Pixel lensing observations towards globular clusters

¹ Dipartimento di Fisica “E.R. Caianiello”, Università di Salerno and INFN, Sezione di Napoli, Gruppo Collegato di Salerno, via S. Allende, 84081 Baronissi (Salerno), Italy
² INAF – Osservatorio Astronomico di Collurania, via M. Maggini, 64100 Teramo, Italy

Corresponding author: V. F. Cardone, winny@na.infn.it

Received: 4 December 2002
Accepted: 31 March 2003

Abstract

It has been suggested that a monitoring program employing the pixel lensing method to search for microlensing events towards galactic globular clusters may increase the statistics and discriminate among different halo models. Stimulated by this proposal, we evaluate an upper limit to the pixel lensing event rate for such a survey. Four different dark halo models have been considered changing both the flattening and the slope of the mass density profile. The lens mass function has been modelled as a homogenous power – law for and both the mass limits and the slope of the mass function have been varied to investigate their effect on the rate. The target globular clusters have been selected in order to minimize the disk contribution to the event rate. We find that a pixel lensing survey towards globular clusters is unable to discriminate among different halo models since the number of detectable events is too small to allow any reliable statistical analysis.