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- Ultraviolet spectra (11)
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Articles 31 - 41 of 41
Full-Text Articles in Instrumentation
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
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 …
Radio And Optical Observations Of The R Aquarii Jet, R. J. Sopka, G. Herbig, Menas Kafatos, A. G. Michalitsianos
Radio And Optical Observations Of The R Aquarii Jet, R. J. Sopka, G. Herbig, Menas Kafatos, A. G. Michalitsianos
Mathematics, Physics, and Computer Science Faculty Articles and Research
VLA observations at 6 cm and Lick Observatory optical plates of R Aquarii indicate the existence of a jetlike feature extending 7" -10" from the central star. A wide field map at 6 cm shows an unresolved compact radio source which lies close to the axis defined by the jet at a distance of ~ 3' from R Aqr. Episodic mass transfer in this symbiotic variable could explain the erratic outbursts that R Aqr is known to undergo. Formation of an accretion disk and the accompanying radio-optical jet may characterize the observed outbursts in this system.
A Brightening Of The Symbiotic Variable Sy Muscae, A. G. Michalitsianos, Menas Kafatos, W. A. Feibelman, G. Wallerstein
A Brightening Of The Symbiotic Variable Sy Muscae, A. G. Michalitsianos, Menas Kafatos, W. A. Feibelman, G. Wallerstein
Mathematics, Physics, and Computer Science Faculty Articles and Research
The symbiotic variable SY Muscae has been observed with IUE in September 1980 and June 1981 and in the photographic region in May 1981. The entire ultraviolet spectrum brightened between September and June by about a factor of 5. The spectrum shows high excitation including emission from N v and high electron density, about 10^10 cm^-3 as determined from various line ratios in the ultraviolet. The optical spectrum is dominated by permitted lines; even [0 m] is very weak again indicating high density in the ionized region. The increase in ultraviolet continuum and line emission may be due to enhanced …
International Ultraviolet Explorer Observations Of The Aquarii Jet, A. G. Michalitsianos, Menas Kafatos
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 …
Iue Observations Of The Peculiar Star Rx Puppis, Menas Kafatos, A. G. Michalitsianos, W. A. Feibelman
Iue Observations Of The Peculiar Star Rx Puppis, Menas Kafatos, A. G. Michalitsianos, W. A. Feibelman
Mathematics, Physics, and Computer Science Faculty Articles and Research
We have obtained the first high-dispersion observations of RX Pup in the wavelength region 1200-2000 A with the International Ultraviolet Explorer. RX Pup has been classified a symbiotic star and has been compared to slow novae as well as to 11 Carinae. The anomalies that we observed in high-excitation lines in RX Pup such as He II, 0 III], C III], C IV, and Si IIIl that show split line profiles, Doppler displaced multiple components, and possible inverse P Cygni profiles inN III] and N IV J suggest dynamic activity in circumstellar material that probably has the form of rings …
Iue Observations And Interpretation Of The Symbiotic Star Rw Hya, Menas Kafatos, Andrew G. Michalitsianos
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 …
Iue Observations Of Two Late Type Stars Bx Mon (M4 + Pec) And Tv Gem (M1 Iab), Andrew G. Michalitsianos, R. W. Hobbs, Menas Kafatos
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 …
Superbubbles, T. R. Gull, F. C. Bruhweiler, Menas Kafatos, S. Sofia
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.
Preliminary Report On Iue Spectra Of Crab Nebula, K. Davidson, T. R. Gull, S. P. Maran, T. P. Stecher, Menas Kafatos, V. L. Trimble
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.
Iue Observations Of Circumstellar Emission From The Late Type Variable R Aqr (M7 + Pec), R. W. Hobbs, Andrew G. Michalitsianos, Menas Kafatos
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, …
Ingress Observations Of The 1980 Eclipse Of The Symbiotic Star Ci Cygni, R. E. Stencel, Andrew G. Michalitsianos, Menas Kafatos, Alexander A. Boyarchuk
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 …