ALBERT

Description: We have cataloged 160 CMEs detected in the HELIOS 1 and 2 90 deg zodiacal light photometers observed from 1975-1985. The HELIOS 1 and 2 spacecraft orbited from 0.3 to 1.0 AU on 6-month orbits. From the photometer observations of Thomson-scattered light in the inner heliosphere, we have determined CME masses for these events using two methods: (1) by integration over the contours drawn between the three photometers at a given time; and (2) by integration of the mass flow over time past a given photometer. The second method, not readily available using coronagraph observations, is derived from CME speeds measured by using the timing of the peak CME brightness from the 16 deg to 31 deg sets of photometers. The two different HELIOS methods of determining CME mass are consistent with one another for individual CMEs. We find that the CME mass values range from 10(exp 15)g to nearly 10(exp 17)g. We compare the mass distributions of HELIOS-measured CMEs with those from coronagraphs and find that CMEs measured by HELIOS over the same time interval are generally more massive. The solar cycle variation of the total CME mass present in the heliosphere varies by over a factor of approximately 15 from solar minimum to solar maximum. Slightly more massive CMEs carry the bulk of the CME mass during maximum. The total CME mass at solar maximum is found to be near 15% of the total solar wind mass.

Description: Fe, Ni, and Cr abundances in Type I cosmic spherules recovered from the deep sea, and also the isotopic fractionation of these elements during passage of the spherules through the terrestrial atmosphere was determined. Isotopic fractionation for all three elements is typically large, approx. 16%o/amu, corresponding to evaporative mass losses of approx. 80-85%, assuming Rayleigh distillation from an open system. The corrected, pre-atmospheric, Cr/Ni and Fe/Ni ratios are shown, where they are compared to these ratios in bulk chondrites and chondritic metal. Although the calculated pre-atmospheric Fe/Ni ratio for the spherules is relatively constant at 19 plus or minus 4 (sigma (sub mean)), the calculated pre-atmospheric Cr/Ni ratios vary by about two orders of magnitude. The Cr/Ni ratios are thus powerful discriminators for possible modes of origin of the spherules. For example, iron meteorites typically have low Cr contents and low Cr/Ni ratios, less than or equal to 3 x 10(exp -4). Thus, Type I spherules do not appear to be ablation products of iron meteorites, in contrast to an earlier suggestion..

Description: The conceptual basis of reference frames defined by extragalactic objects is straightforwaxd: that the universe as a whole does not rotate so very distant objects cannot have an overall rotational motion. Experimentally, the global rotation of the universe is less than 10(exp -12) arcsecond/yr as inferred from the 3K microwave background radiation. At the distance of 10(exp 8) parsecs, even if an object were moving transversely at the speed of light, its angular velocity would be less than 0.6 x 10(exp -3) arcsecond/yr, while an object moving at a physically more reasonable speed comparable to the Sun would show a motion of 10(exp -6) arcsecond/yr, entirely undetectable by current technology. Since neither systematic universal motion nor random motion at such great distance is measurable, it is reasonable to construct a static celestial reference frame on the basis that such objects axe fixed in the sky.

Description: Halide and sulfate efflorescences are common on meteorite finds, especially those from cold deserts. Meanwhile, the late-stage sulfate veins in Orgueil are universally accepted as having originated by the action of late-stage high fO2 aqueous alteration on an asteroid. I suggest here that these phenomena have essentially the same origin.

Description: The ten HED polymict breccias EET82600, EET87503, EET87509, EET87510, EET87512, EET87513, EET87518, EET87528, EET87531, and EET92022 were found over a broad area in the Elephant Moraine collecting region of Antarctica. Locations are scattered among the Main (Elephant Moraine), Meteorite City, and Texas Bowl icefields and the Northern Ice Patch. It was previously suggested that these polymict breccias are paired. However, degree of terrestrial alteration among these meteorites varies from relatively pristine (type A) to extensively altered (type B/C) and there are textural, mineralogical, and compositional differences. This study is a reevaluation of the pairing of these meteorites.

Description: These are exciting times in the study of planetary system formation with a steadily expanding inventory of exo-planet detections, and imaging of dust disks around nearby young and main sequence stars. While these discoveries imply that our Solar System is far from unique, linking the data for the protoplanetary and debris disks to mature planetary systems requires a demonstration that disk evolution proceeds via planetesimal production and growth to the formation of planets. Theoretical studies of planet formation indicate that planetesimals grow, via runaway accretion, to lunar-sized (approx. = 2000 km) embryos in 10(exp 5) years. Recent gas giant planet formation studies have suggested that most of the action in planet formation occurs over 1-16 Myr, with formation of planets similar to Jupiter in t less than 10 Myr, within the time interval that infrared (IR) and optical emission line studies have demonstrated that circumstellar material remains detectable around both solar mass and intermediate mass stars. Direct imaging of exo-planetesimals is not feasible with current and foreseeable technology, since such bodies have substantially less surface area than micron-sized grains distributed in a disk, and thus are inefficient IR emitters. However, such bodies may be indirectly detectable.

Description: In addition to a smooth rotation of the magnetic field vector, magnetic clouds have a low proton temperature T(sub p). Their expansion in the solar wind leads to depletion and therefore the ion component cools down. It has been shown recently that the electron component in magnetic clouds behaves differently: when the cloud expands, electron temperature Te anti correlates with density and therefore Te increases in the cloud, creating favorable conditions for the rise of ion-acoustic waves. For the magnetic cloud observed by Ulysses on June 10 - 12, 1993 at 4.64 AU at S 32.5 deg, we present observations for both electron and proton components and related plasma wave activity. Our results confirm the anti correlation between T(sub e) and electron density and also exhibit a high ratio of T(sub e)/T(sub P) in the cloud. Since Landau damping is not effective for T(sub e)/T(sub p) much greater than 1, Doppler shifted ion acoustic waves are expected in the cloud. Calculation of ion acoustic wave frequencies in the cloud and comparison with observed wave activity confirm this expectation. As in our previous work, we show that the electron component in the cloud obeys a polytropic law with gamma is less than 1 (gamma approximately equals 0.3-0.4). The dynamics of the magnetic cloud are determined to a large degree by the dominating electron pressure.

Description: During the Helios mission a total of 391 fast forward non-corotating interplanetary shock waves was identified. For most of the 12 years between 1974 and 1986 unique shock detection was possible for more than 80 % of the time. The occurrence rate (in shocks per day) varied from 0.02 at activity minimum in 1976 to 0.17 in 1979 and 0.22 in 1982 with a significant drop to 0.13 in 1980, i.e. right at activity maximum. The average properties of all events as functions of solar distance. phase in the solar cycle, heliographic and -magnetic latitude and others are discussed.

Description: As a CME pushes its way through preceding slower solar wind, large disturbances in the interaction region may evolve to form transient MHD shocks. The shocks can be slow shocks in the coronal space but they appear as fast shocks near 1 AU. We use a polytropic MHD model to study the transition of slow shocks to fast shocks in an interaction region sandwiched between a faster solar wind and a slower solar wind near the equatorial plane. The polytropic index controls the radial increase of Beta outside the interaction region. The transition process is attributed chiefly to the increase of Beta and theta to a lesser degree to the radial increase of the shock angle 0. Under the initial condition of small Beta and theta near 0.1 AU, the interaction region evolves to form a pair of slow shocks inside 0.15 AU. As the interaction region convects outward. the increases of B and theta cause a transition of the shock system between 0.15 and 0.3 AU from a slow shock pair to a double shock pair consisting of both slow and fast shocks. As the system moves outward, and Beta continue to increase, the fast shock grows stronger, and the slow shock becomes weaker. Eventually. the slow shocks fade away, and the shock system finally evolves to a pair of fast shocks. Parametric studies of the transition process are carried out for shocks formed over a wide range of disturbances.

Description: Application of various geomagnetic data to restoration of the heliospheric current sheet configuration in the past is discussed. Technique for such a restoration is proposed based on analysis of information on the interplanetary magnetic field polarity inferred from diurnal variation of the geomagnetic field in polar regions outer solar corona pictures resulting from solar eclipse observations are concerned with the heliospheric sheet configuration. So, days of past solar eclipses must serve as a kind of reference points in the course of the heliospheric sheet reconstruction.

Description: Spectral observations of cool stars enable study of the presence and character of winds and the mass loss process in objects with effective temperatures, gravities, and atmospheric compositions which differ from that of the Sun. A wealth of recent spectroscopic measurements from the Hubble Space Telescope, and the Extreme Ultraviolet Explorer complement high resolution ground-based measures in the optical and infrared spectral regions. Such observations when combined with realistic semi-empirical atmospheric modeling allow us to estimate the physical conditions in the atmospheres and winds of many classes of cool stars. Line profiles support turbulent heating and mass motions. In low gravity stars, evidence is found for relatively fast (approximately 200 km s(exp -1)), warm winds with rapid acceleration occurring in the chromosphere. In some cases outflows commensurate with stellar escape velocities are present. Our current understanding of cool star winds will be reviewed including the implications of stellar observations for identification of atmospheric heating and acceleration processes.

Description: We have designed a full compressible MHD code working on unstructured meshes in order to be able to compute accurately sharp structures embedded in large scale simulations. The code is based on a finite volume method making use of a kinetic flux splitting. A bidimensional version of the code has been used to simulate the interaction of a moving interstellar medium, magnetized or unmagnetized with a rotating and magnetized heliopspheric plasma source. Being aware that these computations are not realistic due to the restriction to two dimensions, we present it to demonstrate the ability of this new code to handle this problem. An axisymetric version, now under development, will be operational in a few months. Ultimately we plan to run a full 3d version.

Description: The heliospheric termination shock is expected to move in response to variation in upstream solar wind conditions. Using numerical techniques, we extend an earlier strictly one-dimensional analytic gas dynamic model of shock motion to two dimensions, to investigate the qualitative features of global behavior of shock motion, and the consequences of latitudinal variation in dynamic pressure. The boundary conditions of the calculation are given by the solar wind parameters as a function of latitude and time on an inner spherical boundary, and a constant pressure (roughly simulating the effect of the local interstellar medium) on an outer boundary. Density variations, specified at the inner boundary as a function of time, are convected into the termination shock. Immediately after the interaction, the shock moves with speeds given by the earlier analytic model. However, as the termination shock propagates outward (or inward), it begins to slow down. After about 2 to 10 years, depending on details of boundary conditions, the signal from the shock interaction has reached the outer boundary and propagates inward to the position of the termination shock, strongly affecting the behavior of the shock. Assuming no further disturbances in the solar wind, the termination shock will reach its new equilibrium after some tens of years. In reality, large-scale variations in solar wind dynamic pressure occur on time scales short in comparison with the eleven year solar cycle, so that one expects that the termination shock is never in an equilibrium position, but rather oscillates inward and outward; this oscillation will vary with heliographic latitude. The effects of a variety of types of solar wind disturbances are investigated and summarized.

Description: The locations of the termination shock and the heliopause are studied taking into account the effects of pickup protons. The study uses available plasma and magnetic field data from Voyagers over a 14-year period (1978-1991) and Voyager observation of the 1992-93 radio emission event. Outside 30 AU, pickup protons have a significant influence on dynamical structures of the outer heliosphere. The solar wind is treated as a mixture of electrons, solar wind protons, and interstellar pickup protons. If the magnitude of the interstellar magnetic field B(sub int) is given, one can quantitatively study the motion and location of the termination shock. The location is anti-correlated with the sun spot number and the shock has an average speed of approx. 24 km/s. Because B(sub int) is poorly known, additional information is needed in studying the termination shock. Cummings, et al. have used observations of anomalous cosmic rays to estimate the location of the shock. The observations of the 1991 GMIR and GMIR shock and the 1992-93 radio emission event provide another handle for the study of the termination shock and the heliopause. After its penetration through the termination shock, the GMIR shock continued to propagate in the subsonic region of the solar wind and eventually interacted with the heliopause. This interaction produces a transmitted shock propagating outward in the interstellar medium and a reflected shock propagating inward toward the sun in the subsonic solar wind. The plasma frequencies behind the reflected and the transmitted shock can be, respectively, responsible for the 2- and 3-kHz radio emissions. Taking into account the effects of pickup protons we found that the average locations of the termination shock and the heliopause in 1991-92 are at approximately 66 AU and 150 AU, respectively.

Description: We have developed a computer code which can be used to study 3-dimensional and time-dependent effects of the solar cycle on the interplanetary (IP) hydrogen distribution. The code is based on the inverted Monte Carlo simulation. In this work we have modelled the temporal behaviour of the solar ionisation rate. We have assumed that during the most of the time of the solar cycle there is an anisotopic latitudinal structure but right at the solar maximum the anisotropy disappears. The effects of this behaviour will be discussed both in regard to the IP hydrogen distribution and IP Lyman a a-intensity.

Description: During average solar wind flow conditions at 1 AU, ionization rates of interstellar neutrals that penetrate into the inner heliosphere are dominated by charge exchange with solar wind protons for H atoms, and by photoionization for He atoms. During occurrences of strong, coronal mass ejection (CME)-driven interplanetary shock waves near 1 AU, electron impact ionization can make substantial, if not dominating, contributions to interstellar neutral ionization rates in the regions downstream of the shocks. However, electron impact ionization is expected to be relatively less important with increasing heliocentric distance because of the decrease in electron temperature. Ulysses encountered many CME-driven shocks during its journey to and beyond Jupiter, and in addition, encountered a number of strong corotating interaction region (CIR) shocks. These shocks generally occur only beyond approximately 2 AU. Many of the CIR shocks were very strong rivalling the Earth's bow shock in electron heating. We have compared electron impact ionization rates calculated from electron velocity distributions measured downstream from CIR shocks using the Ulysses SWOOPS experiment to charge-exchange rates calculated from measured proton number fluxes and the photoionization rate estimated from an assumed solar photon spectrum typical of solar maximum conditions. We find that, although normally the ratio of electron-impact ionization rates to charge-exchange (for H) and to photoionization (for He) rates amounts to only about one and a few tens of percent, respectively, downstream of some of the stronger CIR shocks they amount to more than 10% and greater than 100%, respectively.

Description: We have investigated and intercompared the typical features of the magnetic field of two types of solar wind transient disturbances with shock waves: the shock wave is accompanied by a magnetic cloud (MC), and the shock wave is followed by a region with bidirectional solar wind electron heat flux (BEHF), with no MC present. In this case, a separate study was made of the field features in two typical TD structures: in the region of impact-compressed solar wind between the shock wave and MC or BEHF, as well as in MC and BEHF. The study has provided new results on the influence of the ambient SW upon the TD magnetic field and the relationship between fields in various TD structures. A new test for the existence of interplanetary magnetic field draping around MC and BEHF is proposed and verified. It is concluded that the magnetic field configuration around MC is more adequately consistent with the concept of magnetic line draping than is the case around BEHF Two methods are proposed to infer the location of solar sources of TD from their characteristics at R = 1 AU.

Description: Young supernova remnants (SNRs) are often assumed to be the source of cosmic rays up to energies approaching the slight steepening in the cosmic ray spectrum at around 1000 TeV, known as the "knee." We show that the observed X-ray emission of 14 radio-bright shell remnants, including all five historical shells, can be used to put limits on E(sub max), the energy at which the electron energy distribution must steepen from its slope at radio-emitting energies. Most of the remnants show thermal spectra, so any synchrotron component must fall below the observed X-ray fluxes. We obtain upper limits on E(sub max) by considering the most rapid physically plausible cutoff in the relativistic electron distribution, an exponential, which is as sharp or sharper than found in any more elaborate models. This maximally curved model then gives us the highest possible E(sub max) consistent with not exceeding observed X-rays. Our results are thus independent of particular models for the electron spectrum in SNRs. Assuming homogeneous emitting volumes with a constant magnetic field strength of 10 uG, no object could reach 1000 TeV, and only one, Kes 73, has an upper limit on E(sub max), above 100 TeV. All the other remnants have limits at or below 80 TeV. E(sub max) is probably set by the finite remnant lifetime rather than by synchrotron losses for remnants younger than a few thousand years, so that an observed electron steepening should be accompanied by steepening at the same energy for protons. More complicated, inhomogeneous models could allow higher values of E(sub max) in parts of the remnant, but the emission-weighted average value, that characteristic of typical electrons, should obey these limits. The young remnants are not expected to improve much over their remaining lives at producing the highest energy Galactic cosmic rays; if they cannot, this picture of cosmic-ray origin may need major alteration.

Description: By comparing positions on a spectral color-color diagram from 10 black hole candidates (BHCS) observed with Ginga (1354-64, 1826-24, 1630-47, LMC X-1, LMC X-3, GS 2000+25, GS 2023+33, GS 1124-68, Cyg X-1, and GX 339-4) with the observed broadband noise (BBN) (0.001-64 Hz) and quasi-periodic oscillation (QPO) variability, we find that the "very high state" is spectrally intermediate to the soft/high state and hard/low state. We find a transition point in spectral hardness where the dependence of the BHC QPO centroid frequency (of GS 1124-68 and GX 339-4) on spectral hardness switches from a correlation to an anticorrelation; where the BBN variability switches from high state to low state; and where the spectral hardness of the QPO relative to that of the BBN variability is a maximum. This coincidence of changing behavior in both the QPO and the broadband variability leads us to hypothesize that the QPO is due to interaction between the physical components which dominate the behaviors of BHCs when they occupy the hard/low and soft/high states. We conclude that these QPOs should be observed from BHCs during transition between these two states. Comparison with QPO and BBN behavior observed during the 1996 transition of Cyg X-1 supports this hypothesis. We also report 1-3 Hz QPOs observed in GS 2000+25 and Cyg X-1 in the hard/low state, and we compare these to the QPOs observed in GS 1124-68 and GX 339-4.

Description: Infrared photometry at 1.2, 1.6, and 2.2 micrometer (JHK) is reported for 56 asteroids in the Eos, Koronis and, Maria dynamical families. These data are consistent with similar surface composition for all of the asteroids of each family. The infrared colors within each family cluster in the region observed for the S taxonomic class, but Eos asteroids may belong to a separable K class. Asteroid 243 Ida, which was observed by the Galileo spacecraft, is a typical member of the Koronis family. The average infrared colors of the Maria family are slightly redder than those of the Eos and Koronis families.

Description: Infrared spectroscopy of pre-main sequence stars with dusty protostellar disks provide information about the evolution of refractory materials in such systems. These systems exhibit varying degrees of strength and structure in the silicate emission band situated at 10 microns wavelength. Band strength is affected by the mean grain size, while band structure is determined by the chemical composition and degree of crystallinity. In some objects, the silicate band is strong and featureless, similar to that seen in the interstellar medium. In others, the band is often weaker, and exhibits structure consistent with the presence of crystalline olivine. In these latter objects, the band is similar to that of some solar system comets. The strength and structure of the silicate band may be related to the processing history of the system.

Description: The debris disks surrounding the pre-main-sequence stars HD 31648 and HD 163296 were observed spectroscopically between 3 and 14 microns. Both stars possess a silicate emission feature at 10 Am that resembles that of the star P Pictoris and those observed in solar system comets. The structure of the band is consistent with a mixture of olivine and pyroxene material, plus an underlying continuum of unspecified origin. The similarity in both size and structure of the silicate band suggests that the material in these systems had a processing history similar to that in our own solar system prior to the time that the grains were incorporated into comets.

Description: Trajectory design of the orbit phase of the NEAR mission involves a new process that departs significantly from those procedures used in previous missions. In most cases, a precise spacecraft ephemeris is designed well in advance of arrival at the target body. For NEAR, the uncertainty in the dynamic environment around Eros does not allow the luxury of a precise spacecraft trajectory to be defined in advance. The principal cause of this uncertainty is the limited knowledge oi' the gravity field a,-id rotational state of Eros. As a result, the concept for the NEAR trajectory design is to define a number of rules for satisfying spacecraft, mission, and science constraints, and then apply these rules to various assumptions for the model of Eros. Nominal, high, and low Eros mass models are used for testing the trajectory design strategy and to bracket the ranges of parameter variations that are expected upon arrival at the asteroid. The final design is completed after arrival at Eros and determination of the actual gravity field and rotational state. As a result of the unplanned termination of the deep space rendezvous maneuver on December 20, 1998, the NEAR spacecraft passed within 3830 km of Eros on December 23, 1998. This flyby provided a brief glimpse of Eros, and allowed for a more accurate model of the rotational parameters and gravity field uncertainty. Furthermore, after the termination of the deep space rendezvous burn, contact with the spacecraft was lost and the NEAR spacecraft lost attitude control. During the subsequent gyrations of the spacecraft, hydrazine thruster firings were used to regain attitude control. This unplanned thruster activity used Much of the fuel margin allocated for the orbit phase. Consequently, minimizing fuel consumption is now even more important.

Description: This paper describes The Cosmic Background Explorer Satellite Mission that was lost. It also describes the author's experiences as a youth, his college years, and employment with NASA.

Description: We have developed a new numerical approach to the dynamics of minor bodies and dust particles, which enables us to increase, without using a supercomputer, the number of employed particle positions in each model up to 10(exp 10) - 10(exp 11), a factor of 10(exp 6) - 10(exp 7) higher than existing numerical simulations. We apply this powerful approach to the high-resolution modeling of the structure and emission of circumstellar dust disks, incorporating all relevant physical processes. In this Letter, we examine the resonant structure of a dusty disk induced by the presence of one planet of mass in the range of (5 x 10(exp -5) - 5 x 10(exp -3))M. It is shown that the planet, via resonances and gravitational scattering, produces (i) a central cavity void of dust; (ii) a trailing (sometimes leading) off-center cavity; and (iii) an asymmetric resonant dust belt with one, two, or more clumps. These features can serve as indicators of planet(s) embedded in the circumstellar dust disk and, moreover, can be used to determine the mass of the planet and even some of its orbital parameters. The results of our study reveal a remarkable similarity with various types of highly asymmetric circumstellar disks observed with the JCMT around Epsilon Eridani and Vega.

Description: A recent X-ray observation of the cluster 1E 0657-56 (z = 0.296) with ASC,4 implied an unusually high temperature of approx. 17 keV. Such a high temperature would make it the hottest known cluster and severely constrain cosmological models since, in a Universe with critical density (Omega = 1) the probability of observing such a cluster is only approx. 4 x 10(exp -5). Here we test the robustness of this observational result since it has such important implications. We analysed the data using a variety of different data analysis methods and spectral analysis assumptions and find a temperature of approx. 11 - 12 keV in all cases, except for one class of spectral fits. These are fits in which the absorbing column density is fixed at the Galactic value. Using simulated data for a 12 keV cluster, we show that a high temperature of approx. 17 keV is artificially obtained if the true spectrum has a stronger low-energy cut-off than that for Galactic absorption only. The apparent extra absorption may be astrophysical in origin, (either intrinsic or line-of-sight), or it may be a problem with the low-energy CCD efficiency. Although significantly lower than previous measurements, this temperature of kT approx. 11 - 12 keV is still relatively high since only a few clusters have been found to have temperatures higher than 10 keV and the data therefore still present some difficulty for an Omega = 1 Universe. Our results will also be useful to anyone who wants to estimate the systematic errors involved in different methods of background subtraction of ASCA data for sources with similar signal-to-noise to that of the IE 0657-56 data reported here.

Description: A list of the interplanetary (IP) shocks observed by WIND from its launch (in November 1994) to May 1997 is presented. Forty two shocks were identified. The magnetohydrodynamic nature of the shocks is investigated, and the associated shock parameters and their uncertainties are accurately computed using a practical scheme which combines two techniques. These techniques are a combination of the "pre-averaged" magnetic-coplanarity, velocity-coplanarity, and the Abraham-Schrauner-mixed methods, on the one hand, and the Vinas and Scudder [1986] technique for solving the non-linear least-squares Rankine-Hugoniot shock equations, on the other. Within acceptable limits these two techniques generally gave the same results, with some exceptions. The reasons for the exceptions are discussed. It is found that the mean strength and rate of occurrence of the shocks appears to correlated with the solar cycle. Both showed a decrease in 1996 coincident with the time of the lowest ultraviolet solar radiance, indicative of solar minimum and start of solar cycle 23, which began around June 1996. Eighteen shocks appeared to be associated with corotating interaction regions (CIRs). The distribution of their shock normals showed a mean direction peaking in the ecliptic plane and with a longitude (phi(sub n)) in that plane between perpendicular to the Parker spiral and radial from the Sun. When grouped according to the sense of the direction of propagation of the shocks the mean azimuthal (longitude) angle in GSE coordinates was approximately 194 deg for the fast-forward and approximately 20 deg for the fast-reverse shocks. Another 16 shocks were determined to be driven by solar transients, including magnetic clouds. These shocks had a broader distribution of normal directions than those of the CIR cases with a mean direction close to the Sun-Earth line. Eight shocks of unknown origin had normal orientation well off the ecliptic plane. No shock propagated with longitude phi(sub n) 〉= 220 +/- 10 deg, this would suggest strong hindrance to the propagation of shocks contra a rather tightly winding Parker spiral. Examination of the obliquity angle theta(sub Bn) (that between the shock normal and the upstream interplanetary magnetic field) for the full set of shocks revealed that about 58% was quasi-perpendicular, and some were very nearly perpendicular. About 32% of the shocks were oblique, and the rest (only 10%) were quasi-parallel, with one on Dec. 9, 1996 that showed field pulsations. Small uncertainty in the estimated angle theta(sub Bn) was obtained for about 10 shocks with magnetosonic Mach numbers between 1 and 2, hopefully significantly contributing to studies researching particle acceleration mechanisms at IP shocks, and to investigations where accurate values of theta(sub Bn) are crucial.

Description: Interior layers of stars that have been exposed by surface mass loss reveal aspects of their chemical and convective histories that are otherwise inaccessible to observation. It must be significant that the surface hydrogen abundances of luminous blue variables (LBVs) show a remarkable uniformity, specifically X(sub surf) = 0.3 - 0.4, while those of hydrogen-poor Wolf-Rayet (WN) stars fall, almost without exception, below these values, ranging down to X(sub surf) = 0. According to our stellar model calculations, most LBVs are post-red-supergiant objects in a late blue phase of dynamical instability, and most hydrogen-poor WN stars are their immediate descendants. If this is so, stellar models constructed with the Schwarzschild (temperature-gradient) criterion for convection account well for the observed hydrogen abundances, whereas models built with the Ledoux (density-gradient) criterion fail. At the brightest luminosities, the observed hydrogen abundances of LBVs are too large to be explained by any of our highly evolved stellar models, but these LBVs may occupy transient blue loops that exist during an earlier phase of dynamical instability when the star first becomes a yellow supergiant. Independent evidence concerning the criterion for convection, which is based mostly on traditional color distributions of less massive supergiants on the Hertzsprung-Russell diagram, tends to favor the Ledoux criterion. It is quite possible that the true criterion for convection changes over from something like the Ledoux criterion to something like the Schwarzschild criterion as the stellar mass increases.

Description: The shock between the colliding winds in binary systems containing two massive stars accelerates particles to relativistic energies. These energetic particles can produce observable non-thermal radiation from the radio to gamma-rays. The important physical processes in such systems are very similar to those we have proposed for non-thermal emissions from single hot stars, which have shocks generated by instabilities in the radiatively driven stellar winds. This paper discusses the theory and observations of non-thermal radiation in the radio, X-ray, and gamma-ray regions from both single stars and massive binaries. Similarities and differences between the two types of systems are outlined. We discuss two important physical effects that apparently have been neglected in previous theoretical work on colliding wind binaries.

Description: Symbiotic systems are long period binaries in which a white dwarf usually.

Description: We have measured [O I] 63 mm and [Si II] 35 mm in the central 44' (700 pc) of the starburst galaxy M82. The luminosities in these transitions are each ~0.1 percent of the bolometric luminosity. We model the [O I] in M82 as arising from warm neutral gas photodissociated by FUV flux from OB stars, while most of the [Si II] emission arises from associated H II regions.!.

Description: We analyze the properties of IRAS maps of interstellar clouds using Laplacian Pyramid.

Description: A model is described in which radio jet formation in accreting objects is suppressed by processed which occur when the accretion rate approaches the Eddington limit. This was motivated by GRO J1655-40 and other objects which show an anticorrelation between high luminosity and the onset of a radio jet.

Description: The vertical scales of turbulence at the Mt. Wilson observatory are inferred from data from the University of California at Berkeley Infrared Spatial Interferometer (ISI), by modeling path length fluctuations observed in the interferometric paths to celestial objects and those in instrumental ground- based paths. The correlations between the stellar and ground-based path length fluctuations and the temporal statistic of those fluctuations are modeled on various time scales to constrain the vertical scales.

Description: In the electron-impact-induced fluorescence spectrum on neon in the wavelength range of 120 270 nm at a spectral resolution of 0.43 nm, the strongest lines in the far ultraviolet (FUV) spectrum of neon are assigned to items of the Doublet system of Ne II and the Triplet system of Ne III. FUV spectral data at 300 eV electron impact energy provide absolute emission cross sections of these Ne II and Ne III lines and are compared to previous measurements.

Description: High-resolution imaging of the protostar HH24MMS at wavelengths of 7 mm and 3.4 mm shows.

Description: Preliminary results of a continuing search microvariations in a selected sample.

Description: We have detected the T Tauri star, DO Tauri, in a 0.6'-resolution VLA map of 43.3 GHz (l = 7 mm) continuum emission. Upper limits to the flux densities at 8.4 and 22.5 GHz limit the contribution of free-free emission due to a compact ionized wind to less than 49%.

Description: The spin-induced quadrupole moment of a rapidly rotating star changes the orbital dynamics in a binary system, giving rise to advance (or regression) of periastron and precession of the orbital plane. We show that these effects are important in the recently discovered radio pulsar/mail sequence star binary system PSR J0045-7319, and reliably account for the observed peculiar timing residuals. Precise measurements of the apsidal motion and orbital plane precession can yield valuable information on the internal structure and rotation of the star. The detection of orbital precession implies that the spin of the companion star is not aligned with the orbital angular momentum, and suggests that the supernova gave the pulsar a kick out of the original orbital plane. Excitations of g-mode oscillations near periastron (the dynamical tide) can induce measurable changes in the orbital period and eccentricity at each passage for this system. We also discuss the spin-orbit coupling effects for the accreting X-ray pulsars and the other know radio pulsar/main sequence binary, PSR B1259-63.

Description: Millimeter CO (1-〉0) interferometry and high resolution, Hubble Space Telescope (HST) 1.1, 1.6, and 2.2 meu imaging of the radio compact galaxy PKS 1345+12 are presented.

Description: We report the discovery of four field methane (T-type) brown dwarfs using 2MASS survey data. One additional methane dwarf, previously discovered by SDSS, was also identified.

Description: We report extensive observations of striation patterns in the dust tail of comet Hale-Bopp (C/1995 O1) over a period of more than 10 weeks, from mid-february until early May 1997.

Description: Dust plays a key role in the optical, thermodynamic and gas dynamical behavior of collapsing molecular cores. Because of relative velocities of the individual dust grains, coagulation and shattering can modify the grain size distribution and due to corresponding changes in the medium's opacity significantly influence the evolution during early phase of star formation.

Description: We report the detection of emission from methanol in a compact source coincident with the position of the L1157 infrared source, which we attribute to molecules in the disk surrounding this young, class 0 protostellar object.

Description: WL16 is unique among the members of the young, forming star cluster embedded in the nearby p Oph cloud core in exhibiting an extended, high surface brightness disk in the emission features originating from solid-state aromatic hydrocarbons.

Description: We present thirty VLBI images of the Tev blazar Markarian 421 (1101+384) at fifteen epochs spanning the time range from 1994 to 1997, and at six different frequencies form 2.3 to 43 GHz.

Description: Ground-based, equal-arm-length laser interferometers are being built to measure high-frequency astrophysical graviatational waves. Because of the arm-length equality, laser light experiences the same delay in each arm and thus phase or frequency noise from the laser itself precisely cancels at the photodetector.

Description: Long thought by some researchers to be an oddity, GD 165B has instead proven to be the first example of a class of very cool objects (the L dwarfs) which, due to dust formation in their photosphere, lack the dominant bands of TiO seen in warmer M dwarfs.

Description: In an attempt to use Cepheid variables to determine the distance to the Centaurus cluster, we have obtained images of NGC 4603 with the Hubble Space Telescope for 9 epochs (totalling 24 orbits) over 14 months in the F555W filter and 2 epochs (totalling 6 orbits) in the F814W filter.

Description: We report Hubble Space Telescope observations of variability within the reflection nebulosity of HH 30, a compact bipolar nebula which is a nearly edge-on accretion disk system.

Description: We present the discovery of a widely separated (258.3+/-0.4) T dwarf companion to the G1 570ABC system.

Description: We report on the determination of the visual orbit of the double-lined spectroscopic binary system 64 Piscum with data obtained by the Palomar Testbed Interferometer in 1997 and 1998.

Description: Spatially resolved profiles of the H (alpha), [N II] 6584 A and [O III] 5007 A nebular emission lines, obtained with the Manchester echelle spectrometer combined with the 2.1 m San Pedro Martir telescope have revealed the velocity structure of the nebular core and of one of the three (A,B and C) inner haloes of the high excitation planetary nebula NGC 3242.

Description: Dust plays a key role in the optical, thermodynamic and gas dynamical behavior of collapsing molecular cores. Because of relative velocities of the individual dust grains, coagulation and shattering can modify the grain size distribution and -- due to corresponding changes in the medium's opacity significantly -- influence the evolution during early phases of star formation.

Description: We report the discovery of three proplyd-like structures in the giant HII region NGC 3603.

Description: The structure of AGN accretion disks on sub-parsec scales can be probed through free-free absorption of synchrotron emission from the base of symmetric radio jets.

Description: Evidence of a north-south asymmetry in the global heliosphere, first inferred from Ulysses cosmic ray observations, is investigated using simultaneous Ulysses and WIND magnetic field observations.

Description: Measurements of the abundances of cosmic-ray (sup 59)Ni and (sup 59)Co are reported form the Cosmic Ray Isotope Spectrometer (CRIS) on the Advanced Composition Explorer (ACE).

Description: We present a survey for extended 2.2 emission in 20 new visual reflection nebulae, illuminated by stars with temperatures of 3,600 - 33,000 K. We detect extended 2.2 emission in 13 new nebulae we have measured J - K, H - K, and K - L', as well as obtaining surface brightness measurements of the 3.3 emission feature. All of the reflection nebulae with extended near infrared emission in excess over scattered starlight have very similar near infrared colors and show the 3.3 feature in emission with similar feature-to-continuum ratios. The 3.3 feature-to-continuum ratio ranges from 3 to 9, both within individual nebulae and from nebula to nebula, which suggests that the 3.3 feature and its underlying continuum arises from different materials, or from different ranges of sizes within a size distribution of particles. No dependence on the temperature of the illuminating star is seen in the near infrared colors or 3.3 feature-to-continuum ratio, over a factor of two in stellar temperature. This is similar to our previous IRAS results, in which we found no dependence of the ratio 12 to 100 surface brightness in reflection nebulae illuminated by stars with temperatures of 5,000-33,000 K.

Description: We have performed magnetohydrodynamic (MRD) simulations of the production of jets from magnetized accretion disks with a factor of 5 greater extent in space and time, and with more models, than any study published so far. We find that jets are produced by such disks in a broad range of parameter space, and by at least two different mechanisms. We also are able to follow the propagation of the jet well beyond the accretion disk into the region of hydrodynamic collimation. The code used is our MHD simulation code FLOW (K. Lind, D. Payne, D. Meier, and R. Blandford, 1989), converted to run on Caltech's massively parallel Intel Touchstone Delta supercomputer. Some of these models may be directly applicable to observed radio sources.

Description: The Earth, Mars, Sun, Jupiter system allows for a sensitive.

Description: The abundance ratios of carbon monoxide with isotopes 17 and 18 were mapped in three nearby molecular clouds (B335, L134, and rho Oph), two of which are active star-forming regions. It is suggested that there may be a spatial variability of the two oxygen isotopes resulting from local enrichment and that this may have major implications for galactic nuclear evolution.

Description: An asymmetry in the radial variation of electron density above the east and west limbs of the Sun was inferred from centimeter wavelength ranging measurements conducted by Voyager 2 during its 1985 solar conjunction. These older data are compared with white- light coronagraph measurements of the underlying corona collected by the Mark III K-coronameter at the Mauna Loa Solar Observatory.

Description: We report on multi-frequency radio timing observations of the unique binary pulsar PSR J0045-.

Description: Until very recently, all known radio pulsars in binary orbits had as companions old, degenerate stars, either neutron stars or white dwarfs. In this talk we introduce a new class of binary radio pulsars having as companions young, massive stars. Concentrating on one system in particular, we show that these systems open a new phase space for studying a variety of physical phenomena, including post-Keplerian dynamics, physics of stellar winds and interiors, and binary evolution theory.

Description: This paper presents a study of a dense molecular region, NGC.

Description: HL Tauri is considered a prototype solar-mass T Tauri star. Planetary camera images of HL Tauri have been obtained through V, R, and I band filters using the Wide Field Planetary Camera 2 aboard the refurbished Hubble Space Telescope. These images show that HL Tauri is entirely reflection nebulosity at optical wavelengths, with no optical star visible to a limiting magnitude of V=25.5.

Description: Large-scale dust heating and cooling in the diffuse medium of M31 is studied using the high resolution (HiRes) IRAS maps in conjunction with UV, optical (UBV), and the HI maps. A dust heating/cooling model is developed based on a radiative transfer model which assumes a 'Sandwich' configuration of dust and stars takes account of the effect of dust grain scattering.

Description: Corrections to the Earth's precession and nutation have been derived from VLBI observations of extragalactic sources carried out by JPL's Deep Space Network between 1978 and 1994. The analysis is based on the source right ascensions and declinations given in annual position catalogues. These catalogues result from adopting specific conventions on precession and a nutation model, using VLBI data.

Description: Near infrared images are presented of the Herbig-Haro 110 jet centered at the molecular hydrogen lines. The ratio of these lines provides a preliminary diagnostic of molecular gas excitation, which is expected from low velocity shocks and turbulent processes. It is suggested that the morphological properties of the molecular hydrogen emission are consistent with that of a boundary layer.

Description: This paper reviews recent progress in the understanding of.

Description: We have used massively parallel supercomputer simulations to perform an extensive study of a plausible mechanism for producing the jets seen in extragalactic radio sources - acceleration and collimation by coronal magnetic fields in an accretion disk orbiting a central black hole. We find that such disks can propel jets for a wide range of coronal conditions. The terminal jet velocity is a strong function of the magnetic field equatorial component. Acceleration and collimation are produced by a tight azimuthal field coil generated in the corona, rather than by a stiff poloidal field extending to large distances. The jets are pressure-confined when the external medium pressure is high, but magnetically- confined when it is low.

Description: Extensive mass-loss in red giant (AGB) stars, preceding and.

Description: Knowledge of the density, velocity and chemical profiles around protostars is of fundamental importance for testing dynamical models of protostar evolution and understanding the nature of the material falling onto circumstellar disks. Presented are single dish and interferometric spectral line observations of CCS towards the core of B335, a classic example of a young, low mass stellar object.

Description: We compare Far-UV, H alpha, and optical broadband images of the nearby spiral galaxy M33, to investigate the massive stars associated with the diffuse ionized gas. The H-alpha/FUV ratio is higher in HII regions than in the DIG, possibly indicating that an older population ionizes the DIG. The broad-band colors support this conclusion. The HII region population is consistent with a young burst, while the DIG colors resemble an older population with constant star formation. Our results indicate that there may be enough massive field stars to ionize the DIG, without the need for photon leakage from HII regions.

Description: Low mass pre-main sequence stars in the nearby Lynds 1551 star forming cloud are studied with the ROSAT and ASCA X-ray satellites. An 8 ksec ROSAT image reveals 38 sources including 7 well-known T Tauri stars, 2 likely new weak-lined T Tauri stars, 5 potential new weak-lined T Tauri stars, one is a young B9 star, and the remaining sources are unrelated to the cloud or poorly identified. A 40 ksec ASCA image of the cloud detects seven of the ROSAT sources. Spectral fitting of the brighter X-ray emitting stars suggests the emission is produced in either a multi-temperature plasma, with temperatures near 0.2 and 1 keV, or a single-temperature plasma with low metal abundances. XZ Tau, a young classical T Tauri star, is much stronger in ASCA than ROSAT observations showing a harder (1.5-2.0 kev) component. Timing analysis reveals all but one of the T Tauri stars are variable on timescales ranging from one hour to a year. A powerful flare, emitting 3 x 10(exp 34) ergs within a 40 minute rise and fall, was observed by ASCA on the weak-lined T Tauri star V826 Tau. The event was preceded and followed by constant quiescent X-ray emission. The extreme classical T Tauri star XZ Tau was also caught during both high and low states, varying by a factor of 15 between the ASCA and ROSAT observations. Neither of the luminous infrared embedded protostars L1551-IRS 5 or L1551NE were detected by ROSAT or ASCA.

Description: Knowing the impact effects of the space environment on engineering materials is critical if we are to build space hardware which will last for the duration of the mission. This study will perform measurements on impacted materials in order to determine the effects of the high velocity impacts on structures which are planned for long duration in space.

Description: We study the dust in the Small Magellanic Cloud using our polarization and extinction data (Paper 1) and existing dust models. The data suggest that the monotonic SMC extinction curve is related to values of lambda(sub max), the wavelength of maximum polarization, which are on the average smaller than the mean for the Galaxy. On the other hand, AZV 456, a star with an extinction similar to that for the Galaxy, shows a value of lambda(sub max) similar to the mean for the Galaxy. We discuss simultaneous dust model fits to extinction and polarization. Fits to the wavelength dependent polarization data are possible for stars with small lambda(sub max). In general, they imply dust size distributions which are narrower and have smaller mean sizes compared to typical size distributions for the Galaxy. However, stars with lambda(sub max) close to the Galactic norm, which also have a narrower polarization curve, cannot be fit adequately. This holds true for all of the dust models considered. The best fits to the extinction curves are obtained with a power law size distribution by assuming that the cylindrical and spherical silicate grains have a volume distribution which is continuous from the smaller spheres to the larger cylinders. The size distribution for the cylinders is taken from the fit to the polarization. The 'typical', monotonic SMC extinction curve can be fit well with graphite and silicate grains if a small fraction of the SMC carbon is locked up in the grain. However, amorphous carbon and silicate grains also fit the data well. AZV456, which has an extinction curve similar to that for the Galaxy, has a UV bump which is too blue to be fit by spherical graphite grains.

Description: Spectroscopic studies of the following potential diffuse interstellar band (DIB) carriers are reviewed: unspecified organics, carbon chains, polycyclic aromatic hydrocarbons (PAHs), fullerenes and derivatives, as well as porphyrins and related material. An assessment of each is given, along with suggestions for further experimental studies needed to fully test each candidate. Of the experimental techniques in common use matrix isolation spectroscopy with neon matrices is the most appropriate for the DIBs. The low vapor pressure and high reactivity of these materials preclude gas phase studies on many of these species. At this point, given the type and quality of published data available, carbon chains and PARs are the most promising candidates for a number of the DIBs.

Description: In order to investigate the relative importance of dry metamorphism and aqueous alteration in the history of chondruies, chondruies were hand-picked from the Semarkona (petrographic type 3.0), Bishunpur (3. 1), Chainpur (3.4), Dhajala (3.8) and Allegan (5) chondrites, and matrix samples were extracted from the first three ordinary chondrites. The thermoluminescence (TL) properties of all the samples were measured, and appropriate subsets of the samples were analyzed by electron-microprobe and radiochemical neutron activation and the water and H-isotopic composition determined. The TL data for chondrules from Semarkona and Bishunpur scatter widely showing no unambiguous trends, although group B1 chondrules tend to have lower sensitivities and lower peak temperatures compared with group A5 chondrules. It is argued that these data reflect the variety of processes accompanying chondrule formation. The chondrules show remarkably uniform contents of the highly labile elements, indicating mineralogical control on abundance and volatile loss from silicates and loss and recondensation of mobile chalcophiles and siderophiles in some cases. Very high D/H values (up to approx. 8000% SMOW) are observed in certain Semarkona chondrules, a confirmation of earlier work. With increasing petrographic type, mean TL sensitivities of the chondrules increase, the spread of values within an individual meteorite decreases, and peak temperatures and peak widths show trends indicating that the TL is mainly produced by feldspar and that dry, thermal metamorphism is the dominant secondary process experienced by the chondrules. The TL sensitivities of matrix samples also increase with petrographic type. Chainpur matrix samples show the same spread of peak temperatures and peak widths as Chainpur chondruies, indicating metamorphism-related changes in the feldspar are responsible for the TL of the matrix. The TL data for the Semarkona and Bishunpur matrix samples provide, at best, only weak evidence for aqueous alteration, but the matrix contains H with approximately terrestrial D/H values, even though it contains much water. Secondary processes (probably aqueous alteration) presumably lowered the D/H of the matrix and certain chondrules. While chondrule properties appear to be governed primarily by formation processes and subsequent metamorphism, the matrix of Semarkona has a more complex history involving aqueous alteration as a meteorite-wide process.

Description: The completion of a complementary optical emission-line survey of the nebulae associated with Wolf-Rayet stars in the southern sky is reported, along with the completion of a survey the large-scale environments of Wolf-Rayet stars using IRAS Skyflux data. HIRES IRAS maps in the four IRAS wavebands for appoximately half of all galactic Wolf-Rayet stars are created.

Description: We show how to detect and correct for non-linear phase shifts in a mainly one-sided interferogram of an emission-line source. We simultaneously detect and correct for an out-of-phase emission background from the spectrometer. The method requires two auxiliary spectra, one of a strong continuum source, and one of an emission-line source with little or no continuum.

Description: We compare production rates of H20 derived from International Ultraviolet Explorer (IUE) spectra from multiple apparitions of 2 comets, 2P/Encke and 9P/Tempel 1, whose orbits are in near-resonance with that of the Earth. Since model-induced errors are primarily a function of observing geometry, the close geometrical matches afforded by the resonance condition results in the cancellation of such errors when taking ratios of production rates. Giving careful attention to the variation of model parameters with solar activity, we find marginal evidence of change in 2P/Encke: a 1-sigma pre-perihelion decrease averaging 4%/revolution over 4 apparitions from 1980-1994, and a 1-sigma post-perihelion increase of 16%/revolution for 2 successive apparitions in 1984 and 1987. We find for 9P/Tempel 1, however, a 7-sigma decrease of 29%/revolution over 3 apparitions from 1983-1994, even after correcting for a tracking problem which made the fluxes systematically low. We speculate on a possible association of the character of long-term brightness variations with physical properties of the nucleus, and discuss implications for future research.

Description: We discuss simultaneous dust model fits to our extinction and polarization data for the Small Magellanic Cloud (SMC) using existing dust models. Dust model fits to the wavelength dependent polarization are possible for stars with small lambda(sub max). They generally imply size distributions which are narrower and have smaller average sizes compared to those in the Galaxy. The best fits for the extinction curves are obtained with a power law size distribution. The typical, monotonic SMC extinction curve can be well fit with graphite and silicate grains if a small fraction of the SMC carbon is locked up in the grains. Amorphous carbon and silicate grains also fit the data well.

Description: The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer (IUE) for 9.3 days, yielding a pair of LWP and SWP spectra every 70 minutes, and during four-hour periods for 4 days prior to and 5 days after the continuous monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy.

Description: Recent investigations of magnetospheric plasma structure are summarized under the broad categories of empirical models, transport across boundaries, formation, and dynamics of the plasma sheet. This report reviews work in these areas during the period 1991 to 1993. Fully three-dimensional empirical models and simulations have become important contributors to our understanding of the magnetospheric system. Some new structural concepts have appeared in the literature: the 'entry boundary' and 'geo-pause', the plasma sheet 'region 1 vortices', the 'low-energy layer', the 'adia-baticity boundary' or 'wall region', and a region in the tail to which we refer as the 'injection port'. Traditional structural concepts have also been the subject of recent study, notably the plasmapause, the magnetopause, and the plasma sheet. Significant progress has been made in understanding the nature of plasma sheet formation and dynamics, but the acceleration of electrons to high energy remains somewhat mysterious.

Description: The formation of hydrocarbons in the oxygen-rich outflows from red giants was studied. The existence of organic molecules in such outflows has been known for several years; however, their surprisingly high abundances has been a mystery since all of the carbon had been thought to be irretrievably locked up in CO, the most strongly bound molecule. CO is the first molecule to form from the atoms present in the star's extended atmosphere, and as strong stellar winds drive a cooling outflow, dust grains condense out. In oxygen-rich outflows, the dust is thought to be composed mainly of silicates and other metal oxides. Perhaps the noble metals can condense out in metallic form, in particular the relatively abundant transition metals iron and nickel. We proposed that perhaps the carbon reservoir held as CO can be accessed through a catalytic process involving the chemisorption of CO and H2 onto grains rich in metallic iron. CO and H2 are the two most abundant molecules in circumstellar outflows, and they both are known to dissociate on transition metal surfaces at elevated temperatures, freeing carbon to form organic molecules such as methane. We believe methane is a precursor molecule to the organics observed in oxygen-rich red giants. We have developed a nonequilibrium numerical model of a surface chemical (catalytic) process. Based on this model, we believe that methane can be formed under the conditions present in circumstellar outflows. Although the methane formation rates are exceptionally low under these conditions, over dynamical timescales, a significant amount of CO can be converted to methane and driven further out in the envelope, explaining the presence of organics there.

Description: If gamma-ray bursters are at cosmological distances-a possibility suggested by their isotropic distribution and spatial inhomogeneity-then the temporal profiles and spectra of more distant sources will be time dilated compared to those of relatively nearby sources. Analyses of bright and dim Burst and Transient Source Experiment (BATSE) gamma-ray bursts yield a relative time-dilation factor of 2.3 on timescales of pulses and event durations. We redshift the spectra of time intervals near the intensity peaks of the bright sample on a trial grid and compare with spectra of the dim sample. A redshift factor of order two-with wide latitude permitted-brings the spectra of the two brightness groups into alignment. Thus there is coarse agreement with the time-dilation factor found in the temporal domain.

Description: We present ground-based images of the z=1.824 radio galaxy 3C 256 in the standard BVRIJHK filters and an interference filter centered at 8800 A, a Hubble Space Telescope image in a filter dominated by Ly alpha emission (F336W), and spectra covering rest-frame wavelengths from Ly alpha to [O III} lambda 5007.

Description: New data are presented and analyzed, and are combined with the results from the earlier sample to address the properties of this class of circumstellar disk.

Description: Absolute measurements have been made of single electron charge exchange cross sections of H(sup +), He(sup +) and He(sup 2+) in H(sub 2)O and CO(sub 2) in the energy range 0.3 - 7.5 keV/amu.

Description: We use Python I, II, and III cosmic microwave background anisotropy data to constrain cosmogonies.

Description: We have carried out K-band speckle observations of a sample of 114 X-ray selected weak-line T Tauri stars in the nearby Scorpius-Centaurus OB association.

Description: We present color-magnitude diagrams and luminosity functions or stars in two halo regions of the irregular galaxy in M82, based on F555W and F814W photometry taken with the Hubble Space Telescope and Wide Field Planetary Camera 2.

Description: A causality connection between molecular outflows and the optical proto-stellar jets is becoming stronger as the number of objects with a consistent set of radio, IR and optical observations has grown.