arXiv subjects

Hong-Zhou Wu

Publications and source records attributed to Hong-Zhou Wu.

3 recordsLinked to original sources

arXiv2026

Infrared Echoes of Precessing Tidal Disruption Events

A tidal disruption event (TDE) occurs when a star is torn apart by a supermassive black hole. The resulting UV/optical flare irradiates parsec-scale dust, producing delayed mid-infrared echoes that persist for years. These echoes provide unique calorimetric probes of the total radiated energy and dust geometry. Existing models usually assume static axisymmetric illumination patterns. However, the TDE accretion disk is likely misaligned and undergoes relativistic precession. In this work, we present a theoretical framework for infrared dust echoes from a precessing TDE disk. The precession will lead to highly variable infrared light curves, which can be revealed by high-cadence observations. The overall profile of the infrared light curves shows double-peaked to single-peaked pattern transitions as a result of the changes in the viewing angle or precession angle. The results indicate that infrared echoes are dynamic tracers of the evolving lighting patterns of the central engine.

astro-ph.HE↗

arXiv2026

A fast X-ray transient with chromatic flares: signatures of violent collisions induced by late-time central engine reactivation

Extragalactic Fast X-ray Transients (EFXTs) represent an emerging class of high-energy phenomena characterized by X-ray outbursts lasting from tens to hundreds of seconds. However, for more than half of the EFXTs, their physical origins remain elusive. In this Letter, we report the discovery of EP250302a, a luminous EFXT detected by the Einstein Probe (EP) at a redshift of $z = 1.131$. The multi-wavelength light curves of EP250302a reveal remarkable temporal features that distinguish it from the previously known EP-detected EFXT population, most notably a needle-like X-ray flare accompanied by smooth optical rebrightening during the afterglow phase. We suggest that the distinct X-ray and optical behaviors constitute the first observed instance of late-time violent collision of two relativistic shells in an EFXT. Drawing on insights from GRB studies, such a collision process strongly indicates the reactivation of a central engine, making EP250302a-like transients a unique laboratory for probing the late-time activity and jet physics of EFXT central engines.

astro-ph.HE↗

arXiv2025

Propagation of Precessing Jet in Envelope of Tidal Disruption Events

It is likely that the disk of a tidal disruption event (TDE) is misaligned with respect to the equatorial plane of the spinning supermassive black hole (SMBH), since the initial stellar orbit before disruption is most likely has an inclined orbital plane. Such misaligned disk undergoes Lense-Thirring precession around the SMBH spin axis, leading to a precessing jet if launched in the vicinity of the SMBH and aligned with the disk angular momentum. The bound debris can also build a thick envelope which powers optical emission. In this work, we study the propagation of the precessing jet in the TDE envelope. We adopt a ''zero-Bernoulli accretion'' (ZEBRA) envelope model. A episodic jet will be observed if the line of sight is just at the envelope pole direction and $θ_{\rm LT}=θ_{\rm env}$, since the jet can freely escape from this low density rotation funnel, where $θ_{\rm LT}$ and $θ_{\rm env}$ are the jet precessing angle and the angle between the envelope polar axis and the SMBH spin axis, respectively. The jet will be choked at other directions. For $θ_{\rm LT} < θ_{\rm env}$, the jets can also break out of the envelope for very small precession angle $θ_{\rm LT}$ or if the jet is aligned with SMBH spin. If the jet is choked within the envelope, the radiation produced during cocoon shock breakout will imprint characteristic signatures on the X-ray emission, such as low-amplitude fluctuation in the light curve.

astro-ph.HE↗