CAMPANA, SergioSergioCAMPANACoti Zelati, F.F.Coti ZelatiPAPITTO, ALESSANDROALESSANDROPAPITTORea, N.N.ReaTorres, D. F.D. F.TorresBaglio, M. C.M. C.BaglioD'AVANZO, PaoloPaoloD'AVANZO2020-05-262020-05-2620160004-6361http://hdl.handle.net/20.500.12386/25180The binary system PSR J1023+0038 (J1023) hosts a neutron star and a low-mass companion. J1023 is the best studied transitional pulsar, alternating a faint eclipsing millisecond radio pulsar state to a brighter X-ray active state. At variance with other low-mass X-ray binaries, this active state reaches luminosities of only ~10<SUP>34</SUP> erg s<SUP>-1</SUP>, showing strong, fast variability. In the active state, J1023 displays: I) a high state (L<SUB>X</SUB> ~ 7 × 10<SUP>33</SUP> erg s<SUP>-1</SUP>, 0.3-80 keV) occurring ~80% of the time and during which X-ray pulsations at the neutron star spin period are detected (pulsed fraction ~ 8%); II) a low state (L<SUB>X</SUB> ~ 10<SUP>33</SUP> erg s<SUP>-1</SUP>) during which pulsations are not detected (≲ 3%); and III) a flaring state during which sporadic flares occur in excess of ~ 10<SUP>34</SUP> erg s<SUP>-1</SUP>, with no pulsation too. The transition between the high and the low states is very rapid, on a ~10 s timescale. Here we propose a plausible physical interpretation of the high and low states based on the (fast) transition among the propeller state and the radio pulsar state. We modelled the XMM-Newton spectra of the high, low and radio pulsar states, and found a good agreement with this physical picture.STAMPAenArticle10.1051/0004-6361/2016290352-s2.0-84990855349000385832200111https://www.aanda.org/articles/aa/abs/2016/10/aa29035-16/aa29035-16.html2016A&A...594A..31CFIS/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_11 Relativistic astrophysics