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Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminars

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Events During the Week of November 14th through November 20th, 2021

Monday, November 15th, 2021

No events scheduled

Tuesday, November 16th, 2021

The fate of twin stars on the unstable branch
Time: 2:00 pm - 3:00 pm
Place: Meeting ID: 994 6425 2867
Speaker: Pedro Espino, University of California, Berkeley and Pennsylvania State University
Abstract: Hybrid hadron-quark equations of state that give rise to a third family of stable compact stars have been shown to be compatible with the LIGO-Virgo event GW170817. Stable configurations in the third family are called hybrid hadron-quark stars. The equilibrium stable hybrid hadron-quark star branch is separated by the stable neutron star branch with a branch of unstable hybrid hadron-quark stars. The end-state of these unstable configurations has not been studied, yet, and it could have implications for the formation and existence of twin stars — hybrid stars with the same mass as neutron stars but different radii. We modify existing hybrid hadron-quark equations of state with a first-order phase transition in order to guarantee a well-posed initial value problem of the equations of general relativistic hydrodynamics, and study the dynamics of non-rotating or rotating unstable twin stars via 3-dimensional simulations in full general relativity. We find that unstable twin stars naturally migrate toward the hadronic branch. Before settling into the hadronic regime, these stars undergo (quasi)radial oscillations on a dynamical timescale while the core bounces between the two phases. Our study suggests that it may be difficult to form stable twin stars if the phase transition is sustained over a large jump in energy density, and hence it may be more likely that astrophysical hybrid hadron-quark stars have masses above the twin star regime. We also study the minimum-mass instability for hybrid stars, and find that these configurations do not explode, unlike the minimum-mass instability for neutron stars. Additionally, our results suggest that oscillations between the hadronic and quark phases could provide gravitational wave signals associated with such phase transitions in core-collapse supernovae and white dwarf-neutron star mergers. Meeting ID: 994 6425 2867
Host: Baha Balantekin
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Wednesday, November 17th, 2021

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Thursday, November 18th, 2021

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Friday, November 19th, 2021

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