Abstract
BF Cygni is a classical symbiotic binary. Its optical light curve occasionally shows outbursts of the Z And-type, whose nature is not well understood. During the 2006 August, BF Cyg underwent the recent outburst, and continues its active phase to the present. The aim of this contribution is to determine the fundamental parameters of the hot component in the binary during the active phase. For this purpose we used a high- and low-resolution optical spectroscopy and the multicolour <em>UBV R<sub>C</sub>I<sub>C</sub></em> photometry. Our photometric monitoring revealed that a high level of the star’s brightness lasts for unusually long time of &gt; 7 years. A sharp violet-shifted absorption component and broad emission wings in the Hα profile developed during the whole active phase. From 2009, our spectra revealed a bipolar ejection from the white dwarf (WD). Modelling the spectral energy distribution (SED) of the low-resolution spectra showed simultaneous presence of a warm (&lt; 10 000 K) disk-like pseudophotosphere and a strong nebular component of radiation (emission measure of ~1061 cm<sup>−3</sup>). The luminosity of the hot active object was estimated to &gt; 5−8×10<sup>3</sup> <em>L</em><sub>ʘ</sub>. Such high luminosity, sustained for the time of years, can be understood as a result of an enhanced transient accretion rate throughout a large disk, leading also to formation of collimated ejection from the WD.
Highlights
Symbiotic stars (SSs) are the largest interacting binary systems with known orbital periods in order of years
Assuming that the optical continuum consists of the three basic radiative components of radiation, the resulting flux in the continuum, F (λ), can be expressed as their superposition, F (λ) = FWD(λ) + FN(λ) + FG(λ), (1)
The lower limit of the total hot component luminosity was ∼ 8 100 L, because only a fraction of the burning white dwarf (WD) radiation can be converted to the WSC and the nebular emission
Summary
Symbiotic stars (SSs) are the largest interacting binary systems with known orbital periods in order of years. They consist of a cool giant and a WD accreting from the giant’s wind. As a result the spectrum of SSs consists of three basic components of radiation – two stellar and one nebular. Skopal et al (2013) reported an evidence of highly-collimated bipolar ejection from BF Cyg. Recently, Skopal et al (2013) reported an evidence of highly-collimated bipolar ejection from BF Cyg In this contribution we analyze our optical spectroscopy and U BV RCIC photometry from the current active phase of BF Cyg, with the aim to determine fundamental parameters of the hot component. The SED-fitting analysis was described by Skopal (2005) and Skopal et al, (2011)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
