Calibration of the Timing Performance of GECAM-C

TL;DR

This paper calibrates the timing accuracy of GECAM-C, achieving the highest time resolution among GRB detectors, and demonstrates its effectiveness in timing analysis and localization of X-ray and gamma-ray transients.

Contribution

It introduces a calibration method using cosmic-ray secondary particles to achieve precise relative and absolute timing calibration for GECAM-C, enhancing its timing analysis capabilities.

Findings

Relative timing accuracy of 0.1 μs achieved.

Absolute timing accuracy of about 2-6 μs established.

Spectral lag of Crab pulsar observed as approximately -0.2 μs/keV.

Abstract

As a new member of the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) after GECAM-A and GECAM-B, GECAM-C (originally called HEBS), which was launched on board the SATech-01 satellite on July 27, 2022, aims to monitor and localize X-ray and gamma-ray transients from $\sim$ 6 keV to 6 MeV. GECAM-C utilizes a similar design to GECAM but operates in a more complex orbital environment. In this work, we utilize the secondary particles simultaneously produced by the cosmic-ray events on orbit and recorded by multiple detectors, to calibrate the relative timing accuracy between all detectors of GECAM-C. We find the result is 0.1 $\mu \rm s$, which is the highest time resolution among all GRB detectors ever flown and very helpful in timing analyses such as minimum variable timescale and spectral lags, as well as in time delay localization. Besides, we calibrate the absolute time accuracy using the one-year Crab pulsar data observed by GECAM-C and Fermi/GBM, as well as GECAM-C and GECAM-B. The results are $2.02\pm 2.26\ \mu \rm s$ and $5.82\pm 3.59\ \mu \rm s$, respectively. Finally, we investigate the spectral lag between the different energy bands of Crab pulsar observed by GECAM and GBM, which is $\sim -0.2\ {\rm \mu s\ keV^{-1}}$.