A freely precessing magnetar following an X-ray outburst.

Magnetars-highly magnetized neutron stars-are thought to be the most likely progenitors for fast radio bursts (FRBs). Freely precessing magnetars are further invoked to explain the repeating FRBs. We report here on new high-cadence radio observations of the magnetar XTE J1810-197 recorded shortly after an X-ray outburst.

Does Cardiac Arrhythmia Predict Worse Outcome in Mild or Moderate Covid-19 Infection?

Covid-19 is a multisystem disease with the lungs being predominantly affected. Cardiac involvement is mostly seen as a rise in troponins, arrhythmias, and ventricular dysfunction. This study aimed to estimate the incidence of arrhythmias seen in Covid-19 infection and assess if arrhythmias predict worsening or mortality Prospective observational study involving patients with mild to moderate Covid illness admitted in a tertiary care centre.

A repeating fast radio burst source in a globular cluster.

Fast radio bursts (FRBs) are flashes of unknown physical origin. The majority of FRBs have been seen only once, although some are known to generate multiple flashes. Many models invoke magnetically powered neutron stars (magnetars) as the source of the emission.

Gravitational Test beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole.

The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in the strong-field regime. We show analytically that spacetimes that deviate from the Kerr metric but satisfy weak-field tests can lead to large deviations in the predicted black-hole shadows that are inconsistent with even the current EHT measurements.