Binary Neutron Star Mergers: Learning from the Afterglow of the > August 17th 2017 Event

On August 17 2017, gravitational waves from the inspiral
phase of a binary neutron star merger were detected. Then, with a slight
delay, a weak short gamma-ray burst GRB170817A was observed. These two
historical detections triggered a hitherto unseen series of astronomical
observations. First, follow-up ground-based searches inside the
uncertainty region inferred by the gravitational wave signal promptly
found an optical transient--the first observed kilonova--in the
spheroidal galaxy NGC4993. Then, at the position of this optical
transient was later discovered a multi-wavelength afterglow emission,
which is still detected today. This afterglow likely originates from
shock-accelerated electrons during the deceleration by the external
medium of matter ejected from the merger event. In this talk, we will
briefly describe these multi-messenger observations, and review some
teachings the afterglow emission brings regarding the merger event:
geometry and dynamical structure of the ejected matter, characteristics
of the external medium, the possibility for a relativistic jet to have
been produced, and finally the formation of GRB170817A and short
gamma-ray bursts from merger events in general.

Raphaël Duque
KIAA, 1st meeting room
Fri, 2018-07-06 12:00 to 13:00