Spectroscopic and light curve characterization of bulge microlensing events ^*,**

¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands e-mail: soto@strw.leidenuniv.nl
² Departamento de Astronomía y Astrofísica, P. Universidad Católica de Chile, Av. Vicuña Mackenna, 4860 Santiago, Chile e-mail: dante@astro.puc.cl
³ European Southern Observatory, Karl-Schwartzschild-Strasse 2, 85748 Garching, Germany e-mail: mrejkuba@eso.org

Received: 8 August 2006
Accepted: 7 January 2007

Abstract

Aims.Microlensing events have been observed regularly by surveys such as MACHO, OGLE and MOA. They offer an excellent way to probe the galactic structure, kinematics and stellar content. We have undertaken a follow-up study of 16 galactic microlensing events to determine masses and locations of the sources of these events within the Galaxy.

Methods.Spectroscopy allows us to obtain information about the sources of the events. Low resolution spectra obtained with the Magellan I and II telescopes were analyzed to obtain radial velocities, spectral type and extinction by the method of Kane & Sahu. We also present results for the lens of the event using the microlensing light curve when possible. Light curves have been analyzed with the standard and the parallax models.

Results.We have inferred a configuration inside our galaxy for each event, and therefore a lens mass estimation using a suitable galaxy model. Lens mass determination in some cases shows massive lenses that can be considered black hole candidates. This is the case for the events MACHO-98-BLG-6, and OGLE-00-BUL-43. In our sample only three events do not have enough parallax signal for a successful estimation of the lens mass.