Catalog of Outbursts of Neutron Star Low-mass X-Ray Binaries

Abstract Many X-ray binaries (XRBs) are transiently accreting. Having statistics on their recurrence times is helpful to address questions related to binary evolution and populations, as well as the physics of binary systems. We compile a catalog of known outbursts of 87 transient neutron stars (identified through bursts or pulsations) and low-mass XRBs until mid-2025. Most outbursts are taken from the literature, but we also identify some outbursts from public X-ray monitoring lightcurves. We find 109 outbursts not previously identified in the literature; most are from the frequent transients GRS 1747-312 and the Rapid Burster MXB 1730-335, though we suspect that two outbursts from Liller 1 may be from another transient besides the Rapid Burster. We also find new outbursts for 10 other systems, and verify substantial quiescent intervals for XMM J174457-2850.3, XMMU J174716.1-281048, and AX J1754.2-2754. Outburst detection has been relatively efficient since 1996 for outbursts above F X (2–10 keV) = 3 × 10 −10 erg cm −2 s −1 . While several systems have many known outbursts, 40 of the 87 systems we track have zero or one recorded outburst between 1996 and 2023. This suggests that many faint Galactic center XRBs may be neutron star XRBs, though we cannot completely rule out the proposition that most neutron star XRBs undergo frequent outbursts below all-sky monitor detection limits.