Recurrent Symbiotic Nova T Coronae Borealis before Outburst
N. A. Maslennikova, А. М. Татарников, A. А. Татарникова, А. В. Додин, В. И. Шенаврин, М. А. Бурлак, S. G. Zheltoukhov, Ivan A. Strakhov
Abstract
The results of photometric and spectral observations of T CrB obtained in a wide range of wavelengths in 2011–2023 are presented. We use the near-IR light curves to determine a new ephemeris $$JD_{\textrm{min}}=2455828.9+227.55E$$ for the times of light minima when the red giant is located between the observer and the hot component. The flux ratio H $$\alpha$$ /H $$\beta$$ varied from $${\sim}3$$ to $${\sim}8$$ in 2020–2023, which may be due to a change in the flux ratio between the X-ray and optical ranges. It is shown that the value of H $$\alpha$$ /H $$\beta$$ anticorrelates with the rate of accretion onto the hot component of the system. Based on high-speed follow-up observations obtained on June 8, 2023, we detected a variability of the He II $$\lambda 4686$$ line with a characteristic time-scale of $${\sim}25$$ min, the amplitude of variability in the $$B$$ -band was $${\sim}0\overset{\textrm{m}}{.}07$$ . Simulations of the near-IR light curves accounting for the ellipsoidal effect allowed us to obtain the parameters of the binary system: the Roche lobe filling factor of the cool component $$\mu=1.0$$ , the mass ratio $$q=M_{\textrm{cool}}/M_{\textrm{hot}}\in[0.5,0.77]$$ , the orbital inclination $$i\in[55^{\circ},63^{\circ}]$$ . A comparison of the light curve obtained in 2005–2023 with the 1946 outburst template made it possible to predict the date of the upcoming outburst—January 2024.