WeCAPP - The Wendelstein Calar Alto Pixellensing Project I Tracing Dark and Bright Matter in M31

TL;DR

WeCAPP is a long-term microlensing survey towards M31 using dual-site observations and optimal image subtraction, aiming to detect dark and bright matter through microlensing events.

Contribution

The project introduces a novel long-term monitoring approach with dual-site observations and advanced image analysis to detect microlensing events in M31.

Findings

Achieved 53% observational coverage of M31 during visibility.

Successfully detected variable sources at photon noise levels.

Demonstrated the effectiveness of optimal image subtraction in crowded fields.

Abstract

We present WeCAPP, a long term monitoring project searching for microlensing events towards M 31. Since 1997 the bulge of M 31 was monitored in two different wavebands with the Wendelstein 0.8 m telescope. In 1999 we extended our observations to the Calar Alto 1.23 m telescope. Observing simultaneously at these two sites we obtained a time coverage of 53 % during the observability of M 31. To check thousands of frames for variability of unresolved sources, we used the optimal image subtraction method (OIS) by Alard & Lupton (1998) This enabled us to minimize the residuals in the difference image analysis (DIA) and to detect variable sources with amplitudes at the photon noise level. Thus we can detect microlensing events with corresponding amplifications A > 10 of red clump giants with M_I = 0.