Search Publications
Mass accretion rate in the jet-driving symbiotic binary MWC 560
Zamanov, R. K.; Marchev, V. D.
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⊙ to 3000 L⊙, corresponding to a mass accretion rate in the range 1 × 10−7 − 2 × 10−6 M⊙ yr−1…
BV Photometric Observations of the Dwarf Novae DX And and AR And
Zamanov, R. K.; Dankova, L.; Kostov, A.
We report photometric observations of the intranight variability of the dwarf novae DX And and AR And in two bands (B and V) on a few nights in late October 2022. The observations are performed with the 50/70 cm Schmidt telescope of the National Astronomical Observatory Rozhen. The results indicate that both stars exhibit intranight variability wi…
BV photometric observations of the flickering of the dwarf nova RX And
Stoyanov, K. A.; Ivanov, V. D.; Minev, M. +3 more
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 with the 50/70~cm Schmidt telescope of the Rozhen National Astronomical Observatory. The observations indicate that the amplitude of the flickering is about 0.5 mag i…
Hα spectroscopy of the recurrent nova RS Oph during the 2021 outburst
Stoyanov, K. A.; Marchev, D.; Zamanov, R. K. +3 more
We report spectroscopic observations of the Hα emission line of the recurrent nova RS~Oph obtained between 2021 August 12 and 2021 August 23 during the recent outburst. On the basis of the sharp P~Cyg profile superimposed onto the strong Hα emission, we estimate that the outflowing velocity of the material surrounding RS~Oph is in the range 32 km …
Ultra-short period contact binaries: restricting the parameters of the primary using Gaia parallax
Kurtenkov, Alexander
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 2MASS photometry to obtain G and J-band absolute magnitudes of 674 red variable stars catalogued as contact binaries in the VSX database. The absolute magnitude of main seq…
UBVRI observations of the flickering of the dwarf nova RX And
Zamanov, R. K.; Nikolov, G.; Georgieva, A. T.
We report observations of the flickering variability of the dwarf nova RX And in five bands (UBVRI) on two nights. On 25 October 2019 the brightness of the star was B≈ 13.8 mag, the amplitude of the flickering was 0.47 mag, and we estimate for the flickering source temperature Tfl = 10700 ± 400 K, and radius Rfl =0.046 ± 0.00…
Global parameters of the W UMa binaries NSVS 3777464, NSVS 5810460 and ASAS J212236+0657.3
Petrov, N.; Kjurkchieva, D.; Popov, V. +1 more
Photometric observations in Sloan filters g', i' of the short-period eclipsing stars NSVS 3777464, NSVS 5810460 and ASAS J212236+0657.3 are presented. Their goal was determination of the targets' parameters by light curve solutions. We found the three targets to be overcontact binaries of W subtype: NSVS 3777464 and NSVS 5810460 undergo partial ec…
Kinematical structure of open clusters within 1 kpc by Gaia
Elsanhoury, W. H.
The work is based on proper motions, radial velocities, and absolute magnitudes of 56 open clusters located within 1 kpc. We classify those as a function of their distances into five groups (Freedman and Diaconis's rule) as well as a double frequency table may be achieved. For these groups, we calculated their velocity ellipsoid parameters VEPs, e…
Gaia DR2 and Serbian-Bulgarian investigations
Damljanović, Goran
On April $25^{th}$ 2018, the second release of the Gaia catalog (DR2) appeared. It is based on 640 days of Gaia satellite observations; GAIA means Global Astrometric Interferometer for Astrophysics. The observing period was August $22^{nd}$ 2014 - May $23^{rd}$ 2016 (1.75 yr or 21 months with some interruptions). The reference epoch is J2015.5 . T…
High-resolution optical spectroscopy of Nova V392 Per
Stoyanov, K. A.; Georgiev, S.; Stateva, I. +1 more
Here we analyze high-resolution spectra of the Nova V392 Per obtained during the 2018 outburst. The Hα and Hβ emission lines show a triple-peak structure with radial velocities of about -2000 km/s, -250 km/s and 1900 km/s respectively. The near infrared spectrum is dominated by the narrow and single-peaked Paschen lines of hydrogen and the O I λ84…