arXiv subjects

Ye-Hao Cheng

Publications and source records attributed to Ye-Hao Cheng.

3 recordsLinked to original sources

arXiv2026

Minutes-long soft X-ray prompt emission from a compact object merger

Compact object mergers are multi-messenger sources and known progenitors of some gamma-ray bursts, bright flashes of high-energy radiation powered by a central engine, either an accreting black hole or a neutron star. Our understanding of these events has so far been shaped primarily by observations in the gamma-ray band, leaving their prompt phase poorly constrained at lower energies. A long-lasting ($\approx$100 s) engine-driven X-ray emission was discussed to explain rapidly fading X-ray afterglows following several ($\approx$30%) bursts of short ($\lesssim$2 s) duration. However, this prompt X-ray component was not directly observed and past candidates were not confirmed. Here we report the discovery of EP250704a containing a minutes-long ($\sim$560 s) flash of soft (0.5--4 keV) X-rays immediately following the short ($\sim$0.4 s) GRB 250704B. The variability and spectral shape of this emission are inconsistent with the canonical picture of a hard, accretion-powered spike followed by a standard external-shock afterglow. Instead, the long-soft bump points to a distinct phase of prompt emission in X-rays, which would not have been detected without the soft X-ray coverage of Einstein Probe. The detection of a prompt soft X-ray counterpart in an otherwise ordinary short GRB shows that long-lasting X-ray emission is likely a common feature of merger-driven bursts and a promising electromagnetic counterpart to gravitational wave sources.

astro-ph.HE↗

arXiv2026

A Roadmap for Transient Hunters: Mapping Stellar Mass and Star Formation Rate Anisotropies in the Local Universe

Over the past few decades, an increasing number of transients in nearby galaxies have been discovered through various survey projects. Unlike astrophysical phenomena at cosmological distances, transients in the local universe exhibit a pronounced anisotropy in their sky distribution. Consequently, adopting an appropriate survey strategy is essential to improve the efficiency of transient searches in the local universe. In this work, we utilized a large galaxy catalog to map the sky distributions of stellar mass and star formation rate (SFR) across different luminosity distance thresholds and angular resolutions of the grid on the celestial sphere. These maps can further serve to characterize the anisotropic spatial distribution of nearby extragalactic transients. For different angular resolutions of the celestial sphere, we find that the sky distributions of stellar mass of galaxies are similar to those of the SFR in the main anisotropic structures. As the luminosity distance threshold increases, the anisotropic structures of the sky distributions become more isotropic. We calculate the angular power spectra and fluctuations of the sky distribution of stellar mass and SFR at a given angular resolution and find that the angular power spectra and fluctuations decrease rapidly as the luminosity distance threshold increases. Finally, by qualitatively comparing the sky distribution of core-collapse supernovae with our SFR sky distribution, we find that the two exhibit consistent patterns in several prominent structures. The mapped sky distributions of stellar mass and SFR can serve as valuable references for future surveys in searching for extragalactic transients.

astro-ph.HE↗

arXiv2017

A New Measurement of the Spectral Lag of Gamma-Ray Bursts and its Implications for Spectral Evolution Behaviors

We carry out a systematical study of the spectral lag properties of 50 single-pulsed Gamma-Ray Bursts (GRBs) detected by Fermi/GBM. By dividing the light curves into multiple consecutive energy channels we provide a new measurement of the spectral lag which is independent on energy channel selections. We perform a detailed statistical study of our new measurements. We find two similar power-law energy dependencies of both the pulse arrival time and pulse width. Our new results on the power-law indices would favor the relativistic geometric effects for the origin of spectral lag. However, a complete theoretical framework that can fully account for the diverse energy dependencies of both arrival time and pulse width revealed in this work is still missing. We also study the spectral evolution behaviors of the GRB pulses. We find that the GRB pulse with negligible spectral lag would usually have a shorter pulse duration and would appear to have a "hardness-intensity tracking" (HIT) behavior and the GRB pulse with a significant spectral lag would usually have a longer pulse duration and would appear to have a "hard-to-soft" (HTS) behavior.

astro-ph.HE↗