Description
Magnetars are the most magnetised isolated neutron stars known in the Universe. Their signature
is the unpredictable and and variable flaring activity in the X/gamma-ray bands, with bursts lasting
from a few milliseconds to tens of seconds and reaching peak luminosities of 1037-1043 erg/s. These
flaring events are often accompanied by outbursts in which the persistent X-ray flux increases by
a factor of ~10-1000 and then decays over months to years. Magnetars have also been proposed
as possible progenitors of some of the most extreme transient events in the Universe, such as fast
radio bursts and gamma-ray bursts.
Investigating magnetar emission outside the X-ray band is challenging. In this talk, I will focus
on the treasure hunt for optical magnetar counterparts, reviewing the few known detections and
the ongoing effort with the high-speed optical photometer SiFAP2. I will also discuss possible
mechanisms at the origin of magnetar optical emission - a still open problem for which detailed
theoretical models are currently lacking.