A Search for Transitions between States in Redbacks and Black Widows Using Seven Years of Fermi-LAT Observations

Diego F. Torres, Long Ji, Jian Li, Alessandro Papitto, Nanda Rea, Emma De Oña Wilhelmi, Shu Zhang

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    © 2017. The American Astronomical Society. All rights reserved.. Considering 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.
    Original languageEnglish
    Article number68
    JournalAstrophysical Journal
    Issue number1
    Publication statusPublished - 10 Feb 2017


    • gamma-rays: stars
    • pulsars: individual (PSR J1023+0038, PSR J1227-4853)


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