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Late-type members of young stellar kinematic groups - I. Single stars
Montes, D.; López-Santiago, J.; Cornide, M. +3 more
This is the first paper of a series aimed at studying the properties of late-type members of young stellar kinematic groups. We concentrate our study on classical young moving groups such as the Local Association (Pleiades moving group, 20-150Myr), IC 2391 supercluster (35Myr), Ursa Major group (Sirius supercluster, 300Myr), and Hyades supercluste…
Population effects on the red giant clump absolute magnitude, and distance determinations to nearby galaxies
Salaris, Maurizio; Girardi, Léo
The red giant clump has been recently argued to be a reliable distance indicator for the galaxies in the Local Group. The accuracy of distance determinations based on this method, however, depends on the possible presence of systematic magnitude differences (ΔMIRC) between the local clump revealed by the Hipparcos colour-magnitude diagram (CMD), a…
The local axisymmetric instability criterion in a thin, rotating, multicomponent disc
Rafikov, R. R.
Purely gravitational perturbations are considered in a thin rotating disc composed of gas and several stellar components. The dispersion relation for the axisymmetric density waves propagating through the disc is found and the criterion for the local axisymmetric stability of the whole system is formulated. In the appropriate limit of two-componen…
The SuperCOSMOS Sky Survey - III. Astrometry
Hambly, N. C.; Irwin, M. J.; MacGillivray, H. T. +1 more
In this, the third in a series of three papers concerning the SuperCOSMOS Sky Survey, we describe the astrometric properties of the data base. We describe the algorithms employed in the derivation of the astrometric parameters of the data, and demonstrate their accuracies by comparison with external data sets using the first release of data, the S…
The magnetic field and wind confinement of β Cephei: new clues for interpreting the Be phenomenon?
Donati, J. -F.; Babel, J.; Harries, T. J. +3 more
In this paper, we use the very recent spectropolarimetric observations of β Cep collected by Henrichs et al. and propose for this star a consistent model of the large-scale magnetic field and of the associated magnetically confined wind and circumstellar environment. A re-examination of the fundamental parameters of β Cep in the light of the Hippa…
Timing the millisecond pulsars in 47 Tucanae
Camilo, F.; Lorimer, D. R.; Freire, P. C. +3 more
In the last ten years, 20 millisecond pulsars have been discovered in the globular cluster 47 Tucanae. Hitherto, only three of these pulsars had published timing solutions. Here we improve upon these three and present 12 new solutions. These measurements can be used to determine a variety of physical properties of the pulsars and of the cluster. T…
SCUBA photometry of candidate Vega-like sources
Barlow, M. J.; Sylvester, R. J.; Dunkin, S. K.
New SCUBA measurements at millimetre wavelengths are presented for a sample of Vega-like stars. Six stars were detected, while sensitive upper limits were obtained for a further 11 sources. Most of the sample selected from a recent catalogue of Vega-like stars have infrared excesses similar to those of the prototype Vega-like stars α Lyr and α PsA…
Stellar models and Hyades: the Hipparcos test
Prada Moroni, P. G.; Degl'Innocenti, S.; Castellani, V.
We compare theoretical stellar models for main sequence (MS) stars with the Hipparcos data base for the Hyades cluster to give a warning against the uncritical use of available theoretical scenarios and to show how formal MS fittings can be fortuitous if not fictitious. Moreover, we find that none of the current theoretical scenarios appears able …
Multiperiodicities from the Hipparcos epoch photometry and possible pulsation in early A-type stars
Koen, Chris
A selection criterion based on the relative strength of the largest peaks in the amplitude spectra, and an information criterion are used in combination to search for multiperiodicities in Hipparcos epoch photometry. The method is applied to all stars which have been classified as variable in the Hipparcos catalogue: periodic, unsolved and microva…
UBVRIJH photometry of two new luminous δ Scuti stars and the discovery of δ Scuti pulsation in the most evolved Ap star known
Handler, G.; Kurtz, D. W.; Kilkenny, D. +5 more
Time-series photometry of the Hipparcos variable stars HD 199434 and 21190 is reported. Both stars are pulsators of the δ Scuti type. Reclassifications of the MK types of the stars, based on new spectrograms, are given. HD 21190 is found to be F2III SrEuSi:, making it the most evolved Ap star known. Its Strömgren photometric indices support the pe…