We have no explanations for this sort of slow repeat.
On Wednesday, researchers announced the discovery of a new astronomical enigma. The new object, GPM J1839–10, behaves a bit like a pulsar, sending out regular bursts of radio energy. But the physics that drives pulsars means that they'd stop emitting if they slowed down too much, and almost every pulsar we know of blinks at least once per minute.
GPM J1839–10 takes 22 minutes between pulses. We have no idea what kind of physics or what kind of objects can power that.
If it isn't a magnetar, my money's on it being a binary object like a quasar orbiting something massive. The massive object will be stabilising the quasar's spin in much the same way our Moon stabilises Earth's axis somewhat, but the beam of this object won't cross Earth unless it's at the right point in its orbit.
One might expect a 22 minute orbit around a massive object to have decayed a bit over 35 years (that would definitely be something to test for), but there's nothing that says the orbit or rotation period is 22 minutes, only that there's a resonance of 22 minutes coming from some interaction or another.
Another option involving them is the magnetar, a neutron star with an intense magnetic field that's prone to energetic outbursts. But those outbursts also generate more energetic photons, and the researchers checked the site of GPM J1839–10 with an X-ray telescope and saw nothing. Plus, magnetars are thought to rotate more quickly than the 22-minute gap implies, so they're probably out as well.
Just because some random Google result says it’s a magnetar doesn’t make it true. Considering the team that discovered it doesn’t make that claim and as far as I’m aware no one else has looked at this particular star, I think it unlikely that there’s a definitive, widely accepted explanation.
That's the most likely answer, but they're not certain. As they don't even have a solid theory of how a star can spin so slowly and still be this active.