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We performed optical photometry and spectral observations of the symbiotic stars 4U1954+319 and ZZ CMi. For 4U1954+319 using high-resolution spectra we measure the equivalent widths of diffuse interstellar bands and estimate the interstellar reddening E(B-V)=0.83 +/- 0.09. Using GAIA distances and our photometry, we find (1) absolute V band magnitude of 4U1954+319 M_V=-5.23 +/- 0.08 and that the mass donor is a supergiant of luminosity class Ib, and (2) for ZZ CMi M_V=-0.27 +/- 0.2 and that the mass donor is a giant of luminosity class III., Comment: submitted to Serbian Astronomical Journal

Pre-outburst signal (a decrease of the optical brightness) just before the outburst is clearly detected in the observations of the T CrB obtained before and during the 1946 outburst. A similar decrease is also visible in the light curve of RS Oph during the 2021 outburst. We suppose that this is due to formation of a thick, dense envelope around the white dwarf, and we estimate its size (1000 - 2000 km), mass (5.10$^{-8}$ - 6.10$^{-7}$ M$_\odot$) and average density (5 - 16 g cm$^{-3}$)., Comment: preliminary version

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 and Results: We performed and analysed $UBV$ photometry of the recurrent nova T~CrB. For the hot component of T~CrB, we find average dereddened colours of $(U-B)_0 = -0.70 \pm 0.08$ and $(B-V)_0 = 0.23 \pm 0.06$, which correspond to an effective temperature of $9400 \pm 500$~K and an optical luminosity of $40-110~L_\odot$ during the superactive state (2016-2022). After the end of the superactive state, the hot component became significantly redder, $(U-B)_0 \approx -0.3$ and $(B-V)_0 \approx 0.6$ in August 2023, and its luminosity decreased markedly to $20-25$~$L_\odot$ in April-May 2023, and to $8-9~L_\odot$ in August 2023. The total mass accreted during the superactive state from 2014 to 2023 is $\sim 2 \times 10^{-7}$~M$_\odot$. 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., Comment: Astronomy & Astrophysics (accepted)

We analyze photometric observations of the symbiotic star MWC 560 in B and V bands obtained during the period 1990-2023. We estimate the luminosity and the mass accretion rate of the hot component. We find that the luminosity varies in the range from 200 $L_\odot$ to 3000 $L_\odot$, corresponding to a mass accretion rate in the range $1 \times 10^{-7} - 2 \times 10^{-6} \; M_\odot \; yr^{-1}$ (for a 0.9 $M_\odot$ white dwarf and distance 2217 pc). The optical flickering disappears at mass accretion rate of about $1\times 10^{-6}\; M_\odot \; yr^{-1}$, which sets an upper limit for the short-term variability from accreting white dwarf.

We report photometric observations of the hidden symbiotic star SU Lyn in the optical bands. In five nights we detect a weak flickering in U band with amplitude of about 0.05 magnitudes. No intranight variations are found in B, V, g' and r' bands. This is one more indication that the secondary component is a white dwarf accreting at low accretion rate. We also searched for intranight variability of a dozen related object (RR Boo, RT Boo, AM Cyg, AG Peg, BF Cyg, NQ Gem, StHa190, V627 Cas, XX Oph, FS Cet and Y Gem) in which no variability above the observational errors is detected., Comment: 8 pages, to appear in Bulgarian Astron. Journal

Using TESS photometry and Rozhen spectra of the Be/gamma-ray binaries MWC 148 and MWC 656, we estimate the projected rotational velocity ($ {v} \sin i$), the rotational period (P$_{\rm rot}$), radius (R$_{\rm 1}$), and inclination ($i$) of the mass donor. For MWC 148 we derive P$_{\rm rot} = 1.10 \pm 0.03$~d, R$_{\rm 1}= 9.2 \pm 0.5$~R$_\odot$, $i = 40^\circ \pm 2^\circ$, and $ {v} \sin i =272 \pm 5$~km~s$^{-1}$. For MWC 656 we obtain P$_{\rm rot} = 1.12 \pm 0.03$~d, R$_{\rm 1}= 8.8 \pm 0.5$~R$_\odot$, $i = 52^\circ \pm 3^\circ$, and $ {v} \sin i =313 \pm 3$~km~s$^{-1}$. For MWC 656 we also find that the rotation of the mass donor is coplanar with the orbital plane., Comment: 6 pages, Accepted by Astronomische Nachrichten / Astronomical Notes

Using diffuse interstellar bands (DIBs) at 5780 A, 5797 A and 6613 A, visible in the high resolution spectra, and measuring their equivalent widths, we estimate the interstellar extinction toward seven symbiotic stars. We find $E_{B-V}$= $1.28 \pm 0.10$ for AS 289, $E_{B-V}$= $1.55 \pm 0.10$ for BI Cru, $E_{B-V}$= $0.63 \pm 0.10$ for HD330036, $E_{B-V}$= $0.33 \pm 0.05$ for V2756 Sgr, $E_{B-V}$= $0.30 \pm 0.05$ for V2905 Sgr, $E_{B-V}$= $1.52 \pm 0.11$ for V417 Cen, $E_{B-V}$= $0.81 \pm 0.10$ for PN Sa 3-22. The derived values are in agreement with the extinction through the Galaxy., Comment: Bulgarian Astronomical Journal (accepted)

Using diffuse interstellar bands (DIBs) at 5780 A, 5797 A and 6613 A, visible in the high resolution spectra, and measuring their equivalent widths, we estimate the interstellar extinction toward seven symbiotic stars. We find $E_{B-V}$= $1.28 \pm 0.10$ for AS 289, $E_{B-V}$= $1.55 \pm 0.10$ for BI Cru, $E_{B-V}$= $0.63 \pm 0.10$ for HD330036, $E_{B-V}$= $0.33 \pm 0.05$ for V2756 Sgr, $E_{B-V}$= $0.30 \pm 0.05$ for V2905 Sgr, $E_{B-V}$= $1.52 \pm 0.11$ for V417 Cen, $E_{B-V}$= $0.81 \pm 0.10$ for PN Sa 3-22. The derived values are in agreement with the extinction through the Galaxy., Comment: Bulgarian Astronomical Journal (accepted)

We present spectroscopic observations of the Be/X-ray binary X Per obtained during the period December 2017 - January 2020 (MJD~58095 - MJD~58865). In December 2017 the $H\alpha$, $H\beta$, and HeI 6678 emission lines were symmetric with violet-to-red peak ratio $V/R \approx 1$. During the first part of the period (December 2017 - August 2018) the V/R-ratio decreased to 0.5 and the asymmetry developed simultaneously in all three lines. In September 2018, a third component with velocity $\approx 250$~km~s$^{-1}$ appeared on the red side of the HeI line profile. Later this component emerged in $H\beta$, accompanied by the appearance of a red shoulder in $H\alpha$. Assuming that it is due to an eccentric wave in the circumstellar disc, we find that the eccentric wave appeared first in the innermost part of the disc, it spreads out with outflowing velocity $v_{wave} \approx 1.1 \pm 0.2 $~km~s$^{-1}$, and the eccentricity of the eccentric wave is $e_{wave} \approx 0.29 \pm 0.07$. A detailed understanding of the origin of such eccentricities would have applications to a wide range of systems from planetary rings to AGNs., Comment: MNRAS (accepted)

We present spectroscopic observations of the Be/X-ray binary X Per obtained during the period December 2017 - January 2020 (MJD~58095 - MJD~58865). In December 2017 the $H\alpha$, $H\beta$, and HeI 6678 emission lines were symmetric with violet-to-red peak ratio $V/R \approx 1$. During the first part of the period (December 2017 - August 2018) the V/R-ratio decreased to 0.5 and the asymmetry developed simultaneously in all three lines. In September 2018, a third component with velocity $\approx 250$~km~s$^{-1}$ appeared on the red side of the HeI line profile. Later this component emerged in $H\beta$, accompanied by the appearance of a red shoulder in $H\alpha$. Assuming that it is due to an eccentric wave in the circumstellar disc, we find that the eccentric wave appeared first in the innermost part of the disc, it spreads out with outflowing velocity $v_{wave} \approx 1.1 \pm 0.2 $~km~s$^{-1}$, and the eccentricity of the eccentric wave is $e_{wave} \approx 0.29 \pm 0.07$. A detailed understanding of the origin of such eccentricities would have applications to a wide range of systems from planetary rings to AGNs., Comment: MNRAS (accepted)

Argon plasma torch at atmospheric pressure sustained by travelling electromagnetic surface wave is theoretically studied by means of self-consistent model. The model is based on self-consistently linked kinetic and electrodynamic sets of equations describing both the gas discharge properties and the wave propagation characteristics along the axially inhomogeneous Argon plasma column surrounded by vacuum. A steady-state Boltzmann equation coupled with a collisional radiative model for Argon discharge is numerically solved together with Maxwell s equations for an azimuthally symmetric TM surface wave. The Argon ground state and seven excited states (4s, 4p, 3d, 5s, 5p, 4d, 6s) considered as blocks of levels are taken into account. The axial distributions of wave and plasma characteristics as well as a 3D plot of electron energy distribution function (EEDF) are obtained., See also ADA594770. International Conference on Phenomena in Ionized Gases (31st) (ICPIG) Held in Granada, Spain on 14-19 July 2013, The original document contains color images.