Torres, Diego F.Diego F.TorresJi, LongLongJiLi, JianJianLiPAPITTO, ALESSANDROALESSANDROPAPITTORea, NandaNandaReade Oña Wilhelmi, EmmaEmmade Oña WilhelmiZhang, ShuShuZhang2021-02-102021-02-1020170004-637Xhttp://hdl.handle.net/20.500.12386/30267Considering about seven years of Fermi-Large Area Telescope (LAT) data, we present a systematic search for variability that is possibly related to transitions between states in redbacks and black widow systems. The transitions are characterized by sudden and significant changes in the gamma-ray flux that persist on a timescale that is much larger than the orbital period. This phenomenology was already detected in the case of two redback systems, PSR J1023+0038 and PSR J1227-4853, which we present here. We show the existence of only one transition for each of these systems over the past seven years. We determine their spectra, establishing high-energy cutoffs at a few GeV for the high gamma-ray state of PSR J1023+0038, and for both states of PSR J1227-4853. The surveying capability of the Fermi-LAT allows further study of whether similar phenomenology has occurred in other sources. Although we have not found any evidence of a state transition for most of the studied pulsars, we note two black-widow systems, PSR J2234+0944 and PSR J1446-4701, whose apparent variabilities are reminiscent of the transitions in PSR J1023+0038 and PSR J1227-4853. For the other systems, we set limits on potential transitions in their measured gamma-ray light curves.STAMPAenArticle10.3847/1538-4357/836/1/682-s2.0-85014382403000397304500020https://iopscience.iop.org/article/10.3847/1538-4357/836/1/682017ApJ...836...68TFIS/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