scatter of points but also an apparent linear trend, we decided to skip these data in our primary fitting procedure and check their influence separately. During $2t_{\rm E} = 128.7~{\rm d}$ period centered on $t_0$ altogether 528 $I$-band data points were collected ($t_{\rm E}$ is Einstein crossing time, $t_0$ is time of the closest approach). The sky area, where the event is located, was also observed during the third phase of the OGLE project. Altogether, more than 4300 epochs were collected since 2001, and no other variability was seen except the analyzed event.

The light curve of the event is presented in Figure \[fig:lc\]. At the baseline $I = 16.459~{\rm mag}$ and $V = 19.268~{\rm mag}$. The uncertainties of photometry were scaled as is typically done in the analysis of microlensing events: $\sigma_{\rm new} = 1.5\sqrt{\sigma_{\rm old}^2 + (4~{\rm mmag})^2}$ [see, e.g., @skowron11]. We transformed photometry to the standard system using @szymanski11 photometric maps.

Microlensing model
==================

The light curve clearly shows anomalies and cannot be fitted with the standard point source-point lens Paczyński light-curve ($\Delta\chi^2\approx10000$). The rough estimates of the event properties can be found using analytical approximations presented by @han06 (see Appendix). We start our search with a 