Iacolina, M. N.M. N.IacolinaPELLIZZONI, ALBERTO PAOLOALBERTO PAOLOPELLIZZONIEGRON, ELISE MARIE JEANNEELISE MARIE JEANNEEGRONPOSSENTI, ANDREAANDREAPOSSENTIBreton, R.R.BretonLyutikov, M.M.LyutikovKramer, M.M.KramerBURGAY, MARTAMARTABURGAYMotta, S. E.S. E.MottaDE LUCA, AndreaAndreaDE LUCATiengo, A.A.Tiengo2020-05-192020-05-1920160004-637Xhttp://hdl.handle.net/20.500.12386/24965The relativistic double neutron star binary PSR J0737-3039 shows clear evidence of orbital phase-dependent wind-companion interaction, both in radio and X-rays. In this paper, we present the results of timing analysis of PSR J0737-3039 performed during 2006 and 2011 XMM-Newton Large Programs that collected ∼20,000 X-ray counts from the system. We detected pulsations from PSR J0737-3039A (PSR A) through the most accurate timing measurement obtained by XMM-Newton so far, the spin period error being of 2 × 10<SUP>-13</SUP> s. PSR A’s pulse profile in X-rays is very stable despite significant relativistic spin precession that occurred within the time span of observations. This yields a constraint on the misalignment between the spin axis and the orbital momentum axis {δ }<SUB>{{A</SUB>}}≈ {6.6}<SUB>-5.4</SUB><SUP>+1.3</SUP> deg, consistent with estimates based on radio data. We confirmed pulsed emission from PSR J0737-3039B (PSR B) in X-rays even after its disappearance in radio. The unusual phenomenology of PSR B’s X-ray emission includes orbital pulsed flux and profile variations as well as a loss of pulsar phase coherence on timescales of years. We hypothesize that this is due to the interaction of PSR A’s wind with PSR B’s magnetosphere and the orbital-dependent penetration of the wind plasma onto PSR B closed field lines. Finally, the analysis of the full XMM-Newton data set provided evidence of orbital flux variability (∼7%) for the first time, involving a bow-shock scenario between PSR A’s wind and PSR B’s magnetosphere.STAMPAenArticle10.3847/0004-637X/824/2/872-s2.0-84978218314000381912800023https://iopscience.iop.org/article/10.3847/0004-637X/824/2/87/meta2016ApJ...824...87IFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation::PE9_10 High energy and particle astronomy – X-rays, cosmic rays, gamma rays, neutrinos