A novel method for measuring spectral lags by dynamic time warping

¹ School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, PR China
² Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing, Guizhou Normal University, Guiyang 550001, PR China

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 18 December 2025
Accepted: 16 April 2026

Abstract

Context. Measuring spectral lags in gamma-ray bursts (GRBs) across different energy bands is important for studying prompt-emission physics and related applications.

Aims. We assessed the reliability and applicability of the constrained dynamic time warping (DTW) method for measuring spectral lags in GRBs.

Methods. We applied the constrained DTW method to a sample of 50 single-pulse GRBs observed by Fermi/GBM and compared the resulting spectral lags with those obtained using Gaussian peak-time fitting and the modified cross-correlation function (MCCF). We also performed simulation-based tests with known input lags to validate the method.

Results. The spectral lags derived from DTW are overall consistent with those obtained from Gaussian fitting and MCCF, with no significant differences found within 3σ. For evidently asymmetric pulses, fitting the full pulse with a symmetric Gaussian function can bias the inferred lag, while peak-focused Gaussian fitting yields results more consistent with DTW and MCCF. Simulations show that DTW can reliably recover the input lag and provide robust uncertainty estimates.

Conclusions. Dynamic time warping provides a robust and complementary approach to spectral-lag measurement in GRBs and is promising for future applications to more complex light curves and related studies such as gravitational-lensing searches.