Einstein Probe FXT timing calibrated to 6 μs using Crab and millisecond pulsars
Pulsar timing observations confirm Einstein Probe FXT meets microsecond-level requirements for multi-messenger follow-up. Absolute accuracy reaches 6 μs in the fastest mode, with a 20 μs inter-module offset now quantified for future data analysis. Further observations of additional millisecond pulsars will tighten the systematic error budget.
The calibration used 1RXS J170849.0–400910 in full-frame mode, PSR B1509–58 in partial-window mode, and Crab, PSR B1821–24, and PSR B1937+21 in timing mode. TOAs from both FXTA and FXTB modules were compared directly to NICER and Jodrell Bank ephemerides, confirming internal consistency across readout modes and a systematic offset of 20 ± 21 μs between the two modules. The measured Crab main-peak advance of ~357–394 μs relative to radio ephemerides matches known NICER behavior, validating the end-to-end chain from pnCCD readout through on-board clock to ground processing.
Zhang et al.: Additional 50 Crab observations by March 2027 will reduce the systematic timing uncertainty below 30 μs for both modules.
Sources (3)
- [1]Primary Source(https://arxiv.org/abs/2610.12943)
- [2]Supporting Source(https://arxiv.org/abs/2309.14573)
- [3]Supporting Source(https://heasarc.gsfc.nasa.gov/docs/nicer/)