XMM-Newton Observation and Optical Monitoring of the Candidate Redback Millisecond Pulsar 1FGL J0523.5$-$2529

J. P. Halpern, S. Bogdanov

1FGL J0523.5$-$2529 is a Fermi selected redback millisecond pulsar candidate that exhibited luminous optical and X-ray flares in 2020-2021. We obtained a simultaneous X-ray and $U$…