Open Access. Powered by Scholars. Published by Universities.®

Astrophysics and Astronomy Commons™

Open Access. Powered by Scholars. Published by Universities.®

Instrumentation

Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 301 - 313 of 313

Full-Text Articles in Astrophysics and Astronomy

International Ultraviolet Explorer Observations Of The Aquarii Jet, A. G. Michalitsianos, Menas Kafatos Jan 1982

International Ultraviolet Explorer Observations Of The Aquarii Jet, A. G. Michalitsianos, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Ultraviolet spectra were obtained with the International Ultraviolet Explorer of the newly discovered optical-radio jet feature in the symbiotic variable R Aquarii. The far-UV continuum of the jet is characterized by strong continuum which rises with decreasing wavelength in the 1200-2000 A wavelength range and is considerably different in appearance from the relatively flat continuum exhibited by ionized nebulosity in the central star. Prominent Si III] and Si II emission lines seen in the central region are virtually absent in the jet. This could reflect the depletion of silicon in the feature, the result of grain formation in material that …

Go to article

Ultraviolet Spectrum Of The Crab Nebula, K. Davidson, T. R. Gull, S. P. Maran, T. P. Stecher, R. A. Fesen, R. A. Parise, C. A. Harvel, Menas Kafatos, V. L. Trimble Jan 1982

Ultraviolet Spectrum Of The Crab Nebula, K. Davidson, T. R. Gull, S. P. Maran, T. P. Stecher, R. A. Fesen, R. A. Parise, C. A. Harvel, Menas Kafatos, V. L. Trimble

Mathematics, Physics, and Computer Science Faculty Articles and Research

Data from 65 hours of observation of the Crab Nebula with the International Ultraviolet Explorer are reported, together with new ground-based spectrophotometry. We have measured the important C IV λ1549, He II λ1640, and C III] λ1908 emission line intensities and placed upper limits on other ultraviolet features for the brightest filamentary region in the nebula. We have also measured some ultraviolet continuum surface brightnesses at two places in the Crab. The emission lines imply an average ionic abundance ratio n(C^+2)/n(O^+2 ) in the range from 0.4 to 1.5 in the observed gaseous condensations. The elemental abundance ratio of carbon …

Go to article

Uv Emission From The M1 Supergiant Tv Gem, Andrew G. Michalitsianos, Menas Kafatos Jan 1982

Uv Emission From The M1 Supergiant Tv Gem, Andrew G. Michalitsianos, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

Low and high dispersion ultraviolet spectra were obtained of the Ml supergiant TV Gem with IUE. Previous IUE observations of this late type supergiant revealed unexpected W continuum emission, perhaps arising from an early B companion. Low resolution spectra obtained approximately one year apart suggest that the strong Si I11 in-combination perhaps with 0 I at wavelengths % A1300 A varies considerably with time. Large variation the column density is required to explain these changes. Sporadic mass expulsion with mass loss rates dM/dt * 10-5 S y r - l from the M supergiant could lead to a dense circumstellar …

Go to article

Observations And Analysis Of The Aquarii Jet, Menas Kafatos, Andrew G. Michalitsianos Jan 1982

Observations And Analysis Of The Aquarii Jet, Menas Kafatos, Andrew G. Michalitsianos

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

Ultraviolet, optical and radio observations of the symbiotic star R Aquarii are discussed in the light of the discovery of a bright radio and optical jet from this star. The star is probably a binary with a period of 44 years. The VLA maps of the jet reveal a protruding structure extending-10 arc sec from the central radio source with a position angle virtually identical to that of the optical jet observed at Lick. We interpret the observations of R Aqr as indicating the existence of an accretion disk around an unseen companion. The hot subdwarf has effective temperature ,(65,000 …

Go to article

Ci Cygni Since The 1980 Eclipse, R. E. Stencel, Andrew G. Michalitsianos, Menas Kafatos Jan 1982

Ci Cygni Since The 1980 Eclipse, R. E. Stencel, Andrew G. Michalitsianos, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

Following the 1980 eclipse of the 855 day period symbiotic binary CI Cyg, we were confronted with a data set showing high excitation resonance lines which were largely uneclipsed but brightening on an orbital timescale, and intercombination lines exhibiting pronounced but nontotal eclipses and which were fading on an orbital timescale. Our model invoked a low density dissipating nebula surrounding the hot companion to explain the intercombination lines, and a shock between stellar winds to interpret the resonance lines. Subsequent synoptic observations have revealed continuing changes in the W emission line fluxes, consistent with those described above, except for the …

Go to article

Iue Observations And Interpretation Of The Symbiotic Star Rw Hya, Menas Kafatos, Andrew G. Michalitsianos Jan 1981

Iue Observations And Interpretation Of The Symbiotic Star Rw Hya, Menas Kafatos, Andrew G. Michalitsianos

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

IUE observations of the high excitation symbiotic star RW Hya (gM2 + pec) have been obtained. Analysis of the intense UV continuum observed between II00 A to 2000 A suggests this star is a binary system in which the secondary is identified as a hot subdwarf with T _. _I0 D K. We deduce a distance to the system of ~1000 pc. The UV spectrum consists of mainly semi-forbidden and allowed transition lines of which the ClV (1548 A, 1550 A) emission lines are particularly strong, and UV continuum at both shorter and longer wavelengths. Strong forbidden lines seem to …

Go to article

Preliminary Report On Iue Spectra Of Crab Nebula, K. Davidson, T. R. Gull, S. P. Maran, T. P. Stecher, Menas Kafatos, V. L. Trimble Jan 1981

Preliminary Report On Iue Spectra Of Crab Nebula, K. Davidson, T. R. Gull, S. P. Maran, T. P. Stecher, Menas Kafatos, V. L. Trimble

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

The Crab Nebula is marginally observable with the IUE. Observations of the optically brightest filamentary regions, made with IUE in August 1979, show the C IV x1549, He II x1640, and C III] x1909 emission lines. The intensities of these lines have been compared with visual-wavelength data. It appears that carbon is not overabundant in the Crab; carbon/- oxygen is approximately "normal" oxygen is slightly scarcer than "normal" as a fraction of the total mass.

Go to article

Ingress Observations Of The 1980 Eclipse Of The Symbiotic Star Ci Cygni, R. E. Stencel, Andrew G. Michalitsianos, Menas Kafatos, Alexander A. Boyarchuk Jan 1981

Ingress Observations Of The 1980 Eclipse Of The Symbiotic Star Ci Cygni, R. E. Stencel, Andrew G. Michalitsianos, Menas Kafatos, Alexander A. Boyarchuk

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

One of the major results from the IUE may prove to be the new knowledge gained by studies of the ultraviolet spectra of symbiotic stars. Symbiotics combine spectral features of a cool M giant-like photosphere with strong high excitation emission lines of nebular origin, superposed. An excellent pre-UV review has been given by Swings (i). The UV spectra are dominated by intense permitted and semi-forbidden emission lines and weak continua indicative of hot compact objects and accretion disks. Two symbiotics, AR Pay and CI Cyg are thought to be eclipsing binaries, and we have begun IUE observations during the predicted …

Go to article

Iue Observations Of Two Late Type Stars Bx Mon (M4 + Pec) And Tv Gem (M1 Iab), Andrew G. Michalitsianos, R. W. Hobbs, Menas Kafatos Jan 1981

Iue Observations Of Two Late Type Stars Bx Mon (M4 + Pec) And Tv Gem (M1 Iab), Andrew G. Michalitsianos, R. W. Hobbs, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

IUE observations of two late type stars BX Mon and TV Gem have been obtained that reveal the emission properties in the ultraviolet of subluminous companions. Analysis of the continuum emission observed from BX Mon suggests the companion is a middle A III star. High excitation emission lines observed between 1200 A and 2000 A (C IV, Si Ill], C III ) that generally do not typify emission observed in either late M type variables or A type stars are also detected. It is suggested that these strong high-excitation lines arise in a large volume of gas heated by non-radiation …

Go to article

Superbubbles, T. R. Gull, F. C. Bruhweiler, Menas Kafatos, S. Sofia Jan 1981

Superbubbles, T. R. Gull, F. C. Bruhweiler, Menas Kafatos, S. Sofia

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

Individual massive stars with Mbol < -6 have huge stellar winds that create interstellar bubbles. Stars with masses greater than 8Mo (4Mo?) are considered supernova progenitors. These massive stars are numerous in OB associations where few supernova remnants are detected. Model calculations describing the evolution of an association show: i) that large, hot cavities are formed by pushing the ambient gas into neutral shells; 2) that the shell radii change with galactocentric radius, 3) that only thirty percent of the interstellar medium is in the form of supercavities and 4) that a consequence is that only a small fraction of supernovae form supernova remnants. These results have strong bearing on interpretation of interstellar studies being done by IUE and by HEAO-B.

Go to article

Iue Observations Of Circumstellar Emission From The Late Type Variable R Aqr (M7 + Pec), R. W. Hobbs, Andrew G. Michalitsianos, Menas Kafatos Jan 1981

Iue Observations Of Circumstellar Emission From The Late Type Variable R Aqr (M7 + Pec), R. W. Hobbs, Andrew G. Michalitsianos, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Books and Book Chapters

As part of a program to observe circumstellar emission from late type stars, IUE observations of R Aqr (M7 + pec) have been obtained in low dispersion. Strong permitted, semi-forbidden and forbidden emission lines are seen, superimposed on a bright ultraviolet continuum. We deduce that the strong emission line spectrum that involves C III], C IV, Si III], [0 II] and [0 lll] probably arises from a dense compact nebula the size of which is comparable to the orbital radius of the binary system of which R Aqr is the primary star. The low excitation emission lines of Fe II, …

Go to article

El Instituto Nacional De Técnica Aeroespacial, Un Ejemplo De Muchas Cosas, Aldemaro Romero Jr. Jan 1974

El Instituto Nacional De Técnica Aeroespacial, Un Ejemplo De Muchas Cosas, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Go to article

The Spectroscope In Astronomy, W. W. Payne Dec 1880

The Spectroscope In Astronomy, W. W. Payne

Journal of the Minnesota Academy of Science

No abstract provided.

Go to article

First Prev