206 research outputs found
Stellar magnetic fields. 1: The role of a magnetic field in the peculiar M giant, HD 4174
Coronal heating by resonant absorption of Alfvenic surface waves (quiescent), and magnetic tearing instabilities (impulsive), is discussed with emphasis on three principles which may have application to late-type evolved stars. (1) If sq B/8 pi greater than sq. rho V is observed 2 in a stellar atmosphere, then the observed magnetic field must originate in an interior dynamo. (2) Low mass loss rates could imply the presence of closed magnetic flux loops within the outer atmosphere which constrain hydrodynamic flows when the magnetic body forces exceed the driving forces. (3) given that such magnetic loops effect an enhancement of the local heating rate, a positive correlation is predicted between the existence of a corona and low mass loss rates. These principles are applied to the M giant star HD 4174, which is purported to have a kilogauss magnetic field. Several of its spectroscopic peculiarities are shown to be consistent with the above principles, and further observational checks are suggested
High resolution absolute flux profiles of the MC 2 h and k lines in evolved F8 to M5 stars
The central results of a survey of the Mg II resonance line emission in a sample of over 50 evolved late type stars, including spectral-luminosity type F8 to M5 and La to IV are presented. Observed and surface fluxes are derived and correlations noted. The major findings include: (1) Mg II k emission core asymmetry transition near K1 III, analogous to that known for Ca II K; (2) a small gravity and temperature dependence of the Mg II chromospheric radiative loss rate
Process for Removing Sulfur and Producing Enhanced Quality and Environmentally Acceptable Products for Energy Production from Coal
A process for producing enhanced quality adsorbent carbons and environmentally acceptable materials for energy production from coal includes an initial step of physically cleaning the coal to remove organic sulfur and mineral tailings. Next, a coal slurry of feedstock and water is prepared. Phosphoric acid is then mixed into the water of the coal slurry to provide by volume 15-85% and more preferably 50-85% phosphoric acid. The slurry is then heated and held in a temperature range between 85° and 230° C. for a period of at least five minutes to allow the phosphoric acid to penetrate deeply into the coal. Then the coal slurry is carbonized at a temperature of between 200°-700° C. for at least five to sixty minutes. The processing produces unique products including a low ash content, low sulfur content carbon solid, a tar with a sulfur content of less than 0.05% of the original feedstock and a gas product having a hydrogen to methane ratio of at least 4:1
Ultraviolet and X-ray detection of the 56 Peg system (KO 2p + WD)
Both IUE short and long wavelength exposures of the 56 Peg system are discussed. This mild barium star has an X-ray luminosity of 3 x 10 to the 31st power ergs/1, comparable to the rapidly rotating RS CVn binary systems, yet lies in a region of the HR diagram where stellar X-rays are generally not observed. This cool, bright giant is not a rapid rotator and the key to understanding its emission lies in the recent discovery of its white dwarf companion. Accretion onto the white dwarf of approximately 0.1% of the stellar wind of the primary is sufficient to power an X-ray source of the observed luminosity. Reprocessing of the X-rays in the cool dense stellar wind explains the origin of the UV emission line spectrum, and may explain the time varying asymmetry of the Mg 2 kappa line profile that is observed. Graphs which show observed fluxes and wavelengths are discussed
Direct UV observations of the circumstellar envelope of alpha Orionis
Observations were made in the IUE LWP camera, low dispersion mode, with alpha Ori being offset various distances from the center of the Long Wavelength Large Aperture along its major axis. Signal was acquired at all offset positions and is comprised of unequal components of background/dark counts, telescope-scattered light, and scattered light emanating from the extended circumstellar shell. The star is known from optical and infrared observations to possess an extended, arc-minute sized, shell of cool material. Attempts to observe this shell with the IUE are described, although the deconvolution of the stellar signal from the telescope scattered light requires further calibration effort
Morphology Studies of Iron-Manganese Thin Films
Fe-based catalysts are known to be effective for Fischer-Tropsch synthesis from coal but are sensitive to sulfur poisoning. Addition of manganese to these catalysts has been proposed in an effort to combat this catalyst deactivation. To investigate the fundamental physical aspects of Mn incorporation into Fe, different compositions of model thin films of Fe-Mn, ranging from 100% Fe to 100% Mn were studied for the very first time, using scanning tunneling microscopy (STM), atomic force microscopy (AFM) and scanning electron microscopy. Our preliminary results indicate that the grain size of iron varied from 50 nm to 150 nm using the AFM image, in general agreement with others. Also the mixture with small amounts of manganese had large oxidic area. The surface was modified by the addition of manganese. The STM images of the samples showed similarities between pure iron and 75% Fe-25% Mn, while the 25% Fe-75% Mn looked very similar to 100% Mn. The mixture of 50% Fe-50% Mn seemed to contain two distinct surface features. This leads us to believe that STM and AFM can be useful tools to further investigate the model iron-manganese thin films and hence give insight into the unknown atomic scale interactions and also to study the catalytic properties better
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Princeton Plasma Physics Laboratory (PPPL) annual site environmental report for calendar year 1991
This report gives the results of the environmental activities and monitoring programs at the Princeton Plasma Physics Laboratory (PPPL) for CY91. The report is prepared to provide the US Department of Energy (DOE) and the public with information on the level of radioactive and nonradioactive pollutants, if any, added to the environment as a result of PPPL operations, as well as environmental initiatives, assessments, and programs. The objective of the Annual Site Environmental Report is to document evidence that DOE facility environmental protection programs adequately protect the environment and the public health
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