1995 Annual Report, U of Wisconsin-Madison Astronomy Department

Annual Report, The Department of Astronomy
The University of Wisconsin-Madison

This report covers the period October 1, 1994 - September 30, 1995. It includes a few of the activities in the Physics Department that are astrophysical in nature.

1. Personnel

Professors Code and Bless retired in July and were granted Emeritus status. John S. Gallagher III was appointed Chairman of the Department, replacing John Hoessel after three years excellent service. Jason Cardelli accepted a faculty position in the Department of Physics and Astronomy at Villanova University, Villanova, PA. Richard Edgar accepted a position with the AXAF X-ray telescope team at the Center for Astrophysics in Cambridge, MA. Eric Wilcots joined the staff as Assistant Scientist/Lecturer and is engaged in teaching and research, after serving as a Hubble Fellow at NOAO in Tucson. Ted von Hippel has joined the staff as the new McKinney Assistant Scientist, coming from the Institute of Astronomy, University of Cambridge. He is stationed in Tucson at the NOAO headquarters and supports Wisconsin observers at the newly operational 3.5-meter advanced technology WIYN Telescope (WIYN is a consortium consisting of the University of Wisconsin, Indiana University, Yale University, and NOAO). Bart Wakker from the University of Illinois joined the scientific research staff. He will be working on the interstellar gas of the Galaxy and the LMC with an emphasis on high velocity clouds.

Gallagher continues his membership on the U.S. and international Gemini Project science advisory committees, NASA Space Science Advisory Committee, NAIC Visiting Committee (Chair 1995), WFPC2 Investigation Definition Team, and various NASA review panels. Savage was elected to a three year team as Councilor of the American Astronomical Society. K. Bjorkman was appointed to a four year term on the AAS Publications Board, to start Jan 1996. J. Bjorkman & K. Bjorkman received a 5 year Long Term Space Astrophysics Research Program grant from NASA for work on the effects of rotation on hot stars.

Savage continued to serve as President of the WIYN Board of Directors. Mathieu was appointed to the WIYN Board and the WIYN Scientific Advisory Committee.

Savage gave invited reviews at AAS meetings. At Tucson (January) he talked on "HST and ISM Science"; at Pittsburgh he gave a review on "HST UV Spectroscopic Observations of Milky Way Halo Gas." Percival was on the organizing committee of SPIE's conference on telescope control systems (Orlando 1995).

Peter Hofner obtained his Ph. D. with a thesis entitled "A Study of the Hot Molecular Gas Associated with Ultracompact HII Regions." He now holds a postdoctoral fellowship at the University of Cologne. James O'Donnell obtained his PhD with a thesis on "Dust Grain Size Distributions and the Abundance of Refractory Elements in the Diffuse Interstellar Medium." He now has a postdoctoral position at UNAM, Mexico City. Lea Shanley received her Masters and is continuing graduate study in environmental science in Madison.

Graduate student J. Acord returned from two years at the Max Planck Institute f&uumlr Radioastronomie, Bonn, Germany, where he worked with Walmsley and Wilson on high velocity molecular gas associated with ultracompact HII regions. Andrea Cox held a VLA Predoctoral Fellowship in Socorro, NM.

Balantekin (Physics) was a Japan Society for Promotion of Science Senior Fellow. He served as a member of the Steering Committee for the U.S. Nuclear Science Advisory Committee Town Meeting on Electroweak Interactions, Astrophysics, and Non-Accelerator Experiments in 1995; as the Organizer of the program on Solar Neutrinos and Neutrino Astrophysics at the National Institute for Nuclear Theory at Seattle in 1994; and as the Chairperson of the Organizing Committee for International Workshop on Strategies of the Detection of Dark Matter Particles at Berkeley in 1994.

2. Stars

A. Hot Stars

The Extreme Ultraviolet Explorer (EUVE) observations of Epsilon CMa have generated considerable interest because they show an excess of a factor of about 30 over that predicted in the 500 to 700 &Aring region. The continuum of Beta CMa is also enhanced (see Cassinelli, IAU Symposium 152). The excesses require that the EUV continuum formation region in the atmosphere have a temperature enhancement of 2000 K for Epsilon CMa and 1000 K for Beta CMa. Since both stars lie in or near the Beta Cephei instability strip on the HR diagram, Cassinelli, Cohen, and MacFarlane suggest that perhaps the heating is associated with residual mechanical flux that reaches the outer atmosphere before becoming deposited. In collaboration with Hubeny (GSFC) they are investigating the effects of the X-ray radiation from the stellar wind impinging on the top of the atmosphere. The EUV/X-ray radiation field strongly affects the mass loss rates determined from UV spectral analysis.

Besides the modeling of high energy emission from hot star winds, Cohen is compiling a database of partial photoionization cross sections for abundant elements of arbitrary ionization stage, considering using ISO infrared spectra to determine the temperature structure in the outer atmospheres of B stars having temperature excesses, and using the ROSAT High Resolution Imager to search for pre-main-sequence stars away from known regions of star formation.

Howk, Cassinelli, J. Bjorkman and Lamers have begun to study the anomalously hard X-ray radiation from the B0.2V star Tau Sco. The UV spectrum of the star also shows evidence for infall. The modeling will be aimed at explaining both the infall and the X-ray emission. J. Bjorkman has been investigating the solution topology of radiatively driven stellar winds when the line-driving force is non-linear in the velocity gradient. Such solution topology diagrams have proven to be a powerful tool for determining which solutions are allowed. Future extensions of this work will include additional effects, such as rotation, where the allowed solutions to the standard wind equations are only poorly understood.

The Wisconsin Ultraviolet PhotoPolarimeter Experiment (WUPPE) on the Astro-2 Shuttle mission observed the luminous blue variable (LBV) P Cygni, searching for UV and optical polarimetric variability on several timescales. The Pine Bluff Observatory (PBO) 0.9-meter telescope also obtained three nearly simultaneous optical observations. Quick-look data reduction shows that variability was detected in both the optical and UV. Lupie (CSC), Karen and Jon Bjorkman, with Wood, are involved in the analysis. Additional LBV's and OB supergiants were observed, as well as various cataclysmic variables both in and out of outburst. The preliminary analysis shows that at least one dwarf nova (YZ Cnc) is more highly polarized (roughly 5-6% at 2000 &Aring) than predicted by models. Over the past few years random polarimetric variations of several OB supergiants have been observed at PBO. The only model consistent with the data is the random ejection of blobs into the wind (Fox & Griscom 1996).

Anderson continues to monitor the state of the symbiotic star AG Draconis, not detected by EUVE in 1993 when in a low state. AG Dra has been redefined as a target of opportunity and is spectropolarimetrically observed at least monthly at PBO. These observations show phases with the reported 554 day period. The ultraviolet lines of OVI Raman scattered (and polarized) into the red by hydrogen were detected.

During the Astro-2 mission, WUPPE obtained ultraviolet spectropolarimetry of three classical novae. All appear to have intrinsic polarization changes across emission lines, showing that the ejecta were quite aspherical. Various lines have different degrees of polarization, suggesting that they are formed in regions of differing geometry. J. Johnson is leading the investigations.

Shanley, Gallagher and collaborators have analyzed HST ultraviolet spectrophotometric observations of the nova GQ Muscae. The spectral energy distribution is that of a hot object with weak emission lines. Low level variability may be present, but they do not see pronounced flickering or other signatures of time-variable accretion.

B. Cool Stars; Star Clusters

T. von Hippel, with G. Gilmore (IoA, Cambridge) and D.H.P. Jones (RGO, Cambridge), is analyzing CCD trigonometric parallaxes for candidate cool white dwarfs (WDs) and very cool red dwarfs in order to find the volume density of cool WDs (the oldest observable remnants of star formation in the Galaxy) and to better calibrate the color - luminosity relation for very cool main sequence stars, constraining the age of the Galactic disk. They are also searching for WDs in open clusters, to intercompare WD cooling ages with main sequence stellar evolutionary ages. With N. Tanvir (IoA, Cambridge) and D. Robinson (IoA, Cambridge) they are determining the low-mass luminosity functions for these two clusters.

The WUPPE team found that the peculiar post-asymptotic supergiant, HR4049 has intrinsic variable polarization with a 90 degree position angle flip in the UV, indicating two different scattering geometries. The star might be forming a bipolar planetary nebula.

With the WIYN Multi-Object Spectrograph Anderson has begun to monitor the strength of the Ca II H & K-line emission feature in > 50 stars in the range 11 < V < 14 and B-V > 0.5 in the young cluster NGC2264, in order to track variations on short (flare), intermediate (rotational modulation) and long (spot cycle) time scales.

von Hippel is working with A. Sarajedini (NOAO) to obtain color - magnitude diagrams for selected open clusters at both the KPNO 0.9m and WIYN in support of the WIYN Open Cluster Key Project. They are currently obtaining data for NGC 188, one of the oldest open clusters.

Gallagher and Cole are collaborating with W. Freedman and R. Phelps (Carnegie Observatories) in an investigation of hot stars in rich, intermediate age LMC star clusters. Observations taken with the Woods UV filter on the WFPC2 produce color-magnitude diagrams for hot stars in several clusters. Results on the 1 Gyr age NGC 1783 cluster show a population of stars which resemble blue stragglers or some classes of B subdwarfs. They are defining the evolutionary status of these stars.

C. Disks and Circumstellar Matter

As part of a general theoretical investigation into the polarization arising from scattering in circumstellar disks and bipolar jets, Jon Bjorkman and Wood have developed radiation transfer techniques in a 3-D Monte Carlo radiation transfer code. They find that multiple scattering serves to increase the polarization of the disk/jet above the levels predicted by single scattering models. Another variation of the 3-D Monte Carlo radiation transfer code treats the transfer of resonance line radiation in moving atmospheres, to be applied to the WUPPE observations of three novae.

WUPPE expanded the sample of stars with disks to 14 stars, covering spectral types from O7 to B9.5 and v sin i values from 25 to 400 km/s. The new data provide K. Bjorkman an excellent set of observations of Oe/Be stars across spectral types and v sin i values. The geometry of the disk is suggested by the wavelength dependence of the polarization. The new WUPPE data also allow the team to investigate whether gravity darkening effects can be seen in the continuum polarization.

Fits to the PBO data on Zeta Tau impose rigid constraints on models of the disk. The Fe line blanketing of the UV polarization, modeled with I. Hubeny (GSFC), will provide an estimate of the disk temperature. The large wavelength range of the combined data helps to determine the relative contributions of interstellar and intrinsic polarization.

Ignace, Cassinelli, and J. Bjorkman have investigated the effects of rotation in the stellar winds of a broad range of stellar objects, from Wolf-Rayet stars to Asymptotic Giant Branch stars to nova white dwarf objects. A significant equatorial compression of the wind is likely to occur if the star is rapidly rotating, the terminal speed is small and/or the radial velocity distribution is shallow. In favorable cases stellar rotations that are of order 10-30% of critical are sufficient to produce highly compressed equatorial flows or even dense shock-bounded disks. Wind compression resulting from stellar rotation may be produce many instances of observed axisymmetric winds.

J. Bjorkman and Wood have investigated the interaction of a rotationally compressed stellar wind and a Keplerian circumstellar disk. They find that adding low angular momentum wind material to the disk results in inflow of material onto the star, while the outer disk is removed by either entrainment or ablation. This wind-induced accretion implies that a Keplerian disk surrounding a Be star would be removed in less than a year unless it is continually resupplied, so Be-star disks must be formed by stellar outflow. The next step will be to include the effects of iron line opacities, working with Hubeny. Maheswaran (UW Marathon) and Bjorkman find that a Wind-Compressed Disk cannot occur whenever the surface magnetic field is large, such as in the He strong stars.

Four Herbig Ae/Be stars observed with WUPPE are being analyzed by K Bjorkman. A primary question is whether they show bipolar outflows. Accreting gas was detected in the contemporaneous IUE observations obtained with C. Grady (ARC). Bjorkman continues to study Herbig Ae/Be stars with Grady, M. Sitko (U. Cincinnati), and others, involved with multi-wavelength, multi-technique studies in order to better understand the stars' circumstellar environment, evolutionary status, and their similarities and differences to the lower mass T Tauri stars. A UV and optical spectroscopic survey shows that a subset of these stars have spectral characteristics similar to the those of the protoplanetary system Beta Pictoris (Grady et al. 1995).

K. Bjorkman has been collaborating with A. Quirrenbach (MPI) on a study of seven Be stars using the MarkIII optical interferometer of the USNO and contemporaneous spectropolarimetric observations at PBO. The find good agreement between the position angles of the Be star disks as determined from interferometry and polarimetry. J. Bjorkman has also provided theoretical models. For four of the seven stars observed estimates of the inclination angle could be derived (Quirrenbach et al., 1995 ApJ).

B. Whitney, S. Kenyon (CfA), Wood and J. Bjorkman have considered the rotationally modulated photopolarimetric variability arising from the currently favored magnetic accretion models for T-Tauri stars. These models predict the formation of UV hot spots off the stellar rotation axis, providing a non-axisymmetric illumination of the circumstellar material. Such photometric variability has been observed and correlates with the stellar rotation period. Existing polarimetric data have insufficient time resolution compared to the stellar rotation period, so stellar hot spots had not been considered as the source of the polarimetric variation.

Fox, Brown and Bjorkman interpreted polarimetric observations of k Cas and a Cam in terms of grain formation occurring in an extended shell where the stellar wind and ISM interact. Fox developed a simple model to estimate if polarimetry can detect small star spots. Stars brighter than 4th magnitude can be detected in polarization when no magnitude variations were present, provided that the rotation period exceeds 8 days.

D. Binary Stars

Metcalfe (Arizona), Mathieu, Latham (CfA) and Torres (CfA) determined a very precise spectroscopic orbital solution for the low-mass double-lined eclipsing binary CM Draconis, containing two completely convective stars of 0.2 solar masses. Since their interior structure is well defined, the radii and luminosities of the stars reflect the helium abundance: 0.31+/-0.04, surprisingly large given the Population II space velocity of this binary.

Casey, Mathieu, Suntzeff (CTIO) and Walter (Stony Brook) published their second spectroscopic study of TY CrA. They discovered both the secondary spectrum, found a tertiary spectrum in the Li and other metal lines, and derived relative masses and luminosities of the three components. Both the secondary and tertiary are pre-main-sequence stars. Mathieu, Jensen and collaborators published their submillimeter study of the T Tauri spectroscopic binary GW Ori. The source is unusually luminous but spatially confined at submillimeter wavelengths, indicative of a massive circumbinary disk. With Vaz (Brazil) and Andersen (Copenhagen), they are completing analysis of their uvby light curves. Pre-main-sequence evolutionary tracks are being tested against the stellar parameters derived from observations.

Jensen, Mathieu and Fuller (NRAO) completed their submillimeter survey of pre-main-sequence binaries in Sco-Oph, complementary to those in Tau-Aur. Systems with projected separations between 1 AU and 100 AU have less submillimeter emission than wider binaries or single stars, caused either by gap clearing or disk dispersal. Present results are ambiguous, but the prevalence of 60-micron emission shows that at least the inner (circumstellar) disks are not entirely dispersed. Jensen, Koerner (JPL), and Mathieu continued to use the Owens Valley Millimeter Interferometer to study disks in young binary environments. They made a 1.3 mm continuum map (1.2" resolution) of the pre-main-sequence triple system UZ Tau. As expected from the previous single dish survey, the flux from the binary (50 AU projected separation) was 1/5 of the flux from the distant tertiary star (500 AU projected separation). Nonetheless, unresolved emission from the binary was detected, showing the continued presence of a massive circumstellar disk. Evidently the inner region has not been cleared by the binary, despite its lack of 10-micron emission. The disk around the tertiary was resolved and shows a Keplerian-like velocity gradient, much like disks found around single stars.

Mathieu, Lattanzi (Torino) and Zinnecker (Wurzburg) began a three-year HST Fine Guidance Sensor program to obtain an astrometric orbit of the pre-main-sequence single-lined spectroscopic binary 045251+3016, providing absolute orbits of both stars and both the orbital inclination and the mass ratio. When the astrometric data are combined with the existing spectroscopic orbital elements, precise masses of the stars and the distance to the binary will be obtained.

In order to explore the circumstellar gas in several young binaries, Carr (Ohio State), Mathieu and Najita (CfA) began a program of high-resolution near-IR spectroscopy of CO. Detection of overtone emission was made on three systems. Mathieu, Stassun, Mazeh (Tel Aviv) and Vrba (USNO) began a program of I-band photometric monitoring of the Trapezium cluster in order to search for pre-main-sequence eclipsing binaries. Longer time coverage of half the surface area was obtained in Israel. Mathieu, Latham (CfA) and Marschall (Gettysburg) continued their precise radial-velocity studies of pre-main-sequence binary populations and stellar kinematics in star-forming regions. Mathieu, Latham, Davis (CfA) and Milone (CfA) continued their precise radial-velocity surveys of members of the open cluster M67.

The eclipsing binary 32 Cyg, observed during its Oct. 1993 eclipse, was considered by Fox and Griscom. Mass transfer from the K giant to the B dwarf only occurs around periastron. WUPPE observations of a number of binary systems, together with PBO data, are being studied by Fox and Nordsieck.

3. The Interstellar Medium

Savage and Sembach (MIT), using ultraviolet data from the GHRS to study the abundances of heavy elements in neutral clouds of the galactic halo, find that there is a progression toward increasing gas-phase abundances from the Galactic disk to the halo. Many halo clouds have very similar but depleted gas phase abundances, suggesting that grain cores are resilient and that the processes ejecting gas into the halo are gentle enough to avoid destroying dust completely. Sembach (MIT), Savage, Lu (CIT) and Murphy (NRAO) are studying a new type of Galactic high velocity cloud, the C IV-HVCs. The first, seen in GHRS spectra toward the bright Seyfert galaxy M509, exhibits strong C IV absorption from -170 to -340 km /sec, with no associated Si II or N V absorption. The absorption likely arises at the ionized boundary of a H I-HVC with the source of ionization being the extragalactic EUV background. GHRS data will be obtained for two additional extragalactic sight lines to search for additional examples of C IV-HVCs. These clouds may provide useful insights about the origin of the very common highly ionized QSO absorption line systems, often detected in the C IV doublet lines.

Cardelli (Villanova), Meyer (Northwestern), Jura (UCLA), and Savage have determined the abundance of carbon in the diffuse neutral interstellar gas toward six stars in the Galactic disk using the very weak C II] intersystem line at 2325 &Aring. The mean gas phase abundance is so large that it places substantial restrictions on using carbon to explain the continuous ultraviolet and optical extinction of interstellar dust. Mathis has modeled interstellar dust with these abundance restrictions and finds that models with graphitic carbon fit appreciably better than those with amorphous carbon.

Wakker with colleagues have long probed high-velocity clouds (HVCs), using Ca H and K absorption lines in spectra of distant stars or extragalactic light sources such as Seyfert galaxies. Some HVCs are apparently very distant. The IUE spectra of stars in the LMC showed that C IV and Si IV occurs in association with superbubbles or supergiant shells, rather than in a general hot gaseous halo around the LMC. Data were taken with the Australia Telescope to make a 1 arcmin-resolution map of a southern HVC.

Maciejewski, Savage, Lockman (NRAO) and Murphy (NRAO) are studying the 21-cm emission from the galactic supershell in the Sagitarius arm, at the galactocentric distance of 6 kpc, extending to the galactic halo but with a clear connection with a molecular cloud and star forming regions in the galactic plane.

Shepherd and Churchwell have obtained images in CO(J = 1-0) of ten candidate outflow sources with the NRAO 12m telescope. Four have massive outflows, and Shepherd has obtained high resolution BIMA images of two. With A. Watson (U New Mexico), Shepherd and Churchwell have obtained NIR images of several ultracompact HII regions using the Lowell Observatory 72" telescope, showing that outflows are more massive than the central star, with ages of ~104 yr. Such large masses are unlikely to have originated at the surface of the star, so perhaps the outflow mass was originally infalling but had too much angular momentum.

Acord and Churchwell, in collaboration with Walmsley (MPIfR), are observing the high- velocity molecular gas associated with ultracompact HII regions using the IRAM 30-meter and the MPIfR 100-meter telescopes in lines of SiO, H2O, and NH3. VLA observations of high velocity H2O masers have been obtained toward four nebulae. Probably the water masers are entrained at the interface of the outflowing material and the interstellar medium. We are testing this hypothesis as well as the nature of the driving mechanism of such outflows. It is found that SiO has larger line wings than any other molecular probe. Chemical models indicate that SiO should be sensitive to shocks and the broad line wings are thought to be produced by shocks in the environment around newly formed stars.

Afflerbach, Churchwell, and Werner (JPL), are measuring the abundances of O, N, and S by means of fine-structure FIR lines observed with the Kuiper Airborne Observatory. They have new data for about 20 objects distributed from 0 - ~16 kpc in galactocentric radius. The same nebulae have been observed in multiple radio H recombination lines with the VLA to determine physical conditions.

D. Meyer (Northwestern Univ.) and Haffner searched for interstellar C3 towards HD 147889, a heavily obscured sightline through part of the Rho Ophiucus dark cloud, with the Kitt Peak 4-meter telescope. They have a tentative detection of the strongest line in the C3 4050 &Aring band and new strengths for other interstellar molecules. The star was found to be a spectroscopic binary.

Haffner, Savage and K. Sembach are investigating highly ionized gas toward Xi Persei. This investigation has used the GHRS to probe interstellar absorption by Al III, S III, C IV, Si IV, and N V. Xi Per is a hot, runaway star with a sizable stellar wind, providing a unique environment to study the interaction of such dynamic stars with the ISM. The Si IV and C IV provide evidence for both photoionized and collisionally ionized gas, and there is evidence for Al depletion in the ionized gas toward Xi Per.

Weitenbeck and Anderson have begun a study of the region around open cluster NGC 1502, in which WUPPE observed four stars. Data from several other studies of the cluster, polarimetry from PBO, and spectroscopy from WIYN will provide the distribution of interstellar matter along the line of sight to the cluster.

As an additional part of the galactic interstellar polarization program, WUPPE observations of the reflection nebula NGC7023 were made in order to better characterize the interstellar particles. Preliminary analysis indicates an increase in reflected light across the 2175 &Aring bump, rather than the expected decrease in albedo.

Reynolds and students Tufte and Kung, with McCullough (U Ill-Urbana) and Heiles (UC-Berkeley), have made the first comparison of maps of velocity-resolved interstellar H-alpha emission with 21 cm emission. They found that within the 10 x 12 sq. deg. region at least 30% of the H-alpha and between 10% and 30% of the 21 cm emission are spatially and kinematically associated with "clouds" containing both neutral and ionized hydrogen. These H-alpha emitting H I clouds appear to have a distribution in height from the plane larger than that of the non H-alpha emitting H I, extending up to 1 kpc from the midplane where the clouds are approximately 40% ionized and have densities of 0.2 - 0.3 cm^-3.

Wood has begun an investigation into the effects of clumping on the transfer of radiation within the ISM. O'Donnell and Mathis have studied the processes of shattering and coagulation of dust grains, together with the depletion of gas-phase heavy ions. Circulation between clouds and the diffuse gas is not sufficient to account for the observations: molecular clouds must be important in grain processing.

Apparently the visible plasma in H II regions is confined by hot, tenuous plasma produced from the collision of the stellar winds with the dense material. Maciejewski, Edgar (CfA), and Mathis considered the conductive interfaces between the hot gas and visible matter to see if they produce appreciable amounts of highly excited emission lines. They found that the effect is not large. They also discussed why nebular abundances, as determined from the usual collisionally excited forbidden lines, might be seriously in error.

Nova Cyg 1992 served as a X-ray source of illumination for scattering by dust grains. Mathis, Cohen, and others analyzed the halo around the central point source and found that grains models with about 50% vacuum fitted the observations better than those without vacuum.

Gallagher is cooperating with J. Hester and P. Scowen (Arizona State) in using WFPC2 imaging to improve the understanding of the Crab nebula. The basic structure in emission lines and continuum has been described, and in both cases the dominant role of magnetic fields is evident. A program is now in progress with HST, the WIYN Telescope, and other facilities to monitor the structure of the non-thermal nebula near the pulsar as a means to explore the dynamics of the coupling between the pulsar and surrounding nebula.

4. Extragalactic

Gallagher is advising L. Matthews (SUNY Stony Brook student) in her study of Sd-Sm spiral systems which fall between the normal spirals and true irregulars. She has used NRAO 140-ft telescope HI pencil beam surveys of candidate systems and follow-up optical photometry from CTIO. Gallagher and Utrecht exchange student E. de Feijter studied faint field stars in the outer LMC disk, using deep HST Wide Field/Planetary Camera (WFPC-2) images in the visual and red. The resulting color-magnitude diagram indicates that the LMC disk star formation rate has been roughly constant over about the past 3 Gyr with the exception of a starburst 2 Gyr ago. Work is in progress with Holtzman (NM State) addressing the long term evolution of the LMC and stellar luminosity function.

Gallagher, with the WFPC-2 team, have discussed a normal region of the M101 disk showing how star formation is grouped on larger scales into star forming complexes that have relatively long time scales for active star formation. They also address the problem of large scale coherence of star formation processes in normal spiral galaxies.

Firmani and Hernandez (UNAM) worked with Gallagher to model the evolution of galactic gaseous disks with viscosity provided via gas motions powered by Pop I stars, producing the expected inner exponential stellar disks with flatter radial gas distributions.

Watson and Gallagher are collaborating in leading a WFPC2 team program to image the centers of nearby spiral galaxies with various current star formation rates. Most of the starburst region in NGC 253 is optically obscured, but an extremely compact, luminous star cluster is probably the best nearby example of a young globular cluster. Work is also in progress on other systems.

Under Gallagher's direction, D. Burns (now at Ohio State University) studied the brightness profiles of nearby luminous blue galaxies for her senior thesis. Luminous blue galaxies appear to be nearby analogs to the distant blue galaxies which make up the majority of apparently faint galaxies. Some luminous blue galaxies are due to starbursts in systems whose outer disk structures are similar to low or intermediate luminosity late-type spirals, while the intrinsic structures of others are uncertain, most likely due to the after effects of a merger of major collision.

Gallagher and several collaborators are exploring the use of dE galaxies as local tests of tidal fields in clusters of galaxies. He and Sparke examined the major impact on dEs of tides produced by clusters where gravitational lens arcs are found. A further collaboration with L. Aguilar (UNAM), M. Han, S. Levine (UNAM), and R. Wyse (Johns Hopkins) is measuring properties of dE galaxies in Virgo and other galaxy clusters.

HI mapping of the warped gas layer in the disk galaxy NGC 3718 by Sparke (with G. van Moorsel, VLA, and U.J. Schwarz, Groningen) shows that the gas orbits twist through nearly 90 degrees. If this is interpreted as precession in the gravitational field of the galaxy, then the total gravitational potential, including that of the dark mass, must be spherical to within 10%. Currently Sparke is working with Andrea Cox on mapping the HI gas and radio continuum emission from polar ring galaxies, which have rings of gas, dust and stars circling over the pole of the central S0 or elliptical system. High-resolution VLA HI maps of five polar rings provide velocity fields to measure the gravitational potential. Diffuse HI may link the rings to neighboring galaxies. With Alan Watson (New Mexico State U.) they are using multicolor optical and H-band images to constrain the ages of stars in the rings. Sparke is involved in a single-dish survey of polar ring galaxies with the Nancay radio telescope that will yield average HI masses and linewidths and provide candidates for high-resolution mapping. She is collaborating with Magda Arnaboldi and Ken Freeman (Mt Stromlo) on optical and near-IR imaging of southern polar ring galaxies.

Erwin and Sparke are investigating the vertical motions of gas orbiting in a system with "lopsided" asymmetry: an unequal-mass binary, or a galaxy with an off-center bar such as the Large Magellanic Cloud. They find that orbits in a disk which orbits the lopsided center can be excited into vertical motion, perhaps leading to gas being thrown high above the galaxy midplane. They are also conducting an imaging program with WIYN to search the centers of nearby barred galaxies for small nuclear bars or asymmetries.

Wesley Colley (Princeton) and Sparke have been using a tilted-ring formalism to study the way tilted gas disks in a galaxy may settle to the symmetry planes of the potential. Disks in triaxial galaxy potentials settle somewhat more rapidly than in axisymmetric systems, since they are simultaneously being twisted about two axes. Unfortunately some of the results from hydrodynamic simulations of settling gas disks seem not to be general, but rather reflect the particular form of viscous dissipation present in the codes.

Savage is a member of a team undertaking one of the three "Key Projects" being pursued with the HST: a spectroscopic survey of bright quasars with the HST to study the quasar absorption line phenomena at low redshift. Spectra of about 60 quasars are available, enabling Savage and Lu (CIT) to study the Milky Way absorption by Mg II and Fe II in order to determine the sky covering factor of Galactic high velocity Mg II and Fe II. The covering factor of these clouds will be compared to that of H I 21 cm emission. The Milky Way lines will provide an important example of the absorption properties of a zero redshift (current epoch) galaxy for comparison with absorption seen at higher redshift in QSO metal line systems.

Lu (Caltech), Savage, and Tripp finished analysis of a high signal/noise, high resolution spectrum of the QSO HS 1946+7658 (z=3.05). The abundances in two damped Lyman alpha systems in the direction of this quasar are remarkably similar to abundances in low metallicity Milky Way halo stars, suggesting that these absorption systems are galaxies in early stages of chemical enrichment (see Lu et al. 1995). Photoionization modeling shows that the associated absorption system of HS 1946+7658 has a solar (or super-solar) metallicity, but the associated system gas is more than 300 kpc away from the quasar (see Tripp, Lu, & Savage 1996). Analysis of a similar high signal/noise high resolution spectrum of HS 1700+6416 (z = 2.72) is underway.

Tripp, Lu, and Savage have started a study of the relationship between low redshift (z < 0.3) Lyman alpha clouds and galaxies. The HST will measure the equivalent widths and redshifts of low z Ly alpha clouds in 3 quasar sight lines, and the WIYN multiobject spectrograph will provide the redshifts of all galaxies brighter than B = 19 within 0.5 degrees of the QSOs.

Hunter (Lowell Obs.) and Gallagher are also working together in studies of diffuse ionized gas and stellar populations in samples of field irregular galaxies. Wilcots is also interested in the distribution and kinematics of H I gas in and around late-type galaxies. He, with Lehman (RPI) and Miller (DTM), completed work on an H I survey of barred Magellanic spiral type galaxies using the VLA, showing small H I clouds accompanying the primary galaxies. The H I morphologies and kinematics suggest that the systems are interacting. The study of SBm galaxies is continuing with high resolution H I observations. Wilcots and Westphal (NMIMT) continued work on the post-starburst galaxy NGC 1569. Unlike other similar dwarf and irregular galaxies, the ISM in NGC 1569 has not yet been punctured with holes, implying that the starburst in the center of NGC 1569 is very young.

Wilcots, Gallagher, Hunter, and van Woerden (Leiden) initiated a study of the very extended H I distribution of the nearby irregular galaxies, especially NGC 4449. This object sits in a large envelope of low surface brightness H I, surrounded by an extensive arc of gas. The study of NGC 4449 parallels work by Wilcots, Miller (DTM), and P. Hodge (U. Washington) on the Local Group dwarf galaxy IC 10. Wilcots, P. Hodge (U. Washington), and K. Olsen (U. Washington) began an investigation of the H I content of IC 1613, another Local Group dwarf. In other H I projects E. Wilcots and E. Brinks (NRAO) initiated a study of extended H I gas in the vicinity of Seyfert galaxies.

Wilcots, Hodge, and N. King (NMSU) completed work on an IUE study of young star clusters in the Large Magellanic Cloud. Comparing the observing IUE spectra with model stellar atmospheres, they found that the extinction curve found to be most accurate in the 30 Doradus complex is also applicable to more modest star forming regions. In the two clusters surveyed (NGC 17709 and NGC 2014) there was little evidence of an age spread among the most massive stars. Wilcots and V. Galarza (U. Minnesota, NMSU) continued work on a survey of the physical properties of a sample of single-star H II regions in the LMC.

5. The WIYN Project

The WIYN Observatory consortium is composed of the University of Wisconsin, Indiana University, Yale University and the National Optical Astronomy Observatory (NOAO). The WIYN advanced technology optical observatory is located on the western ridge at the Kitt Peak National Observatory. The University of Wisconsin has a 26% share in the observing time. WIYN achieved a very significant milestone with the commencement of scientific operations on July 15, 1995. WIYN is producing optical images of excellent quality. The statistics for image quality show a median RMS FWHM for the R band, based on exposures with integration times of more than 10 seconds, of 0.9" for the period 1994 September to 1995 September, and 10 % of the time the R band images have been 0.6" or better; 25% of the time 0.7" or better. The best images obtained so far have FWHM of approximately 0.4".

The "general use" instruments for WIYN, which are available to all WIYN institutions and to the general astronomical community, include the multi-object spectrograph (MOS) and fiber positioner (HYDRA) and an imaging camera system. Both instruments are fully operational and producing excellent data. MOS/HYDRA with its fiber positioner and bench mounted spectrograph allows the simultaneous acquisition of 100 optical spectra with low to moderate spectral resolution over the full one degree field of WIYN. The imaging camera contains a 2048 x 2048 CCD with 0.2" pixels providing a field of 6.7' x 6.7' and 0.2" per pixel sampling.

The WIYN Telescope Control System was produced by the UW's Space Astronomy Laboratory and the Space Science and Engineering Center. The Control System was completed in 1995, and represents a state-of-the-art distributed system that permits interactive remote access, and incorporates innovative ultra-low-bandwidth techniques for remote observing.

Several faculty members, scientists, and graduate students have already used the WIYN telescope for scientific purposes and are very impressed with its ability to produce data at a large rate.

6. Instrumentation

The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE). The space shuttle Endeavour carried WUPPE on the Astro-2 mission during March 1995, together with the Hopkins Ultraviolet Telescope and the Ultraviolet Imaging Telescope. WUPPE obtained spectropolarimetry in the range 1450-3230 &Aring with a resolution of about 8 &Aring. Contemporaneous observations obtained at PBO extended the total spectropolarimetric coverage to 10500 &Aring. WUPPE took 369 observations of 244 objects. There were 112 observations of 79 WUPPE prime targets (including three Guest Investigator programs).

HST, Goddard High Resolution Spectrograph (GHRS). Savage and Wakker are continuing their participation in the technical evaluation and scientific interpretation of high and medium resolution UV spectroscopic data obtained by the GHRS on the Hubble Space Telescope. These efforts are being supported by students Howk and Tripp. The GHRS has performed extremely well since the HST repair mission of late 1993.

The Wide-field Imaging Survey Polarimeter (WISP). Nordsieck was the PI for a suborbital rocket payload telescope flown successfully in December, 1994, taking the first ever astronomical wide-field polarimetric images in the ultraviolet. The target was the extended nebulosity near the Pleiades. The instrument has two broadband filters centered at 1640 and 2180 &Aring and a field of 5.0 x 1.7 degrees. WISP observations of geometrically simple reflection nebulae should constrain both the currently controversial UV scattering properties of interstellar dust grains and the 3-D geometry of the reflection nebula. The next mission, scheduled for November 1995, will study diffuse galaxian light in the LMC.

Pine Bluff Observatory (PBO). A new CCD detector is now in use on the spectropolarimeter at PBO. The observations are quite varied and include both surveys and long-term monitoring of many types of objects: novae, planets, Be stars, pre-main sequence (e.g. Herbig Ae/Be and T Tauri type) stars, symbiotic stars, OB supergiants, luminous red variables (e.g. Alpha Ori), binary star systems, interstellar medium probes, and polarization standard stars. Babler continues to lead the PBO data reduction effort, overseeing data reduction and archiving, and maintaining the complete logs of the PBO observations. From October 1994 through September 1995, the 36-inch telescope observed 144 nights. As of the beginning of 1995 the HPOL detector was modified from a dual Reticon to a CCD system, extending the wavelength coverage to 10500 &Aring while the blue end continues to cut off at 3200 &Aring. Development of catalogs of spectropolarimetric observations based on the PBO data archive is being considered.

Wisconsin Hydrogen-Alpha Mapper (WHAM). Reynolds, with Tufte and Haffner, is currently working on WHAM, a high-throughput Fabry-Perot spectrometer rapidly approaching first light at PBO. After a year of testing in Wisconsin, WHAM will be moved to Kitt Peak, Arizona, and map the diffuse H alpha emission over the entire northern sky. Past studies by Reynolds suggests that a significant portion of this diffuse emission originates from a warm ionized component of the interstellar medium. The WHAM project will reveal how this phase of the ISM is distributed relative to other features of our galaxy. It should also provide many clues about the source of power required to maintain this ionized gas. Percival designed and built the Telescope Control System software, modeled on the WIYN 3.5m Telescope Control System.

The Spatial Heterodyne Spectrometer (SHS). This sounding rocket payload is under construction with Reynolds, Roesler, Scherb, and Sanders (Physics) and their students. SHS is a new type of Fourier transform spectrometer which will be used to explore the distribution and kinematics of faint, far-ultraviolet line emission from the hot (100,000 K) component of the interstellar medium.

Automatic stellar classification. von Hippel, with C. Jones (IoA, Cambridge), Storrie-Lombardi (IoA, Cambridge), Irwin (RGO, Cambridge), and Houk (U. Michigan) is working on automating the visual MK stellar classification work of Houk using Artificial Neural Network techniques. A large amount of plate extraction software has been written and 100 plates have been scanned. Deeper CCD data for nearly 20 square degrees has also been acquired at the Curtis Schmidt Telescope at Cerro Tololo. The purpose of this project is to use classified stars at brighter magnitudes (V < 11) as a foundation for classification to fainter magnitudes, which ultimately will yield temperatures, luminosities and metallicities for a very large sample of Galactic stars. These data will be used for galactic structure studies and to find peculiar objects.

Computing and teaching. Percival continued work on a NASA grant to enhance his progressive transmission protocol for data transmission and develop a Graphical User Interface suitable for use by specialists and non-specialists alike. The educational goal is to allow efficient browsing of digital libraries over the Internet, to deliver space science images to schools, libraries, and other users, some of which may have only dial-up access to the Internet. Mathieu and Dolan are developing computer-based laboratory exercises for use in the introductory astronomy course.

7. Miscellaneous

Neutrino astronomy. Neutrino astrophysics in the Department of Physics is an interdisciplinary area with input from nuclear physics, particle physics, and astrophysics. With student John Beacom, Balantekin (Physics) is investigating analytic methods for calculating the probability of neutrino oscillation in the transport from the solar core to detectors on earth. These methods will allow a greater understanding of the effects of parameter changes, and may be useful for extracting information about the solar density from the measured neutrino fluxes. With Fetter, Balantekin is putting a limit on solar density fluctuations by their effects on neutrino propagation. With the neutrino astrophysics group at University of California, San Diego, he is investigating the effects of neutrinos on supernova shock reheating and the possibility of r-process nucleosynthesis in the supernova hot bubble.

The solar system. WUPPE observed solar system objects Mars, Jupiter, Io, and the Moon. Two approximately contemporaneous ground based observations were taken at PBO in the wavelength range 3500A-10,500 &Aring. The Mars observation showed that in the UV the Martian atmosphere begins to dominate over surface scattering. The atmospheric polarization is probably due to an optically thin aerosol layer. The data are modeled according to two models for rough surface scattering (Fox 1995b). The other solar system objects are currently being investigated. Polarization levels on the moon reached 20% at 2000 &Aring.

8. Refereed Publications, Invited Reviews, and Books

Acker, A., Balantekin, A. B, and Loreti, F. "Three-Flavor Vacuum Oscillations of Atmospheric and Solar Neutrinos", 1994, Phys. Rev. D, 49, 328

Afflerbach, A., Churchwell, E., Werner, M. W. "Compact HII Regions-Deriving Galactic Abundances and Local Properties", 1995, in Airborne Astronomy Symposium on the Galactic Ecosystem: From Gas to Stars to Dust, Eds. M. R. Haas, J. A. Davidson, and E. F. Erickson, ASP Conf. Series, 73, 111

Balantekin, A. B. "Astrophysical Implications of Neutrino Mass and Mixings", 1995, invited review in Intersections Between Particle and Nuclear Physics, St. Petersburg, S. Seestrom, Editor (AIP Conf. Proc. No. 338, New York), p. 67

Balantekin, A.B. and Bahcall, J.N., editors, "Solar Modeling", 1995, (World Scientific, Singapore). (Book)

Bergeron, J., Petitjean, P, Sargent, W.L.W., Bahcall, J.N., Boksenberg, A., Hartig, G.F., Jannuzi, B.T., Sofia Kirhakos, Savage, B.D., Schneider, D.P., Turnshek, D., Weymann, R.J. and Wolfe, A.M. " The HST Quasar Absorption Line Key Project VI: Properties of Metal-Rich Systems" 1994, ApJ, 436, 33

Bjorkman, J.E., Ignace, R., Tripp, T.M., and Cassinelli, J.P. "Evidence for a Disk in the Wind of HD93521: UV Line Profiles from an Axisymmetric Model," 1994, ApJ, 435, 416

Bjorkman, J.E., and Bjorkman, K.S.,"Effects of Gravity Darkening on the UV Continuum Polarization Produced by Circumstellar Disks", 1994, ApJ, 436, 818

Boyd, P. T., van Citters, G. W., Dolan, J. F., Wolinski, K. G., Percival, J. W., Bless, R. C., Elliot, J. L., Nelson, M. J., and Taylor, M. J. 1995, "High Speed Photometer Observations of the LMC Pulsar B0540-69," ApJ, 448, 365

Brandt, J. C. and 24 co-authors (including Savage, B.D). "The Goddard High Resolution Spectrograph: Instrument , Goals and Science Results", 1994, AJ, 106, 890

Brandt, J.C. and 19 co-authors (including Savage, B.D.) "Observations of Alpha Orionis with The Goddard High Resolution Spectrograph on the Hubble Space Telescope", 1995, PASP, 107, 871

Brown, T.R., Buss, R.H., Grady, C.A., and Bjorkman, K.S., "The Growth of Solids and Radiation Shielding in the Young Stellar Disk of HD 45677", 1995, ApJ, 440, 865

Cardelli, J.A., Sembach, K.S., and Savage, B.D. " Gas Phase Abundances and Conditions Along the Sight Line to the Low-Halo, Inner-Galaxy Star HD 167756" 1995, ApJ, 440, 241

Cardelli, J.A., Sofia, U.J., Savage, B.D., Keenan, F.P., and Dufton, P.L. "Interstellar Detection of the Intersystem Line Si II] l2335 &Aring Toward Zeta Ophiuchi", 1994, ApJ, 420, L29

Cardelli, J.A.and Savage, B.D. "Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. II. Oscillator Strengths for Singly Ionized Iron", 1995, ApJ, 452, 275

Casey, B.W., Mathieu, R.D., Suntzeff, N.B. and Walter, F.M. "The Pre-Main-Sequence Triple TY CrA: Spectroscopic Detection of the Secondary and Tertiary Components", 1995, AJ, 109, 2156

Cassinelli, J. P. "EUV Radiation from B-stars: the Broad Implications for Stellar and Interstellar Astronomy" 1995, in IAU Colloquium 152, "Astrophysics in the Extreme Ultraviolet." (Cambridge Univ Press: Cambridge), 330

Cassinelli, J.P., Cohen, D.H., MacFarlane, J.J., Drew, J.E., Lynas-Gray, A.E., Hoare, M.G., Vallerga, J.V., Welsh, B.Y., Vedder, P.W., Hubeny, I., and Lanz, T. "EUVE Spectroscopy of Epsilon CMa from 70 &Aring to 730 &Aring", 1995, ApJ, 438, 932

Chu, Y.-H., Wakker, B.P., MacLow, M.-M., Garciacutea-Segura, G., "Ultraviolet interstellar absorption lines in the LMC", 1994, AJ, 108, 1696

Churchwell, E. "Newly Formed Massive Stars: Are They Good for the Neighborhood?", 1994, Astrophys. Space Sci., 224, 157

Clayton, G. C., Whitney, B. A., Meade, M.R., Babler, B. L., Bjorkman, K.S., and Nordsieck, K. H., "Long Term Spectroscopic and Polarimetric Monitoring of R Coronae Borealis Near Maximum Light", 1995, P.A.S.P., 107, 416

Diplas, A. and Savage, B.D. "An IUE Survey of Interstellar H I Ly a Absorption I. Column Densities" 1994, ApJS, 93, 211

Diplas, A. and Savage, B.D. "An IUE Survey of Interstellar H I Ly Alpha Absorption II. Interpretations " 1994, ApJ, 427, 274

Dolan, J. F., Michalitsianos, A. G., Thompson, R. W., Boyd, P. T., Wolinski, K. G., Bless, R. C., Nelson, M. J., Percival, J. W., Taylor, M. J., Elliot, J. L., and van Citters, G. W. "The Gravitational Lens System Q0957+561 in the Ultraviolet," 1994, ApJ, 442, 87

Espey, B.R., Turnshek, D.A., Lee, L., Bergeron, J., Boksenberg, A., Hartig, G.F., Jannuzi, B.T., Sargent, W.L.W., Savage, B.D., Schneider, D.P., Weymann, R., and Wolfe, A.M. " The HST Quasar Absorption Line Key Project IX: An Emission Line Study of PG 2251+113 " 1994, ApJ, 434, 484

Fox, G.K. " Can the variability of solar-like spotted stars be detected polarimetrically?" 1995, ApJ, 441, 408

Fox, G.K., Brown J.C., and Bjorkman, K.S. "The visual and ultraviolet data of Alpha Cam and Kappa Cas: Evidence of shocked regions", 1995, ApJ, 447, 332

Freedman, W. L. et al. (including Gallagher) "First Hubble Space Telescope Observations of the Brightest Stars in the Virgo Galaxy M100=NGC4321" 1994, ApJ, 435, L31

Gallagher, J. S., Littleton, J. E., and Matthews, L. D. "HI Observations of Southern Extreme Late-Type Galaxies. I. An Optically Faint Sample" 1995, AJ, 109, 2003

Hester, J. J., Scowen, P. A., Sankrit, R., Burrows, C. J., Gallagher, J. S. et al. "WFPC2 Studies of the Crab Nebula. I. HST and ROSAT Imaging of the Synchrotron Nebula", 1995, ApJ, 448, 240

Korista, K. T., and others including L. S. Sparke. "Steps Towards Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei: VIII An Intensive HST, IUE and Ground-Based Study of NGC 5548", 1995, ApJS, 97, 285

Linsky, J.L., Diplas, A., Wood, B.E., Brown, A., Ayres, T.R., and Savage, B.D. "Deuterium and the Local Interstellar Medium for the Procyon and Capella Lines of Sight", 1995, ApJ, 451, 335

Lockman, J., and Savage, B.D. " The HST Quasar Absorption Line Key Project X: Galactic H I Emission Toward 143 Quasars and AGNs", 1995, ApJS, 97, 1

Loreti F., and A.B. Balantekin "Neutrino Oscillations in Noisy Media", 1994, Phys. Rev. D50, 4762

Lu, L., Savage, B.D., and Sembach, K. R. "Probing the Galactic Disk and Halo: Metal Abundances in the Magellanic Stream" 1994, ApJ, 437, L119

Lu, L., Savage, B.D., and Sembach, K.R. "Probing the Galactic Disk and Halo I: The NGC 3783 Sight Line" 1994, ApJ, 426, 563

Lu, L., Savage, B.D., Tripp, T. M. and Meyer, D.M. "Metal Abundances and Physical Conditions in Two Damped Lyman Alpha Systems Toward HS1946+76" 1995, ApJ, 447, 597

MacFarlane, J.J., Cohen, D.H., and Wang, P. "X-ray Induced Ionization in the Winds of Near-Main-Sequence O and B Stars", 1994, ApJ, 437, 351

Matthews, L. D., Gallagher, J. S. and Littleton, J. E. "HI Observations of Southern Extreme Late-Type Galaxies. II. Small Angular Size Galaxies and Galaxies Near the Galactic Plane" 1995, AJ, 110, 581

Mathieu, R.D., Adams, F.C., Fuller, G.A., Jensen, E.L., Koerner, D.W. and Sargent, A.I. "Submillimeter Continuum Observations of the T Tauri Spectroscopic Binary GW Orionis", 1995, AJ, 109, 2655

Mathieu, R. D. "Binary Frequencies Among Pre-Main-Sequence Stars" in Origins, Evolution, and Destinies of Binary Stars in Clusters, Calgary, June 1995

Mathieu, R. D. "Observations of Disks around Pre-Main-Sequence Binary Stars", in NATO Advanced Study Institute, Evolutionary Processes in Binary Stars, Cambridge, UK, July 1995

Mathis, J. S. "The Diffuse Interstellar Bands and Interstellar Dust", 1995, in The Diffuse Interstellar Bands, ed. A. G. G. M. Tielens and T. P. Snow, (Dordrecht: Kluwer), 241

Mathis, J. S., Cohen, D., Finley, J. P., and Krautter, J. "The X-Ray Halo of Nova V1974 Cyg (1992) and the Nature of Interstellar Dust", 1995, ApJ, 449, 320

Murphy, E., Lockman, F.J. and Savage, B.D. " A Sensitive Search for High Velocity Clouds" 1995, ApJ , 447, 642

O'Connell, R. W., Gallagher, J. S., and Hunter, D. A. "Hubble Space Telescope Imaging of Super-Star Clusters in NGC 1569 and NGC 1705" 1994, ApJ, 433, 65

O'Connell, R. W., Gallagher, J. S., Hunter, D. A., and Colley, W. N. "Hubble Space Telescope Imaging of Super-Star Clusters in M82, 1995, ApJ, 446, L1

Percival, J. W., Boyd, P. T., Biggs, J. D., Dolan, J. F., Bless, R. C., Elliot, J. L., Nelson, M. J., Robinson, E. L., Taylor, M. J., van Citters, G. W., and Wolinski, K. G. 1995, "A Search for a Pulsar in the Remnant of SN1987A with the Hubble Space Telescope High Speed Photometer," ApJ, 446, 832

Reynolds, R.J. and Tufte, S. L. "A Search for the He I 5876 Recombination Line from the Diffuse Interstellar Medium", 1995, ApJ, 439, L17

Reynolds, R.J., Tufte, S.L., Kung, D.T., McCullough, P.R., and Heiles, C. "A Comparison of Diffuse Ionized and Neutral Hydrogen Away from the Galactic Plane: H-Alpha Emitting H I Clouds", 1995, ApJ, 448, 715

Reynolds, R.J. "Diffuse Optical Emission Lines as Probes of the Interstellar and Intergalactic Ionizing Radiation", 1995, invited paper in The Physics of the Interstellar Medium and Intergalactic Medium, ASP Conference Series Vol. 80, eds. A. Ferrara, C. Heiles, C. McKee and P. Shapiro, p. 388

Robinson, R. D., Carpenter, K. G., Percival, J. W., Bookbinder, J. A. "A Search for Microflaring Activity on dMe Flare Stars. I. Observations of the dM8e Star CN Leonis," 1995, ApJ, 451, 795

Robinson, E. L., Wood, J. H., Bless, R. C., Clemens, J. C., Dolan, J. F., Elliot, J. L., Nelson, M. J., Percival, J. W., Taylor, M. J., van Citters, G. W, and Zhang, E. "HST Observations of the Dwarf Nova Z Chamaeleontis Through Two Eruption Cycles," 1995, ApJ, 443, 295

Robinson, E. L., Mailloux, T. M., Zhang, E., Koester, D., Steining, R. F., Bless, R. C., Percival, J. W., Taylor, M. J., and van Citters, G. W. "The Pulsation Index, Effective Temperature, and Thickness of the Hydrogen Layer in the Pulsating White Dwarf G117-B15A," 1995, ApJ, 438, 908

Roesler, F.L., Reynolds, R.J., and Scherb, F. "Fabry-Perot Spectroscopy of Extremely Faint Astronomical Sources" 1995, invited paper in Tridimensional Optical Spectroscopic Methods in Astrophysics, IAU Colloquium No. 149 (ASP Conference Series Vol. 71), eds. G. Comte and M. Marcelin, 95

Savage, B.D. "The Galactic Corona", 1995, invited review in Physics of The Interstellar and Intergalactic Medium , eds. A. Ferrara, C. Heiles, C. Mc Kee, and P. Shaprio ( San Francisco: ASP Conference Series ), 233

Savage, B.D. and Sembach, K.S. "Properties of the Highly Ionized Disk and Halo Gas Toward Two Distant High Latitude Stars" 1994, ApJ, 434, 145

Savage, B.D., Sembach, K. R., and Lu, L. "Probing the Galactic Disk and Halo III: The Galactic and Intergalactic Sight line to H 1821+643" 1995, ApJ, 49, 145

Savage, B.D., Sembach, K.S., and Cardelli, J.A. "Highly Ionized Gas Absorption in the Disk and Halo Toward HD 167756 at 3.5 kilometers per Second Resolution" 1994, ApJ, 420,183

Sembach, K. R., Savage, B.D., and Lu, L. "Probing the Galactic Disk and Halo II: Hot Interstellar Gas Toward the Inner Galaxy Star HD 156359" 1995, ApJ, 439, 672

Sembach, K.R., Savage, B.D., Lu, L. and Murphy, E. M. "Discovery of Higly Ionized High Velocity Clouds Toward Markarian 509" 1995, ApJ, 451, 616

Sembach, K.R.and Savage, B.D. 1994, "Gas Kinematics and Ionization Along the Extended Sight Line to HD 116852", 1994, ApJ, 431, 201

Sembach, K.S., Savage, B.D., and Jenkins, E.B. " Al III, Si IV, and C IV Absorption Toward Zeta Ophiuchi: Evidence for Photoionized Gas and Collisionally Ionized Gas" 1994, ApJ, 421, 585

Shanley, L. Ogelman, H., Gallagher, J. S., Orio, M. and Krautter, J. "The Soft X-ray Turnoff of Nova Muscae 1983" 1995, ApJ, 438, L95

Shepherd, D., Churchwell, E., Goss, W. M. "High Velocity Gas Associated with the Massive, Evolved Star in G25.5+0.2" 1995, ApJ, 448, 426

Sofia, U.J., Cardelli, J.A., and Savage, B.D. "The Abundant Elements in Interstellar Dust", 1994, ApJ, 430, 650

Sparke, L. S. "A Bowl-Shaped Mode of Galactic Disks", 1995, ApJ, 439, 42

Sparke, L. S. "Self-Gravitating Models for Polar Rings", N.Y. Acad. Sci., 752, 12

Stapelfeld, K. R. et al. (including Gallagher) "WFPC2 Imaging of the Circumstellar Nebulosity of HL Tau" 1995, ApJ, 449, 888

Stengler-Larrea, E.A., Boksenberg, A., Steidel, C.C., Sargent, W.L.W., Bahcall, J.N., Bergeron, J., Hartig, G.F., Jannuzi, B.T., Sofia Kirhakos, Savage, B.D., Schneider, D.P., Turnshek, D., and Weymann, R.J "The HST Quasar Absorption Line Key Project V: Redshift Evolution of Lyman Limit Absorption in the Spectra of a Large Sample of QSOs" 1995, ApJ, 444, 64

Trauger, J. T. et al. (including Gallagher) "The On-Orbit Performance of WFPC2" 1994, ApJ, 435, L3

Tripp, T.M., Cardelli, J.A., and Savage, B.D. "A Weak Interstellar Band in the Far-Ultraviolet Spectrum of Zeta Ophiuchi?" 1994, AJ, 107, 645

Turnshek, D., Espey, B.R., Kipko, M.Jr., Rauch, M., Weymann, R., Jannuzi, B.T., Jannuzi, B.T., Boksenberg, A., Bergeron, J., Hartig, G.F., Sargent, W.L.W., Savage, B.D., Schneider, D.P., and Wolfe, A.M. "The HST Quasar Absorption Line Key Project IV: HST Faint Object Spectrograph and Ground-Based Observations of the Unusual Low-Redshift Broad Absorption Line QSO PG0043+039", 1994, ApJ, 428, 93

Vogelaar, M.G.R., Wakker, B.P., 1994, "The fractal structure of interstellar clouds", AandA 291, 557

von Hippel, T., Gilmore, G., and Jones, D.H.P. 1995, "An Independent Calibration of Stellar Ages: HST Observations of White Dwarfs at V=25", MNRAS, 273, L39

Wakker, B.P., Adler, D.S., "A CO map of the inner spiral arms of NGC628", 1995, AJ, 109, 134

Watson, A. M., Mould, J. R., Gallagher, J. S. et al. "Far Ultraviolet Imaging of the Globular Cluster NGC 6681 with WFPC2" 1994, ApJ, 435, L55

Wood, K., and Bjorkman, J.E. "The Effects of Pre-Scattering Attenuation on Spectropolarimetric Line Profiles", 1995, ApJ, 443, 348 Wood, K., and Fox, G.K. "Inverse Problems in Spectropolarimetry", 1995, Inverse Problems, 11, 795

Zheng, W., Kriss, G.A., Davidsen, A.F., Lee, G., Code, A.D., Bjorkman, K.S., Smith, P.S., Weistrop, D., Malkan, M.A., Baganoff, F.K., and Peterson, B.M., "Astro-1 and Ground-Based Observations of Markarian 335: Evidence for an Accretion Disk", 1995, ApJ, 444, 632

9. Publications in press

Anderson, C.M., and WUPPE Science Team "The General Galactic Ultraviolet Interstellar Polarization Program of the Wisconsin Ultraviolet Photo-Polarimeter Experiment", 1995, in Polarimetry of the Interstellar Medium, ed. W.G. Roberge and D.C.B. Whittet, ASP Conf. Proc., in press.

Arnaboldi, M., Freeman, K.C. , Sackett, P.D., Sparke, L.S. and Capaccioli, M. "Dust and Infrared Imaging of Polar Ring Galaxies", 1995, Planetary and Space Science, in press.

Bahcall, J.N., Bergeron, J., Boksenberg, A., Hartig, G.F., Jannuzi, B.T., Sofia Kirhakos, Sargent, W.L.W., Savage, B.D., Schneider, D.P., Turnshek, D., Weymann, R.J. and Wolfe, A.M. "The HST Quasar Absorption Line Key Project VII: Absorption Systems at zabs < 1.3", 1995, ApJ, in press.

Bjorkman, J.E. "The Solution Topology of Radiation-Driven Winds: I. The X-Type Nature of the CAK Critical Point," 1995, ApJ, in press.

Bjorkman, J.E., and Wood, K. "Wind-Induced Accretion and the Removal of Keplerian Circumstellar Disks by a Rapidly Rotating Stellar Wind", 1995, ApJ, submitted.

Cardelli, J.A., Meyer, D. M., Jura, M., and Savage, B.D. 1996, "The Abundance of Interstellar Carbon", 1996, ApJ, submitted.

Cassinelli, J.P., Cohen, D.H., MacFarlane, J.J., Drew, J.E., Lynas-Gray, A.E., Hubeny, I., Vallerga, J.V., Welsh, B.Y., Hoare, M.G. "EUVE Spectroscopy of beta CMa from 500 A to 700 A", 1995, ApJ, in press.

Cassinelli, J. P., Najarro, F. , Kudritzki, R., Stahl, O., and Hillier, D. J. "Stellar Winds and the EUV Continuum Excess of Early B-Giants" 1995, ApJ, in press.

Cesaroni, R., Olmi, L., Walmsley, C. M., Churchwell, E., Hofner, P. "A Massive Young Embedded Object Associated with the UC HII Region G31.41+0.31" 1995, ApJL, in press.

Chin, Y.-N., Henkel, C. Whiteoak, J. B., Langer, N., and Churchwell, E.B. "Interstellar Sulfur Isotopes and Stellar Oxygen Burning" , 1995, A&A, in press.

Clayton, G.C. et al. "Astro-2 Observations of Interstellar Dust and Gas in the Large Magellenic Cloud", 1995, ApJ, in press.

Cohen, D.H., Cooper, R.G., MacFarlane, J.J., Owocki, S.P., Cassinelli, J.P., and Wang, P. "Evidence for Wind Attenuation and a Multi-Temperature Plasma in the Combined EUVE and ROSAT Observations of epsilon Canis Majoris (B2 II)", 1996, ApJ, April.

Cox, A.L., Sparke, L.S., van Moorsel, G., and Shaw, M. "Optical and 21 cm Observations of the Warped Edge-on Galaxy UGC 7170", 1995, AJ, in press.

Cox, A.L., and Sparke, L. S. "Using HI in Polar Rings to Probe Galaxy Potentials"; 1995, invited lecture in Minneapolis series on HI in Galaxies, ed. Evan Skillman.

Espey, B.R., Schulte-Ladbeck, R.E., Kriss, G.A., Hamann, F.W. III, Schmid, H.M., and Johnson, J.J. "Simultaneous observation of direct and Raman-scattered O VI lines in the symbiotic nova RR Tel", 1995, ApJL, Nov. 20.

Fox, G.K. et al. " The First Ultraviolet Linear Spectropolarimetry of Mars", 1995, ApJL, submitted.

Fox, G.K. "Spectropolarimetry of Mars: The development of two polarization reversals" 1995, MNRAS, submitted.

Fox, G.K., and Griscom, L. "The polarimetric variability of 32 Cyg during its Oct. 1993 eclipse" 1995, MNRAS, in press.

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