Analysis of the Parameters of Pre-Cataclysmic Binaries with sdB-subdwarfs: V1828 Aql

We have investigated the formation of optical radiation and refined the set of parameters for the young pre-cataclysmic binary with an sdB-subdwarf V1828 Aql. We have obtained moderate-resolution spectra with the 6-m BTA telescope and multiband light curves with the Zeiss-1000 telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences. The method of model stellar atmospheres with an accurate allowance for the gravitational and radiative interaction of the components has been used to calculate the optical radiation from the system. We have found that, despite the high temperature of the primary component, \(T_{\textrm{eff}}=41\,200\pm 800\) K, the amplitude of the photometric reflection effects limited by the small sizes of the secondary component does not exceed \(\Delta m_{V}=0\overset{m}{.}16\). The emission features in the HI lines forming on the irradiated part of the surface of the cool star, when added with the absorption lines in the spectrum of the sdB-subdwarfs, weaken them by 10–12\(\%\) and shift them by \(\Delta V_{r}<10\) km s\({}^{-1}\) in a narrow range of phases adjacent to the time of the secondary eclipse. As a result, the distortions of the observed radial velocity curves under the action of reflection effects turn out to be much smaller than the measurement errors and cannot be used to determine the component mass ratio from a model analysis. Therefore, to determine the set of parameters for V1828 Aql, we have used the assumption that the mass of the primary component is close to \(M_{1}=0.47 M_{\odot}\) found previously for a large group of sdB-subdwarfs. Based on our model analysis of the observed spectra and light curves for V1828 Aql, we have estimated the atmospheric parameters of the subdwarf and the fundamental parameters of both components. We have found that using the method of model atmospheres in analyzing the reflection effects reduces the estimate of the radius of the cool star by 20\(\%\) compared to the calculations in the blackbody approximation.