  With a distance of 170 pc, PSR J2144-3933 is the closest isolated radio
pulsar currently known. It is also the slowest and least energetic radio
pulsar; indeed, its radio emission is difficult to account for with standard
pulsar models, since its position in the P-Pdot diagram is far beyond typical
"death lines". Here we present the first deep X-ray and optical observations of
PSR J2144-3933, performed in 2009 with XMM-Newton and the VLT, from which we
can set one of the most robust upper limits on the surface temperature of a
neutron star. We have also explored the possibility of measuring the neutron
star mass from the gravitational lensing effect on a background optical source.
