X-ray and optical observations of the closest isolated radio pulsar

Abstract

With a parallactic distance of 170 pc, PSR J2144-3933 is the closest isolated radio pulsar currently known. It is also the slowest (P= 8.51 s) and least energetic (? erg s^-1) radio pulsar; its radio emission is difficult to account for with standard pulsar models, since the position of PSR J2144-3933 in the period-period derivative diagram is far beyond the typical radio ‘death lines’. Here we present the first deep X-ray and optical observations of PSR J2144-3933, performed in 2009 with XMM-Newton and European Southern Observatory (ESO)/Very Large Telescope (VLT), from which we derive, assuming a blackbody emission spectrum, a surface temperature upper limit of 2.3 × 10⁵ K for a 13 km radius neutron star, 4.4 × 10⁵ K for a 500 m radius hotspot and 1.9 × 10⁶ K for a 10 m radius polar cap. In addition, our non-detection of PSR J2144-3933 constrains its non-thermal luminosity to be <30 and <2 per cent of the pulsar rotational energy loss in the 0.5-2 keV X-ray band and in the B optical band, respectively. Based on observations obtained with XMM-Newton, a European Space Agency (ESA) science mission with instruments and contributions directly funded by ESA Member States and NASA, and with ESO/VLT Antu (UT1).