135 citations · 536 across the 55 of their papers we have counts for
55 papers
H_alpha observations of the Be/X-ray binary MWC 656
R. Zamanov, V. Marchev, K. A. Stoyanov +8
Context. MWC 656 is a Be/X-ray binary identified as an emission-line object, X-ray and radio source and might be a weak gamma-ray source, harbouring an enigmatic secondary componen…
Red giant component of the recurrent nova T Coronae Borealis
R. K. Zamanov, D. Marchev, V. Marchev +5
We performed simultaneous V band photometry and spectroscopic observations of the recurrent nova T CrB and estimate the V band magnitude of the red giant. We find for the red giant…
Interstellar extinction toward MWC 148
R. Zamanov, I. Stateva, J. Marti +2
We analyse high resolution optical spectra of MWC148 (optical counterpart of the gamma-ray source HESS J0632+057) obtained at Observatoire de Haute Provence and Rozhen Observatory.…
Investigation of the Nature of the B[e] Star CI Cam in the Optical Range
E. A. Barsukova, A. N. Burenkov, V. P. Goranskij +10
We report the results of 24 years of photometric and spectroscopic monitoring of CI Cam since its outburst in 1998. In the early years of our research, we identified a system compo…
Evolution of the optical emission lines and the X-ray emission during the super-active stage of T CrB
K. A. Stoyanov, G. J. M. Luna, R. K. Zamanov +6
T CrB is a symbiotic star that experiences nova outbursts every 80~yr. The next, long-anticipated nova outburst should occur during the 2024-2026 period. Here, we present re…
Size of the accretion disc in the recurrent nova T CrB
R. K. Zamanov, K. A. Stoyanov, V. Marchev +7
We present high resolution (0.06 A/px) spectroscopic observations of the recurrent nova T Coronae Borealis obtained during the last 1.5 years (September 2022 -- January 2024), with…
Luminosity class of the symbiotic stars 4U1954+319 and ZZ CMi
R. Zamanov, K. A. Stoyanov, G. Latev +8
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 width…
Symbiotic star T CrB as an extreme SU UMa type dwarf nova
Krystian Ilkiewicz, Joanna Mikolajewska, Kiril A. Stoyanov
T CrB is a symbiotic recurrent nova that exhibits quiescent and active phases between its classical nova eruptions. The statistical properties of these active phases have been poor…
BV photometric observations of the flickering of the dwarf nova RX And
R. K. Zamanov, L. Dankova, M. Moyseev +3
We report photometry of the intranight variability of the dwarf nova RX And in two bands (B and V). The observations are carried out during three nights in November-December 2022 a…
Optical spectroscopy of Be stars: peak separation of Balmer emission lines
R. K. Zamanov, K. A. Stoyanov, S. Y. Stefanov +2
The Be stars display variable optical emission lines originating in the circumstellar disc. Here we analyse high resolution spectroscopic observations of Be stars and the distance…
Mass outflow from the symbiotic binary RS Oph during its 2021 outburst
N. A. Tomov, M. T. Tomova, K. A. Stoyanov +7
RS Oph is a symbiotic recurrent nova containing a massive white dwarf with heavy mass loss during activity. In August 2021, it underwent its seventh optical eruption since the end…
For optical flickering in symbiotic star MWC 560
Dragomir Marchev, Kiril Stoyanov, Vladislav Marchev +5
This study is based on observations of MWC560 during the last two observational seasons (2020/2021 and 2021/2022). Other than looking for flickering we were interested in following…
Optical spectroscopy of the Be/black hole binary MWC656 -- interaction of a black hole with a circumstellar disc
R. K. Zamanov, K. A. Stoyanov, D. Marchev +7
We present new spectroscopic observations of the Be/black hole binary MWC 656 obtained during the period 2015 - 2021. We measure the equivalent width of H (EW), H (…
The hidden symbiotic star SU Lyn -- detection of flickering in U band
R. K. Zamanov, A. Kostov, M. Moyseev +18
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 magni…
The origin of the high-mass X-ray binary 4U 2206+54/BD +53 2790
V. Hambaryan, K. A. Stoyanov, M. Mugrauer +7
Based on the Gaia EDR3 astrometric parameters and our new systemic radial velocity of the high-mass X-ray binary 4U 2206+54/BD+53 2790, we studied the trace back motion of the syst…
SU Lyn -- a transient symbiotic star
Krystian Ilkiewicz, Joanna Mikolajewska, Simone Scaringi +3
SU Lyn is a binary system composed of a white dwarf and a red giant star. Although it is known to be bright and variable at X-ray wavelengths, the optical counterpart of the source…
H-alpha spectroscopy of the recurrent nova RS Oph during the 2021 outburst
R. K. Zamanov, K. A. Stoyanov, Y. M. Nikolov +3
We report spectroscopic observations of the emission line of the recurrent nova RS~Oph obtained between 12 and 23 August 2021 during the recent outburst. On the basis of the s…
The symbiotic binary ZZ CMi: intranight variability and suggested outbursting nature
R. K. Zamanov, K. A. Stoyanov, A. Kostov +9
We present photometric and spectral observations of the symbiotic star ZZ CMi. We detect intranight variability - flickering and smooth variations in U band. The amplitude of the f…
Interstellar extinction toward symbiotic stars
R. K. Zamanov, V. D. Marchev, K. A. Stoyanov
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 ex…
Optical spectroscopy and X-ray observations of the D-type symbiotic star EF Aql
K. A. Stoyanov, K. Iłkiewicz, G. J. M. Luna +6
We performed high-resolution optical spectroscopy and X-ray observations of the recently identified Mira-type symbiotic star EF Aql. Based on high-resolution optical spectroscopy o…
Flickering of the jet-ejecting symbiotic star MWC 560
R. K. Zamanov, S. Boeva, K. A. Stoyanov +4
We analyse optical photometric data of short term variability (flickering) of the accreting white dwarf in the jet-ejecting symbiotic star MWC560. The observations are obtained in…
Intra-night flickering of RS Ophiuchi: III. Modes of quasi-periods in the minute scale and their evolution
Ts. B. Georgiev, R. K. Zamanov, S. Boeva +7
We study the photometric behavior of the recurrent nova RS Oph by 58 monitoring light curves (LCs), taken by 5 telescopes. All LCs show repeating time structures with some quasi-pe…
High-resolution optical spectroscopy of Nova V392 Per
K. A. Stoyanov, T. Tomov, I. Stateva +1
Here we analyze high-resolution spectra of the Nova V392 Per obtained during the 2018 outburst. The H and H emission lines show a triple-peak structure with radial velocities…
An eccentric wave in the circumstellar disc of the Be/X-ray binary X Persei
R. K. Zamanov, K. A. Stoyanov, U. Wolter +7
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 , ,…