arXiv subjects

L. Dankova

Publications and source records attributed to L. Dankova.

4 recordsLinked to original sources

arXiv2026

BV photometry of the cataclysmic variable LY UMa

We performed B- and V-band photometry of the probable dwarf nova LY UMa. We find that it has apparent magnitude V=15.26+/-0.03 on 2024-04-14, V=15.43+/-0.02 on 2025-04-28, and V = 15.57+/-0.02 on 2025-06-02. Using the GAIA distance d=310pc, we find that the lower values correspond to absolute V band magnitude M_V=7.94-8.10 and indicate that the mass donor of LY UMa is a K7-K8V star with M_V=8.0-8.5. Our B-band measurements show slightly bluer B-V index of LY UMa than that of its donor, consistent with its nature as a cataclysmic variable. Close to LY UMa is the Active Galaxy Nucleus Mrk 153, for which we estimate V=14.81+/-0.03.

astro-ph.SR↗

arXiv2026

BV photometry of the ultracompact binary star GP Com

We present optical B and V band photometry of GP Com - an ultracompact binary consisting of an accreting white dwarf and helium secondary component. Our data set contains 7.7 hours observations in V band with the 2.0m telescope and 2.9 hours simultaneous observations in B and V bands with the 1.5m telescope of the Rozhen National Astronomical Obsevatory, Bulgaria. The observations cover of about 13 orbital periods. We find an orbital modulation with amplitude 0.04-0.05 mag in B and V bands. Adopting that it is due to a bright spot, we estimate its temperature 19700 \pm 3000 K. We estimate mass accretion rate onto the white dwarf of about 2.10^{-12} M_sun/yr, consistent with the predicted rate for a cool donor. The data are available on Zenodo: zenodo.org/records/18768211.

astro-ph.SR↗

arXiv2026

Is Mira B a low mass white dwarf?

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 the period August - October 2025, in the course of the last minimum of the Mira pulsations. The observed peak-to-peak amplitude of the flickering is 0.11-0.28 mag in B band. For the flickering source we find luminosity in the range 0.10-0.46 L_sun. Using the amplitude-flux relation, we estimate an average luminosity of the accretion disc L_d = 0.91 +/- 0.28 L_sun. Assuming that the white dwarf accretes material through Wind Roche Lobe Overflow (WRLOF), we find that Mira B is a low mass white dwarf with M_wd = 0.24 +/- 0.04 M_sun accreting at a rate 6.8x10^{-9} M_sun/yr. This value of the mass is in the range of the extremely low mass white dwarfs. The data are available on Zenodo: zenodo.org/records/18756532

astro-ph.SR↗

arXiv2023

BV photometric observations of the flickering of the dwarf nova RX And

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 at 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 in B band when the star is in faint state (m_V=13.5), but it is considerably lower (less than 0.1 mag) when the star is bright (m_V=10.9). The mass accretion rate in high state is estimated to be $1.2 \times 10^{-9}$ M$_\odot$ yr$^{-1}$. Combining our data and GAIA distances we find for the mass donor in RX~And spectral type K6V-K7V. The data are available upon request from the authors.

astro-ph.SR↗