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The Tycho-2 catalogue of the 2.5 million brightest stars
Makarov, V. V.; Bastian, U.; Fabricius, C. +6 more
The Tycho-2 Catalogue presented here is an astrometric reference catalogue containing positions and proper motions as well as two-colour photometric data for the 2.5 million brightest stars in the sky. The Tycho-2 positions and magnitudes are based on precisely the same observations as the original Tycho Catalogue (hereafter Tycho-1) collected by …
Revision of the initial-to-final mass relation
Weidemann, V.
The initial-to final mass relation is revised in view of new theoretical and observational data. Recent stellar evolution models predict core masses at the beginning of the thermally pulsing asymptotic giant branch which practically coincide with final white dwarf masses derived for NGC 3532 and the binary white dwarf PG 0922+162. The Hyades white…
Mid-infrared diagnostics to distinguish AGNs from starbursts
Cesarsky, C.; Madden, S. C.; Sauvage, M. +5 more
We present new mid-infrared (MIR) diagnostics to distinguish emission of active galactic nuclei (AGN) from that originating in starburst regions. Our method uses empirical spectroscopic criteria based on the fact that MIR emission from star forming or active galaxies arises mostly from HII regions, photo-dissociation regions (PDRs) and AGNs. The a…
ISO-SWS spectra of galaxies: Continuum and features
Lutz, D.; Genzel, R.; Sturm, E. +5 more
We present an inventory of mid-infrared spectral features detected in high resolution (R ~ 1500) ISO-SWS 2.4-45mu m spectra of the galaxies
An ISOCAM absorption survey of the structure of pre-stellar cloud cores
Abergel, A.; Puget, J. -L.; Bontemps, S. +3 more
We present the results of a mid-infrared (lambda =~ 7 mu m) imaging survey of a sample of 24 starless dense cores carried out at an angular resolution of 6arcsec with the ISOCAM camera aboard the Infrared Space Observatory (ISO). The targeted cores are believed to be pre-stellar in nature and to represent the initial conditions of low-mass, isolat…
The Nature of the lithium rich giants. Mixing episodes on the RGB and early-AGB
Charbonnel, C.; Balachandran, S. C.
We present a critical analysis of the nature of the so-called Li-rich RGB stars. For a majority of the stars, we have used Hipparcos parallaxes to determine masses and evolutionary states by comparing their position on the Hertzsprung-Russell diagram with theoretical evolutionary tracks. Among the twenty Li-rich giants whose location on the HR dia…
Construction and verification of the Tycho-2 Catalogue
Makarov, V. V.; Bastian, U.; Fabricius, C. +6 more
The construction of the Tycho-2 Catalogue is described. The catalogue contains astrometric positions and proper motions as well as two-colour photometric data for 2.5 million stars. The Tycho-2 positions and magnitudes are based on precisely the same observations as the original Tycho Catalogue (hereafter Tycho-1) collected by the sky mapper of th…
Modelling irradiance variations from the surface distribution of the solar magnetic field
Solanki, S. K.; Unruh, Y. C.; Fligge, M.
An important question in solar physics is to what extent solar surface magnetism affects the solar irradiance. Previous attempts to answer this question have employed proxies of the magnetic field to reconstruct the irradiance and compare it with observations. Here we present the first model calculations of solar irradiance variations based on var…
Exploring the brown dwarf desert with Hipparcos
Queloz, D.; Arenou, F.; Udry, S. +2 more
The orbital elements of 11 spectroscopic binaries with brown dwarf candidates (M2 sin i between 0.01 and 0.08 Msun) are combined with the Hipparcos observations in order to derive astrometric orbits. Estimations of the masses of the secondary components are thus calculated. It appears that 5 secondary masses are more than 2 s…
2.5-11 micron spectroscopy and imaging of AGNs. Implication for unification schemes
Altieri, B.; Clavel, J.; Metcalfe, L. +6 more
We present low resolution spectrophotometric and imaging ISO observations of a sample of 57 AGNs and one non-active SB galaxy over the 2.5-11 mu m range. The sample is about equally divided into type I (<= 1.5; 28 sources) and type II (> 1.5; 29 sources) objects. The mid-IR (MIR) spectra of type I (Sf1) and type II (Sf2) objects are statisti…