de Houtman in 1603, Kepler in 1627 and Halley in 1679 published the earliest modern catalogues of the southern sky. We provide machine-readable versions of these catalogues, make some comparisons between them, and briefly discuss their accuracy on the basis of comparison with data from the modern Hipparcos Catalogue. We also compare our results for de Houtman with those by Knobel (1917) finding good overall agreement. About half of the about 200 new stars (with respect to Ptolemaios) added by de Houtman are in twelve new constellations, half in old constellations like Centaurus, Lupus and Argo. The right ascensions and declinations given by de Houtman have error distributions with widths of about 40-arcmin, the longitudes and latitudes given by Kepler have error distributions with widths of about 45-arcmin. Halley improves on this by more than an order of magnitude to widths of about 3-arcmin, and all entries in his catalogue can be identified. The measurement errors of Halley are due to a systematic deviation of his sextant (increasing with angle to 2-arcmin at 60-degrees) and random errors of 0.7-arcmin. The position errors in the catalogue of Halley are dominated by the position errors in the reference stars, which he took from Brahe.
Mass is one of the most important parameters for determining the true nature of an astronomical object. Yet, many published exoplan- ets lack a measurement of their true mass, in particular those detected as a result of radial-velocity (RV) variations of their host star. For those examples, only the minimum mass, or msini, is known, owing to the insensitivity of RVs to the inclination of the detected orbit compared to the plane of the sky. The mass that is given in databases is generally that of an assumed edge-on system (~90{deg}), but many other inclinations are possible, even extreme values closer to 0{deg} (face-on). In such a case, the mass of the published object could be strongly underestimated by up to two orders of magnitude. In the present study, we use GASTON, a recently developed tool taking advantage of the voluminous Gaia astrometric database to constrain the inclination and true mass of several hundreds of published exoplanet candidates. We find 9 exoplanet candidates in the stellar or brown dwarf (BD) domain, among which 6 were never characterized. We show that 30 Ari B b, HD 141937 b, HD 148427 b, HD 6718 b, HIP 65891 b, and HD 16760 b have masses larger than 13.5 M_J_ at 3{sigma}. We also confirm the planetary nature of 27 exoplanets, including HD 10180 c, d and g. Studying the orbital periods, eccentricities, and host-star metallicities in the BD domain, we found distributions with respect to true masses consistent with other publications. The distribution of orbital periods shows of a void of BD detections below ~100d, while eccentricity and metallicity distributions agree with a transition between BDs similar to planets and BDs similar to stars in the range 40-50M_J_.
We investigate a sample of 2293 ICRF2 extragalactic radio-loud sources with accurate positions determined by VLBI, mostly active galactic nuclei (AGNs) and quasars, which are cross-matched with optical sources in the first Gaia release (Gaia DR1). The distribution of offsets between the VLBI sources and their optical counterparts is strongly non-Gaussian, with powerful wings extending beyond 1 arcsec. Limiting our analysis to only high-confidence difference detections, we find (and publish) a list of 188 objects with normalized variances above 12 and offsets below 1 arcsec. Pan-STARRS stacked and monochromatic images resolve some of these sources, indicating the presence of double sources, confusion sources, or pronounced extended structures. Some 89 high-quality objects, however, do not show any perturbations and appear to be star-like single sources, yet they are displaced by multiples of the expected error from the radio-loud AGN. We conclude that a fraction of luminous AGNs (more than 4%) can be physically dislodged from the optical centers of their parent galaxies.
In the course of other work I have obtained complete identifications for a problematic list of late-type stars by Dolidze (1975AbaOB..47....3D). The charts were used to make the identifications. Since numerous substantial errors were found that have propagated elsewhere in the literature, it was thought useful to publish the list separately. The corrections allow linkage of the stars to other catalogues in the visible and infrared. This complements a second similar list of late-M stars by Dolidze (Dolidze, 1975AbaOB..47..171D, Skiff, 1997IBVS.4417....1S).
We present (table 1) the measurements of 167 visual double stars, made in 2000 and 2001 with the 50 cm refractor of the Nice Observatory and attached CCD camera, using an algorithm based on the adjustment of a tridimensional mathematical surface. Position angle, angular separation and magnitude difference are given. 33 new binaries (discovered by HIPPARCOS (HDS) or newly determined from Tycho-2 database (TDS)) discovered by Hipparcos were measured.
Measures and discoveries of visual double stars made at the Observatoire de la Cote d'Azur at Nice, between 1988 and 1994, with the 50 cm refractor equipped with a filar micrometer and electronic recording device. The programs proposed by J. Dommanget involve the complement of the C.C.D.M. (resolving problems of identification of double stars and of coherency in the Index) and the INput CAtalog Hipparcos (resolution of ambiguities on the binarity and on the position of certain double stars which have seldom or never been observed again from the epoch or their discovery)
Position angle and separation measures of 482 primarily southern binary stars are presented. These were obtained from speckle observations taken at the Carlos U. Cesco Observatory, El Leoncito, Argentina, using a multianode microchannel array detector during the period 1994 July to 1996 July.
The astrometric ground-based observations of latitude / universal time variations, covering the interval 1899.7-2003.0, were used in combination with Hipparcos / Tycho positions and some older ground-based catalogs to construct a family of catalogs, tailored for long-term Earth rotation studies. These catalogs, called Earth Orientation Catalogs (EOC-1 through EOC-3) yielded more accurate proper motions than the original Hipparcos Catalogue, and its latest version, EOC-3, even periodic motions for a large portion of the stars. About 4.5 million observations made at 33 observatories are combined with the catalogs ARIHIP, TYCHO-2 etc... in order to obtain EOC-4. Spectral analysis of ground-based data and comparison with the USNO Sixth Catalog of Orbits of Visual Binary Stars are used to discover which of the observed objects display periodic motions, and improved combination procedures are used. The catalog contains 4418 different objects (i.e., stars, components of double stars, photocenters), out of which 599 have significant orbital motions.