Wind asymmetry imprint in the UV light curves of the symbiotic binary SY Mus

Abstract

Context: Light curves (LCs) of some symbiotic stars show a different slope of the ascending and descending branch of their minimum profile. The origin of this asymmetry is not understood well. Aims: We explain this effect in the ultraviolet LCs of the symbiotic binary SY Mus. Methods: We model the continuum fluxes in the spectra obtained by the International Ultraviolet Explorer at 10 wavelengths, from 1280 to 3080 Å. We consider that the white dwarf radiation is attenuated by $H^0$ atoms, $H^{-}$ ions and free electrons in the red giant wind. Variation in the nebular component is approximated by a sine wave along the orbit as suggested by spectral energy distribution models. The model includes asymmetric wind velocity distribution and the corresponding ionization structure of the binary. Results: We determined distribution of the $H^0$ and $H^{+}$, as well as upper limits of $H^{-}$ and $H^0$ column densities in the neutral and ionized region at the selected wavelengths as functions of the orbital phase. Corresponding models of the LCs match well the observed continuum fluxes. In this way, we suggested the main UV continuum absorbing (scattering) processes in the circumbinary environment of S-type symbiotic stars. Conclusions: The asymmetric profile of the ultraviolet LCs of SY Mus is caused by the asymmetric distribution of the circumstellar matter at the near-orbital-plane area.

9 pages, 9 figures

References in corpus (4)

• Broad H-alpha wings from the optically thin stellar wind of the hot components in symbiotic binaries
• Wind mass transfer in S-type symbiotic binaries II. Indication of wind focusing
• Measuring the orbital inclination of Z Andromedae from Rayleigh scattering
• Photometric search of orbital periods in symbiotic stars

Cited by in corpus (5)

• Wind mass transfer in S-type symbiotic binaries II. Indication of wind focusing
• Wind mass transfer in S-type symbiotic binaries III. Confirmation of a wind focusing in EG Andromedae from the nebular [OIII]λ5007 line
• Wind-mass transfer in S-type symbiotic binaries IV. Indication of high wind-mass-transfer efficiency from active phases
• The emergence of a neutral wind region in the orbital plane of symbiotic binaries during their outbursts
• Density asymmetry and wind velocities in the orbital plane of the symbiotic binary EG Andromedae