Recurrent Symbiotic Nova T Coronae Borealis before Outburst

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(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 ss varied from similar to 3 to similar to 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 ss 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 lambda 4686 line with a characteristic time-scale of similar to 25 min, the amplitude of variability in the B-band was similar to 0(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, themass ratio q = M-cool/M-hot is an element of [0.5, 0.77], the orbital inclination i is an element of [55 degrees, 63 degrees]. 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.