Conveners
Stellar Astrophysics and Interstellar Medium
- Maksym Mohorian
We present a a detailed study of the Double Periodic Variable V4142 Sgr based on photometric and spectroscopic analysis. We re-analized and improved an orbital period of $30.633 \pm 0.002 ~\mathrm{days}$ and a long cycle of $1201 \pm 14 ~\mathrm{days}$. Our spectral analysis reveals H$\alpha$ absorption with a persistent $V \leq R$ asymmetry emission which is considered evidence of a possible...
FUors are young stellar objects characterized by a sudden increase in accretion rate, followed by a slower decline in brightness. Eruptive young stars can sometimes be accompanied by bipolar molecular outflows which can significantly alter the system's environment. Additionally, these energetic processes might represent an important factor in clearing out the environment of the protostar, thus...
Barium stars (Ba stars) have got special spectrum enriched in the elements of the slow neutron-capture process (s-process), created in asymptotic giant branch (AGB) stars. However, these stars have not reached the AGB phase yet, thus they preserve accreted material from an already evolved companion.
In this work, we have studied the elemental abundances of 55 Ba stars, comparing their...
Polarization is an important property of light. It has been regularly detected in scattered light and it could be emitted from the sources with a strong magnetic field (e.g. magnetic cataclysmic binary systems, neutron stars, etc.) and its properties are linked to the internal geometry of a source of radiation and scattering environment. As a consequence, polarimetry complements photometric...
Circumgalactic medium (CGM) has many similarities with interstellar and intergalactic medium yet there are still many questions regarding its nature, inner motion, and interaction with other media. This work is summarizing the general theoretical background of CGM, listing currently available research methods, including computer modeling, and giving a kick-start for future analysis. The main...
In this work we present optical, X-ray, UV photometry, X-ray spectroscopy of dwarf nova Gaia18awg (ASASSN-16le).We report an analysis of photometry, spectroscopy and measurements of physical, orbital characteristics. Gaia18awg is a U Gem + SU Uma dwarf nova system. That system showing non-periodic outbursts and super-outbursts, superhumps during superoutbursts. From Lisnyky (MPC 585) data we...
Stellar flares are the most easily observable manifestations of magnetic activity. With the advent of high precision spaceborn photometry, our knowledge on flares increased significantly. While most of the studies so far focused on simple observables like flare energy or amplitude, here we aim to use all the morphological information encoded in the flare light curves. Using data from the...
Investigating period changes of classical Cepheids through the framework of $O-C$ diagrams provides a unique insight to the evolution and nature of these variable stars. In this work, we carried out the $O-C$ diagram calculation of 148 Galactic Cepheids with century long coverage. In multiple cases we observed peculiar $O-C$ behaviours that indicated the possible presence of a formerly...
The Kepler space telescope observed multiple globular clusters during the K2 mission. These high-quality and continuous measurements constitute a unique opportunity to investigate RR Lyrae stars found in these old clusters. NGC5897 was observed by Kepler in Campaign 15. First, we used Gaia DR2 data to obtain the color-magnitude diagram of the globular cluster. We verified the known RR Lyrae...
Variable stars are stars of variable brightness. This means that their brightness doesn’t remain constant throughout time. Eclipsing variables are binary stars where two stars orbit periodically around their common center of mass. When one of them is situated in front of the other relative to the observer, the total brightness of the system decreases. These brightness variations depend only on...
The main obstacles for low-frequency radio spectroscopy of the interstellar medium lie in the low intensities of studied features and high level of terrestrial interferences. Growing interest to carbon radio recombination lines (RRLs) studies at decametric wavelengths encourage world radio astronomers to search for new methods and hardware which are able to overcome the existing difficulties....
We represent the method of modelling of the HII regions surrounding continuous star-forming regions. The complex "bubble-like" structure of the HII region has been divided into internal and external components. Internal components correspond to the region of free expansion of superwind and the cavity of superwind correspondinly, while the external ones - to a layer of gas, compressed by a...
