Are Delayed Radio Flares Common in Tidal Disruption Events? The Case of the TDE iPTF16fnl

TL;DR

This paper investigates the occurrence of delayed radio flares in tidal disruption events, presenting new data on iPTF16fnl and discussing whether such delays are common, which could reveal new aspects of SMBH accretion physics.

Contribution

The study provides new radio observations of iPTF16fnl and explores the possibility of delayed radio flares, suggesting this phenomenon might be more common in TDEs than previously thought.

Findings

Delayed radio flare observed in iPTF16fnl about 5 months after discovery.

Multiple models, including complex CNM density and delayed outflow ejection, can explain the flare.

Delayed flares may be a common feature in TDEs, indicating varied SMBH accretion processes.

Abstract

Radio emission from tidal disruption events (TDEs) originates from an interaction of an outflow with the super-massive black hole (SMBH) circum nuclear material (CNM). In turn, this radio emission can be used to probe properties of both the outflow launched at the event and the CNM. Until recently, radio emission was detected only for a relatively small number of events. While the observed radio emission pointed to either relativistic or sub-relativistic outflows of different nature, it also indicated that the outflow has been launched shortly after the stellar disruption. Recently, however, delayed radio flares, several months and years after stellar disruption, were reported in the case of the TDE ASASSN-15oi. These delayed flares suggest a delay in the launching of outflows and thus may provide new insights into SMBH accretion physics. Here, we present a new radio dataset of another TDE, iPTF16fnl, and discuss the possibility that a delayed radio flare has been observed also in this case, ~ 5 months after optical discovery, suggesting that this phenomenon may be common in TDEs. Unlike ASASSN-15oi, the data for iPTF16fnl is sparse and the delayed radio flare can be explained by several alternative models: among them are a complex varying CNM density structure and a delayed outflow ejection.