Conveners
Stellar astrophysics and interstellar medium
- Roman Akhmetshyn
The presence of circumstellar matter was discovered over 150 years ago through visual observations of emission lines in spectra of B-type stars. This effect is called the Be phenomenon, found only in fast-rotating stars and not yet fully understood. One explanation of the fast rotation is a consequence of mass transfer from a secondary component, which have been hard to reveal because they are...
The shape of the light curve and the time scales of brightness variations are the main defining factors for classification of variable stars. However, different variability mechanisms can produce light curves of similar shape and period, hindering the determination of their origin. I will discuss the origin of TIC 229741985 variability. Based on TESS photometry, the star can be classified...
Our study reports the discovery of ELM WDs as companions to BSS in the Galactic globular cluster NGC 362. We used data from AstroSat’s UVIT, UVOT, Gaia EDR3, and the 2.2 m ESO/MPI telescope to create SEDs for 26 FUV bright member BSSs. Binary-SED fits revealed ELM WDs as binary companions in 12 of the 26 BSSs studied, suggesting that 12 BSSs are post-mass-transfer systems formed through the...
We present the results of photometric CCD observations of the magnetic cataclysmic variable V405 Aurigae obtained using different instruments. We analysed variability of the spin period of the white dwarf in this system using our observations and previously published maxima timings. We confirmed one of the 2 hypotheses of the spin period variability of this system published earlier. This...
"Betelgeuse, a red supergiant star of semi-regular variability, underwent a historical minimum of brightness in February 2020, the Great Dimming. Even though the brightness has returned to the values prior to the Great Dimming by now, it continues to exhibit highly unusual behavior.
Understanding the long-term atmospheric motions of Betelgeuse and its variability could be a clue to the nature...
About 10 % of upper main sequence stars, classified as chemically peculiar (CP) stars have anomalous abundance of chemical elements on their surface layers. A subgroup of hot CP stars with strong abundance of helium have not only a stellar wind, but also a strong magnetic field. The spin-down of these stars is probably caused by angular momentum loss through their magnetic stellar wind.
The galactic chemical evolution (GCE) describes how the composition of a galaxy changes over time. This variation of the interstellar medium is due to the nuclear reactions in stars and supernovae that enrich the interstellar gas with heavy elements, as well as the inflowing gas from the extragalactic space. This field may be the most exciting when we study the history of the Milky Way, being...
This study, the first light curve analysis of BD-02 873, an spectroscopic binary star system, is presented. We obtained spectroscopic data using the Whoppshel spectrograph attached to the 0.8-meter telescope at Ankara University Kreiken Observatory to derive radial velocity. The light curve from the TESS data was combined with the radial velocity measurements and were analyzed using the PHOEBE...
Since 2007, the TUBITAK National Observatory (TUG) has been conducting precise Doppler surveys of G-K giant stars, which have identified several stars with radial velocities between 1 and 10 $kms^{-1}$. Among these stars is HD 10259, which exhibits a radial velocity variation with an amplitude of about 5 $kms^{-1}$ over a period of 550 days. Using the 1.5m RTT150 telescope at TUG and an iodine...
In this study, we present preliminary stellar parameters of HD 60935 using the spectroscopic and photometric data. We obtained medium resolution spectroscopic data using the Shelyak spectrograph attached to the $0.4$-meter telescope at Ankara University Kreiken Observatory. We utilized two methods to derive stellar parameters: the Bayesian Spectral Energy Distribution Model fitting for...
I will report on the optical-radio study of outbursting cataclysmic variable star CRTS J033349.8-282244 in the LADUMA field. The source has extensively been observed with multiple facilities. I will present the results from observations of CRTS J033349.8-282244 done with MeerLICHT, MeerKAT and SAAO telescopes throughout outbursts, super-outbursts and during quiescence. The LADUMA field is...
