Astrophysics: Finding signals of when stars collide

Oscillating signals detected in two short gamma-ray bursts that may have been created by the formation of a massive neutron star from two merging neutron stars are reported in Nature this week. The detection of such signals could provide an opportunity to study the properties of these events.

Collisions between neutron stars (dense cores of massive stars at the end of their life) can sometimes create short-lived massive neutron stars before collapsing into a black hole, although not all might collapse. Numerical simulations indicate that these hypermassive neutron stars may introduce oscillations in the gamma-ray bursts resulting from the collisions. Cecilia Chirenti and colleagues delved through archives of gamma ray observations (more than 700 in total) in search of such signals.

Two candidate signals with an oscillatory phase were identified in short bursts named GRB 910711 and GRB 931101B. The oscillations are not quite periodic and have frequencies that match predictions for double neutron star mergers. Such detections provide a potentially powerful new tool to study merging neutron stars, the authors conclude, and does not require an accompanying gravitational wave detection.