Orbital period and spin-orbit resonance of CHIME/ILT J1634+44

Determine whether the orbital period of the long-period radio transient CHIME/ILT J1634+44 corresponds to one of the proposed 5:2, 5:3, or 5:1 spin-orbit resonance configurations using pulse-arrival-time measurements.

Background

CHIME/ILT J1634+44 exhibits a primary rotation period of approximately 841 s and pulse-waiting-time patterns that have motivated proposed 5:2 and 5:3 spin-orbit resonance models, with a possible longer orbital period corresponding to a 5:1 resonance. The authors combined pulse arrival times from multiple observatories over a baseline of roughly a decade and fitted binary timing models at the proposed orbital periods.

Although some trial binary models reduced the timing residuals, the fits either improved only marginally, failed to converge, or produced unphysical parameters such as negative projected semi-major axes and unrealistic mass functions. Consequently, the available timing data do not establish which, if any, of the proposed resonant orbital periods describes the system.

References

Therefore, based solely on the timing analysis of 152 ToAs over a decade-long temporal baseline, we cannot constrain the orbital period to correspond to one of the proposed spin-orbit resonance models.

— Pulse Morphology and Spectral Study of LPT J1634+44 Using GMRT  (2610.26128 - Kumar et al., 19 Oct 2026) in Section 4.3, “Pulse Time of Arrival Analysis”; Appendix, Section “Testing Resonant Binary Models”