Discovery of X - ray emission from the young radio pulsar PSR J 1357 − 6429

We present the first X-ray detection of the very young pulsar PSR J1357−6429 (characteristic age of 7.3 kyr) using data from the XMM-Newton and Chandra satellites. We found that the spectrum is well described by a power-law plus blackbody model, with photon index Γ = 1.4 and blackbody temperature kBT = 160 eV. For the estimated distance of 2.5 kpc, this corresponds to a 2–10 keV luminosity of ∼1.2 × 1032 erg s−1, thus the fraction of the spin-down energy channeled by PSR J1357−6429 into X-ray emission is one of the lowest observed. The Chandra data confirm the positional coincidence with the radio pulsar and allow to set un upper limit of 3× 1031 erg s−1 on the 2–10 keV luminosity of a compact pulsar wind nebula. We do not detect any pulsed emission from the source and determine an upper limit of 30% for the modulation amplitude of the X-ray emission at the radio frequency of the pulsar.