On the existence of subdwarfs in the (M bol, log Te)- plane. III.

Abstract

view Abstract Citations (62) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the existence of subdwarfs in the (Mbol, log Te)-plane. III. Eggen, O. J. Abstract A discussion of (R, I) observations of parallax stars indicates that (1) the earlier conclusion that F- and G-typedwarfs populate the Hyades main sequence in the (Mbol, log T,)-plane resulted from the evolved nature of the subdwarfs and (2) the later-type subdwarfs lie about 1 mag below the old-disk main sequence. In the range of R - I between +0.28 and +0.7 mag, which avoids large nuclear-evolution effects in hotter stars and contractual-evolution effects in cooler objects, the data presents two enigmas: (1) the metal-abundance variation that successfully explains the large separation of the halo and disk main sequence appears not to be as effective for the smaller abundance differences among disk stars; and (2) although the range of values of ultraviolet excess within the disk population extends to the values observed in the halo stars, the spectroscopic analyses show that all objects with space motions indicative of halo objects are metal deficient compared to the Sun, by factors near 100, whereas some old disk-population stars with comparable ultraviolet excess are metal deficient by considerably less than a factor of 10. These results depend on the assumption that the (log T,, R - 1)-relation is unaltered by the range of chemical compositions represented in the parallax stars. Subject headings: abundances, stellar - open clusters - photometry - subdwarfs Publication: The Astrophysical Journal Pub Date: June 1973 DOI: 10.1086/152186 Bibcode: 1973ApJ...182..821E full text sources ADS | data products SIMBAD (129) GCPD (1)