The current searches for microlensing events towards the galactic bulge can be used to detect planetary companions around the lensing stars .
The effect of such planets is a short-term modulation on the smooth microlensing lightcurve produced by the main lensing star .
Current and planned experiments should be sensitive enough to discover planets ranging from Jupiter mass down to Earth mass .
In order to be able to successfully detect planets this way , it is necessary to accurately and frequently monitor a microlensing event photometrically , once it has been “ triggered ” .

Here we present a large variety of two-dimensional magnification distributions for systems consisting of an ordinary star and a planetary companion .
We cover planet/star mass ratios from m _ { pl } / M _ { * } = 10 ^ { -5 } to 10 ^ { -3 } .
These limits correspond roughly to M _ { Earth } and M _ { Jupiter } , for a typical lens mass of M _ { * } \approx 0.3 M _ { \odot } .
We explore a range of star-planet distances , with particular emphasis on the case of “ resonant lensing ” , a situation in which the planet is located at or very near the Einstein ring of the lensing star .

We show a wide selection of light curves – one dimensional cuts through the magnification patterns – to illustrate the broad range of possible light curve perturbations caused by planets .
The strongest effects are to be expected for caustic crossings .
But even tracks passing outside the caustics can have considerable effects on the light curves .
The easiest detectable ( projected ) distance range for the planets is between about 0.6 and 1.6 Einstein radii .
Planets in this distance range produce caustics inside the Einstein ring of the star .
For a lensing star with a mass of about 0.3 M _ { \odot } at a distance of 6 kpc and a source at 8 kpc , this corresponds to physical distances between star and planet of about 1 to 3 AU .