相关论文: The Hipparcos parallax for Polaris
We scrutinize the Hipparcos parallax for the bright O supergiant zeta Pup, and confirm that the implied distance of 332+/-11pc appears to be reliable. We then review the implications for the star's physical parameters, and the consequences…
We analyzed the Hipparcos astrometric observations of 47 stars that were discovered to harbor giant planets and 14 stars with brown-dwarf secondary candidates. The Hipparcos measurements were used together with the corresponding stellar…
A magnitude limited population of 18 808 Hipparcos stars is used to calibrate distances for 52 794 RAVE stars, including dwarfs, giants, and pre-main sequence stars. I give treatments for a number of types of bias affecting calculation,…
The prediction of the evolution of individual solar cycles is a developing field, faced with divergence of forecasts even for a few years in the future. Specifically for solar flares, long-term modeling is practically absent even in rough…
According to recent reports there is an excess correlation and an apparent regularity in the galaxy one-dimensional polar distribution with a characteristic scale of 128 $h^{-1}$ Mpc. This aparent spatial periodicity can be naturally…
Recently, it was shown, that the absence of circular polarization of visible light from quasars, severely constrains the interpretation of axion like particles (ALPs) as a solution for the generation of the linear polarization. Furthermore,…
We present new BVRI photometry for a sample of 54 local G and K stars with accurate Hipparcos parallaxes in the metallicity range -0.4 < [Fe/H] < +0.3. We use this sample to develop a completely model-independent main sequence (MS) fitting…
We present results of timing measurements of the binary millisecond pulsar PSR J2145-0750. Combining timing data obtained with the Effelsberg and Lovell radio telescopes we measure a significant timing parallax of 2.0(6) mas placing the…
The Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) has monitored 37 sub-arcsecond binary systems to determine whether their Keplerian orbits are perturbed by faint astrometric companions to either star. Software…
In this talk I focus on how the modelling of the mass-observable relation and the halo mass function can impact the accuracy and precision of cosmological constraints inferred from galaxy clusters. I present a new analysis of clusters…
A single very deep $10'$ field has been imaged to $r \sim 26$. There are 2682 galaxies with $23 \le r \le 26$ with a size significantly larger than the seeing disk in the field. After correcting for telescope aberrations, possible guiding…
We present radial velocity and new interferometric measurements of the double star Atlas, which permit, with the addition of published interferometric data, to precisely derive the orbital parameters of the binary system and the masses of…
We combine extinction maps from the Two Micron All Sky Survey (2MASS) with Hipparcos and Tycho parallaxes to obtain reliable and high-precision estimates of the distance to the Ophiuchus and Lupus dark complexes. Our analysis, based on a…
A criterion, proposed by the present authors, is used to derive numerical results for the stability of a large bipolaron embedded in a polaron gas. The main conclusion is that an isolated metastable bipolaron can be stabilized by the…
The Lutz-Kelker correction is intended to give an unbiased estimate for stellar parallaxes and magnitudes, but it is shown explicitly that it does not. This paradox results from the application of an argument about sample statistics to the…
A subset of 51 Hipparcos astrometric binaries among FG dwarfs within 67pc has been surveyed with the NICI adaptive optics system at Gemini-S, directly resolving for the first time 17 sub-arcsecond companions and 7 wider ones. Using these…
The A5V star Alcor has an M3-M4 dwarf companion, as evidenced by a novel astrometric technique. Imaging spectroscopy combined with adaptive optics coronagraphy allowed for the detection and spectrophotometric characterization of the point…
We present new high-speed, multi-observatory, multi-instrument photometry of the eclipsing polar UZ For in order to measure precise mid-eclipse times with the aim of detecting any orbital period variations. When combined with published…
Polar ring galaxies, where matter is in equilibrium in perpendicular orbits around spiral galaxies, are ideal objects to probe the 3D shapes of dark matter halos. The conditions to constrain the halos are that the perpendicular system does…
According to classical tradition, Thales of Miletus predicted the total solar eclipse that took place on 28 May 585 BCE. Even if some authors have flatly denied the possibility of such a prediction, others have struggled to find cycles…