Bibcode
Gonçalves, D. R.; Magrini, Laura; de la Rosa, I. G.; Akras, Stavros
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 447, Issue 1, p.993-1000
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2
2015
Citations
19
Refereed citations
17
Description
In this paper we discuss the photometric and spectroscopic observations
of newly discovered (symbiotic) systems in the dwarf spheroidal galaxy
NGC 205. The Gemini Multi-Object Spectrograph on-off band [O III] 5007
Å emission imaging highlighted several [O III] line emitters, for
which optical spectra were then obtained. The detailed study of the
spectra of three objects allows us to identify them as true, likely and
possible symbiotic systems (SySts), the first ones discovered in this
galaxy. SySt-1 is unambiguously classified as a symbiotic star, because
of the presence of unique emission lines which belong only to symbiotic
spectra, the well-known O VI Raman-scattered lines. SySt-2 is only
possibly a SySt because the Ne VII Raman-scattered line at 4881 Å,
recently identified in a well-studied Galactic symbiotic as another very
conspicuous property of symbiotic, could as well be identified as N III
or [Fe III]. Finally, SySt-3 is likely a symbiotic binary because in the
red part of the spectrum it shows the continuum of a late giant, and
forbidden lines of moderate to high ionization, like [Fe V] 4180
Å. The main source for scepticism on the symbiotic nature of the
latter systems is their location in the planetary nebula region in the
[O III]4363/Hγ versus [O III]5007/Hβ diagnostic diagram. It
is worth mentioning that at least another two confirmed symbiotics, one
of the Local Group dwarf spheroidal IC 10 and the other of the Galaxy,
are also misplaced in this diagram.
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