No, not aliens (this time), but a transient, circularly-polarised source with no optical counterpart. This is only such source observed so far anywhere in the sky.
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Transient, circularly-polarised sources are more mysterious than pulsars! Marketing department needs to come up with a better name though – perhaps transient-pulsar or t-pulsar.
The reason they came up with the generic name is that they aren’t sure the source is a pulsar. It might be, for example, a flare star (which generates this kind of radio emission) which happens to be so obscured by dust near the galactic centre that the optical telescopes they used couldn’t see it. With only one known source, it’s hard to rule out alternative models.