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Articles 1351 - 1375 of 1375

Full-Text Articles in Stars, Interstellar Medium and the Galaxy

Iue Observations Of A Luminous M Supergiant That Exhibits Emission Continuum In The Far Ultraviolet, A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs Jan 1980

Iue Observations Of A Luminous M Supergiant That Exhibits Emission Continuum In The Far Ultraviolet, A. G. Michalitsianos, Menas Kafatos, R. W. Hobbs

Mathematics, Physics, and Computer Science Faculty Articles and Research

IUE observations of the late-type M supergiant TV Gem (M1 lab) have been obtained that reveal strong UV continuum between 1200 and 3200 A. The continuum is essentially featureless with the exception of a number of broad absorption features in the short wavelength spectral range. UV emission from this star is unexpected because earlier ground-based observations give no indication of a possible association with an early companion or circumstellar ionized nebulosity. We find that a B9 or A1 III-IV type star approximately 2-3 magnitudes fainter than the M star could explain the level of UV continuum observed, but a fully …

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Iue Observations Of Rw Hydrae (Gm2 + Pec), Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs Jan 1980

Iue Observations Of Rw Hydrae (Gm2 + Pec), Menas Kafatos, A. G. Michalitsianos, R. W. Hobbs

Mathematics, Physics, and Computer Science Faculty Articles and Research

IUE observations of the late type star RW Hya (gM2 + pec) have been obtained. Analysis of the intense UV continuum observed between 1100 and 2000 A suggests that this object is a binary system in which the secondary is identified as the central star of a planetary nebula with Teff 105 K. The ultraviolet spectrum is characterized by semiforbidden and allowed transition lines, of which the C IV (1548 A, 1550 A) doublet is particularly strong. A general absence of strong forbidden line emission suggests that the compact nebula in which both primary and secondary stars are embedded has …

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Ca Ii H And K And Hydrogen-Line Variations In V471 Tauri (=Bd + 16°516), Terry D. Oswalt Apr 1979

Ca Ii H And K And Hydrogen-Line Variations In V471 Tauri (=Bd + 16°516), Terry D. Oswalt

Publications

Spectroscopic and narrow-band photoelectric observations of the white dwarf eclipsing binary V471 Tau (= BD + 16°516) are reported. Periodic fluctuations in Ca IIH and K emission and Ha absorption, and a wave-like distortion of the light curve mimic the characteristics of several well-observed RS CVn binaries. A probable correlation between maximum emission-line strength and wave minimum is shown to exist.

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Sporadic Mass Ejection In Red Supergiants, Menas Kafatos, A. G. Michalitsianos Jan 1979

Sporadic Mass Ejection In Red Supergiants, Menas Kafatos, A. G. Michalitsianos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We have applied a general mechanism first proposed by J. A. Burke to red supergiants for determining the spin-down rate and angular momentum loss of rotating stars. This model relies principally on sporadic mass ejection, which is assumed to be the result of turbulent elements accelerating material in cool supergiant.atmospheres. Mass is preferentially expelled in the forward direction of rotation, resulting in a rapid loss of angular momentum on time scales of 1Q^4-10^6 years in the supergiant evolutionary phase. Such rotational breaking will occur if the turbulent elements have characteristic sizes a few percent of the stellar radius, and rms …

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Mass Loss And Oh Maser Emission From Mira Variables, A. G. Michalitsianos, Menas Kafatos Jan 1978

Mass Loss And Oh Maser Emission From Mira Variables, A. G. Michalitsianos, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

We have estimated the mass, radius, and luminosity of 26 Mira variables that are known OH sources of radio emission at 1612 MHz. The time-independent solution of Salpeter's stellar wind equation and a period-density relation are used to solve for basic stellar parameters, with the aid of the terminal expansion velocity of the OH maser cloud. Masses obtained from these calculations are consistent with other estimated values for masses of Mira variables. Good agreement is obtained when comparing the rate of mass loss as determined from Reimers's semiempirical relation to estimates of the mass loss rate as deduced from theoretical …

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The Central, Compact Source In The Cygnus A Galaxy, Menas Kafatos Jan 1978

The Central, Compact Source In The Cygnus A Galaxy, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Single, optically thin, component models as well as double, optically thick at low frequencies, component models have been examined in trying to explain the central source in the nucleus of Cygnus A. In the course of exploring those models, it is found that this compact radio source may be quite similar to other compact and variable sources in Seyfert galaxies and quasars. Double component models generally do better because they fit the X-rays, and there is a good chance that the X-rays arise in the central source; these models can naturally explain variability which may already have been detected in …

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Cygnus A At 99 Ghz: Observations Of The Three Principal Components And The Interpretation Of The Central Source, R. W. Hobbs, S. P. Maran, Menas Kafatos, L. W. Brown Jan 1978

Cygnus A At 99 Ghz: Observations Of The Three Principal Components And The Interpretation Of The Central Source, R. W. Hobbs, S. P. Maran, Menas Kafatos, L. W. Brown

Mathematics, Physics, and Computer Science Faculty Articles and Research

The three principal emission components of Cygnus A have been observed at 99 GHz, the highest frequency at which radio measurements of this source have been accomplished. The observations show no definite indication of a high-frequency cutoff in the spectrum of the compact central component, which perhaps may be attributed to an optically thin synchrotron source that peaks at a frequency of several hundred GHz.

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"Address To Faculty And Students", Timothy Francis Leary Jun 1977

"Address To Faculty And Students", Timothy Francis Leary

Special Collections: Oregon Public Speakers

Dr. Leary's first speech at Portland State University was ten years prior to this date. The recording of his 1967 talk was stolen from the Portland State library.

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El Viento De Las Estrellas, Aldemaro Romero Jr. Jan 1977

El Viento De Las Estrellas, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

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Sources Of Excitation Of The Interstellar Gas And Galactic Structure, J. J. Cowan, Menas Kafatos, W. K. Rose Jan 1975

Sources Of Excitation Of The Interstellar Gas And Galactic Structure, J. J. Cowan, Menas Kafatos, W. K. Rose

Mathematics, Physics, and Computer Science Faculty Articles and Research

The excitation of the interstellar gas. is discussed in the light of recent evidence from γ-ray, molecular, and 21-cm line observations. Previous studies of the excitation of the interstellar gas have not taken into account the substantial density contrast that exists between spiral arms and interarm regions. We examine the role played by the galactic distribution of three sources of excitation (supernovae, OB stars, and ultraviolet stars) in determining the physical state of the interstellar gas in arm and interarm regions.

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Pole Stars Of Other Planets, Paul C. Sharrah Jan 1975

Pole Stars Of Other Planets, Paul C. Sharrah

Journal of the Arkansas Academy of Science

The north celestial pole of the Earth and the other planets is discussed. Right ascension and declination information on the location of the poles on the celestial sphere is summarized. The name of the brightest visible star near each pole is given and the special case of Uranus is discussed.

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Thermal Instability In Supernova Shells, R. Mccray, R. F. Stein, Menas Kafatos Jan 1975

Thermal Instability In Supernova Shells, R. Mccray, R. F. Stein, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Thermal instability in the radiative cooling region behind a shock will cause upstream density fluctuations to collapse into thin sheets aligned parallel to the shock front. A linearized calculation demonstrates the development of this instability. Thermal conduction suppresses the development of small-scale perturbations. Estimates of the scale sizes for the fully developed condensations agree roughly with the scale sizes of fine structure observed in supernova shells such as the Cygnus Loop.

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Cometa Kohoutek: El Espectáculo Fracasado, Aldemaro Romero Jr. Jan 1974

Cometa Kohoutek: El Espectáculo Fracasado, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

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Nubes De Moléculas Orgánicas En El Espacio, Aldemaro Romero Jr. Jan 1974

Nubes De Moléculas Orgánicas En El Espacio, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

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Ionization Of Carbon And Nitrogen In The Intercloud Medium, Menas Kafatos, H. Gerola, S. Hatchett, R. Mccray Jan 1974

Ionization Of Carbon And Nitrogen In The Intercloud Medium, Menas Kafatos, H. Gerola, S. Hatchett, R. Mccray

Mathematics, Physics, and Computer Science Faculty Articles and Research

If the intercloud medium in the solar neighborhood was suddenly ionized less than 106 years ago, the subsequent relaxation of the gas can account for the very low observed column density of C III and N III yet still leave a significant fraction ("'0.05) of ionized hydrogen and of C I in a cold (T ≈ 20° K) intercloud medium. The OAO-C Copernicus observations in the direction of X Sco are consistent with cosmic abundances and a uniform-density medium, except for C III whose predicted column density from the C m ionization zone surrounding the star is a factor ~1Q …

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Statistical Time-Dependent Model For The Interstellar Gas, H. Gerola, Menas Kafatos, R. Mccray Jan 1974

Statistical Time-Dependent Model For The Interstellar Gas, H. Gerola, Menas Kafatos, R. Mccray

Mathematics, Physics, and Computer Science Faculty Articles and Research

We present models for temperature and ionization structure of low, uniform-density (n ~ 0.3 cm^-3) interstellar gas in a galactic disk which is exposed to soft X-rays from supernova outbursts occurring randomly in space and time. The structure was calculated by computing the time record of temperature and ionization at a given point by Monte Carlo simulation. The calculation yields probability distribution functions for ionized fraction x, temperature T, and their various observable moments. These time-dependent models predict a bimodal temperature distribution of the gas with structure in x, T that agrees with various observations. Cold regions in the low-density …

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Giant Loops As Fossil Stromgren Spheres: Their Radio And X-Ray Emission, Menas Kafatos, P. Morrison Jan 1973

Giant Loops As Fossil Stromgren Spheres: Their Radio And X-Ray Emission, Menas Kafatos, P. Morrison

Mathematics, Physics, and Computer Science Faculty Articles and Research

The loops are examined as radio and soft X-ray sources under the assumption that they are objects related to the Gum Nebula but much older than it. The loop diameters are likely on the scale of 100 pc or more, as reported recently. This is naturally understood with the fossil Stromgen sphere model. Further progress in understanding the origin of the loops depends on the resolution of certain observational issues.

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Time-Dependent Radiative Cooling Of A Hot Low-Density Cosmic Gas, Menas Kafatos Jan 1973

Time-Dependent Radiative Cooling Of A Hot Low-Density Cosmic Gas, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Detailed calculations are presented for the radiative cooling of a hot (10^4 K ≤ T ≤ 10^6 K) interstellar gas. Below 10^6 K such a gas is not in ionization equilibrium because it is cooling faster than it is recombining. The gas is more ionized at a particular temperature and emits harder radiation than a gas in equilibrium at the same temperature. Optical forbidden lines, particularly the [0 II], [0 III] lines, are much stronger than the hydrogen Balmer lines. Hydrogen lines, if observable, would show a Balmer decrement not very different from that of a radiatively excited nebula. Results …

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Interferometric Studies Of Interstellar Calcium Lines, Laurence A. Marschall, L. M. Hobbs Apr 1972

Interferometric Studies Of Interstellar Calcium Lines, Laurence A. Marschall, L. M. Hobbs

Physics and Astronomy Faculty Publications

Interferometric, photoelectric scans of the interstellar calcium K-lines in the spectra of 65 stars are presented. The scans were obtained with a PEPSIOS spectrometer having a passband with a full half-intensity width of 1.0 kms(-1) or 0.013A. The fivefold improvement in resolution over that used by Adams reveals numerous line components which correspond very well to those of the interstellar sodium lines, apart from frequent differences in relative intensities.

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Ua66/12 Hardin Planetarium General Program Schedule, Wku Hardin Planetarium Jan 1971

Ua66/12 Hardin Planetarium General Program Schedule, Wku Hardin Planetarium

WKU Administration Documents

Program schedule for Hardin Planetarium.

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Fossil Stromgren Spheres From Supernova Explosions, Menas Kafatos, P. Morrison Jan 1971

Fossil Stromgren Spheres From Supernova Explosions, Menas Kafatos, P. Morrison

Mathematics, Physics, and Computer Science Faculty Articles and Research

Brandt ci at. have shown that consistency in the combined observations of the Gum Nebula requires a giant H ii region, presumably formed by the Vela X supernova explosion. Mouison and Sartori had concluded on the basis of their He ii fluorescence theory of Type I supernovae that a giant H ii region would be formed as result of the ultraviolet burst. (Bottcher ci at., by integrating over the light curve, expect a smaller H ii region.) We present here in brief some consequences of the fluorescence model as illustrated by the Vela X and the Tycho supernovae. We conclude …

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"Planetary Exploration (Lecture One)", Carl Sagan Mar 1968

"Planetary Exploration (Lecture One)", Carl Sagan

Special Collections: Oregon Public Speakers

No abstract provided.

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Photometry, Arthur G. Barkow May 1932

Photometry, Arthur G. Barkow

Bachelors’ Theses

The preparation of this paper was not undertaken primarily with a view of discussing all types of photometer, but mostly for the investigation of the Ritchie Wedge. As for the first part, the history or resume is brief and somewhat incomplete. In the ensuing pages, no reference is given to the portable photometer, so helpful to illuminating engineers. This was not deemed necessary since the principle involved is similar to those discussed.

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Comets And Meteors, Lincoln N. Oatley Jan 1895

Comets And Meteors, Lincoln N. Oatley

Student and Lippitt Prize Essays

Defines and describes named comets and meteor events and their scientific study.

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The Fixed Stars, John F. Downey Dec 1880

The Fixed Stars, John F. Downey

Journal of the Minnesota Academy of Science

The object of this paper is to give, in a popular form, a brief review of what is known about the fixed stars. Although they have always been objects of interest, have guided the mariner over trackless seas, arid have inspired many sublime and noble thoughts, yet, until a comparatively recent date, only three things were known about them; viz., that they retain (approximately) their ·relative positions, that they are self luminous, and that they are very far away.

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