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Luminosity Class of the Symbiotic Stars 4U1954+319 and ZZ CMi
Zamanov, R.; Stoyanov, K. A.; Takey, A. +9 more
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 (DIBs) and estimate the interstellar reddening E(B−V)=0.83 ± 0.09. Using the GAIA distances and our photometry, we find: (1) the absol…
Effective Temperature and the Light Curve Solution of Contact Binary Systems
Filipović, M. D.; Tothill, N. F. H.; Wadhwa, S. +1 more
With an increasing number of contact binary discoveries and the recognition that luminous red novae are the result of contact binary merger events, there has been a significant increase in the number of light curve solutions appearing in the literature. One key element of such solutions is assigning and fixing the effective temperature of the prim…
Independent Analysis of µδ Data of ILS and INDLS Catalogs to Obtain the Spin of the Bright Gaia DR2 Reference Frame
Aleksić, J.; Damljanović, G.; Stojanović, M.
The Gaia DR2 reference frame should be without relative rotation to the quasars (QSOs) and consistent with the International Celestial Reference System (ICRS). For the faint part of DR2 (stars with Gaia magnitude G≥16) that task was done via Gaia's observations of QSOs (G≥17 mag), but the bright DR2 (G≤13 mag) is difficult to validate and it rotat…
Global Parameters of the Newly-discovered W UMa Stars WISEJ004327.7+722407 and WISEJ234557.8+510456
Ibryamov, S.; Kjurkchieva, D.
Photometric observations in g' and i' bands of the newly-discovered W UMa stars WISEJ004327.7+722407 and WISEJ234557.8+510456 are presented. The two targets are with shallow-contact configurations and their components are of G--K spectral type. We found that WISEJ004327.7+722407 is of A subtype while WISEJ234557.8+510456 is of W subtype. The diffe…
New Observations and Transit Solutions of the Exoplanets HAT-P-54b and WASP-153b
Ibryamov, S.; Petrov, N.; Kjurkchieva, D.
We present photometric observations of the newly-discovered transiting exoplanets HAT-P-54b and WASP-153b with the Rozhen 2 m telescope. As a result we improved their periods. The modeling of the new transits led to almost identical values of orbital inclinations and stellar radii to the first published values while the planet radii were slightly …
Anomalous Cepheids Discovered in a Sample of Galactic Short Period Type II Cepheids
Jurkovic, M. I.
We revisited the short period Type II Cepheids (T2Cs), called the BL Herculis (BLHs), in the Galactic Field to derive a homogeneous analysis of their Fourier parameters. Only V-band data were compiled to make sure that it was directly comparable between the known variables of the OGLE-III catalogue and the 59 individual objects classified as short…
Gaia Science Alerts and the Observing Facilities of the Serbian-Bulgarian Mini-Network Telescopes
Damljanovic, G.; Vince, O.; Boeva, S.
The astrometric European Space Agency (ESA) Gaia mission was launched in December 19, 2013. One of the tasks of the Gaia mission is production of an astrometric catalog of over one billion stars and more than 500000 extragalactic sources. The quasars (QSOs), as extragalactic sources and radio emitters, are active galactic nuclei objects (AGNs) who…