In Star Trek resolution, how did two vidiian ships sneak up on Voyager without them being picked up on sensors?

Do they have cloaking technology? This seems unlikely as they don't even have transporters, replicators, or holo technology. But it's possible.

Did they sneak up on them some other way?

In the Star Trek: Voyager episode "Resolutions," how did two Vidiian ships sneak up on Voyager without them being picked up on sensors?

Do they have cloaking technology? This seems unlikely as they don't even have transporters, replicators, or holo technology. But it's possible.

Did they sneak up on them some other way?