Planetpol polarimetry of the exoplanet systems 55 Cnc and tau Boo

We present very sensitive polarimetry of 55 Cnc and τ Boo in an attempt to detect the partially polarized reflected light from the planets orbiting these two stars. 55 Cnc is orbited by a hot Neptune planet (55 Cnc e) at 0.038 au, a hot Jupiter planet (55 Cnc b) at 0.11 au and at least three more distant planets. The polarization of this system is very stable, showing no sign of the periodic variations that would be expected if a short-period planet were detected.