The Wendelstein Calar Alto Pixellensing Project (WeCAPP): First MACHO Candidates
Abstract
We report the detection of the first two microlensing candidates from the Wendelstein Calar Alto Pixellensing Project (WeCAPP). Both are detected with a high signal-to-noise ratio and were filtered out from 4.5 million pixel light curves using a variety of selection criteria. Here we only consider well-sampled events with timescales of 1 day<tfwhm<20 days, high amplitudes, and a low χ2 of the microlensing fit. The two-color photometry (R,I) shows that the events are achromatic and that giant stars with colors of (R-I)~1.1 mag in the bulge of M31 have been lensed. The magnification factors are 64 and 10, which are obtained for typical giant luminosities of MI=-2.5 mag. Both lensing events lasted for only a few days (tGL1fwhm=1.7 days and tGL2fwhm=5.4 days). The event GL1 is likely identical with PA-00-S3 reported by the POINT-AGAPE project. Our calculations favor in both cases the possibility that MACHOs in the halo of M31 caused the lensing events. The most probable masses, 0.08 Msolar for GL1 and 0.02 Msolar for GL2, are in the range of the brown dwarf limit of hydrogen burning. Solar mass objects are a factor of 2 less likely.
Based on observations at the Wendelstein Observatory of the University Observatory Munich and at the German-Spanish Astronomical Center, Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie, Heidelberg, and the Spanish National Commission for Astronomy.- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2003
- DOI:
- 10.1086/381019
- arXiv:
- arXiv:astro-ph/0311135
- Bibcode:
- 2003ApJ...599L..17R
- Keywords:
-
- Cosmology: Dark Matter;
- Galaxies: Halos;
- Galaxies: Individual: Messier Number: M31;
- Galaxy: Halo;
- Cosmology: Gravitational Lensing;
- Astrophysics
- E-Print:
- Accepted for publication in ApJ Letters (28 Oct 2003), 4 pages, 2 color figures, uses emulateapj style