2011A&A...533A.102L

Since the launch of the Fermi satellite, the number of known gamma-ray pulsars has increased tenfold. Most gamma-ray detected pulsars are young and energetic, and many are associated with TeV sources. PSR J1357-6429 is a high spin-down power pulsar ({dot}(E)=3.1x10³⁶erg/s), discovered during the Parkes multibeam survey of the Galactic plane, with significant timing noise typical of very young pulsars. In the very-high-energy domain (E>100GeV), H.E.S.S. has reported the detection of the extended source HESS J1356-645 (intrinsic Gaussian width of 12') whose centroid lies 7' from PSR J1357-6429. We search for gamma- and X-ray pulsations from this pulsar, characterize the neutron star emission and explore the environment of PSR J1357-6429. Using a rotational ephemeris obtained with 74 observations made with the Parkes telescope at 1.4GHz, we phase-fold more than two years of gamma-ray data acquired by the Large Area Telescope on-board Fermi as well as those collected with XMM-Newton, and perform gamma-ray spectral modeling. Significant gamma- and X-ray pulsations are detected from PSR J1357-6429. The light curve in both bands shows one broad peak. Gamma-ray spectral analysis of the pulsed emission suggests that it is well described by a simple power-law of index 1.5±0.3_stat±0.3_syst with an exponential cut-off at 0.8±0.3_stat±0.3_systGeV and an integral photon flux above 100MeV of (6.5 ±1.6_stat ±2.3_syst)x10^–8/cm2/s. The X-ray spectra obtained from the new data provide results consistent with previous work. Upper limits on the gamma-ray emission from its potential pulsar wind nebula (PWN) are also reported. Assuming a distance of 2.4 kpc, the Fermi LAT energy flux yields a gamma-ray luminosity for PSR J1357-6429 of L_γ=(2.13±0.25_stat±0.83_syst)x10³⁴erg/s, consistent with an L_γ∝sqrt({dot}(E)) relationship. The Fermi non-detection of the pulsar wind nebula associated with HESS J1356-645 provides new constraints on the electron population responsible for the extended TeV emission.