Glitch in the millisecond pulsar PSR J0613-0200 and its implications for PTA-based gravitational wave detection

Nearly 30 years of high-precision timing data on PSR J0613-0200 from the Effelsberg (Germany), Lovell (UK), MeerKAT (South Africa), Nançay (France), uGMRT (India), WSRT (Netherlands), and Parkes (Australia) radio telescopes were analyzed using phase-coherent timing, Gaussian process regression, and a hidden Markov model to characterize its rotational behavior. The global timing solution was updated via Bayesian inference with Vela.jl. Notably, the smallest known glitch was confirmed in our analysis, and its parameters were measured with improved precision: the glitch epoch was determined as tg=50914(2), fractional changes in spin frequency and its derivative are ∆νg/ν=2.888(4) ×10−12 and ∆ν˙g/ν˙=−1.504(2)×10−3, respectively. This analysis reveals a rare decrease in the spin-down rate (|ν˙|) following the glitch, accompanied by reduced timing noise. Within the framework of standard glitch models, these results suggest that the internal structure of PSR J0613-0200 resembles that of canonical isolated pulsars, with its microphysical state approaching the threshold for glitch triggering. However, because the main driving factors, namely internal temperature and spin-down rate, are inefficient, the glitch rate in millisecond pulsars remains significantly lower than in ordinary young pulsars. The glitch waiting time of PSR J0613-0200 is estimated to be on the order of 102–104 yr. Taken together, these observational and theoretical results suggest that glitches in millisecond pulsars have no impact on gravitational wave detection within the timescales relevant to current PTA experiments.