Sökresultat

Context. The ESA Gaia mission provides a unique time-domain survey for more than 1.6 billion sources with G ≲ 21 mag. Aims. We showcase stellar variability in the Galactic colour-absolute magnitude diagram (CaMD). We focus on pulsating, eruptive, and cataclysmic variables, as well as on stars that exhibit variability that is due to rotation and eclipses. Methods. We describe the locations of var

Context. The second release of Gaia data (Gaia DR2) contains the astrometric parameters for more than half a million quasars. This set defines a kinematically non-rotating reference frame in the optical domain. A subset of these quasars have accurate VLBI positions that allow the axes of the reference frame to be aligned with the International Celestial Reference System (ICRF) radio frame. Aims. W

Context. Gaia Data Release 2 provides high-precision astrometry and three-band photometry for about 1.3 billion sources over the full sky. The precision, accuracy, and homogeneity of both astrometry and photometry are unprecedented. Aims. We highlight the power of the Gaia DR2 in studying many fine structures of the Hertzsprung-Russell diagram (HRD). Gaia allows us to present many different HRDs,

Where the dust in a protoplanetary disk is as the disk evolves over time is essential to know for further studies of the planet formation process. A new star is created alongside a stellar nebula. The nebula contains rock, ice and gas which are not accreted to the star. Our nebula is constructed using the Minimum Mass Solar Nebula model and the column density is studied as the protoplanetary disk

Context: Data from the recently launched astrometric satellite Gaia will be coming in soon with the final data release expected in 2022. This will provide a very precise map of the Galaxy. The Solar system and Galaxy is thought to be filled with invisible bodies (planetesimals, planets, brown dwarfs, neutron stars, black holes, etc.) and they will affect the observations via gravitational lensing.

Context. With the goal to accurately map about a billion of the Milky Way stars, the astrometric satellite Gaia was launched in December 2013. Its high precision and sensitivity will lead to better understanding of the Galactic structure and evolution. Also, it will be possible to probe the matter distribution in the Galaxy. Aims. To study how well the Galactic matter distribution can be determin

Purpose: In order to study the Galactic Chemical Evolution, elemental abundances are needed. The purpose of this work is to investigate the chemical evolution of the Milky Way by determining several elemental abundances of giants in the local disk. Large surveys are up and coming, and several surveys are already working, and with these, the aim is high quality abundance measurements of several ele

Researchers in the field of Galactic Archaeology have entered the era of industrial revolution. Upcoming surveys are planning on observing tens of millions of stars and high precision and accuracy must be ensured when deriving their stellar parameters and elemental abundances. Unconventional data-driven techniques hold the promise of efficiently dealing with these vast collections of data while st

Purpose: even in the era of exponential increase in the amount of stellar data gathered, binaries are still often overlooked in observational data due to the special handling they require. The goal of this work is to develop a method capable of automatically and efficiently identifying and extract double-lined spectroscopic binaries (SB2) from a spectroscopic survey, while being scalable and techn

Gravitational encounters between a single star and a binary system can frequently occur in the cores of dense stellar systems like globular clusters. These three-body scattering encounters can lead to a variety of outcomes since the energy of the binary components can be exchanged with the interacting single star. The outcome of these interactions strongly depend on the initial conditions of the i

We investigate the radial infall of ice pebbles in a protoplanetary disk, and how these tend to end up in relatively close proximity to eachother, providing a possible spawning ground for planets. These pebbles have dust particles embedded in them, which are released as the pebble crosses the so-called ice- line, where the ice evaporates. This is interesting as the dust will pile up around this ic

We test a new approach to calculate the mean velocity and velocity dispersion for a sample of nearby stars when their radial velocities are not available. The most commonly used method (here called the projection method, PM) was introduced in a paper by Dehnen & Binney (1998). That method is here compared, theoretically and numerically, with an application of the Maximum Likelihood (ML) method

Most of the things that we know about stars come from their spectrum. The properties of the atomic lines, e.g. energy levels, wavelengths, oscillator strengths, must be known to understand the observed spectrum and to perform quantitative analyses. Atomic data of some elements are incomplete, especially in the near-infrared region, which makes it difficult or even impossible to analyze a stellar s

Top quark pairs production and decay are considered in the framework of the smeared-mass unstable particles model. The results are in good agreement with the previous ones in the literature. Suggested approach significantly simplifies calculations compared to the standard perturbative one.