* Astronomy

Title: The low-mass interacting binary system OO Aql revisited: a new quadruple system
Authors: Tugçe çli, Dolunay Koçak, G. Cisem Boz, Kadri Yakut

In this study we present photometric and spectroscopic variation analysis and orbital period study of a low-mass interacting system OO Aql. Simultaneous solution of the light and radial velocity curves provide us a determination of new set of stellar physical parameters for the primary and the secondary companion as M_{1} = 1.05(2) solar masses, M_{2} = 0.89(2) solar masses, R_{1} = 1.38(2) solar radii, R_{2} = 1.28(2) solar radii, \log{(L_1/L_{\odot})} = 0.258 and \log{(L_2/L_{\odot})} = 0.117 and the separation of the components were determined a = 3.333(16) solar radii. Newly obtained parameters yield the distance of the system as 136(8) pc. Analyses of the mid-eclipse times indicate a period increase of \frac{P}{\dot{P}}=4 x 10^{7} yr that can be interpreted in terms of the mass transfer \frac{dM}{dt}=5 x 10^{-8} solar masses/yr from the less massive component to the more massive component. Our new solution confirmed that OO Aql is a multiple system in the form of AB + C + D. We found initial astrophysical parameters for the component of the system and its current age to be 8.6 Gyr using nonconservative stellar evolution model (EV-TWIN code).

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