What is RTModel

RTModel is a computer platform developed by Valerio Bozza for the analysis and interpretation of interesting microlensing events in real time. It is based on the VBBinaryLensing contour integration code, published in MNRAS 408 (2010) 2188. This code is now publicly available here.

This platform works in strict conjunction with ARTEMIS, the system created by Martin Dominik et al. in St. Andrews University, Scotland.

The working flow is as follows:

  • ARTEMIS issues anomaly alerts on microlensing events that deviate from the single lens model.

  • RTModel downloads the data of such interesting events from ARTEMIS.

  • RTModel looks for the best model for the events, by fitting binary lens models, binary source models, with or without parallax and so on.

  • The best models are automatically uploaded to this web page, where everybody can check them.

Events modelled in the following years are available:

The index pages contain the list of events modelled in the corresponding year, sorted by category. Clicking on any of the icons, the respective event page opens, with a list of possible models. For each model, the chi square is displayed along with the blending fraction g (ratio of the background to the source flux), and the parameters of the model.

In particular

- u0 is the impact parameter of the source trajectory to the center of mass
- t0
is the time of the closest approach of the source to the center of mass
tE is the Einstein time
- ρ*
is the source radius in Einstein units
- s is the separation of the two lenses in Einstein units
- q is the mass ratio
- θ is the angle between the position vector of the first lens to the source velocity

The source position is thus given in parametric form by

y1 = u0*sin(θ) - (t-t0)/tE*cos(θ)
y2 = -u0*cos(θ) - (t-t0)/tE*sin(θ)

The first lens has mass 1/(1+q). The second has mass q/(1+q). They both lie on the y2 = 0 axis. Their positions are

y1(M1) = - sq/(1+q)
y1(M2) = s/(1+q)

For models including parallax, the two components of the parallax vector are given in the North-East directions. The magnitude of the parallax vector is given by the ratio of the astronomical unit and the Einstein radius projected to the observer plane. If available, the light curve as would be seen by Spitzer is displayed in red, the light curve as seen by Kepler is displayed in blue, and that as seen by Gaia in green.

For models with orbital motion, the orbit is assumed to be circular. The three components of the orbital velocity are expressed in terms of (ds/dt)/s, dθ/dt and (dsz/dt)/s.

Errors in all models are obtained by inverting the Fisher matrix and normalizing by requiring a 10% increase in the chi square at the extrema of the uncertainty range. Residuals in the plots are already normalized by the respective error bars.

For all use of these models and for any questions, please inquire Valerio Bozza