Marelli, M.M.MarelliMIGNANI, RobertoRobertoMIGNANIDE LUCA, AndreaAndreaDE LUCASaz Parkinson, P. M.P. M.Saz ParkinsonSalvetti, D.D.SalvettiDen Hartog, P. R.P. R.Den HartogWolff, M. T.M. T.Wolff2020-03-182020-03-1820150004-637Xhttp://hdl.handle.net/20.500.12386/23346We thank Andrea Belfiore (“Mario”) for the useful discussions on the γ -ray timing positions of LAT pulsars. The research leading to these results has received funding from the European Commission Seventh Framework Programme (FP7/2007–2013) under grant agreement n. 267251. This work was supported by the ASI-INAF contract I/037/12/0, art.22 L.240/2010 for the project “Calibrazione ed Analisi del satallite NuSTAR.” Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Numbers GO2-13093X and GO3-14075X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics and Space Administration under contract NAS8-03060. Facilities: XMM , CXO , ESO:VISTA , UKIRTWe present new Chandra and XMM-Newton observations of a sample of eight radio-quiet (RQ) γ-ray pulsars detected by the Fermi Large Area Telescope. For all eight pulsars we identify the X-ray counterpart, based on the X-ray source localization and the best position obtained from γ-ray pulsar timing. For PSR J2030+4415 we found evidence for a ∼10″-long pulsar wind nebula. Our new results consolidate the work from Marelli et al. and confirm that, on average, the γ-ray-to-X-ray flux ratios (F<SUB>γ</SUB>/F<SUB>X</SUB>) of RQ pulsars are higher than for the radio-loud (RL) ones. Furthermore, while the F<SUB>γ</SUB>/F<SUB>X</SUB> distribution features a single peak for the RQ pulsars, the distribution is more dispersed for the RL ones, possibly showing two peaks. We discuss possible implications of these different distributions based on current models for pulsar X-ray emission.STAMPAenArticle10.1088/0004-637X/802/2/782-s2.0-84926632544000353014500006https://iopscience.iop.org/article/10.1088/0004-637X/802/2/782015ApJ...802...78MFIS/05 - ASTRONOMIA E ASTROFISICA