2005A&A...440..239B -
Astronomy and Astrophysics, volume 440, 239-248 (2005/9-2)
The spectroscopic orbits and other parameters of the symbiotic binary FN Sgr.
BRANDI E., MIKOLAJEWSKA J., QUIROGA C., BELCZYNSKI K., FERRER O.E., GARCIA L.G. and PEREIRA C.B.
Abstract (from CDS):
We present a study of the eclipsing symbiotic binary FN Sgr with a period of 568.3 days determined photometrically and confirmed spectroscopically. The hot component underwent a 2.5mag eruption covered by most of our spectroscopic observations. In particular, we have determined for the first time spectroscopic orbits based on the radial velocity curves for both components. A set of blue absorption lines resembling an A-F type star is present in all our spectra and they seem to be associated with the hot component. Based on the light curve, we derive the red giant's radius (140R☉) and the orbital inclination (i=80°). We find that FN Sgr is similar to other S-type symbiotic binaries, composed by an M 5-type giant (Mg=1.5M☉) and a hot white dwarf (Mh=0.7M☉, Rh=0.2R☉) with a binary separation of ∼1.6AU. The red giant is just filling its Roche lobe and a geometrically and optically thick accretion disk is likely to be present around the low-mass accretor. The evolution of Th and Lh along the active phase argues in favour of accretion disk instabilities similar to those of Z And. We have also studied spectral changes and photometric variations as a function of both the hot component activity and the orbital motion.
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Journal keyword(s):
stars: binaries: eclipsing - stars: binaries: symbiotic - stars: fundamental parameters - stars: individual: FN Sgr
Simbad objects:
7
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