X-rays: individual: Sw J1644+57

We report the discovery by the Swift hard X-ray monitor of the transient source Swift J2058.4+0516 (Sw J2058+05). Our multi-wavelength follow-up campaign uncovered a long-lived (duration >åisebox-0.5ex months), luminous X-ray (L $_X, iso$ ≈ 3 × …