Discovery of gamma- and X-ray pulsations from the young and energetic PSR J1357−6429 with Fermi and XMM-Newton

¹ Université Bordeaux 1, CNRS/IN2P3, Centre d’Études Nucléaires de Bordeaux Gradignan, 33175 Gradignan, France
e-mail: lemoine@cenbg.in2p3.fr; smith@cenbg.in2p3.fr
² Space Science laboratory, Universities Space Research Association, NASA MSFC VP62, Huntsville, AL 35805, USA
e-mail: vyacheslav.zavlin-1@nasa.gov
³ Institut für Astronomie und Astrophysik, Universität Tübingen, 72076 Tübingen, Germany
e-mail: grondin@astro.uni-tuebingen.de
⁴ CSIRO Astronomy and Space Science, Australia Telescope National Facility, Epping NSW 1710, Australia
e-mail: Ryan.Shannon@csiro.au
⁵ INAF – Cagliari Astronomical Observatory, 09012 Capoterra ( CA), Italy
⁶ Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA
⁷ Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3, Montpellier, France
⁸ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁹ High Energy Space Environment Branch, Naval Research Laboratory, Washington, DC 20375, USA
¹⁰ Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, M13 9PL, UK
¹¹ W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305, USA
¹² Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030, resident at Naval Research Laboratory, Washington, DC 20375, USA
¹³ Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064, USA

Received: 6 June 2011
Accepted: 20 July 2011

Abstract

Context. 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 (Ė = 3.1 × 10³⁶ erg s^-1), 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 > 100 GeV), 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.

Aims. We search for gamma- and X-ray pulsations from this pulsar, characterize the neutron star emission and explore the environment of PSR J1357−6429.

Methods. Using a rotational ephemeris obtained with 74 observations made with the Parkes telescope at 1.4 GHz, 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.

Results. 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_syst GeV and an integral photon flux above 100 MeV of (6.5 ± 1.6_stat ± 2.3_syst)    ×    10^-8 cm^-2 s^-1. 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.

Conclusions. 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) × 10³⁴ erg s^-1, consistent with an 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.