Extended variability of the symbiotic star AG Draconis

Kafatos, Menas; Meier, Steven R.; Martin, Ian

doi:10.1086/191751

Cited by 6 publications

(3 citation statements)

References 18 publications

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“…The continuum level was considerably higher in the 1980/1981 outburst (SWP 11002, SWP 15709) than in the 1985/1986 outburst (SWP 27542). N v, C IV, and He II are the strongest emission lines in both active and quiescent states, while Si III] and C III] are always weak or absent, consistent with a high-density nebula (10 10 ~ ne ~ 10 11 cm-3 ) (Kafatos, Meier, & Martin 1993).…”

Section: Ag Draconismentioning

confidence: 68%

A far-ultraviolet atlas of symbiotic stars observed with IUE. 1. The SWP range

Meier

Kafatos²,

Fahey

et al. 1994

ApJS

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This atlas contains sample spectra from the far-ultraviolet observations of32 symbiotic stars obtained with the ln~ernational Ultraviolet Exp~orer (IUE) satellite. In all.; 394 low-resolution spectra from the short-wavelength pnmary (SWP) camera c?venng the range 1200-2000 A have been extracted from the IUE archive, calibrated, and measured. Absolute hne fluxes and wavelengths for the prominent emission lines have been tabulated. Tables of both the general properties of these symbiotics and of features specific to the spectrum of each are included The spectr~ shown are repres~nt~tive of the different classes of symbiotic stars that are currently in the IUE archive. These mclude kn?wn echpsmg systems and those that have been observed in outburst (as well as quiescence).

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Section: Ag Draconismentioning

confidence: 68%

A far-ultraviolet atlas of symbiotic stars observed with IUE. 1. The SWP range

Meier

Kafatos²,

Fahey

et al. 1994

ApJS

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“…Kafatos et al (1993) and González-Riestra et al (1999) have performed extensive studies of variability in the ultraviolet spectral region. There are many studies of optical spectra available, some of which we will refer later.…”

Section: Introductionmentioning

confidence: 99%

Emission lines in the spectrum of the symbiotic star AG Draconis from 1997 to 2003

Leedjärv

Burmeister

Mikołajewski

et al. 2004

A&A

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Abstract. The halo symbiotic star AG Dra has been monitored spectroscopically at the Tartu Observatory, Estonia, from September 1997 to March 2003. Altogether 189 spectra are used in the present paper. In addition, photometric UBVri observations at the Piwnice Observatory, Poland, from March 1996 to May 2003 are presented. Equivalent widths (EW) of the strongest emission lines (Hα, Hβ, He  λ 4686, O  Raman scattered λ 6825) appear to be strongly variable, and in general, correlate with the U brightness of the star. No apparent correlation with the orbital motion of the binary system was found, except for Hβ in the quiescent state. At the same time, there is a clear convergence of the high values of EW to certain phases according to the shorter photometric period (378.5 days) proposed by Bastian (1998) and the pulsational period of the cool giant (355.27 days) by Gális et al. (1999). Higher resolution spectra show variability of the Hα profiles, with weak absorption component on the blue wing of the line around photometric minimum if the star is in quiescent state. The significant role of the cool giant in the activity of AG Dra is discussed.

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“…In many of the studies, International Ultraviolet Explorer ( IUE ) spectra have been used. HM Sge (see Feibelman 1982; Schmid & Schild 1990; Nussbaumer & Vogel 1990; Wallerstein et al 1991) and AG Dra (Wallerstein et al 1991; Kafatos, Meier & Martin 1993; Mikolajewska et al 1995) are among the sources in which Bowen lines are definitely formed. In total, such lines have been detected or are suspected in about 15 symbiotic systems.…”

Section: Introductionmentioning

confidence: 99%

Bowen fluorescence lines in symbiotic stars -- I. Observational data, line ratios and efficiency

Pereira

Araújo

Landaberry

1999

Monthly Notices of the Royal Astronomical Society

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Spectroscopic observations have been taken for eight type‐D symbiotic systems in the spectral regions λλ3100–4100 and λλ3700–5700. We show that the O iii permitted lines formed by the O1 and O3 Bowen processes are definitely present in these objects. In this paper the data have been used to calculate ratios of lines arising from the same upper level. The results indicate that the intermediate‐coupling radiative rates calculated by Froese Fischer are the most accurate for O iii Bowen fluorescence lines. The efficiencies of the Bowen mechanism for both processes are derived. In spite of the relatively small size of our sample, we find that the efficiencies increase with the fractional abundance of ionized helium and electronic density, but decrease with electron temperature, confirming previous results from studies of planetary nebulae.

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Extended variability of the symbiotic star AG Draconis

Cited by 6 publications

References 18 publications

A far-ultraviolet atlas of symbiotic stars observed with IUE. 1. The SWP range

A far-ultraviolet atlas of symbiotic stars observed with IUE. 1. The SWP range

Emission lines in the spectrum of the symbiotic star AG Draconis from 1997 to 2003

Bowen fluorescence lines in symbiotic stars -- I. Observational data, line ratios and efficiency

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