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A Multiple System iUMA

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    Recent studies indicate that stars are most likely forming within the binary and multiple systems. In our Galaxy, according to various estimates, at least 50 percent of stars have companions. Therefore, the study of binary and multiple stars is important for understanding the mechanisms of star formation in general. During several years we are conducting the observations of such multiple stellar systems at the BTA telescope in order to find their companions and study the properties therein. A speckle interferometer, designed and manufactured at the observatory is used for the observations. This instrument, in particular, can detect companions of stars at the angular scales of up to a hundredth of a second of arc.
    One of the objects in the programme of speckle interferometric observations at the BTA is a quadruple star i Uma. This star is interesting in that it may be a dynamically unstable multiple star, meaning that over time, such systems will split into individual stars. The parameters of orbital motion of the stars in this multiple system were determined, their physical parameters: luminosity, mass, and temperature were computed. The figure shows a detailed image of the star, obtained at the BTA. A bright component is a very tight spectroscopic binary star. Based on these results, we have conducted a mathematical modeling, which showed that with the probability of nearly 100 percent i Uma should break up into individual stars over the time of about one million years. Possible explanations for the phenomenon of the break-up are: either the quadruple system has formed as a result of an approach of two double, previously not bound systems, or as a result of the dynamical evolution of a quadruple system at a loss of stability due to an approach with a massive object.
Zhuchkov R.Ya., Malogolovets E.V., Kiyaeva O.V., Orlov V.V., Bikmaev I.F., Balega Yu.Yu. Astronomical Journal, 2012, Volume 89, Issue 7, p. 568-580.

Contact - Malogolovets E.V.
Fig.1. A speckle image of the star i Uma in the visible range, obtained at the BTA telescope