Bulge Microlensing Optical Depth from EROS 2 observations

Astrophysics, abstract
astro-ph/0303100

From: Cristina Afonso <cafonso@nmsu.edu>

Date: Tue, 4 Mar 2003 23:44:01 GMT   (1091kb)

Authors:
C.Afonso,
J.-N.Albert,
C.Alard,
J.Andersen,
R.Ansari,
E.Aubourg,
P.Bareyre,
F.Bauer,
J.P.Beaulieu,
G.Blanc, et al. (The EROS collaboration)

Comments: 18 pages, 15 images, accepted for publication in A&A

Report-no: 3031

We present a measurement of the microlensing optical depth toward the
Galactic bulge based on the analysis of 15 contiguous1 square degrees fields
centered on (l=2.5 deg, b=-4.0 deg) and containing 1.42 million clump-giant
stars (belonging to the extended clump area) monitored during almost three
bulge seasons by EROS (Experience de Recherche d’Objets Sombres). We find a
microlensing optical depth towards the bulge tau_bulge=0.94 +/- 0.29 10^-6
averaged over all fields, based on 16 microlensing events with clump giants as
sources. This value is substantially below several other determinations by the
MACHO and OGLE groups and is more in agreement with what is expected from
axisymmetric and non-axisymmetric bulge models.

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