81 citations · 243 across the 23 of their papers we have counts for
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Is Mira B a low mass white dwarf?
R. K. Zamanov, V. Irincheva, B. Spassov +8
We report photometric observations in Johnson B and V bands of the short term variability (flickering) of Mira (omicron Ceti). The observations were performed during 7 nights in th…
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…
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…
A Long-Term Spectral Study of the Single Active Giant OP Andromedae
Stefan Georgiev, Renada Konstantinova-Antova, Ana Borisova +10
We present a spectral study of the single magnetically active K giant OP And in the period 1979 -- 2018, monitoring the variability of the activity indicator line H. Original da…
Ultra-short period contact binaries: restricting the parameters of the primary using Gaia parallax
Alexander Kurtenkov
Possible M-type contact binaries were investigated by selecting W UMa-type variables with orbital periods below the 0.22-day cutoff. Gaia parallaxes were combined with Gaia and 2MA…
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…
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…
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…
The observed temperature distribution of contact binaries derived from SDSS photometry
Alexander Kurtenkov, Mirela Napetova
Data from the VSX, SDSS DR12, and Gaia DR2 catalogs were combined in order to explore the observed temperature distribution of known contact binaries. Color-temperature relations w…
Optical flickering of the symbiotic star CH Cyg
K. A. Stoyanov, J. Marti, R. Zamanov +6
Here we present quasi-simultaneous observations of the flickering of the symbiotic binary star CH Cyg in U, B and V bands. We calculate the flickering source parameters and discuss…
Searching for twins of the V1309 Sco progenitor system: a selection of long-period contact binaries
Alexander Kurtenkov
The only well-studied red nova progenitor (V1309 Sco) was a contact binary with a 1.4-day period. The prospects for searching for similar systems, as well as stellar merger candida…
Improved proper motion determinations for 15 open clusters based on the UCAC4 catalog
Alexander Kurtenkov, Nadezhda Dimitrova, Alexander Atanasov +1
The proper motions of 15 nearby (d < 1 kpc) open clusters were recalculated using data from the UCAC4 catalog. Only evolved or main sequence stars inside a certain radius from the…
The January 2015 outburst of a red nova in M31
Alexander Kurtenkov, Peter Pessev, Toma Tomov +19
M31N 2015-01a (or M31LRN 2015) is a red nova that erupted in January 2015 -- the first event of this kind observed in M31 since 1988. Very few similar events have been confirmed as…