NOAO >   Observing Info >   Approved Programs >   2001B-0070

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Proposal Information for 2001B-0070


PI: Krzysztof Z. Stanek, Harvard-Smithsonian Center for Astrophysics, kstanek@cfa.harvard.edu
Address: 60 Garden St., MS20, Cambridge, MA 02138, USA

CoI: Janusz Kaluzny, Copernicus Astronomical Center
CoI: Dimitar D. Sasselov, Harvard-Smithsonian Center for Astrophysics
CoI: Barbara J. Mochejska, Copernicus Astronomical Center
CoI: Andrew H. Szentgyorgyi, Harvard-Smithsonian Center for Astrophysics

Title: DIRECT Distances to M31 and M33 Using Detached Eclipsing Binaries and Cepheids: Accurate BVI Lightcurves

Abstract: We shall use the direct CCD imaging on the KPNO 2.1-m telescope to obtain accurate multiband BVI light curves for five selected detached eclipsing binaries and ~500 Cepheids in M31 and M33. We have discovered detached eclipsing binaries and large number of new Cepheids in these galaxies as part of the project DIRECT. Combining accurate light curves with the radial velocity curves of these systems (which for some of the systems we have obtained with the Keck II telescope in 1997 and we will obtain more using Keck and MMT) is a classic method for determining accurate, fundamental distances, although it has never been applied outside of the Milky Way and its satellites. We propose to obtain accurate multiband BVI light curves of a handful of these binary stars in M31 and M33 which would enable us to derive a precise independent distance to these stepping stones in the distance ladder, with its ramifications for cosmology and stellar ages. As a by-product, accurate light curves of ~ 500 Cepheids located near the eclipsing systems will be obtained, which will be used for Baade-Wesselink based distance to M31 and M33. A limited number of exposures taken in the U band will allow us to map the reddening in the observed fields.


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