Microlensing towards the Small Magellanic Cloud. EROS 2 first year survey
Loading...
Date
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Description
We present here an analysis of the light curves of 5.3 million stars in the Small Magellanic Cloud observed by EROS (Expérience de Recherche d'Objets Sombres). One star exhibits a variation that is best interpreted as due to gravitational microlensing by an unseen object. This candidate was also reported by the MACHO collaboration. Once corrected for blending, the Einstein radius crossing time is 123 days, corresponding to lensing by a Halo object of $2.6^{+8.2}_{-2.3} M_{\odot}$. The maximum magnification is a factor of 2.6. The light curve also displays a periodic modulation with a 2.5% amplitude and a period of 5.1 days. Parallax analysis of the candidate indicates that a Halo lens would need to have a mass of at least $0.3 M_{\odot}$, although a lens in the SMC could have a mass as low as $0.07 M_{\odot}}$. We estimate the optical depth for microlensing towards the SMC due to this event to be $\sim 3.3 \times 10^{-7}$, with an uncertainty dominated by Poisson statistics. We show that this optical depth corresponds to about half that expected for a spherical isothermal Galactic Halo comprised solely of such objects, and that it is consistent with SMC self-lensing if the SMC is elongated along the line-of-sight by at least 5 kpc.
10 pages, 11 figures (9 included .eps and 2 separate .gif). Numerical value for constrain on mass and distance of deflector from parallax analysis less severe than previously. Minor changes otherwise. Accepted for publication in Astronomy & Astrophysics
10 pages, 11 figures (9 included .eps and 2 separate .gif). Numerical value for constrain on mass and distance of deflector from parallax analysis less severe than previously. Minor changes otherwise. Accepted for publication in Astronomy & Astrophysics