Program: GS-2021A-FT-101

Title:Spectroscopic Monitoring of a New Neutron Star Binary
PI:Jay Strader
Co-I(s):

Abstract

We have discovered a new low-mass X-ray binary located near the center of the error ellipse of the Fermi/LAT gamma-ray source 4FGL J0540.0-7552. The presumed X-ray and optical couterpart shows emission consistent with an accreting redback binary: a compact binary with a low-mass, non-degenerate companion accreting onto a millisecond pulsar. We propose a 2.6-hour spectroscopic monitoring campaign using GMOS at Gemini-South to study the orbit of the binary by measuring radial velocity shifts of the low-mass secondary star, allowing a definitive classification of the source. If confirmed, 4FGL J0540.0-7552 would be one of only six gamma-ray bright low-mass X-ray binaries with ongoing accretion onto a recycled neutron star, providing valuable insights into the millisecond pulsar recycling process.

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