FRB121102 was the first fast radio burst (FRB) known to repeat,
i.e., additional FRBs have come from the same direction,
This created much research interest given the opportunities to
locate and study the source and study the repeating FRBs in
more depth. As of 9/2022, hundreds of bursts have been detected
from that location, as well as a persistent radio source
(apparently synchrotron radiation) and
an optical source consisting of a dwarf galaxy
with redshift 0.193.
Also, a 157-day cycle has been discerned, consisting of
some weeks of activity followed by a longer quiescent time,
suggestive of an orbital period.
Theories include some involving
flashes from a neutron star.
In 2019, a second repeating FRB source was discovered and
as of 2025, FRB searches have discovered over 60 more.