arXiv subjects

J. Supíková

Publications and source records attributed to J. Supíková.

3 recordsLinked to original sources

arXiv2026

Cluster characteristics of Galactic open clusters

Star clusters are perfectly suited for studying the formation, evolution, and dynamics of stars and their host galaxies. For this, we need to estimate total masses, radii and shapes of star clusters. These parameters strongly influence their fates in the host galaxies. However, there is no agreement about these characteristics in the literature. The published values widely disagree. We estimated total masses and cluster radii using a very conservative approach: calculating member masses and summing them. Furthermore, we investigated the three-dimensional characteristics of open clusters and their limitations. We used a commonly used grid of evolutionary tracks for different photometric sources, including 2MASS, Gaia, and Pan-STARRS. The interpolation method was tested using synthetic clusters built with ASteCA. To estimate three-dimensional shapes, we used the distribution of the well-known Galactic coordinates and inverse parallaxes. We estimated the total masses and radii of about 7000 open clusters and observed traces of tidal tails. Individual values can be used in future $Gaia$ data releases to obtain even more precise values. The current DR3 allows the study of only three-dimensional shapes up to 500 pc. Beyond this distance, we find a significant needle-like shape due to uncertainties in observed parallaxes.

astro-ph.GA↗

arXiv2024

Chemically peculiar stars on the pre-main sequence

Context. The chemically peculiar (CP) stars of the upper main sequence are defined by spectral peculiarities that indicate unusual elemental abundance patterns in the presence of diffusion in the calm, stellar atmospheres. Some of them have a stable local magnetic field of up to several kiloGauss. The pre-main-sequence evolution of these objects is still a mystery and contains many open questions. Aims. We identify CP stars on the pre-main sequence to determine possible mechanisms that lead to the occurrence of chemical peculiarities in the (very) early stages of stellar evolution. Methods. We identified likely pre-main-sequence stars by fitting the spectral energy distributions. The subsequent analysis using stellar spectra and photometric time series helped us to distinguish between CP and non-CP stars. Additionally, we compared our results to the literature to provide the best possible quality assessment. Results. Out of 45 candidates, about 70 % seem to be true CP stars or CP candidates. Furthermore, 9 sources appear to be CP stars on the pre-main sequence, and all are magnetic. We finally report a possible CP2 star that is also a pre-main-sequence star and was not previously in the literature. Conclusions. The evolution of the peculiarities seems to be related to the (strong) magnetic fields in these CP2 stars.

astro-ph.SR↗

arXiv2021

A case study of ACV variables discovered in the Zwicky Transient Facility survey

Magnetic chemically peculiar (mCP) stars exhibit complex atmospheres that allow the investigation of the interplay of atomic diffusion, magnetic fields, and stellar rotation. A non-uniform surface distribution of chemical elements and the non-alignment of the rotational and magnetic axes result in the variability of several observables. Photometrically variable mCP stars are referred to as alpha2 Canum Venaticorum (ACV) variables. The present work presents a case study of known variables from the Zwicky Transient Facility (ZTF) survey, with the aim of investigating the survey's suitability for the detection and study of new ACV variables. Using suitable selection criteria based on the known characteristics of ACV variables, candidate ACV stars were selected from the ZTF Catalog of Periodic Variable Stars. All light curves were inspected in detail to select the most promising candidates. Where available, low-resolution spectra from the LAMOST were employed to classify the stars on the MK system and confirm their status as mCP stars. We have identified 86 new promising ACV star candidates. 15 of these stars have LAMOST spectra available, which, in all cases, confirm them as classical mCP stars, which highlights the viability of our approach. The sample stars can be sorted into four subgroups characterized by distinct light curve shapes. Anti-phase variations in different photometric passbands, in particular, is a unique characteristic of a subset of ACV stars readily usable for their identification. The availability of data in three different passbands (g, r, and i) is a major advantage of the ZTF survey. On the basis of our experience with other photometric surveys and the analysis of light curves, we conclude that the ZTF is well suited for the search for, and the analysis of, ACV variables, which, however, are not considered in the available ZTF variable star catalogues.

astro-ph.SR↗