Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

We have measured the projected rotational velocities (v sin i) of the mass donors for 29 S-type symbiotic stars (SSs) using high-resolution spectrosc

We have measured the projected rotational velocities (v sin i) in a number of symbiotic stars and M giants using high-resolution spectroscopic observ

Context. T CrB (NOVA CrB 1946) is a famous recurrent nova with a recurrence timescale of 80 years. Aims. We aim to estimate the colours, luminosity, and mass-accretion rate for T CrB (NOVA CrB 1946) during and after the superactive state. Methods. We performed and analysed UBV photometry of the recurrent nova T CrB. Results. For the hot component of T CrB, we find average dereddened colours of (U − B)₀ = −0.70 ± 0.08 and (B − V)₀ = 0.23 ± 0.06, which correspond to an effective temperature of 9400 ± 500 K and an optical luminosity of 40 − 110 L_⊙ during the superactive state (2016–2022). After the end of the superactive state, the hot component became significantly redder, (U − B)₀ ≈ −0.3 and (B − V)₀ ≈ 0.6 in August 2023, and its luminosity decreased markedly to 20 − 25 L_⊙ in April–May 2023, and to 8 − 9 L_⊙ in August 2023. The total mass accreted during the superactive state from 2014 to 2023 is ∼2 × 10⁻⁷ M_⊙. Conclusions. This is a significant fraction of the mass required to cause a thermonuclear runaway (TNR). Overall our results support a model in which a large accretion disc acts as a reservoir with increased accretion rate onto the central white dwarf during disc high states, ultimately leading to a TNR explosion, which now seems to be imminent.

We report observations of the flickering variability of the symbiotic recurrent nova RS Oph at quiescence in five bands (UBVRI). We find evidence of a correlation between the peak-to-peak flickering amplitude (ΔF) and the average flux of the hot component (F_av). The correlation is highly significant, with a correlation coefficient of 0.85 and a p-value of ∼10⁻²⁰. Combining the data from all wavebands, we find a dependence of the type $$\Delta F \propto F_{{\rm av}}^k$$, with power-law index k = 1.02 ± 0.04 for the UBVRI flickering of RS Oph. Thus, the relationship between the amplitude of variability and the average flux of the hot component is consistent with linearity. The rms amplitude of flickering is on average 8 per cent (±2 per cent) of F_av. The detected correlation is similar to that found in accreting black holes/neutron stars and cataclysmic variables. The possible reasons are briefly discussed. The data are available upon request from the authors.

We present spectroscopic observations of the Be/X-ray binary X Per obtained during the period 1999–2018. Using new and published data, we found that during “disc-rise” the expansion velocity of the circumstellar disc is 0.4–0.7 km s⁻¹. Our results suggest that the disc radius in recent decades show evidence of resonant truncation of the disc by resonances 10:1, 3:1, and 2:1, while the maximum disc size is larger than the Roche lobe of the primary and smaller than the closest approach of the neutron star. We find correlation between equivalent width of Hα emission line (Wα) and the X-ray flux, which is visible when 15 Å < Wα ≤ 40 Å. The correlation is probably due to wind Roche lobe overflow.