scholarly journals On the nature of the cool component of MWC 560

2006 ◽  
Vol 463 (2) ◽  
pp. 703-706 ◽  
Author(s):  
M. Gromadzki ◽  
J. Mikołajewska ◽  
P. A. Whitelock ◽  
F. Marang
Keyword(s):  
Cool Component

scholarly journals Molecular Envelopes of Planetary Nebulae and Proto-Planetary Nebulae

1994 ◽  
Vol 140 ◽  
pp. 152-153
Author(s):  
Sun Kwok
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
High Rate ◽  
Radiative Transfer Model ◽  
Spectral Energy ◽  
Transfer Model ◽  
Energy Distributions ◽  
Cool Component ◽  
Dust Envelope ◽  
Peak Energy

As stars evolve up the asymptotic giant branch (AGB), they begin to lose mass at a high rate, and in the process they create extended circumstellar molecular envelopes. Since the transition from AGB to planetary nebula stages is of the order of 1000 yr, the remnant of such molecular envelopes should still be observable in pro to-planetary nebulae (PPN) and planetary nebulae (PN). Recent ground-based survey of cool IRAS sources have discovered ~30 candidates of PPN (Kwok 1992). These sources show the characteristic “double-peak” energy distribution. The cool component is due to the remnant of the AGB dust envelope, and the hot component represents the reddened photosphere. The fact that the two components are clearly separated suggests that the dust envelope is well detached from the photosphere. Radiative transfer model fits to the spectral energy distributions of PPN suggest a typical separation of ~1 arc sec between the dust envelope and the photosphere, and such “hole-in-the-middle” structure can be mapped by millimeter interferometry in CO.

scholarly journals The symbiotics as binary stars

1982 ◽  
Vol 70 ◽  
pp. 231-251
Author(s):  
Mirek J. Plavec
Keyword(s):  
Mass Transfer ◽  
Binary Stars ◽  
Binary Star ◽  
Evolutionary Stage ◽  
Cool Component ◽  
Second Stage ◽  
Star Evolution ◽  
Red Giant ◽  
Helium Star ◽  
Central Stars

AbstractSymbiotic stars have become an important testing ground of various theories of binary star evolution. Several physically different models can explain them, but in each case certain fairly restrictive conditions must be met, so if we manage to identify a definite object with a model, it will tell us a lot about the structure and evolutionary stage of the stars involved. I envisage at least three models that can give us a symbiotic object: I have called them, respectively, the PN symbiotic, the Algol symbiotic, and the novalike symbiotic. Their properties are briefly discussed. The most promising model is one of a binary system in the second stage of mass transfer, actually at the beginning of it: The cool component is a red giant ascending the asymptotic branch, expanding but not yet filling its critical lobe. The hot star is a subdwarf located in the same region of the Hertzsprung-Russell diagram as the central stars of planetary nebulae. It may be closely related to them, or it may be a helium star, actually a remnant of an Algol primary which underwent the first stage of mass transfer. In these cases, accretion on this star may not play a significant role (PN symbiotic).

scholarly journals Molecular Spectroscopy as Diagnostics of Outer Atmosphere of Cool Luminous Stars: Quasi-Static Turbulent Molecular Formation Zone and Stellar Mass-Loss

1988 ◽  
Vol 108 ◽  
pp. 158-166
Author(s):  
Takashi Tsuji
Keyword(s):  
Mass Loss ◽  
Molecular Spectroscopy ◽  
Recent Theory ◽  
Cool Component ◽  
Giant Stars ◽  
Molecular Formation ◽  
Formation Zone ◽  
Thermally Driven ◽  
Molecular Cooling ◽  
Outer Atmosphere

AbstractThe origin of mass-loss in cool luminous stars is still obscure; several known mechanisms such as thermally driven wind, radiation-driven wind(via dust), wave-driven wind etc all have serious difficulties, if examined in the light of recent observations. At the same time, recent observations in the infrared and radio spectral domains revealed that outer envelope of red (super)giant stars has highly complicated spatial and velocity structures, while inner envelope may have new component that had not been recognized before. For example, recent high resolution infrared spectroscopy revealed a possible presence of a quasi-static turbulent molecular dissociation zone somewhere in the outer atmosphere. This new component may represent a transition zone between the warm chromosphere and the huge expanding molecular envelope, and may be a cool component of chromospheric inhomogeneity or a moleclar condensation in a cool corona extended by turbulent pressure. Such a result can be regarded as observational evidence in support of a recent theory of autocatalytic molecular formation by thermal instability due to molecular cooling. Thus, observation and theory consistently show the presence of a new component - quasi-static turbulent molecular formation zone - in outer atmosphere of cool luminous stars, and a possibility of a unified understanding of outer atmospheric structure and mass-loss, in which turbulence may play important role, can be proposed.

scholarly journals The Symbiotic Binary System AG Pegasi

1980 ◽  
Vol 88 ◽  
pp. 535-542 ◽  
Author(s):  
Charles D. Keyes ◽  
Mirek J. Plavec
Keyword(s):  
Binary System ◽  
Emission Lines ◽  
Complete Coverage ◽  
Cool Component ◽  
Relative Contribution ◽  
Photometric Observations

A complete coverage of the spectrum of AG Peg has been obtained between wavelengths 1200 − 7000 A by us, and can be supplemented by IR photometric observations by others. Our IUE observations yield a lower value of E(B-V), about 0.12. The two stellar components are easily recognized, but their characteristics are still rather uncertain.The cool component may be a normal M1.7 III giant, but the temperature and luminosity of the hot star remain largely indeterminate. Firstly, there are no good models for a hot subdwarf, and secondly, it is difficult to determine the relative contribution of the star itself and the surrounding hydrogen cloud.The emission lines observed in the UV have double or triple structure, indicating two or three distinct emitting regions.

scholarly journals Slow and Rapid Changes of the Radial Velocities in the Symbiotic Binary CH Cygni

1988 ◽  
Vol 103 ◽  
pp. 223-224
Author(s):  
A. Skopal
Keyword(s):  
Light Curve ◽  
Orbital Motion ◽  
Radial Velocities ◽  
Cool Component ◽  
Absorption Component ◽  
Middle Position ◽  
Rapid Changes ◽  
Red Wing

In the period 1982–1986, new 98 radial velocities (RVs) were determined (at the figures denoted by □). All spectrograms were obtained at the Toruń Observatory. RVs were measured at the Skalnaté Pleso Observatory. The main results are summarized in the figures 1-3. The phase is determined from the middle position of the hot component eclipse (JD 2 446 272) and from the minima difference observed in U light curve (5700d) (Mikolajewski et al., 1987).Slow changes of the RVs of the absorption components of ionized metals reflect the orbital motion of the hot component only between the phases 0.7 and 0.0. The rapid changes are observed mainly between the phases 0.8 and 0.9. They are created by combination of the emission red wing with the absorption component (Skopal et al., 1987). RVs of the cool component are in antiphase (Tomov and Luud, 1984).

scholarly journals On the role of evaporative wind in precataclysmic binaries (PCB)

1997 ◽  
Vol 180 ◽  
pp. 131-131
Author(s):  
I. Pustylnik ◽  
V. Pustynski
Keyword(s):  
Optical Depth ◽  
Black Body ◽  
Temperature Inversion ◽  
Light Curves ◽  
Gravitational Acceleration ◽  
Cool Component ◽  
First Results ◽  
The Mean ◽  
Absolutely Black Body ◽  
Definition Of

Recently we have started a systematic reevaluation of the existing observational methods of analysis hitherto applied to PCB-s. Here we report the first results of our investigations. The improved Napier's algorithm (Napier, 1968) to model the light curves of PCB (with the aid of the set of our computer programs in Turbo Pascal) is used. The source function is taken either from Sobieski (1965) or Strittmatter (1974). The entire luminosity received from the cool companion is calculated by integration of the emerging radiation over its disk; contributions from the illuminated and unilluminated portions of the disk are accounted for. We assume: a) the validity of the LTE in the photosphere of cool component, b) constancy of the monochromatic to mean absorption coefficient ratio within the photosphere, c) the hot star radiates as the absolutely black body, d) there are no other effects influencing the light curve except for the reflection effect. We have modelled the light curves of EC11575-1845 (Chen et al (1995). The analysis of the temperature distributions in the heated photosphere indicates the occurence of the temperature inversion. To make a rough estimate of physical conditions which can induce generation of evaporative wind we have used two criteria: i) the temperature inversion, ii) relation between radiative pressure and the effective gravitational acceleration. We assumed the density varies with the height in the atmosphere of the illuminated star as ρ ≃ exp(−Φ/RgT), Φ - being the Roche potential. The integral equation following from the definition of the mean optical depth was solved numerically to establish the relation between the mean optical depth and the distance in the atmosphere. We find the characteristic height scale for X-ray and EUV radiation is ∼ 106 − 107cm (for concentration of particles ∼ 1013cm−3). To check the validity of the ii) criterium we used a simplified model of radially expanding evaporative stellar wind and mass flux J conservation condition along the stream tube of the form J ∼ ρsvsrs2 exp −(Φ/RgT) (Pustylnik (1995)) and found M ∼ 10−12–10−11M/y. Although mass loss of such a rate cannot compete with the effects of the angular momentum loss which is responsible for a secular orbital shrinkage, the evaporative wind should significantly alter the structure of the the cool irradiated components.

scholarly journals Lithium Abundance and Activity for 57 Rs Cvn Systems

1993 ◽  
Vol 137 ◽  
pp. 657-657
Author(s):  
Liu Xuefu ◽  
Zhao Gang ◽  
Tan Huisong ◽  
Lu Fangjun
Keyword(s):  
Model Atmosphere ◽  
Spectral Lines ◽  
High Signal ◽  
Activity Levels ◽  
Lithium Abundance ◽  
Cool Component ◽  
Rs Cvn Stars ◽  
Metal Abundance ◽  
Line Analysis

AbstractHigh-resolution (0.145A/diode, high signal-to-noise (> 100) Reticon spectra of 57 RS CVn systems, which were observed with the coudé spectrographs of the McDonald 2.1m telescope and Yunnan lm telescope, were used to analyse a correlation between Li abundance and chromospere activity. Li abundances of 57 RS CVn stars, which include 76 detected components have been determined through the determination of equivalent widths of Li doublet (6707.761A + 6707.912A) and Kuruz’s model atmosphere. The model metal abundance and line analysis of 10 RS CVn stars were determined from the present spectral lines data. The main results are the following: 1, Lithium abunances of 76 RS CVn components for 57 RS CVn systems are obviously reduced with the the effective temperatures gradually decreasing. 2, Li abundance has staistically decreasing trend in RS CVn stars with the rotational velocities vsini increasing. 2, The position of 168 RS CVn stars in the (U-B, B-V) Figure show that they can be devided into two groups. The most of them seem to be not poor-metal stars. Li abundances of these stars seem to have no obious correlations with their stellar chromosphery activity levels, but 7 RS CVn systems, in which cool component is more active show that the more active component has a lower Li abundance.

scholarly journals Magnetic Reconnection as the Origin of Galactic Ridge X-Ray Emission

1998 ◽  
Vol 188 ◽  
pp. 269-270 ◽  
Author(s):  
S. Tanuma ◽  
T. Yokoyama ◽  
T. Kudoh ◽  
K. Shibata ◽  
R. Matsumoto ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Galactic Plane ◽  
Thermal Emission ◽  
Mhd Equations ◽  
Magnetic Islands ◽  
Cool Component ◽  
X Ray ◽  
Hot Plasma ◽  
Helical Tubes

We present a scenario for the origin of the hot plasma in our Galaxy, as a model of a strong X-ray emission (LX(2 – 10keV) ~ 1038 erg s−1), called Galactic Ridge X-ray Emission (GRXE), which has been observed near the Galactic plane. GRXE is thermal emission from hot component (~ 7 keV) and cool component (~ 0.8 keV). Observations suggest that the hot component is diffuse, and is not escaping away freely. Both what heats the hot component and what confines it in the Galactic ridge are still remained puzzling, while the cool component is believed to be made by supernovae. We propose a new scenario: the hot component of GRXE plasma is heated by magnetic reconnection, and confined in the helical magnetic field produced by magnetic reconnection or in the current sheet and magnetic field. We solved also the 2-dimensional magnetohydrodynamic (MHD) equations numerically to study how the magnetic reconnection creates hot plasmas and magnetic islands (helical tubes), and how the magnetic islands confine the hot plasmas in Galaxy. We conclude that the magnetic reconnection is able to heat up the cool component to hot component of GRXE plasma if the magnetic field is localized into intense flux tube with Blocal ~ 30 μG (the volume filling factor of f ~ 0.1).

scholarly journals Elemental Abundances in Symbiotic Stars

1993 ◽  
Vol 155 ◽  
pp. 402-402
Author(s):  
H.M. Schmid ◽  
H. Nussbaumer
Keyword(s):  
Binary Systems ◽  
Carbon Star ◽  
Molecular Data ◽  
Diagnostic Tools ◽  
Cool Component ◽  
Elemental Abundances ◽  
Mira Variable ◽  
Different Types ◽  
Red Giant ◽  
Late Stages

Symbiotic objects are related to planetary nebulae in that they represent late stages of stellar evolution. They are interacting binary systems where a hot companion star ionizes the stellar wind of a red giant. This configuration offers the unique possibility for deriving elemental abundances for cool giants from a nebular spectrum with the diagnostic tools employed for HII regions. The analysis can be applied to different types of symbiotic systems having a G, K or M giant, a Mira variable or a carbon star as cool component. The great advantage of this technique is, that it does not depend on stellar parameters or molecular data, and that it can therefore be used as a test or an alternative for the traditional photospheric abundance determinations.

scholarly journals More on the pulsation period of the cool component in the symbiotic binary AG Dra

2003 ◽  
Vol 400 (2) ◽  
pp. 595-598 ◽  
Author(s):  
M. Friedjung ◽  
R. Gális ◽  
L. Hric ◽  
K. Petrík
Keyword(s):  
Pulsation Period ◽  
Cool Component
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