Issue |
A&A
Volume 459, Number 1, November III 2006
|
|
---|---|---|
Page(s) | 321 - 331 | |
Section | Online catalogs and data | |
DOI | https://doi.org/10.1051/0004-6361:20065667 | |
Published online | 12 September 2006 |
Eclipsing binaries suitable for distance determination in the Andromeda galaxy
1
Departament d'Astronomia i Meteorologia, Universitat de Barcelona, c/ Martí i Franquès, 1–11, 08028 Barcelona, Spain e-mail: [fvilarde;carme.jordi]@am.ub.es
2
Institut de Ciències de l'Espai-CSIC, Campus UAB, Facultat de Ciències, Torre C5-parell-2a, 08193 Bellaterra, Spain e-mail: iribas@ieec.uab.es
3
Institut d'Estudis Espacials de Catalunya (IEEC), Edif. Nexus, c/ Gran Capità, 2–4, 08034 Barcelona, Spain
Received:
23
May
2006
Accepted:
22
June
2006
The Local Group galaxies constitute a fundamental step in the definition of
cosmic distance scale. Therefore, obtaining accurate distance determinations to
the galaxies in the Local Group, and notably to the Andromeda Galaxy (M 31), is
essential for determining the age and evolution of the Universe. With this
ultimate goal in mind, we started a project of using eclipsing binaries as
distance indicators to M 31. Eclipsing binaries have been proved to yield direct
and precise distances that are essentially assumption-free. To do so,
high-quality photometric and spectroscopic data were needed. As a first step in
the project, broad band photometry (in Johnson B and V) was obtained in a
region () in the north eastern quadrant of the
galaxy over 5 years. The data, containing more than 250 observations per
filter, were reduced by means of the so-called difference image analysis
technique and the DAOPHOT program. A catalog with 236 238 objects with
photometry in both B and V passbands was obtained. The catalog is the
deepest (
mag) obtained so far in the studied region and it contains
3964 identified variable stars, with 437 eclipsing binaries and 416 Cepheids.
The most suitable eclipsing binary candidates for distance determination were
selected according to their brightness and from the modelling of the obtained
light curves. The resulting sample includes 24 targets with photometric errors
around 0.01 mag. Detailed analysis (including spectroscopy) of some 5-10 of these eclipsing systems should result in a distance determination to M 31 with a
relative uncertainty of 2-3% and essentially free of systematic errors, thus
representing the most accurate and reliable determination to date.
Key words: stars: variables: general / stars: binaries: eclipsing / stars: fundamental parameters / stars: distances / techniques: photometric / catalogs
© ESO, 2006
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