V1898 Cygni: An interacting eclipsing binary in the vicinity of North America nebula

Abstract

We present spectroscopic observations of the double-lined early type eclipsing binary V1898\,Cyg. The radial velocities were obtained by means of the cross-correlation technique. Analyses of the BV light curves and RVs led to determination of the fundamental stellar parameters of the V1898\,Cyg's components. We derived new ephemerides for the eclipsing pair using the observed times of mid-eclipses. The residuals between the observed and computed times of mid-eclipses were analysed and a rate of the period change $\dot{P}/P= 6.68 \times 10^{-7}\,yr^{-1}$ was obtained. The orbital period is increased by about 0.38 s in the last 24 years due to the mass transfer from less massive secondary to the more massive primary star with an amount of $1.88\times10^{-7}\,$ \Msun in a year, assuming conservative case. Results of the light and radial velocity curves' analyses were combined and the physical parameters of the components were revealed. The absolute parameters for the stars are derived as: M$_1$=6.054$\pm$0.037 M$_{\odot}$, M$_2$=1.162$\pm$0.011 M$_{\odot}$, R$_1$=3.526$\pm$0.009 R$_{\odot}$, R$_2$=2.640$\pm$0.010 R$_{\odot}$, T$_{eff_1}$=18\,000$\pm$600 K, and T$_{eff_2}$=6\,200$\pm$200 K. We have calculated the distance to the system of V1898\,Cyg as 501$\pm$5 pc using the infrared JHK magnitudes and bolometric corrections for the primary star. While the more massive star locates in the main-sequence band the less massive secondary appears in the giant branch which is common in the classical Algols. Any attempt for comparison with current stellar evolution models was made because the system seems in the phase of fast mass transfer. Moreover, the components of the system's proper motions present some indications about membership of the North America nebula.