Why do many TDEs produce radio outflows years later?
In plain words
Many tidal disruption flares start to shine in radio waves years after the visible flare, showing that fast-moving gas appears late. Why the black hole would launch matter so late is unknown.
Precise statement
A large fraction of optically selected TDEs (up to about 40 percent in one sample, Cendes et al., ApJ, 2024) show radio emission rising hundreds to thousands of days after disruption. Determine whether this reflects delayed launching of outflows (for example an accretion state change), off-axis jets, outflows reaching denser circumnuclear gas, or collisions of debris or orbiting stars with the disk.
What would settle it
Radio spectral monitoring that measures outflow launch time, speed and energy, combined with X-ray state tracking in the same events.
Status in the literature
Unverified note
A 2026 model attributes delayed radio flares to outflows from repeated collisions of an orbiting star with the TDE disk (Linial, Metzger and Beloborodov, ApJ, 2026); no model is yet established.