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

TL;DR

This study presents deep X-ray and optical observations of the closest isolated radio pulsar, PSR J2144-3933, providing upper limits on its surface temperature and non-thermal luminosity, challenging existing pulsar emission models.

Contribution

First deep X-ray and optical observations of PSR J2144-3933, setting constraints on its temperature and non-thermal emission, and informing pulsar emission theories.

Findings

Surface temperature upper limit of 2.3E5 K for a 13 km radius neutron star.

Non-thermal luminosity constrained to less than 30% of rotational energy loss in X-ray band.

Optical non-thermal luminosity constrained to less than 2% of rotational energy loss.

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 (Edot = 2.6E28 erg/s) 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 2.3E5 K for a 13 km radius neutron star, 4.4E5 K for a 500 m radius hot spot and 1.9E6 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 per cent 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.