Relaxation Oscillations in Red-Giant Envelopes and the Symbiotic Stars

1973 ◽  
Vol 2 (4) ◽  
pp. 198-200 ◽  
Author(s):  
P. R. Wood
Keyword(s):  
Absorption Spectrum ◽  
Light Curves ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Relaxation Oscillations ◽  
Cool Component ◽  
Cool Star ◽  
Red Giant ◽  
Eruptive Behaviour

The spectrum of a symbiotic star consists of an M-type absorption spectrum, a B-type shell spectrum and nebula emission lines, the relative contributions of these three components varying with time. The light curves of the symbiotic stars vary with a semi-regular period typically 200-800 days while larger eruptions occur on a timescale of ~ 3.5 years. Some suggestions which have been advanced to explain the combination spectrum, variability and eruptive behaviour of the symbiotic stars are: (a)the symbiotic stars are binaries consisting of a hot and cool component.(b)the symbiotic stars consist of a single hot star surrounded by a large optically thick envelope giving the appearance of a hot continuum with the absorption spectrum of a cool star superimposed on it.(c)the symbiotic stars are single stars surrounded by a shock wave heated chromosphere.Although some of the symbiotic stars are undoubtedly binaries (for example, T Coronae Borealis), observatienal evidence suggests that others may be explained by hypothesis (c) above. The calculations described below provide an explanation of the symbiotic stars in conjunction with hypothesis (c).

scholarly journals Comparison of Planetary Nebulae and Symbiotic Star Emitting Regions

1983 ◽  
Vol 103 ◽  
pp. 321-322
Author(s):  
C. D. Keyes
Keyword(s):  
Spatial Distribution ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
High Excitation ◽  
Cool Star

The spectra of symbiotic stars generally display many emission lines seen in moderate to high-excitation planetary nebulae, but are superposed upon a strong continuum characteristic of a cool star, typically of type M. Furthermore, the spatial distribution of symbiotics has been noted to resemble that of planetaries. These similarities suggest that the symbiotic stars and planetary nebulae might have some relationship (causal or otherwise) or that they might arise from similar progenitors.

scholarly journals Properties Of Cool Stellar Components in S-Type Symbiotic Stars

1988 ◽  
Vol 103 ◽  
pp. 37-41
Author(s):  
O.G. Taranova ◽  
B.P. Yudin
Keyword(s):  
Spectral Type ◽  
Dust Emission ◽  
Roche Lobe ◽  
Red Giants ◽  
Symbiotic Stars ◽  
Cool Component ◽  
Cool Star ◽  
Type D ◽  
Red Giant

In 1975 Webster and Allen (1975) divided all symbiotic stars into two groups-those in which the 1-4μm continuum show only the presence of a cool star (type S),and those in which dust emission dominates (type D). With the exception of some of yellow symbiotic stars, the dust presence in others correlates with the spectral type of their cool components. That is why one can say that S-type symbiotics contain red giants with spectral type earlier than M6-M7.At the IAU Colloq. N 7Q Allen (1982) noted that it is difficult to escape the conclusion that symbiotic stars contain normal cool giants. Nowadays it is certaiu to be correct because the modern observations of S-type symbiotic stars have not yet discovered any specific distinctions between their cool stellar components and normal red giants. At the same time it should be noted that some of these, for example, Z And, CI Cyg may be interacting binaries in which the cool component apparently fields its Roche lobe and unstable accretion of gas from the red giant onto its hot companion leads to the out bursts of the latter (Kenyon and Webbink 1984; Yudin 1987).

Symbiotic Stars in the Local Group of Galaxies: POINT-AGAPE Catalogue Revisited

2017 ◽  
Vol 14 (S339) ◽  
pp. 291-294
Author(s):  
K. Drozd ◽  
J. Mikołajewska ◽  
M. Darnley ◽  
K. Iłkiewicz ◽  
N. Caldwell ◽  
...  
Keyword(s):  
Light Curve ◽  
Local Group ◽  
Light Curves ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Original Point

AbstractThis research was prompted by the discovery of 35 new or candidate symbiotic stars during a targeted search in the Local Group of Galaxies. A catalogue of a further 200 or so such objects has now been compiled. Many of them could be identified with counterparts in the POINT-AGAPE Catalogue. However, information in the Catalogue is limited to position, brightness and possible period, and light-curves are not available. The poster presented an example of a light-curve of a symbiotic star retrieved from original Point-Agape Catalogue data.

scholarly journals Symbiotic Star as 201: a Planetary Nebula

1987 ◽  
Vol 93 ◽  
pp. 781-784
Author(s):  
L. Kohoutek
Keyword(s):  
Absorption Spectrum ◽  
Mass Loss ◽  
Planetary Nebula ◽  
Optical Spectrum ◽  
Interstellar Extinction ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Cool Stars ◽  
Central Stars

AbstractOptical spectrum of AS 201 is presented: this object shows emission lines of moderate excitation (exc.class 5) and absorption spectrum of a G2III star. For the interstellar extinction and distance the values c=0.45 and d=1.5 kpc were estimated. The hot components of AS 2Ol, Cn 1–1 and M 1–2 are located on the Harman-Seaton sequence in the region of evolved central stars of PN. It is suggested that the hot components of some SS are evolved nuclei of PN; high el.density of their nebulae may be explained due to mass loss from the respective cool stars of the binaries.

scholarly journals X-Ray and Ultraviolet Observations of AG Draconis during Quiescence and Outburst

1987 ◽  
Vol 93 ◽  
pp. 763-763
Author(s):  
A. Cassatella ◽  
F.A. Córdova ◽  
M. Friedjung ◽  
J. Kenyom ◽  
L. Piro ◽  
...  
Keyword(s):  
Orbital Motion ◽  
Uv Light ◽  
Low Energy ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Uv Spectrum ◽  
X Ray ◽  
High Ionization ◽  
Ultraviolet Observations

AbstractWe describe the first X-ray monitoring of a symbiotic star during phases of enhanced activity. AG Dra is a Pop II object with a composite spectrum, characterized by a cool K-type component, prominent high ionization emission lines and a strong UV continuum which is attributed to a hot dwarf companion. Periodic variability of the UV radiation during minimum could be attributed to the orbital motion of the system. In April 1980 HEAO-2 detected an intense, soft X-ray flux from AG Dra, stronger than in other symbiotic stars. After one major outburst of November 1980, which continued until 1983, two more outbursts occurred in February 1985 and January 1986, and coordinated X-ray (EXOSAT) and ultraviolet (IUE) observations were organized to study the behaviour of AG Dra during different activity phases. EXOSAT observations made during decline after the 1985 outburst, revealed a weak X-ray flux in the Thin Lexan filter of the Low Energy dedtector. Observations made during minimum, in June and November 1985, at phases 0.22 and 0.50 of the UV light curve, disclosed the presence of an intense X-ray flux, which was not occulted in November. AG Dra was again observed with EXOSAT in February 1986 when the stellar luminosity was still at maximum. No X-ray flux was detected, in spite of the prominent, high ionization UV spectrum observed with IUE.A detailed discussion of the X-ray and ultraviolet results on AG Dra in the light of possible models is in progress.

scholarly journals Spectral Synthesis of Cool Components of Symbiotic Stars

1992 ◽  
Vol 150 ◽  
pp. 409-410
Author(s):  
Claudio B. Pereira ◽  
Sayd Codina Landaberry
Keyword(s):  
Satisfactory Agreement ◽  
Spectral Synthesis ◽  
Optical Spectra ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Cool Component ◽  
Synthesis Technique ◽  
Solar Abundances

We analyzed the optical spectra of cool component of symbiotic star SY Mus by means of spectral synthesis technique in order to derive the atomic abundances using the Minneart formulae for computing the atmospheric opacities. We obtained a satisfactory agreement between the observed and computed spectra and the resulting abundances were consistent to the solar abundances.

Determination of the term Symbiotic Star

1982 ◽  
Vol 70 ◽  
pp. 225-230
Author(s):  
A. A. Boyarchuk
Keyword(s):  
Spectral Type ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Absorption And Emission ◽  
Long Period ◽  
T Tau Type Stars ◽  
The Common ◽  
T Tau

Symbiotic stars have been studied for many years. But the common determination of the term “symbiotic star” does not exist even now. Merrill (1958) introduced this term in order to emphasize unusual spectral features – absorption TiO bands and emission lines belonging to highly ionized ions.If we look on the eruptive stars spectra we well see absorption and emission features in the spectra of many stars which we cannot certainly consider as symbiotic stars. For example the U Gem type stars have absorption and emission features in their spectra. A similar situation exists in the case of the old novae. The T Tau type stars have many emission lines, and their spectral type corresponds to G-K. Even the long period variables have some emission lines though their spectral type is M. On the other hand, there are also the BQ[]type stars which are characterized by the presence in their optical spectrum of forbidden emission lines and of a rather hot absorption spectrum.

scholarly journals The discovery of Raman lines in NGC 7027

1997 ◽  
Vol 180 ◽  
pp. 130-130
Author(s):  
D. Péquignot ◽  
J.-P. Baluteau ◽  
C. Boisson ◽  
C. Morisset
Keyword(s):  
Raman Scattering ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Broad Emission ◽  
Ngc 7027

Broad emission lines λλ 682.5, 708.2 nm, observed for years in the spectrum of symbiotic stars, have been identified by Schmid (1989) as due to Raman scattering of O VI 103.2, 103.6 nm by H0. In one symbiotic star, van Groningen (1993) detected Raman scattered He II.

scholarly journals Periodic Variations in the Symbiotic Star Spectra

1987 ◽  
Vol 93 ◽  
pp. 713-723 ◽  
Author(s):  
J. Mikolajewska
Keyword(s):  
Emission Line ◽  
Radial Velocities ◽  
Emission Lines ◽  
Symbiotic Star ◽  
Symbiotic Stars ◽  
Line Intensities ◽  
Physical Conditions

AbstractPeriodic variations of emission line intensities and radial velocities in three S-type symbiotic stars: BF Cyg, CI Cyg and AX Per are presented and discussed. The behavior of emission lines is different in these objects and suggests that significant differences in physical conditions and geometry may occur in these seemingly similar systems.

scholarly journals Models for symbiotic stars in the light of the data

1982 ◽  
Vol 70 ◽  
pp. 253-267
Author(s):  
Michael Friedjung
Keyword(s):  
Accretion Disks ◽  
Radial Velocities ◽  
Symbiotic Stars ◽  
Single Star ◽  
Cool Component ◽  
Cool Star ◽  
Star Models ◽  
Excess Heating

AbstractDifferent single and binary models of symbiotic stars are examined. Single star models encounter a number of problems, and binary models are probable. There are however difficulties in the interpretation of radial velocities. Accretion disks play a role in some cases, but winds especially from the cool component must be taken into account in realistic models. There is some evidence of excess heating of the outer layers of the cool component. Outbursts may be related to sudden changes in the characteristics of the cool star wind.

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