X-ray pulsations from the radio-quiet gamma-ray pulsar in CTA 1

TL;DR

This study reports the detection of X-ray pulsations from the radio-quiet gamma-ray pulsar PSR J0007+7303 in CTA 1, revealing thermal and non-thermal emission components and advancing understanding of pulsar emission mechanisms.

Contribution

First detection of X-ray pulsations from PSR J0007+7303 combining XMM-Newton and Fermi data, showing thermal and non-thermal emission components in a radio-quiet gamma-ray pulsar.

Findings

Detected 4.7 sigma X-ray pulsations from PSR J0007+7303.

Phase-resolved spectroscopy indicates thermal emission from a hot polar cap.

Off-pulse emission is dominated by non-thermal power-law spectrum.

Abstract

Prompted by the Fermi LAT discovery of a radio-quiet gamma-ray pulsar inside the CTA 1 supernova remnant, we obtained a 130 ks XMM-Newton observation to assess the timing behavior of this pulsar. Exploiting both the unprecedented photon harvest and the contemporary Fermi LAT timing measurements, a 4.7 sigma single peak pulsation is detected, making PSR J0007+7303 the second example, after Geminga, of a radio-quiet gamma-ray pulsar also seen to pulsate in X-rays. Phase-resolved spectroscopy shows that the off-pulse portion of the light curve is dominated by a power-law, non-thermal spectrum, while the X-ray peak emission appears to be mainly of thermal origin, probably from a polar cap heated by magnetospheric return currents, pointing to a hot spot varying throughout the pulsar rotation.