LMC S63: a historical reappraisal of the outburst behaviour of a deeply eclipsing Magellanic symbiotic star

The elemental abundances of symbiotic giants are essential to address the role of chemical composition in the evolution of symbiotic binaries, to map their parent population, and to trace their mass transfer history. However, the number of symbiotic giants with fairly well determined photospheric composition is still insufficient for statistical analyses. This is the third in a series of papers on the chemical composition of symbiotic giants determined from high resolution (R ∼ 50000), near-infrared spectra. Here we present results for 24 S-type systems. Spectrum synthesis methods employing standard local thermal equilibrium analysis and atmosphere models were used to obtain photospheric abundances of CNO and elements around the iron peak (Fe, Ti, Ni, and Sc). Our analysis reveals metallicities distributed in a wide range from slightly supersolar ([Fe/H]∼ +0.35 dex) to significantly subsolar ([Fe/H]∼ −0.8 dex) but principally with near-solar and slightly subsolar metallicity ([Fe/H]∼ −0.4 to −0.3 dex). The enrichment in 14 N isotope, found in all these objects, indicates that the giants have experienced the first dredge-up. This was confirmed in a number of objects by the low 12 C/ 13 C ratio (5-23). We found that the relative abundance of [Ti/Fe] is generally large in red symbiotic systems.

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“…A good example is symbiotic S63 in LMC where C/O ratio seems to grow continuously ( Fig. 14) after active phases (Iłkiewicz et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Chemical abundance analysis of symbiotic giants – III. Metallicity and CNO abundance patterns in 24 southern systems

Gałan

Mikołajewska

Hinkle

et al. 2015

Monthly Notices of the Royal Astronomical Society

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“…Moreover, in some SySt the He i emission line ratios are correlated with the orbital phase (e.g. Iłkiewicz et al 2015), so some SySt can possibly be found in the region occupied by PNe only at certain orbital phase. Furthermore, in some SySt He i lines can be observed only during active phases (e.g.…”

Section: Distinguishing Between Syst and Pnementioning

confidence: 99%

Distinguishing between symbiotic stars and planetary nebulae

Iłkiewicz

Mikołajewska

2017

A&A

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Context. Number of known symbiotic stars (SySt) is still significantly lower than their predicted population. One of the main problems in finding complete population of SySt is the fact that their spectrum can be confused with other objects, such as planetary nebulae (PNe) or dense H ii regions. The problem is reinforced by a fact that in significant fraction of established SySt the emission lines used to distinguish them from other objects are not present. Aims. We aim at finding new diagnostic diagrams that could help separate SySt from PNe. Additionally, we examine known sample of extragalactic PNe for candidate SySt. Methods. We employed emission line fluxes of known SySt and PNe from the literature. Results. We found that among the forbidden lines in the optical region of spectrum, only the [O iii] and [N ii] lines can be used as a tool for distinguishing between SySt and PNe, which is consistent with the fact that they have the highest critical densities. The most useful diagnostic that we propose is based on He i lines which are more common and stronger in SySt than forbidden lines. All these useful diagnostic diagrams are electron density indicators that better distinguishes PNe and ionized symbiotic nebulae. Moreover, we found six new candidate SySt in the Large Magellanic Cloud and one in M81. If confirmed, the candidate in M81 would be the furthest known SySt thus far.

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“…Moreover, in the case of a SySt with a C-rich giant, a weak He ii 4686 line can be also easily buried in the C 2 4737 band. This effect is clearly visible in the spectra of the known SySt LMC S63 taken near the hot component eclipse (Iłkiewicz et al 2015). We maintain, however, that this is a price that the SySt community must be willing to pay to prevent wholesale contamination of extragalactic SySt catalogs with imposters that have nothing to do with SySt.…”

Section: M33sys Jmentioning

confidence: 93%

“…However, the colour changes are larger for larger amplitudes and longer pulsation periods (Mira or LPV variables), and often negligible in low-amplitude semiregular (SR) variables. The orbital variability can be detected only in S-type SySt where the red giant is nonvariable or an SR variable (Gromadzki et al 2013;Iłkiewicz et al 2015). In these SySt, the orbital modulation is best visible in the visual and blue bands while the low amplitude SR pulsations in these SySt dominate in the red bands (in SySt with strong emission lines the SR pulsations are visible only during the orbital minimum).…”

Section: M33sys Jmentioning

confidence: 98%

A survey of the Local Group of galaxies for symbiotic binary stars – I. First detection of symbiotic stars in M33

Mikołajewska

Shara

Caldwell

et al. 2016

Mon. Not. R. Astron. Soc.

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We present and discuss initial selection criteria and first results in M33 from a systematic search for extragalactic symbiotic stars. We show that the presence of diffuse interstellar gas emission can significantly contaminate the spectra of symbiotic star candidates. This important effect forces upon us a more stringent working definition of an extragalactic symbiotic star. We report the first detections and spectroscopic characterisation of 12 symbiotic binaries in M33. We found that four of our systems contain carbon-rich giants. In another two of them the giant seems to be a Zr-enhanced MS star, while the remaining six objects host M-type giants. The high number ratio of C to M giants in these binaries is consistent with the low metallicity of M33. The spatial and radial velocity distributions of these new symbiotic binaries are consistent with a wide range of progenitor star ages.

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LMC S63: a historical reappraisal of the outburst behaviour of a deeply eclipsing Magellanic symbiotic star

Cited by 5 publications

References 64 publications

Chemical abundance analysis of symbiotic giants – III. Metallicity and CNO abundance patterns in 24 southern systems

Chemical abundance analysis of symbiotic giants – III. Metallicity and CNO abundance patterns in 24 southern systems

Distinguishing between symbiotic stars and planetary nebulae

A survey of the Local Group of galaxies for symbiotic binary stars – I. First detection of symbiotic stars in M33

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