WoU-MMA: Engine-Powered Transients from Compact Object Birth

Surveys of the night sky have discovered classes of objects that are hundreds of times brighter than ordinary stellar explosions. The origins of these events are not understood, because they require a novel source of power. One potential power source is a rapidly spinning neutron star, which emits a magnetized wind of charged particles similar to, but more extreme, than our own Sun’s solar wind. Over a three year program, a team led by the principal investigator at Columbia University will perform computer simulations that predict the radiation emitted from neutron star winds and how it propagates through the debris of an explosion. The calculations will also be applied to spinning neutron stars created from the merger of two neutron stars. These events represent sources of gravitational wave emission whose electromagnetic counterparts will be predicted. The research program will provide training for undergraduate students with technical skills in radiation hydrodynamics and computation. A week-long international workshop will be organized on gravitational wave astrophysics to train the larger community. A growing number of stellar explosions have been discovered with peak luminosities too high to be powered by traditional energy sources, such as radioactive decay. These include the rare class of stellar core collapse known as “superluminous supernovae” (SLSNe), as well as luminous transients with fast evolving light curves, indicative of explosions with lower ejecta masses (“Fast Blue Optical Transients”; FBOTs). The best-studied FBOT, AT2018cow, peaked on a timescale of only a few days and was accompanied by non-thermal emission from radio to X-rays to gamma-rays. Powering the light curves of SLSNe and FBOTs requires prolonged heating of the ejecta by a central energy source, such as an accreting black hole or the rotationally-powered wind of a magnetar with a millisecond spin period. The investigators will create computer models of engine-powered transients that predict the radio, optical, X-ray, and gamma-ray emissions. Synchrotron radio emission from the nebula will be calculated. The predictions of this work will be tested with data obtained with ground and space-based observatories. Their results will also enable predictions for the emission from binary neutron star mergers that might be detected with LIGO/Virgo. Research and educational goals will be integrated in two ways: (1) Undergraduate students are directly involved in key aspects of the proposed research, exposing them to an active and supportive research environment; (2) A week-long international workshop will be organized on time-domain gravitational wave astrophysics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.