相关论文: Main-sequence fitting and the Hipparcos open clust…

We present strong-lensing models, as well as mass and magnification maps, for the cores of the six HST Frontier Fields galaxy clusters. Our parametric lens models are constrained by the locations and redshifts of multiple image systems of…

New and existing X-ray, UBVJHKsW(1-4), and spectroscopic observations were analyzed to constrain fundamental parameters for M25, NGC 7790, and dust along their sight-lines. The star clusters are of particular importance given they host the…

Principal components (PCA) and hierarchical clustering are two of the most heavily used techniques for analyzing the differences between nucleic acid sequence samples sampled from a given environment. However, a classical application of…

Recent literature reports a color deviation between observed Gaia color-magnitude diagrams (CMDs) and theoretical model isochrone predictions, particularly in the very low-mass regime. To assess its impact on cluster age determination via…

For an understanding of Galactic stellar populations in the SDSS filter system well defined stellar samples are needed. The nearby stars provide a complete stellar sample representative for the thin disc population. We compare the filter…

The LM method, designed to exploit the Hipparcos data to obtain luminosity calibrations, is applied to derive luminosity calibrations for RR Lyrae and classical Cepheids. From these calibrations the distance to the Large Magellanic Cloud…

Hubble Space Telescope photometry from the ACS/WFC and WFPC2 cameras is used to detect and measure globular clusters (GCs) in the central region of the rich Perseus cluster of galaxies. A detectable population of Intragalactic GCs is found…

Strong gravitational lensing by galaxy clusters is a fundamental tool to study dark matter and constrain the geometry of the Universe. Recently, the Hubble Space Telescope Frontier Fields programme has allowed a significant improvement of…

We present an outline of a new reduction of the Hipparcos astrometric data, the justifications of which are described in the accompanying paper. The emphasis is on those aspects of the data analysis that are fundamentally different from the…

Given a set of $n$ points $P$ in the plane, each colored with one of the $t$ given colors, a color-spanning set $S\subset P$ is a subset of $t$ points with distinct colors. The minimum diameter color-spanning set (MDCS) is a color-spanning…

We infer distances and their asymmetric uncertainties for two million stars using the parallaxes published in the Gaia DR1 (GDR1) catalogue. We do this with two distance priors: A minimalist, isotropic prior assuming an exponentially…

We present wide-field multiband photometry of globular cluster (GC) systems in NGC 1399, NGC 1404, and NGC 1387 located at the central region of the Fornax galaxy cluster. Observation was carried out through U, B, V, and I bands, which…

Using the technique of spectral disentangling, it is possible to determine the individual spectra of the components of a multiple star system from composite spectra observed at a range of orbital phases. This method has several advantages:…

In this study we investigate the calibration of surface brightness--color (SBC) relations based solely on eclipsing binary stars. We selected a sample of 35 detached eclipsing binaries with trigonometric parallaxes from Gaia DR1 or…

Star clusters are good tracers for formation and evolution of galaxies. We compared different fitting methods by using spectra (or by combining photometry) to determine the physical parameters. We choose a sample of 17 star clusters in M33,…

The status of the determination of the Hubble constant is reviewed, setting out the evidence for the long distance scale with H_0=55+/-5. In parallel, various precepts said to favor the short distance scale with H_0>70 are discussed. The…

Seismic structure inversions have been used to study the solar interior for decades. With the high-precision frequencies obtained using data from the Kepler mission, it has now become possible to study other solar-like oscillators using…

If NGC 6397 contains a large fraction of "second generation" stars (>70% according to recent analysis), the helium abundance of its stars might also be affected, show some star-to-star variation, and be larger than the standard Big Bang…

We have developed photometric techniques that can be applied to images with highly-variable backgrounds, as well as to slightly-extended objects (object size comparable to or smaller than PSF size). We have shown that ordinary stellar…

We present a study of the source positioning accuracy of the LECS and MECS instruments on-board BeppoSAX. From the analysis of a sample of archival images we find that a systematic error, which depends on the spacecraft roll angle and has…