Related papers: The Hipparcos parallax for Polaris
Large magnification factors near gravitational lensing caustics of galaxy cluster lenses allow the study of individual stars or compact stellar associations at cosmological distances. We study how the presence of sub-galactic subhalos, an…
In this article I discuss the fragments of Hipparchus' star catalogue and compare them to Hipparchus' Exegesis to trace the early history of stellar catalogues in Greek astronomy.
We show that a straightforward application of the predicted relation connecting the absolute K magnitude of fundamental RR Lyrae variables to their period and metal content, together with current evolutionary predictions on the mass and…
Using the Hipparcos data, absolute magnitudes and thus the evolutionary status for the group of lambda Bootis stars were derived. The origin of this small group of non-magnetic, chemically peculiar stars, still remains a matter of debate.…
We present the results of a comprehensive assessment of companions to solar-type stars. A sample of 454 stars, including the Sun, was selected from the Hipparcos catalog with {\pi} > 40 mas, {\sigma}_{\pi}/{\pi} < 0.05, 0.5 < B - V < 1.0 (~…
Since the discovery of Sirius-B about 130 yr ago, there have been several claims of a possible second companion around the brightest star Sirius-A. Such a companion could, in particular, be responsible of the suspected colour change of the…
From common proper motion and signatures of youth, researchers have identified about 30 members of a putative TW Hydrae Association. Only four of these had parallactic distances from Hipparcos. We have measured parallaxes and proper motions…
Polar fields at the minimum of a sunspot cycle -- which are a manifestation of the radial component of the Sun's poloidal field -- are deemed to be the best indicator of the strength of the toroidal component, and hence the amplitude of the…
We use recently updated globular cluster distances to estimate the distance to the Galactic centre, finding 7.4 \pm 0.2|stat \pm 0.2|sys kpc from symmetry considerations. We recalibrate the red clump magnitude from Hipparcos stars, finding…
Gaia two-parameter (G2P) stars have cumulative errors in parallax and proper motion so great that only their mean positions were reported in DR3. One potential cause of these high errors is another star as indicated by two intensity peaks…
Hipparcos Intermediate Astrometric Data (IAD) have been used to derive astrometric orbital elements for spectroscopic binaries from the newly released Ninth Catalogue of Spectroscopic Binary Orbits (SB9). Among the 1374 binaries from SB9…
Polaris is the nearest and brightest classical Cepheid, and pulsates with a period of about 4 days. It has long been known as a single-lined spectroscopic binary with an orbital period of 30 yr. Historical photometric and spectroscopic…
We discuss main experimental works, where dipole polarizabilities of charged pions have been determined. Possible reasons for the differences between the experimental data are discussed. In particular, it is shown that the account of the…
The recent distance determinations by HIPPARCOS have allowed to locate very precisely a reasonable set of subdwarfs in the HR diagram. A detailed comparison with evolutionary models is now possible and it has been recently claimed that the…
The search of a rational explanation of eclipses pervades the beginnings of philosophical and scientific thought. Within this intellectual frame, the knowledge of the "saros cycle" (a cycle of 18 years, 10 or 11 days and 1/3 of a day that…
CONTEXT. Massive stars have high-multiplicity fractions, and many of them have still undetected components, thus hampering the study of their properties. AIMS. I study a sample of massive stars with high angular resolution to better…
I show that for a substantial fraction of planets detected in a space-based survey, it would be possible to measure the planet and host masses and distances, if the survey satellite were placed in geosynchronous orbit. Such an orbit would…
Microlensing has established itself as a powerful new method for the detection of baryonic dark matter in the Galaxy. The theory of microlensing is sketched and its similarity with the optical effect of twinkling is explained. The bulk of…
For about 100 years the amplitude of the 4-day pulsation in Polaris has decreased. We present new results showing a significant increase in the amplitude based on 4.5 years of continuous monitoring from the ground and with two satellite…
Pulsars with compact companions in close eccentric orbits are unique laboratories for testing general relativity and alternative theories of gravity. Moreover, they are excellent targets for future gravitational wave experiments like LISA…