Propagation of Precessing Jet in Envelope of Tidal Disruption Events

TL;DR

This paper investigates how precessing jets from tidal disruption events propagate through the surrounding envelope, affecting observable emissions and jet breakout conditions.

Contribution

It introduces a model for jet propagation in a TDE envelope considering jet precession and envelope geometry, highlighting conditions for jet breakout and observational signatures.

Findings

Episodic jets are observable when aligned with the envelope pole.

Jets can be choked or break out depending on precession angle and alignment.

Choked jets produce distinctive X-ray signatures during cocoon shock breakout.

Abstract

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 $\theta_{\rm LT}=\theta_{\rm env}$, since the jet can freely escape from this low density rotation funnel, where $\theta_{\rm LT}$ and $\theta_{\rm env}$ 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 $\theta_{\rm LT} < \theta_{\rm env}$, the jets can also break out of the envelope for very small precession angle $\theta_{\rm LT}$ 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.