Delayed Launch of Ultrafast Outflows in the Tidal Disruption Event AT2020afhd

TL;DR

This study documents the first observed full evolution of ultrafast outflows in a tidal disruption event, revealing delayed onset, deceleration, and complex ionization behavior through multi-instrument X-ray observations.

Contribution

It provides the first detailed observation of the complete lifecycle of X-ray outflows in a TDE, including their delayed appearance and deceleration.

Findings

Outflows appeared between days 172 and 194 post-discovery.

Outflows decelerated from ~0.19c to ~0.0097c over 10 days.

Inverse correlation between outflow velocity and ionization parameter.

Abstract

We report the detection and characterization of ultrafast outflows (UFOs) in the X-ray spectra of the tidal disruption event (TDE) AT2020afhd, based on observations from NICER, Swift, and XMM. Prominent blueshifted absorption features were detected exclusively during the intermediate phase of the event, occurring between days 172 and 212 within the first 300 days post-discovery. During this period, the UFO appeared no earlier than day 74, strengthened between days 172 and 194, and disappeared after day 215. This marks the first time that the full evolutionary sequence of X-ray outflows has been observed in a TDE. Moreover, the outflows exhibited a dramatic deceleration from ~0.19c to ~0.0097c over a span of approximately 10 days. Photoionization spectral analysis reveals an inverse correlation between outflow velocity and ionization parameter, in contradiction to the predictions from radiation pressure-driven wind. Eventually, we propose that the delayed onset of the outflows may result from an increase in the wind opening angle and/or metal enrichment, particularly iron and oxygen, during the disk formation phase.