temperature variations and to non-LTE effects. These observations will allow us to directly connect flux changes below 1200 \AA\ to the known abundance variations over the stellar surface, and will allow us to test models produced from optical Doppler imaging methods. These will permit us to look for any significant sources of opacity which are absent from our calculations. We expect that this study will result in better determinations of photospheric structure and of the elemental abundances. ------------------------------------------------------------------------------ PGMID: A133 PI: Fullerton, Alex Institution: Dept. of Physics and Astronomy, University of Victoria, Canada Title: FUV diagnostics of structure in hot star winds We propose to use the unique capabilities of {\it FUSE}\ to monitor the time-dependent behavior of the stellar wind profiles of an O4 supergiant in the Large Magellanic Cloud. These observations will enable us to: \begin{enumerate} \item observe how of the state of wind material changes as it traverses structures in the wind; \item perform a meaningful search for the high excitation, small scale shocks that are thought to generate the X-rays from O stars; and \item determine how wind activity is affected by metallicity. \end{enumerate} Previous surveys and monitoring campaigns with {\it IUE}\ and {\it HST}\ have shown that stellar wind variability is both continuous and ubiquitous in the unsaturated P~Cygni profiles of Galactic OB stars. However, because the Si {\sc iv} $\lambda\lambda$1400 doublet is the only unsaturated resonance wind line in early O stars available to these instruments, progress has been hampered in understanding the fundamental behavior of how the wind material evolves as it varies, and in studying the highest excitation wind structures. In contrast, the FUV region accessible to {\it FUSE}\ contains a wealth of resonance line diagnostics which will enable us to study these topics. ------------------------------------------------------------------------------ PGMID: A134 PI: Espey, Brian Institution: Center for Astrophysical Sciences, Johns Hopkins University, USA Title: Emission and absorption line studies of symbiotic binaries Symbiotic stars are binary systems consisting (generally) of a type K or M giant in orbit with a white dwarf companion. The short wavelength continuum of the white dwarf ionizes the outer atmosphere and wind of the giant, resulting in a rich nebular emission spectrum. The lines from this gas can therefore be used to diagnose conditions both close to the giant, and also in the extended shell of wind material. We propose to obtain emission and absorption line data on a sample of symbiotic binary systems. High resolution far-UV data will enable us to probe the physical conditions in the highest temperature emitting gas, to diagnose conditions in the tenuous white dwarf wind, and the irradiated giant wind. Absorption line data will enable us to probe the coolest gas in the binary systems, including molecular material close to the giant, as well as that in the circumbinary nebula. FUSE data will extend work begun with our analysis of HST, Orfeus and HUT data and will, for the first time, permit comparison of the UV and far-UV line profiles at comparable resolution. Temperature, density and abundance measurements using far-UV lines will provide the basis for improved models of these systems. ------------------------------------------------------------------------------ PGMID: A139 PI: Zheng, Wei Institution: Department of Physics and Astronomy, Johns Hopkins University, USA Title: Tomographic diagnosis of the ionization cone in NGC 1068 Of all the Seyfert Galaxies, NGC~1068, by reason of its proximity, brightness and spatially extended ionization cone provides an ideal case for spectral and spatial diagnostic mapping aimed at determining the nature of excitation mechanisms. In particular, the far-UV lines of C {\sc iii} $\lambda 977$ and N {\sc iii} $\lambda 991$ provide a unique diagnostic capability, and can be used not only to separate between photoionization and shocks, but also to determine quantitative values of the parameters of such models. We know from earlier Hopkins Ultraviolet Telescope (HUT) observations that the NGC~1068 ionization cone is characterized by very high electron temperatures. The spatial resolution (close to HST) and the sensitivity of FUSE provide us with the only means of mapping the radial distribution of the electron temperature, and measuring the far-UV line flux data needed to uniquely determine the excitation mechanism. We propose to make maximum use of the FUSE capabilities to: (1) map the radial distribution of electron temperature in the C {\sc iii} $\lambda 977$ and N {\sc iii} $\lambda 991$ zones; (2) investigate 'hot spots' thought to be the locations of ionizing shocks; and (3) study the spatial structure of the sharp boundary between high and low ionization zones. For this purpose, we propose a set of observations with different slit sizes and positions to provide an optimum compromise between spatial resolution and sensitivity in the different parts of the ionization cone. In addition, we will combine the FUSE, HST and optical data to provide a set of points on key diagnostic diagrams that we have developed to distinguish between shock and photoionization models. These data will be analyzed using the combined shock/photoionization code {\it MAPPINGS II} to provide a realistic global model for the ionization cones. This study will have application to other AGN, and the data serve as a Seyfert template in studies of the unified model of AGN. ------------------------------------------------------------------------------ PGMID: A149 PI: Bruhweiler, Frederick Institution: Institute for Astrophysics & Computational Sciences/Physics, The Catholic University of America, USA Title: Coronal emission and mass loss in the hottest stars of the H-R diagram We will use FUSE to probe the relationship between mass loss and the ultra-high ionization emission and absorption seen in the pre-white dwarfs, the hottest stars (T$_{eff}$ $\sim$ 100-170k K) in the H-R diagram. The presence of these ultra-high ionization species signifies temperatures far in excess of the stellar photospheres. Speculation provides two possible explanations for the ultra-high ionization features. First, uncertain wavelengths for the detected absorption suggest slight blue-shifts and that these features are formed in shocks at the base of the wind. Alternately, the simultaneous appearance of ultra-high ionization and lower ionization photospheric absorption might imply the stars are partially covered by "hot spots", which produce the ultra-high ionization features. A two component wind might also explain recent far-UV observations showing strong C~III and O~VI P Cygni features in NGC~246. We will observe five targets, RXJ~2117+3412, and the nuclei of NGC~5315, NGC~6905, NGC~6189, and NGC~2371-2. We will use FUSE time-tagged data to search for temporal variability in the O~VI $\lambda\lambda$1032,1038 and C~III $\lambda$977 mass loss features and in the anticipated strong O~VIII $\lambda$1165 emission. Since the time span of the FUSE observations should be comparable to the rotational period, any spectral variations due to spots should also be seen. Correlation or variability among the O~VI, C~III, and O~VIII features would represent a fundamental first test of any model. This study will ascertain if spherical geometry and steady-state modeling are even appropriate for modeling mass loss. We will also use non-LTE model atmospheres and spectral synthesis codes including the effects of winds to estimate elemental abundance patterns from lines of C, N, O, and Fe and mass loss rates from O~VI and C~III from the observed FUSE spectra. ------------------------------------------------------------------------------ PGMID: A151 PI: Clarke, John Institution: Space Physics Research Lab., University of Michigan, USA Title: FUSE spectra of Lyman series emissions from the interplanetary medium Neutral atoms from the local ISM flow into the solar system producing diffuse emissions through resonant scattering of solar emissions. This wind contains the velocity distribution of the local ISM, plus modifications by solar gravity and radiation pressure near the Sun. In addition, the H atom motions are modified by charge exchange collisions with fast protons in the heliospheric interface region, while He atoms are little affected by charge exchange. Recent observations of the He and H flows in the solar system suggest that the He velocity of 26\kms is that of the local ISM cloud, while the lower H velocity of 18-21\kms and greatly increased velocity dispersion in the flow direction are due to an interface modification of the H flow. Remote observations of the H flow thereby provide a method to remotely study the heliospheric interface. The H flow has been studied from H {\lya} line profiles at high spectral resolution observed by Copernicus, IUE, and HST, using the Earth orbital motion to Doppler shift the ISM from the geocoronal emission. One serious ambiguity in the interpretation of these data results from the optically thick {\lya} emission, leading to uncertainties in derived values of the H density. Using FUSE to observe the brightness and line profile of the optically thin H \lyb line, close in time to SOHO observations of the {\lya} emission, we can determine accurately the optical depth and density n(H) along lines of sight upwind, downwind, and cross-flow. Comparing n(H) with the heliospheric helium density, and with the interstellar cloud HI/HeI ratio measured recently by the EUVE, will give the fraction of H atoms removed by charge exchange at the entrance to the heliosphere, and then the Local Cloud (or ambient ISM) electron density which governs the size of the heliosphere. We request FUSE sky aperture spectra in the two narrow science apertures obtained during other pointed observations, through cooperation in scheduling pointed observations in the correct look directions at the proper times of year. ------------------------------------------------------------------------------ PGMID: A152 PI: Kirshner, Robert Institution: Harvard College Observatory, Harvard University, USA Title: FUV observations of a supernova to be named later We propose observing a newly-discovered supernova with FUSE as a target of opportunity. Our experience with HST and IUE ultraviolet spectra shows how informative they can be. With FUSE, we can explore a previously unobserved part of the spectrum where many important lines will help in building a complete picture, especially of circumstellar interactions. The resolution of FUSE is excellent for this purpose because it neatly separates circumstellar features from interstellar lines and the ability to move promptly to a good target is a very large advantage over HST. A recent example of a type~II, SN 1998S, illustrates what a STIS spectrum can (and cannot) do, and gives us a solid basis for predicting what is required for measurements with FUSE. We hope to continue our HST Target-of-Opportunity program, and we would aim to combine our FUSE observations both with our ground-based data and with STIS data. The probability of having one suitable target per year is high. ------------------------------------------------------------------------------ PGMID: A153 PI: Weaver, Harold Institution: Department of Physics and Astronomy, Johns Hopkins University, USA Title: Investigating the excitation mechanism for cometary X-ray, EUV, FUV emission We propose using FUSE to address two fundamental issues in cometary science: the nature of the X-ray, EUV, and FUV emissions from comets and the D/H ratio. We will use FUSE to make a sensitive search for line emission from OVI and other highly ionized species in a suitably bright comet \mbox{($m_{0} \leq 7$)} observed as a Target of Opportunity. The presence of these emissions at the predicted brightnesses would provide unambiguous evidence that charge exchange of solar wind ions with cometary neutrals is the dominant source of x-rays in comets. FUSE is the only observatory with sufficient spectral resolution and sensitivity to detect these faint line emissions. If the comet has \mbox{$m_{0} \leq 6 $}, we also propose searching for the Ly-$\beta$ lines of D and H, as the deuterium abundance is an important indicator of cometary formation conditions. Accurate determinations of the D/H ratio in many comets are needed to determine whether or not they could have supplied most of the water currently present on the Earth. ------------------------------------------------------------------------------ PGMID: A155 PI: Peters, Geraldine Institution: Space Sciences Center, University of Southern California, USA Title: Observations of accretion-driven bipolar flows in TTHya and V356 Sgr We propose FUSE observations of the interacting binaries TT~Hya (B9.5Ve+K1III-IV) \& V356~Sgr (B2V+A2II) during total eclipse to determine the physical conditions in the bipolar flows these systems. The polar flows are inferred from HST/FOS UV spectropolarimetry that reveals polarizations of 30\% \& 4\% (TT~Hya \& V356~Sgr, respectively) in the faint continuum light of the B star that has been scattered into our line-of-sight by free electrons in this region. {\it During totality, only the light from the bipolar region will be observed in the FUSE/FUV}. Based upon eclipse observations of these stars with {\it HST} we expect to see a scattered continuum ($\sim$5\% of the B star's light) and broad (FW$\sim$800--1200~$\rm km~s^{-1}$) emission resonance lines from C~II,III, N~II,III, O~VI, S~IV, and Fe~III. Analysis of the strengths, profiles, and structure of the resonance lines will provide information on the ionization temperature and density, and variations of these features throughout eclipse will allow us to investigate geometry and especially separate the equatorial component of the plasma near the primary from the more extended bipolar flow region. The bipolar flows in a disk (TT~Hya) and non-disk system (V356~Sgr)will be compared. This study will lead to a better understanding of the accretion process (that must supply the energy to power the flow) and the formation of bipolar flows in interacting binaries that do not contain compact objects. ------------------------------------------------------------------------------