相关论文: Atmospheric parameters of Cepheids from flux ratio…
The technique of line depth ratios (LDR) is one of the methods to determine the effective temperature of a star. They are crucial in the spectroscopic studies of variable stars like Cepheids since no simultaneous photometry is usually…
We gathered more than 1130 high-resolution optical spectra for more than 250 Galactic classical Cepheids. The spectra were collected with different optical spectrographs: UVES at VLT, HARPS at 3.6m, FEROS at 2.2m MPG/ESO, and STELLA. To…
Standard spectroscopic analyses of variable stars are based on hydrostatic one-dimensional model atmospheres. This quasi-static approach has theoretically not been validated. We aim at investigating the validity of the quasi-static…
In order to better determine the physical properties of hot, massive stars as a function of metallicity, we obtained very high SNR optical spectra of 26 O and early B stars in the Magellanic Clouds. These allow accurate modeling even in…
One of the outstanding problems in modern physics is the origin is of accelerated expansion of the universe. High-precision determinations of the Hubble parameter $\mbox{H}_0$ at different redshifts provide direct insight into the Universe…
Classical Cepheids are the most popular distance indicators and tracers of young stellar populations. The key advantage is that they are bright and they can be easily identified in Local Group and Local Volume galaxies. Their evolutionary…
The derivation of the effective temperature of a star is a critical first step in a detailed spectroscopic analysis. Spectroscopic methods suffer from systematic errors related to model simplifications. Photometric methods may be more…
Various effective temperature scales have been proposed over the years. Despite much work and the high internal precision usually achieved, systematic differences of order 100 K (or more) among various scales are still present. We present…
We perform a global fit to ~5,000 radial velocity and ~177,000 magnitude measurements in 29 photometric bands covering 0.3 to 8.0 microns distributed among 287 Galactic, LMC, and SMC Cepheids with P > 10 days. We assume that the Cepheid…
Context. One challenge for measuring the Hubble constant using Classical Cepheids is the calibration of the Leavitt Law or period-luminosity relationship. The Baade-Wesselink method for distance determination to Cepheids relies on the ratio…
In this paper we present and analyse determinations of effective temperatures of planet-hosting stars using infrared (IR) photometry. One of our goals is the comparison with spectroscopic temperatures to evaluate the presence of systematic…
Milky Way Cepheid variables with accurate {\it Hubble Space Telescope} photometry have been established as standards for primary calibration of the cosmic distance ladder to achieve a percent-level determination of the Hubble constant…
The ratio of the depths of spectral lines is a powerful indicator of the effective temperature. The method based on this analysis is capable of discerning small temperature variations of individual stars. We apply this spectroscopic data…
Based on new observations and improved modeling techniques, we have reanalyzed seven Cepheids in the Large Magellanic Cloud. Improved physical parameters have been determined for the exotic system OGLE LMC-CEP-1718 composed of two…
S Mus is the Cepheid with the hottest known companion. The large ultraviolet flux means that it is the only Cepheid companion for which the velocity amplitude could be measured with the echelle mode of the HST GHRS. Unfortunately, the high…
The apparent size of stars is a crucial benchmark for fundamental stellar properties such as effective temperatures, radii and surface gravities. While interferometric measurements of stellar angular diameters are the most direct method to…
We present new calibrations of stellar parameters of O stars at solar metallicity taking non-LTE, wind, and line-blanketing effects into account. Gravities and absolute visual magnitudes are derived from results of recent spectroscopic…
The period of pulsation and the structure of the light curve for Cepheid and RR Lyrae variables depend on the fundamental parameters of the star: mass, radius, luminosity, and effective temperature. Here we train artificial neural networks…
We develop a statistical method for using multicolor photometry to determine distances using Cepheid variables including the effects of temperature, extinction, and metallicity and apply it to UBVRIJHK photometry of 694 Cepheids in 17…
The OGLE data base is used in conjunction with Kurucz atmosphere models to generate sets of period, effective temperature and luminosity for fundamental and overtone Magellanic Cloud Cepheids. The Florida pulsation code (with linear…