Search Publications
Hubble Space Telescope Observations of the Gravitationally Lensed Cloverleaf Broad Absorption Line QSO H1413+1143: Modeling the Lens
Turnshek, David A.; Chae, Kyu-Hyun
We investigate gravitational lens models for the quadruply lensed Cloverleaf broad absorption line QSO H1413+1143 based on the Hubble Space Telescope (HST) WFPC/WFPC2 astrometric and photometric data of the system by Turnshek et al. and the HST NICMOS-2 data by Falco et al. The accurate image positions and the dust-extinction-corrected relative am…
Microscopic diffusion and subdwarfs
Morel, P.; Baglin, A.
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 observed lower part of the main-sequence is cooler than the computed one. In this paper we show that microsco…
UVCS/SOHO Observations of Spectral Line Profiles in Polar Coronal Holes
Cranmer, S. R.; Modigliani, A.; Ciaravella, A. +6 more
Ultraviolet emission line profiles have been measured on 15-29 September 1997 for H I 1216 Å, O VI 1032, 1037 Å and Mg X 625 Å in a polar coronal hole, at heliographic heights ϱ (in solar radii) between 1.34 and 2.0. Observations of H I 1216 Å and the O VI doublet from January 1997 for ϱ = 1.5 to 3.0 are provided for comparison. Mg X 625 Å is obse…
Deep Hubble Space Telescope Observations of Blue Star Clusters in NGC 3597
Ballester, Gilda E.; Crisp, David; Grillmair, Carl J. +15 more
We have analyzed HST/WFPC2 images of NGC 3597 and find ~700 compact objects surrounding the galaxy with an average (B-R)_0~0.6. We propose that the majority of these objects are young globular clusters. They have a spread in colors that is consistent with that expected for a population of young clusters with a common age and spread induced by phot…
Period-Luminosity-Colour distribution and classification of Galactic oxygen-rich LPVs. I. Luminosity calibrations
Luri, X.; Mennessier, M. O.; Alvarez, R. +1 more
The absolute K magnitudes and kinematic parameters of about 350 oxygen-rich Long-Period Variable stars are calibrated, by means of an up-to-date maximum-likelihood method, using Hipparcos parallaxes and proper motions together with radial velocities and, as additional data, periods and V-K colour indices. Four groups, differing by their kinematics…
Construction of the TYCHO Reference Catalogue
Makarov, V. V.; Lindegren, L.; Bastian, U. +5 more
The Tycho Reference Catalogue (TRC) project, as proposed in 1992 by the present authors, aimed to extend the Hipparcos reference system to fainter magnitudes. To assure rigidity of the reference system realization, the project relied on the Tycho Catalogue that provides highly-accurate positions of more than one million stars on the Hipparcos syst…
Hubble Space Telescope Observations of the Central-Cusp Globular Cluster NGC 6752: the Effect of Binary Stars on the Luminosity Function in the Core
Bailyn, Charles D.; Rubenstein, Eric P.
We consider the effect of binary stars on the main-sequence luminosity functions observed in the core of globular clusters, with specific reference to NGC 6752. We find that mass segregation results in an increased binary fraction at fainter magnitudes along the main sequence. If this effect is not taken into account when analyzing luminosity func…
Long-term coherent variations in the WR system EZ Canis Majoris: the binary scenario revisited
Koenigsberger, G.; Ivanov, M. M.; St. -Louis, N. +2 more
An analysis of seven different spectroscopic and eight photometric sets of observations of the WN5 star HD 50896=EZ CMa, distributed over more than 15 years is used to refine the known 3.76 days period. The value of P = 3.7650 +/- 0.0001 d yields variations which have coherent phase-dependence. Although not conclusive, this coherence in the 3.7650…
Time-resolved HST and IUE UV spectroscopy of the intermediate polar FO AQR
Mukai, K.; Gänsicke, B. T.; de Martino, D. +4 more
Time resolved spectroscopy of the Intermediate Polar FO Aqr reveals the presence of multiple periodicities in the UV range. A strong orbital modulation dominates both continuum and emission line flux variabilities, while line velocity motions are only detected at the rotational frequency. A prominent orbital periodicity is also observed in coordin…
Mining in the HIPPARCOS raw data
Mignard, F.; Falin, J. L.
The Hipparcos solutions flagged as unreliable after the completion of the standard data processing have been systematically revisited in the light of additional information, primarily related to their multiplicity. In many cases improved solutions have been obtained, yielding at the same time an Hipparcos based separation and position angle and a …