arXiv subjects

Fei-Fan Song

Publications and source records attributed to Fei-Fan Song.

3 recordsLinked to original sources

arXiv2025

Time Evolution of Optical Darkness in GRB Afterglow: The Case of GRB 240825A

Long-duration gamma-ray bursts (GRBs) are believed to occur in star-forming regions. The multiwavelength follow-up observations of the early afterglow of GRB 240825A provided insights into the evolution of the optical-to-X-ray spectral feature of the afterglow. We comprehensively investigate the evolution of X-ray spectral properties through time-resolved spectral analysis and calculate optical darkness ($\beta_\mathrm{OX}$) to reveal the physical properties of the afterglow. The X-ray-to-optical SEDs of afterglow in different time intervals are fitted to derive the extinction curves. The $\beta_\mathrm{OX}$ exhibits a trend of decreasing and then increasing, reaching its minimum value at $\sim1000\mathrm{\,s}$ post-trigger. However, at 11 hours post-trigger, $\beta_\mathrm{OX}$ does not meet the criteria for an optically dark burst. The extinction curves in different time intervals indicate that GRB 240825A occurred in a dust-obscured environment.

astro-ph.HE↗

arXiv2025

Possible Quasi-Period Oscillation Signals in the Unique Event of GRB 250702DBE/EP250702a?

GRB 250702DBE was time-consequently triggered by GBM onboard the Fermi satellite. It is uncertain which celestial catalog is suitable for this special ultra-long event to belong to. In this paper, we comprehensively investigate the lightcurves obtained by Fermi-GBM detectors. In the energy band of 8-1000 keV, no Quasi-Period Oscillation (QPO) signals are found in the lightcurve of the first burst 250702D, a possible QPO signal of 0.046 Hz corresponding to a period of 21.7 s is found in the lightcurve of the second burst 250702B, and a possible QPO signal of 0.024 Hz corresponding to a period of 41.7 s is found in the lightcurve of last burst 250702E. The significance level of the possible QPO signals is comprehensively examined. In addition, we examine the spectral properties of the sources. In general, a broken power law is suitable for modeling the spectral data from 8 keV to 40 MeV. We qualitatively suggest some kinds of celestial object with the periodic characteristic that might be the progenitors of this unique event.

astro-ph.HE↗

arXiv2024

On the Detection and Characterization of Quasiperiodic Oscillations in Astronomical Time Series: Gamma-Ray Burst X-Ray Light Curves as a Test Case

The study of temporal properties of variable sources can elucidate their physical processes. In this context, we present a critical study comparing three approaches to periodic or quasiperiodic behavior: Gaussian process, power spectrum, and wavelet analysis, using celerite, Lomb-Scargle periodograms, and weighted wavelet-Z transforms, respectively. We use 15 Swift-X-ray Telescope light curves of short gamma-ray bursts (sGRBs) as examples. A comprehensive analysis of two sGRB X-ray light curves is performed. The results reveal the importance of artifacts, largely in the form of false quasiperiodic oscillation signals, possibly introduced by preprocessing (such as detrending) or other aspects of the analysis. The exploration described in this paper can be helpful for future studies of variability in GRBs, active galactic nuclei, and other astronomical sources.

astro-ph.HE↗