High-energy photons from the Crab Nebula: The Crab Nebula contains a pulsar that excites the surrounding gas to emit high-energy radiation. The combination of the pulsar's youth and nearby location makes the nebula the brightest gamma-ray source in the sky. The LHAASO Collaboration report observations of this source at energies of tera– to peta–electron volts, extending the spectrum of this prototypical object. They combine these data with observations at lower energies to model the physics of the emission process. The multiwave-length data can be explained by a combination of synchrotron radiation and inverse Compton scattering. Science , abg5137, this issue p. 425

In this Letter, we propose that a fast radio burst (FRB) could originate from the magnetic interaction between double neutron stars (NSs) during their final inspiral within the framework of a unipolar inductor model. In this model, an electromotive force is induced on one NS to accelerate electrons to an ultra-relativistic speed instantaneously. We show that coherent curvature radiation from these electrons moving along magnetic field lines in the magnetosphere of the other NS is responsible for the observed FRB signal, that is, the characteristic emission frequency, luminosity, duration, and event rate of FRBs can be well understood. In addition, we discuss several implications of this model, including double-peaked FRBs and possible associations of FRBs with short-duration gamma-ray bursts and gravitational-wave events.

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

We have performed a multiwavelength study of supernova remnant (SNR) G57.2+0.8 and its environment. The SNR hosts the magnetar SGR 1935+2154, which emitted an extremely bright millisecond-duration radio burst on 2020 April 28. We used the ¹²CO and ¹³CO J = 1–0 data from the Milky Way Image Scroll Painting CO line survey to search for molecular gas associated with G57.2+0.8, in order to constrain the physical parameters (e.g., the distance) of the SNR and its magnetar. We report that SNR G57.2+0.8 is likely impacting the molecular clouds (MCs) at the local standard of rest (LSR) velocity and excites a weak 1720 MHz OH maser with a peak flux density of 47 mJy beam⁻¹. The chance coincidence of a random OH spot falling in the SNR is ≤12%, and the OH–CO correspondence chance is 7% at the maser spot. This combines to give <1% false probability of the OH maser, suggesting a real maser detection. The LSR velocity of the MCs places the SNR and magnetar at a kinematic distance of 6.6 ± 0.7 kpc. The nondetection of thermal X-ray emission from the SNR and the relatively dense environment suggests G57.2+0.8 be an evolved SNR with an age . The explosion energy of G57.2+0.8 is lower than , which is not very energetic even assuming a high ambient density . This reinforces the opinion that magnetars do not necessarily result from very energetic supernova explosions.