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We present low-resolution spectropolarimetry for the symbiotic star Z Andromedae at four different epochs during the quiescent phase. The linear polarization of the continuum showed a temporal variation; the difference between the maximum and the minimum is 0.3%–0.6% in Stokes q and is larger with shorter wavelengths. Applying scattering models to this variation, we found the variation in the continuum may be correlated with the orbital motion of the binary and estimated the orbital inclination angle ic = 73 ◦ ± 14 ◦ and the orientation angle Ωc = 80 ◦ ± 5 ◦ . We also confirmed that the intrinsic linear polarization of the Raman line λ683 varies with the orbital phase; from this modulation, the orbital elements were derived as ir = 41 ◦ ± 8 ◦ and Ωr = 82 ◦ ± 2 ◦ . The inclination derived from the continuum has a large error, and the value is larger by twice the error than the inclination angle value derived from the Raman line. The derived orientation, in contrast, is comparable with that derived from the Raman line. The possible inconsistency in the inclination may be due to the simplicity of our adopted model, or it may be caused by a bias effect due to the low quality of the observed continuum polarization data. An accurate estimation of the inclination from the continuum polarization could settle the question, but that estimation requires more frequent observations that cover at least more than a few orbital cycles during the quiescent phase when the observations are not interrupted by the activity of the hot component.

We report on the analysis of high-resolution optical spectra of four symbiotic stars CD-43°14304, Hen 3-863, Hen 3-1213, and StHα176. The chemical composition of the atmospheres of the investigated stars shows that they are all metal-poor K giants with metallicities around [Fe/H] ≈ –1.0. All stars show an enrichment of the elements created by slow neutron-capture reactions. The luminosities obtained for the symbiotic star CD-43°14304 and probably for Hen 3-1213 are below those of the asymptotic giant branch (AGB) stars that started helium-burning (via thermal pulses) and became self-enriched in the neutron-capture elements. Therefore, their abundance peculiarities are due to mass transfer from the previous thermally pulsing AGB star (now the white dwarf), overabundant in s-process elements. For the stars Hen 3-863 and StHα176, the uncertainties due to the distance (and interstellar absorption as well) prevent a reliable determination of the luminosity. The heavy-element abundance distribution of these four analyzed symbiotics is similar to that of the three symbiotics previously analyzed (AG Dra, BD-21°3873, and Hen 2-467). Finally, their general abundance pattern follows the halo standard abundance.

We have used the absolutely calibrated Wing eight-color near-infrared photometric system to quantitatively derive spectral types and luminosity classes for the cool components of 12 symbiotic stars. We examine the advantages and limitations of the system as applied to symbiotic systems. We find that three systems, CI Cyg, T CrB, and S149, have CN strengths corresponding to luminosity class II. For several systems there is a correlation between photometric phase and measured spectral type.

This paper continues the series that identifies new cataclysmic variables found in the Sloan Digital Sky Survey (SDSS). We present 36 cataclysmic variables and one possible symbiotic star from Sloan spectra obtained during 2002, of which 34 are new discoveries, two are known dwarf novae (BC UMa and KS UMa), and one is a known cataclysmic variable identified from the Two-Degree Field survey. The positions, colors, and spectra of all 37 systems are presented, along with follow-up spectroscopic/photometric observations of 10 systems. As in the past 2 yr of data, the new SDSS systems show a large variety of characteristics based on their inclination and magnetic fields, including three eclipsing systems, four with prominent He II emission, and 15 systems showing features of the underlying stars.

We report on the analysis of high-resolution optical spectra of the yellow component of the symbiotic star He2-467. The chemical composition of its atmosphere reveals He2-467 to be a metal-poor K giant with [Fe/H] = -1.1. From a set of 14 Fe I lines, its radial velocity is found to be -106.9 ± 0.5 km s-1. This high velocity plus low metallicity points to He2-467 being a halo star. The K giant in He2-467 is also enriched in the heavy s-process elements. Because its luminosity is below that for an asymptotic giant branch (AGB) star that could have commenced shell helium-burning (via thermal pulses) and become self-enriched in the neutron-capture elements, we ascribe its heavy-element excess to the barium star phenomenon. In this scenario, the secondary component accreted matter from the primary (now the white dwarf) when it was a thermally pulsing AGB star overabundant in s-process elements. The heavy-element abundance distribution of He2-467, as well as its atmospheric parameters, is almost identical to two yellow symbiotics analyzed previously, AG Dra and BD -21°3873. In particular, its neutron exposure parameter, τ, which characterizes the s-process abundance distribution, is larger than for solar metallicities (with a single-exposure τ = 1.1 millibarn-1). Also, analysis of the rubidium abundance in He2-467 reveals that the s-process ratio of N(Rb)/N(Zr) is much larger than for solar metallicity s-process material, indicating that the s-process neutron density is considerably larger at lower metallicities, in agreement with the 13C(α, n)16O neutron source.

We construct a visual light curve of the symbiotic star MWC covering the last 87 years of its history. The data were assembled from the literature and from the AAVSO data bank. Most of the periodic components of the system brightness variation can be accounted for by the operation of three basic clocks of the periods P1 = 19,000 days, P2 = 1943 days, and P3 = 722 days. These periods can plausibly, and consistently with the observations, be attributed to three physical mechanisms in the system: the working of a solar-like magnetic dynamo cycle in the outer layers of the giant star of the system, the binary orbit cycle, and the sidereal rotation cycle of the giant star. MWC 560 is the seventh symbiotic star with historical light curves that reveal similar basic characteristics of the systems. The light curves of all these stars are well interpreted on the basis of the current understanding of the physical processes that are the major sources of the optical luminosity of these symbiotic systems.

Symbiotic stars are key objects in understanding the formation and evolution of interacting binary systems, and are probably the progenitors of Type Ia supernovae. However, the number of known symbiotic stars is much lower than predicted. We aim to search for new symbiotic stars, with particular emphasis on the S-type yellow symbiotic stars, in order to determine their total population, evolutionary timescales, and physical properties. The Two Micron All Sky Survey (2MASS) (J ? H) versus (H ? K s) color-color diagram has been previously used to identify new symbiotic star candidates and show that yellow symbiotics are located in a particular region of that diagram. Candidate symbiotic stars are selected on the basis of their locus in the 2MASS (J ? H) versus (H ? K s) diagram and the presence of H? line emission in the Stephenson & Sanduleak H? survey. This diagram separates S-type yellow symbiotic stars from the rest of the S-type symbiotic stars, allowing us to select candidate yellow symbiotics. To establish the true nature of the candidates, intermediate-resolution spectroscopy is obtained. We have identified the H? emission line source SS?383 as an S-type yellow symbiotic candidate by its position in the 2MASS color-color diagram. The optical spectrum of SS?383 shows Balmer, He I, He II, and [O III] emission lines, in combination with TiO absorption bands that confirm its symbiotic nature. The derived electron density (108-9?cm?3), He I emission line intensity ratios, and position in the [O III] ?5007/H? versus [O III] ?4363/H? diagram indicate that SS?383 is an S-type symbiotic star, with a probable spectral type of K7-M0 deduced for its cool component based on TiO indices. The spectral type and the position of SS?383 (corrected for reddening) in the 2MASS color-color diagram strongly suggest that SS?383 is an S-type yellow symbiotic. Our result points out that the 2MASS color-color diagram is a powerful tool in identifying new S-type yellow symbiotics.

We present an analysis of new and archival photometric and spectroscopic observations of the symbiotic star AG Draconis. This binary has undergone several 1 - 3 mag optical and ultraviolet eruptions during the past 15 years. Our combination of optical and ultraviolet spectroscopic data allow a more complete analysis of this system than in previous papers. AG Dra is composed of a K-type bright giant M(sub g) approximately 1.5 solar mass) and a hot, compact star M(sub h approximatelly 0.4 - 0.6 solar mass) embedded in a dense, low metallicity nebula. The hot component undergoes occasional thermonuclear runaways that produce 2 - 3 mag optical/ultraviolet eruptions. During these eruptions, the hot component develops a low velocity wind that quenches x-ray emission from the underlying hot white dwarf. The photoionized nebula changes its volume by a factor of 5 throughout an eruptin cycle. The K bright giant occults low ionization emission lines during superior conjunctions at all outburst phases but does not occult high ionization lines in outburst (and perhaps quiescence). This geometry and the component masses suggest a system inclination of i approximately 30 deg - 45 deg.

The symbiotic star EG Andromedae has recently been the subject of several studies investigating its wind properties. Late-type giants are usually considered to have winds driven by radiation pressure on dust. Indeed, the derived wind velocity for EG Andromedae is consistent with this model. We point out here that there is no appreciable dust opacity in the wind of EG Andromedae using constraints on extinction limits from International Ultraviolet Explorer (IUE) and far infrared fluxes from Infrared Astronomy Satellite (IRAS). An alternate mechanism must operate in this star. We suggest that the wind can be driven by radiation pressure on molecular lines.

In this note, we show that the ultraviolet and optical spectroscopic variability of this unique symbiotic star can be understood in terms of a time variable collimated stellar wind with a rapid acceleration near the source. Using the radial velocities observed during the ultraviolet bright phase, we find that a variation in the mass loss rate of a factor of ten can explain the ultraviolet spectral changes. The acceleration is far faster than normally observed in radiatively driven stellar winds and may be due to mechanical driving of the outflow from the disk.

We present an analysis of new and existing photometric and spectroscopic observations of the ongoing eruption in the symbiotic star AG Pegasi, showing that this binary has evolved considerably since the turn of the century. Recent dramatic changes in both the UV continuum and the wind from the hot component allow a more detailed analysis than in previous papers. AG Peg is composed of a normal M3 giant and a hot, compact star embedded in a dense, ionized nebula. The hot component powers the activity observed in this system, including a dense wind and a photoionized region within the outer atmosphere of the red giant. The hot component contracted in radius at roughly constant luminosity from 1850 to 1985. Its bolometric luminosity declined by a factor of about 4 during the past 5 yr. Both the mass loss rate from the hot component and the emission activity decreased in step with the hot component's total luminosity, while photospheric radiation from the red giant companion remained essentially constant.

Ultraviolet, optical, and infrared photometry is reported for the symbiotic star AS 296, spanning the first 1200 days of its outburst which began in June 1988. The effects of the outburst were restricted to the wavelength interval 2200

The R Aquarii symbiotic star system is surrounded by a large-scale optical nebula. Observations of the nebular forbidden O III structure are presented and its morphological significance are discussed in context with previously observed small-scale radio-continuum features, which may be related. It is suggested that a precessing accretion disk may explain the global features of both the large-scale optical emission and the small-scale radio emission. Moreover, an accurate position has been determined of the system's Mira, which suggests that a recent theoretical model, yielding an egg-shaped central H II region for symbiotic systems with certain physical parameters, may apply to R Aquarii. The optical position of the 387 d period Mira variable is consistent with previous findings in the radio, that SiO maser emission is far removed from the Mira photosphere.

Optical and ultraviolet spectroscopy of the symbiotic binary BF Cyg obtained during 1979-1988 is discussed. This system consists of a low-mass M5 giant filling about 50 percent of its tidal volume and a hot, luminous compact object similar to the central star of a planetary nebula. The binary is embedded in an asymmetric nebula which includes a small, high-density region and an extended region of lower density. The larger nebula is formed by a slow wind ejected by the cool component and ionized by the hot star, while the more compact nebula is material expelled by the hot component in the form of a bipolar wind. The analysis indicates that disk accretion is essential to maintain the nuclear burning shell of the hot star.