scholarly journals Variable, Optically Thick, Hot Plasma Observed in Interacting Binaries

1984 ◽  
Vol 80 ◽  
pp. 281-286
Author(s):  
Y. Kondo ◽  
G. E. McCluskey ◽  
S. B. Parsons
Keyword(s):  
Binary Systems ◽  
Ultraviolet Spectra ◽  
Hot Plasma ◽  
International Ultraviolet Explorer

AbstractWe report recent International Ultraviolet Explorer (IUE) observations of two interacting binaries, R Arae and HD 207739. The ultraviolet spectra indicate the presence of optically-thick, variable hot plasma in those binary systems. These two binaries may belong to a class of binaries that are currently undergoing a rarely observed and probably short-lived phase in their evolution. Their properties are compared with those of two other interacting binaries, U Cephei and ß Lyrae.

scholarly journals IUE Ultraviolet Spectra of the Interacting Binary U Cephei

1980 ◽  
Vol 88 ◽  
pp. 237-241
Author(s):  
Yoji Kondo ◽  
George E. McCluskey ◽  
Robert E. Stencel
Keyword(s):  
High Resolution ◽  
Ultraviolet Light ◽  
Stellar Evolution ◽  
Binary Systems ◽  
Light Curves ◽  
Close Binary ◽  
Eclipsing Binary ◽  
Ultraviolet Spectra ◽  
International Ultraviolet Explorer ◽  
Far Ultraviolet

The eclipsing binary U Cephei has proven to be of great interest in the study of stellar evolution in close binary systems. Batten (1974), Hall and Walter (1974), Rhombs and Fix (1976), Markworth (1977), and Olson (1978), among others, have recently reported on their intensive ground based studies of U Cephei. Kondo, McCluskey and Wu (1978) have investigated the ultraviolet light curves of U Cephei obtained with Astronomical Netherlands Satellite (ANS). Kondo, McCluskey and Stencel (1979) have discussed the International Ultraviolet Explorer (IUE) spectra of U Cephei. This paper discusses results incorporating additional IUE high resolution spectra of U Cephei obtained in both far-ultraviolet and mid-ultraviolet spectral regions.

scholarly journals High Temperature Structure in Cool Binary Stars

1996 ◽  
Vol 152 ◽  
pp. 141-145
Author(s):  
A.K. Dupree ◽  
N.S. Brickhouse ◽  
G.J. Hanson
Keyword(s):  
High Temperature ◽  
Binary Stars ◽  
Binary Systems ◽  
Emission Measure ◽  
Temperature Structure ◽  
Differential Emission Measure ◽  
Absolute Size ◽  
Hot Plasma ◽  
Short Period ◽  
Different Temperatures

Strong high temperature emission lines in the EUVE spectra of binary stars containing cool components (Alpha Aur [Capella], 44ι Boo, Lambda And, and VY Ari) provide the basis to define reliably the differential emission measure of hot plasma. The emission measure distributions for the short-period (P ≤ 13 d) binary systems show a high temperature enhancement over a relatively narrow temperature region similar to that originally found in Capella (Dupree et al. 1993). The emission measure distributions of rapidly rotating single stars 31 Com and AB Dor also contain a local enhancement of the emission measure although at different temperatures and width from Capella, suggesting that the enhancement in these objects may be characteristic of rapid rotation of a stellar corona. This feature might be identified with a (polar) active region, although its density and absolute size are unknown; in the binaries Capella and VY Ari, the feature is narrow and it may arise from an interaction region between the components.

scholarly journals UV Properties of Symbiotic Stars

1983 ◽  
Vol 6 ◽  
pp. 641-642
Author(s):  
M. Kafatos
Keyword(s):  
Accretion Disk ◽  
Binary Systems ◽  
Main Sequence ◽  
Main Sequence Star ◽  
Symbiotic Stars ◽  
International Ultraviolet Explorer ◽  
Type Variable ◽  
Far Ultraviolet

Symbiotic stars are suspected to be binary systems of large dimensions in which one star is a cool primary giant (regular M-giant or Mira-type variable) and the secondary a hot subdwarf (Boyarchuk 1982) or even a main-sequence star with an accretion disk around it (Bath and Pringle 1982). Observations of symbiotic stars in the far ultraviolet with the “International Ultraviolet Explorer” (IUE) enable us to determine the properties of the system in the binary picture. A number of critical observations are needed to do this including an estimate of the photoionizing radiation and the temperature of the photoionizing source.

Detection of binary systems from their ultraviolet spectra

1992 ◽  
Vol 3 (1) ◽  
pp. 73-80
Author(s):  
S. S. Rustambekyan
Keyword(s):  
Binary Systems ◽  
Ultraviolet Spectra

scholarly journals Observations of Interstellar Molecules with the International Ultraviolet Explorer

1980 ◽  
Vol 87 ◽  
pp. 257-260
Author(s):  
John H. Black
Keyword(s):  
Positive System ◽  
Early Type ◽  
Interstellar Molecules ◽  
Ultraviolet Spectra ◽  
International Ultraviolet Explorer ◽  
Early Type Stars

The ultraviolet spectra of 25 early-type stars have been obtained with the International Ultraviolet Explorer observatory. Bands of the 4th-positive system of interstellar C0 are seen towards 12 of these stars. Spectra of HD46223 have been examined for interstellar lines of CH, C2, CH2, OH, HC1, and H2O.

scholarly journals Flare in Late-type Stars: UV

1995 ◽  
Vol 151 ◽  
pp. 136-145
Author(s):  
P. Brendan Byrne
Keyword(s):  
Continuous Monitoring ◽  
Interactive Mode ◽  
Stellar Flares ◽  
Hot Plasma ◽  
International Ultraviolet Explorer ◽  
Mode Of Operation ◽  
Optical Continuum ◽  
Stellar Chromosphere ◽  
Direct Confirmation ◽  
Limited Sensitivity

Early studies of stellar flares were made entirely in the optical regime. It was recognised that flares arose from the generation of hot plasma within the stellar chromosphere at whose temperature (indicated, for instance, by the presence of a strong, blue optical continuum) a substantial emission in the ultraviolet would be expected. It was not until the advent of space-borne instruments of adequate sensitivity, however, that direct confirmation of this prediction was forthcoming. In this review I examine some results of more than a decade of observation of stellar flares in the UV.The major source of ultraviolet data on stellar flares has been the International Ultraviolet Explorer (IUE) satellite (Boggess et al. 1979). In order to understand the limitations of our current understanding in this area it is important to appreciate some of the characteristics of its instrumentation. IUE’s telescope is of 40 cm aperture and it is equipped with a spectrograph which can operate at two resolutions, i.e. Δλ/λ ∼350 (LORES) and ∼17000 (HIRES). Its detectors are optimised for operation in two wavebands, i.e. ∼1150-1950Å (SW) and ∼1950-3200 Å (LW). IUE’s small apert ure results in a limited sensitivity, a consequence of which is a modest time resolution when studying stellar flares (a long exposure time is needed to gain adequate signal-to-noise). IUE’s elliptical 24-hour quasi-geosynchronous orbit and its resulting interactive mode of operation make continuous monitoring feasible, a feature suiting flare star work.

scholarly journals Ultraviolet Spectroscopy of Cometary Comae

1989 ◽  
Vol 116 (1) ◽  
pp. 139-148
Author(s):  
Paul D. Feldman
Keyword(s):  
Vacuum Ultraviolet ◽  
Hubble Space Telescope ◽  
Sounding Rocket ◽  
Ultraviolet Astronomy ◽  
Ultraviolet Spectra ◽  
International Ultraviolet Explorer ◽  
Ultraviolet Observations ◽  
Comet Halley ◽  
Imaging Spectrograph ◽  
Cometary Comae

AbstractDuring the past decade, vacuum ultraviolet spectra of over 30 comets have been obtained with the International Ultraviolet Explorer (IUE) satellite observatory. With few exceptions, the spectra of these comets appear to be similar, with OH and H produced by the photodissociation of water being the dominant species and emissions of C, O, S, CS and CO+2 usually present. Although signs of variability of many kinds in comet spectra appear, the evidence from the ultraviolet observations suggests that all comets have the same basic chemical composition and that observed differences are due to evolution and ageing processes. The principal exception is S2, which was detected by IUE in comet IRAS-Araki-Alcock (1983 VII), but not in any other comet to date. During the 1985–86 apparition of comet Halley, ultraviolet spectra were also obtained by other spacecraft and by sounding rocket instruments, including a long-slit imaging spectrograph. Further advances await future ultraviolet observations of comets by the Hubble Space Telescope and other planned ultraviolet astronomy missions.

Characteristics of the AM Herculis Type Stars and Review of proposed Interpretations

1979 ◽  
Vol 46 ◽  
pp. 63-64
Author(s):  
S. Tapia
Keyword(s):  
Binary Systems ◽  
Thermal Emission ◽  
Heated Surface ◽  
Close Binary System ◽  
Gravitational Energy ◽  
Close Binary ◽  
Polar Caps ◽  
Hot Plasma ◽  
Cyclotron Emission ◽  
Cooling Effects

Consider a close binary system where mass transfer is underway from a relatively normal star to a highly magnetic degenerate dwarf. The magnetic field is strong enough that the magnetic pressure balances the ram pressure of the infalling plasma at a distance comparable with the separation of the two stars. Under these conditions accretion takes place along the magnetic lines of force, channeling the inflow of plasma towards the magnetic polar caps. Confined to a narrow column the plasma develops a standing shock at some distance above the surface of the degenerate dwarf. Due to its gravitational energy the infalling plasma can reach very high temperatures below the shock, then very efficient cooling effects ensue. Most of our information on such binary systems will be contained in cooling mechanisms involving radiation.Current theoretical trends identify three sources of radiation linked to the accretion column: 1) electron-ion bremsstrahlung in the hot plasma below the shock, 2) thermal emission from the heated surface of the degenerate dwarf, around the magnetic polar caps, and 3) optically thick electron cyclotron emission.

scholarly journals Ultraviolet Spectroscopic Measurements of Cool Stars

1980 ◽  
Vol 5 ◽  
pp. 263-276 ◽  
Author(s):  
A. K. Dupree
Keyword(s):  
Binary Systems ◽  
Stellar Atmospheres ◽  
Late Type ◽  
Near Ultraviolet ◽  
International Ultraviolet Explorer ◽  
Cool Stars ◽  
Late Type Star ◽  
Far Ultraviolet ◽  
Low Dispersion ◽  
Balloon Measurements

A vast increase in the amount of information on cool stars has occurred during the past 3 years starting with the spectroscopy of the brightest objects from the Princeton experiment on Copernicus, the near ultraviolet balloon measurements from BUSS, low dispersion observations in the far ultraviolet from rocket instruments, and most recently, spectra from the International Ultraviolet Explorer satellite (IUE). IUE now gives access to a wide variety of cool stars and stellar systems enabling systematic studies to be made.Drawing on the most recent material from IUE, we discuss the presence and structure of chromospheres and coronae in single stars of varying gravities, surface temperatures, and activity. Evidence of mass loss and the concurrent presence of a corona are also noted. Binary systems of late-type stars (the RS CVn and W UMa type) are briefly discussed since they display extremes of surface activity. A binary system such as VV Cep containing a late-type star and an early-type companion provides a unique probe of cool extended stellar atmospheres.

scholarly journals Ultraviolet Spectroscopy of Binary Systems

1980 ◽  
Vol 88 ◽  
pp. 39-52 ◽  
Author(s):  
A. K. Dupree ◽  
L. Hartmann ◽  
J. C. Raymond
Keyword(s):  
Stellar Wind ◽  
Binary Systems ◽  
Stellar Atmospheres ◽  
Ultraviolet Spectroscopy ◽  
X Rays ◽  
Large Numbers ◽  
International Ultraviolet Explorer

The recent launch of the International Ultraviolet Explorer (IUE) satellite and its spectrographic instruments (Boggess et al. 1978a,b) suddenly made accessible large numbers of diverse types of binary systems. These range from the luminous hot supergiants with compact companions that produce copious amounts of X-rays to the dwarf solar like stars of W UMa-type. For systems such as these and many others the IUE is a new and unique tool with which to probe the structure of extended stellar atmospheres, the presence and acceleration of a stellar wind, and the appearance of stellar chromospheres and coronae.

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