Gamma-ray flares from pulsar wind nebulae in the Large Magellanic Cloud

Abstract

ABSTRACTHigh-energy radiation of young pulsar wind nebulae (PWNe) is known to be variable. This is exemplified by the Crab nebula, which can undergo both rapid brightenings and dimmings. Two pulsars in the Large Magellanic Cloud, PSR J0540–6919 and PSR J0537–6910, are evolutionally close to Crab, so one may expect the same kind of variability from the PWNe around them. In this work, we search for flaring activity in these PWNe in gamma-rays using the data from the Fermi Large Area Telescope in the range 100 MeV–10 GeV collected from 2008 August to 2021 December. We construct light curves of these sources in the three bands, 100–300 MeV, 300–1000 MeV, and 1–10 GeV, with one-week resolution. We find evidence of flaring activity in all the bands, in contrast with Crab, where no flares at E>1 GeV were observed. Analysis of the flaring episode in the 100–300 and 300–1000 MeV bands indicates that the flux of one of the PWNe could grow by a factor of ≈5–10, and the statistical significance of the flare detection reaches 6σ. We are not confident about which of the two PWNe flared because of their proximity in the sky. However, in the 1–10 GeV band, where the angular resolution of LAT is better, we find several episodes of enhanced brightness in both the PWNe. We check possible contaminants which could be responsible for the observed variability but find their contribution not to be relevant.