EDP Sciences
Free access
Volume 445, Number 2, January II 2006
Page(s) 423 - 439
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20042223

A&A 445, 423-439 (2006)
DOI: 10.1051/0004-6361:20042223

The Wendelstein Calar Alto Pixellensing Project (WeCAPP): the M 31 variable star catalogue

J. Fliri1, A. Riffeser1, 2, S. Seitz1 and R. Bender1, 2

1  Universitätssternwarte München, Scheinerstrasse 1, 81679 München, Germany
    e-mail: fliri@usm.uni-muenchen.de
2  Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany

(Received 21 October 2004 / Accepted 24 August 2005)

In this paper we present the WeCAPP catalogue of variable stars found in the bulge of M 31. Observations in the WeCAPP microlensing survey (optical R and I bands) for a period of three years (2000-2003) resulted in a database with unprecedented time coverage for an extragalactic variable star study. We detected 23781 variable sources in a $16.1\arcmin \times 16.6\arcmin$ field centered on the nucleus of M 31. The catalogue of variable stars contains the positions, the periods, and the variation amplitudes in the R and I bands. We classified the variables according to their position in the R-band period-amplitude plane. Three groups can be distinguished; while the first two groups can be mainly associated with Cepheid-like variables (population I Cepheids in group I; type II Cepheids and RV Tauri stars in group II), the third one consists of Long Period Variables (LPVs). We detected 37 RV Tauri stars and 11 RV Tauri candidates, which makes this catalogue one of the largest collections of this class of stars to date. The classification scheme is supported by Fourier decomposition of the light curves. Our data shows a correlation of the low-order Fourier coefficients $\Phi_{21}$ with $\Phi_{31}$ for classical Cepheids, as well as for type II Cepheids and RV Tauri stars. Correlating our sample of variable stars with X-ray based catalogues of Kaaret (2002, ApJ, 578, 114) and Kong et al. (2002, ApJ, 577, 738) results in 23 and 31 coincidences, 8 and 12 of which are M 31 globular clusters. The number density of detected variables is clearly not symmetric, which has to be included in the calculations of the expected microlensing event rate towards M 31. This asymmetry is due to the enhanced extinction in the spiral arms superimposed on the bulge of M 31, which reduces the number of sources to about 60%, if compared to areas of equivalent bulge brightness without enhanced extinction present.

Key words: galaxies: individual: M 31 -- cosmology: dark matter -- stars: variables: general -- stars: variables: Cepheids -- X-rays: stars

SIMBAD Objects

© ESO 2005

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.