News

Accretion Induced Collapse of Neutron Stars in Binary Mergers

Tidal disruption of a neutron star in a high-mass ratio binary neutron star merger
Tidal disruption of a neutron star in a high-mass ratio binary neutron star merger

In an article just published on Monthly Notices of the Royal Astronomical Society we presented the first general-relativistic simulations with microphysics and neutrinos to explore the dynamics of merging binary neutron star systems with large mass ratios. We found that the lower mass neutron star in these binaries is tidally disrupted by the primary neutron star shortly prior to merger. The accretion of the tidal debris can cause the more massive neutron star to collapse and form a black hole surrounded by a large accretion disk. Our simulations showed that, contrary to common expectations, neutron star mergers with prompt black hole formation can be accompanied by bright electromagnetic counterparts. Our work is featured in press releases by Pittsburgh Supercomputing Center and the Pennsylvania State University.

DOE Early Career Award

Our group has been awarded a DOE Early Career Award! The DOE Early Career program is designed to bolster the nation’s scientific workforce by providing support to exceptional researchers during crucial early career years, when many scientists do their most formative work.

The award will fund the development of a new open source numerical relativity code able to perform neutron star merger simulations with advanced neutrino microphysics and exploiting next generation exascale supercomputers.

For more information, see also the University announcement.

Spiral-Wave Wind for the Blue Kilonova

In this manuscript recently accepted on the Astrophysical Journal Letters we investigate the new mechanism of mass ejection from the BNS systems after merger. We find that the interaction between the remnant, should it survive, and the disk creates a characteristic spiral wave structure in the latter and drives the quasi-steady state outflow with total mass ~10^{-2} solar masses and fine-tuned velocity around 0.2c and high electron fraction of >0.25. This spiral-wave wind persists as long as remnant lives and dies out quickly after the BH formation. Its properties are robust with resolution and inclusion of the subgird turbulence. Then we use the data from numerical relativity simulations to compute the kilonova models. We report that the combination of dynamical ejecta and spiral-wave wind can account for early-time observed light curves.