The nature of ultraviolet spectra of AG Pegasi and other symbiotic stars: locations, origins, and excitation mechanisms of emission lines

Eriksson, Mattias; Johansson, Sveneric; Wahlgren, G. M.

doi:10.1051/0004-6361:20053396

Cited by 17 publications

(15 citation statements)

References 31 publications

(29 reference statements)

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“…Zanstra temperatures are in the range 90 kK to 110 kK. Eriksson et al (2006) determined WD wind velocities of 120 to 150 km s −1 based on a re-analysis of the IUE high resolution spectra.…”

Section: Introductionmentioning

confidence: 99%

The spectroscopic evolution of the symbiotic star AG Draconis

Shore

Wahlgren

Genovali³

et al. 2010

A&A

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Context. AG Dra is one of a small group of low metallicity S-type symbiotic binaries with K-type giants that undergoes occasional short-term outbursts of unknown origin. Aims. Our aim is to study the behavior of the white dwarf during an outburst using the optical Raman lines and other emission features in the red giant wind. The goal is to determine changes in the envelope and the wind of the gainer in this system during a major outburst event and to study the coupling between the UV and optical during a major outburst. Methods. Using medium and high resolution groundbased optical spectra and comparisons with archival FUS E and HS T/S T IS spectra, we study the evolution of the

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Section: Introductionmentioning

confidence: 99%

The spectroscopic evolution of the symbiotic star AG Draconis

Shore

Wahlgren

Genovali³

et al. 2010

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“…P-Cygni profiles from UV spectroscopy indicate fast outflows and multiple line components indicate various wind domains as emission sources (Eriksson et al 2006). At the same time as the white dwarf seems to accrete matter from the red giant wind at 8.1 × 10 −8 M per year, the overall system loses matter with a speed of 3.3 × 10 −7 M per year (Skopal 2005).…”

Section: Eg Andmentioning

confidence: 99%

“…Eriksson et al (2006) analyzed over 600 UV emission lines in spectra of symbiotic stars and gave origins of formation as well as identifying the atomic process accounting for the population of the corresponding upper level for a majority of the lines. They concluded that a large fraction of relatively narrow Fe II lines present in UV spectra of symbiotic stars are formed by photo excitation by accidental resonance (PAR), a process originally described by Bowen (1935), and sometimes called Bowen-fluorescence.…”

Section: Introductionmentioning

confidence: 99%

“…Subsequently, Johansson (1983) showed that the presence of the conspicuous Fe ii lines due to decays of the y 4 H 11/2 level in the symbiotic stars RR Tel and V1016 Cyg could be explained by pumping of the a 4 F 9/2 −y 4 H 11/2 channel by C iv λ1548.187. To date, Fe ii PAR pumped fluorescence lines have been found in 12 symbiotic stars (Eriksson et al 2006). In some of these, more than 20 Fe ii channels are activated by various strong UV emission lines (Hartman & Johansson 2000;Eriksson et al 2004).…”

Section: Introductionmentioning

confidence: 99%

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

Eriksson

Nilsson

Veenhuizen³

et al. 2007

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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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“…Even if symbiotic stars are smaller by many magnitudes than the AGN, radiation processes observed in the symbiotic stars could also occur in AGNs. One process with a very strong impact on the UV spectrum of symbiotic stars is photoexcitation by accidental resonance (PAR) (Eriksson et al 2006). The most striking effect of the PAR process in symbiotic stars is the large number of strong Fe II fluorescence lines in the 2300−2800 Å region.…”

Section: Introductionmentioning

confidence: 99%

Radiation processes in the Seyfert galaxy NGC 4151

Eriksson

2012

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Aims. The main aim of this work was to investigate if the radiative process photoexcitation by accidental resonance (PAR) is producing Fe II lines in the UV region of NGC 4151. At the same time I searched for collisionally excited Fe II emission. While doing so, the broad line region (BLR), intermediate line region (ILR) and narrow line region (NLR) contributions to the Mg II resonance doublet were also investigated. Methods. The focus was on the 2000 to 3000 Å wavelength region, in which decay from both the collisionally and PAR excited Fe II levels would form emission lines. I examined three archived Space Telescope Imaging Spectrograph (STIS) spectra of NGC 4151. Theoretical spectra based on calculated ranges for possible fluxes of the collisionally excited lines and pumping rates through the Fe II channels were then fitted to the observed spectra Results. I show that the UV region is influenced by PAR and that the Fe II fluorescence lines are clearly needed to explain the spectrum between 2000 to 3000 Å. The best fit of the theoretical spectra to the STIS spectra was obtained by assuming a similar radiation power of Fe + ions and Mg + ions. Conclusions. The PAR is active in the BLR of NGC 4151 and the total power of the Fe II fluorescence is a significant fraction of the total emission in the 2000 to 3000 wavelength region. Therefore it is important to incorporate this in models of NGC 4151 and possibly also in models of other active galactic nuclei. There are also many collisionally excited Fe II lines that are blended by each other and are therefore not individually observable in the NGC 4151 spectra.

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The nature of ultraviolet spectra of AG Pegasi and other symbiotic stars: locations, origins, and excitation mechanisms of emission lines

Cited by 17 publications

References 31 publications

The spectroscopic evolution of the symbiotic star AG Draconis

The spectroscopic evolution of the symbiotic star AG Draconis

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

Radiation processes in the Seyfert galaxy NGC 4151

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