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Henry Draper catalogue identifications for Tycho-2 stars
Makarov, V. V.; Fabricius, C.; Wycoff, G. L. +1 more
We present identifications in the Tycho-2 Catalogue, for 99.8 per cent of the stars in the Henry Draper Catalogue and for 96 per cent of the Henry Draper Extensions. Based on observations made with the ESA Hipparcos astrometry satellite. The identifications are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.7…
HST observations rule out the association between Cir X-1 and SNR G321.9-0.3
Caraveo, P. A.; De Luca, A.; Mignani, R. P. +1 more
Cir X-1 is one of the most intriguing galactic X-ray sources. It is a ~16.6 days variable X/radio source, a type-I X-ray burster and a QPO emitter. In spite of an uncertain optical counterpart classification, all these properties identify the source as an LMXB. The morphology of the surrounding radio nebula has suggested an association with the ne…
The white dwarf cooling sequence in the old open cluster NGC 188
Andreuzzi, G.; Richer, H. B.; Limongi, M. +1 more
We develop the white dwarf luminosity function (LF) of the old open cluster NGC 188 in order to determine a lower limit to the age of the cluster by using the faint end of the cooling sequence. To produce an extensive sequence of the cooling white dwarfs we imaged four contiguous HST-WFPC2 fields in the center of the cluster in the F555W and F814W…
A morphological comparison between the central region in AGN and normal galaxies using HST data
Papadakis, I. E.; Xilouris, E. M.
We study the morphology of the central region of a sample of Active Galactic Nuclei (AGN) and a ``control'' sample of normal galaxies using archival observations of the WFPC2 instrument onboard the Hubble Space Telescope (HST). We use the ellipse fitting technique in order to get a good description of the inner ``smooth'' light distribution of the…
Precision and accuracy of the orbital parameters derived from 2D & 1D space observations of visual or astrometric binaries
Pourbaix, D.
Recent investigations (e.g. Han et al. \cite{Han-2001:a}) have shown that fitting the Hipparcos observations with an orbital model when the astrometric wobble caused by the companion is below the noise level can have rather unexpected consequences. With new astrometric missions coming out within the next ten years, it is worth investigating the or…
The signature of high-velocity gas in the spectra of NGC 4151
Prieto, M. A.; Contini, M.; Viegas, S. M.
The multiwavelength emission spectrum and associated velocity field of the Seyfert prototype NGC 4151 is modeled. Since the thirties NGC 4151 has been the subject of extensive modeling, nuclear photoionization being the basic approach considered by all authors. HST data has impressively revealed the existence of a large range of velocities (100-15…
CCD photometric search for peculiar stars in open clusters. IV. Collinder 272, Pismis 20, Lyng\aa 14, NGC 6396 and NGC 6611
Paunzen, E.; Maitzen, H. M.; Pintado, O. I.
The time scale on which chemical peculiarity in upper main sequence stars begins is unknown. Results from the Hipparcos measurements indicate that the classical chemically peculiar (CP) stars occupy the whole area from the zero age main sequence to the terminal age main sequence (Gómez et al. \cite{Gom98}). However, Hubrig et al. (\cite{Hub00}) re…
The enigmatic WR46: A binary or a pulsator in disguise. I. The photometry
Sterken, C.; van der Hucht, K. A.; van Genderen, A. M. +3 more
We discuss the observational history of the Wolf-Rayet object WR 46 (WN3p), including a re-investigation of the original discovery plates from early this century. We find that the reported presence of N Iii lines is a mis-interpretation of N V lines and conclude that the object did not change its spectral type since the first recording one century…
Dark matter revealed. More evidence from faint-star proper-motions for a cool and warm component of the local dark matter in the Galaxy
Méndez, R. A.
We present new evidence, based on faint HST proper-motions, for a bi-modal kinematic population of old white dwarfs, representative of the Thick-Disk and Halo of our Galaxy. This evidence supports the idea of a massive Halo comprised of faint and old white dwarfs, along with an extant population of Thick-Disk white dwarfs. We show how most of the …
The pulsation modes and masses of carbon-rich long period variables
Bergeat, J.; Knapik, A.; Rutily, B.
Following our study of the carbon-rich giants in the HR diagram and of their luminosity function (Paper III), we investigate the pulsation data of the long period variables (LPVs) included in our sample. Pulsation modes (fundamental, overtone(s)) for carbon LPVs are identified in the period-radius diagram, making use of observed bi-periodicity in …