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The spectroscopic evolution of the symbiotic star AG Draconis. I.The O VI Raman, Balmer, and helium emission line variations during the outburst of 2006-2008 | | S. N. Shore
; G. M. Wahlgren
; K. Genovali
; S. Bernabei
; P. Koubsky
; M. Šlechta
; P. Škoda
; A. Skopal
; M. Wolf
; | | Date: |
10 Dec 2009 | | Abstract: | 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. 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. Using medium and high
resolution groundbased optical spectra and comparisons with archival $FUSE$ and
$HST/STIS$ spectra, we study the evolution of the Raman O VI features and the
Balmer, He I, and He II lines during the outburst from 2006 Sept. through 2007
May and include more recent observations (2009) to study the subsequent
evolution of the source. The O VI Raman features disappeared completely at the
peak of the major outburst and the subsequent variation differs substantially
from that reported during the previous decade. The He I and He II lines, and
the Balmer lines, vary in phase with the Raman features but there is a
double-valuedness to the He I 6678, 7065 relative to the O VI Raman 6825AA
variations in the period between 2006-2008 that has not been previously
reported. The variations in the Raman feature ratio through the outburst
interval are consistent with the disappearance of the O VI FUV resonance wind
lines from the white dwarf and of the surrounding O$^{+5}$ ionized region
within the red giant wind provoked by the expansion and cooling of the white
dwarf photosphere. | | Source: | arXiv, 0912.1890 | | Services: | Forum | Review | PDF | Favorites | |
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