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The Unevolved Main Sequence of Nearby Field Stars and the Open Cluster Distance Scale

Twarog, Bruce A.; Anthony-Twarog, Barbara J.; Edgington-Giordano, Frederika

The slope and zero point of the unevolved main sequence as a function of metallicity are investigated using a homogeneous catalog of nearby field stars with absolute magnitudes defined with revised Hipparcos parallaxes, Tycho-2 photometry, and precise metallicities from high-dispersion spectroscopy. (B - V) -temperature relations are derived from …

Lacerta OB1 Revisited

Kaltcheva, Nadia

This investigation utilizes precise uvbyβ photometry and the recently recalculated Hipparcos data to provide an improved homogeneous distance scale for the apparent groups of young stars in Lacerta. All existing uvbyβ photometry for stars earlier than A0-type in a 20° × 20° field centered at l = 100°, b = -15° is collated and the individual stella…

Accurate Analytical and Statistical Approaches to Reduce O-C Discrepancies in the Precessional Parameters

Marco, F. J.; Martínez, M. J.; López, J. A.

The Hipparcos catalog provides a reference frame at optical wavelengths for the new International Celestial Reference System (ICRS). This new reference system was adopted following the resolution agreed at the 23rd IAU General Assembly held in Kyoto in 1997. Differences in the Hipparcos system of proper motions and the previous materialization of …