1997/08/22 by B. Fuchs, Fuchs, B., H. Jahreiß +2
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #History and Developments in Astronomy #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9708209
Latex, 6 pages, 3 figures, uses l-aa.sty, to appear in Astronomy and Astrophysics
arxiv created 1997/08/22 · openalex publication_date 1997/08/22 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We have searched the Forth Catalogue of Nearby Stars for halo stars and identified 15 subdwarfs and a high velocity white dwarf in the solar neighbourhood. This search was motivated mainly by the recent determinations of MACHO masses of about 0.5 Msun, which are typical for halo dwarfs. The local mass density of the stars is 1.5 10-4 Msun pc-3, which is only 3% of the current estimate of the local mass density of the MACHO population. We compare the local density of subdwarfs with constraints set by HST observations of distant red dwarfs. Using models of the stellar halo with density laws that fall off like r-α, α= 3.5 to 4, we find that the HST constraints can only be matched, if we assume that the stellar halo is flattened with an axial ratio of about 0.6. The non-detection of the analogues of MACHOs in the solar neighbourhood allows to set an upper limit to the luminosity of MACHOs of MB > 21 magnitudes.