Observational studies of the symbiotic stars. III High-dispersion IUE and H-alpha observations of EG Andromedae

Oliversen, N. A.; Anderson, Christopher M.; Slovak, M. H.; Stencel, R. E.

doi:10.1086/163404

Cited by 35 publications

(42 citation statements)

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“…The quiescent symbiotic star EG And ( HD 4174) is well documented in the literature (e.g., Smith 1980;Stencel 1984;Oliversen et al 1985;Skopal et al 1991;Vogel et al 1992;Vogel 1993;Munari 1993;Tomov 1995;Wilson & Vaccaro 1997) and is considered a prototype for stable, nondusty symbiotic stars. Indeed, it was observed extensively with IUE, where the ultraviolet eclipse effect was used to study the dimensions and wind of the giant star ( Vogel 1991;Vogel et al 1992).…”

Section: Eg Andmentioning

confidence: 98%

EG And:Far Ultraviolet Spectroscopic ExplorerandHubble Space TelescopeSTIS Monitoring of an Eclipsing Symbiotic Binary

Crowley

Espey

McCandliss

2008

ApJ

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We present highlights and an overview of 20 FUSE and HST STIS observations of the bright symbiotic binary EG And. The main motivation behind this work is to obtain spatially resolved information on an evolved giant star in order to understand the mass-loss processes at work in these objects. The system consists of a low-luminosity white dwarf and a mass-losing, nondusty M2 giant. The ultraviolet observations follow the white dwarf continuum through periodic gradual occultations by the wind and chromosphere of the giant, providing a unique diagnosis of the circumstellar gas in absorption. Unocculted spectra display high-ionization features, such as the O vi resonance doublet, which is present as a variable (hourly timescales), broad wind profile, which diagnose the hot gas close to the dwarf component. Spectra observed at stages of partial occultation display a host of low-ionization, narrow absorption lines, with transitions observed from lower energy levels up to $5 eVabove ground. This absorption is due to chromospheric/wind material, with most lines due to transitions of Si ii, P ii, N i, Fe ii, and Ni ii, as well as heavily damped H i Lyman series features. No molecular features are observed in the wind acceleration region despite the sensitivity of FUSE to H 2 . From analysis of the ultraviolet data set, as well as optical data, we find that the dwarf radiation does not dominate the wind acceleration region of the giant and that observed thermal and dynamic wind properties are most likely representative of isolated red giants.

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Section: Eg Andmentioning

confidence: 98%

EG And:Far Ultraviolet Spectroscopic ExplorerandHubble Space TelescopeSTIS Monitoring of an Eclipsing Symbiotic Binary

Crowley

Espey

McCandliss

2008

ApJ

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“…The mass function determined by us is much smaller than the value determined by Oliversen et al (1985),which leads to detached configuration. If our elements are real, the cool component easily overflows the Roche lobe.…”

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confidence: 61%

“…The cool component is an M3 III star, the hot one is a subdwarf with temperature 60 250 K and luminosity 1.45 L» (Boyarchuk, 1985). The eclipsing nature of the system suggested from UV spectroscopy by Oliversen et al (1985) was confirmed photometrically by . The circular spectroscopic orbit of cool component determined by Oliversen et al_Xl985) supposing the orbital period 470 days leads to f(m) « 3.2x10~ M g and detached.configuration.…”

mentioning

confidence: 78%

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Photometric and Spectroscopic Variations of the Symbiotic Star EG Andromedae

Skopal

Chochol

Vittone

et al. 1988

International Astronomical Union Colloquium

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EG And is a symbiotic binary system. The cool component is an M3 III star, the hot one is a subdwarf with temperature 60 250 K and luminosity 1.45 L» (Boyarchuk, 1985). The eclipsing nature of the system suggested from UV spectroscopy by Oliversen et al. (1985) was confirmed photometrically by . The circular spectroscopic orbit of cool component determined by Oliversen et al._Xl985) supposing the orbital period 470 days leads to f(m) « 3.2x10~ M g and detached.configuration.The UBV photometry of EG And was obtained in 1985-87 by 0.6 m telescope at Skalnate" Pleso Observatory. The differential photometry Am = m(EG And) -m(HD 3914) in U colour is presented in Pig. 1. Our observations cover two recent minima, which occured in 1985 and 1986-87. The eclipse is most pronounced in U colour. The details about UBV photoelectric observations of EG And are in the paper of , where orbital period 480 days was suggested. The phase in Pig. 1 was computed using the period 481.7 days, which we obtained from spectroscopic observations. Therefore a new ephemeris for minima is:JD . -2 446 336.7 + 481.7 days x E .(1) min As it is possible to see on Pig. 1, the descending branch of the minimum is steeper than the ascending one, that could be caused by an elliptical orbit. This conclusion has been confirmed from spectroscopic elements.The spectroscopic observations of EG And have been carried out at Asiago Astrophysical Observatory in 1966-69, 1972, 1978, 1983. Altogether 20 spectra were obtained by 1.22 m telescope with a prism spectrograph with dispersion of 6 nm/mm at Ha-. Two spectra with a dispersion 1.8 nm/mm were obtained by 2m telescope at Ondrejov Observatory in 1976, two spectra with the same dispersion were obtained by 0.9m telescope at Torun Observatory in 1986. We measured radial velocities of neutral metals to obtain information about the motion of cool component. The data are presented in Pig. 2, where also the 289

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“…(6)). Oliversen et al (1985) measured the expansion velocity of the common envelope to be 74 km s −1 . Using this velocity in Eq.…”

Section: Eg Andmentioning

confidence: 99%

Modeling of C IV pumped fluorescence of Fe II in symbiotic stars

Eriksson

Nilsson

Veenhuizen³

et al. 2007

A&A

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Aims. We describe how the C iv λ1548.18 line pumps the 1548.20 and 1548.41 Å channels of Fe ii in symbiotic stars through the process known as photo-ionization by accidental resonance (PAR). We describe where and why Fe ii fluorescence arises in symbiotic stars and whether the Fe ii λ1548.41 channel can only be activated when there is a white-dwarf wind present in the system. Further, we aim to show how an analysis of the PAR-pumped lines helps to understand the phyisical conditions that they manifest.Methods. We calculate intensities of the C iv-pumped Fe ii fluorescence lines in symbiotic stars, corresponding to the y 4 H 11/2 and w 2 D 3/2 levels, based on a simple geometrical model of the emitting regions. We apply the model to seven symbiotic stars, known to have Fe ii fluorescence lines pumped by C iv in their spectra. We compare the predicted intensities to the observed intensities of the selected symbiotic stars. Results. We find that we can reproduce the observed fluorescence intensities of the seven symbiotic stars in our sample, using parameters that are consistent with their known properties. We show that PAR-produced lines can be used as a diagnostic tool to derive important physical parameters of a stellar system. We suggest that the detection of Fe ii lines corresponding to the w 2 D 3/2 level in certain symbiotic stars provide evidence of hot shells expanding with velocities of at least hundreds km s −1 in those systems.

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Observational studies of the symbiotic stars. III High-dispersion IUE and H-alpha observations of EG Andromedae

Cited by 35 publications

References 0 publications

EG And:Far Ultraviolet Spectroscopic ExplorerandHubble Space TelescopeSTIS Monitoring of an Eclipsing Symbiotic Binary

EG And:Far Ultraviolet Spectroscopic ExplorerandHubble Space TelescopeSTIS Monitoring of an Eclipsing Symbiotic Binary

Photometric and Spectroscopic Variations of the Symbiotic Star EG Andromedae

Modeling of C IV pumped fluorescence of Fe II in symbiotic stars

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