The influence of thermal pressure on equilibrium models of hypermassive neutron star merger remnants

Journal Article · Sun Jul 20 00:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/790/1/19· OSTI ID:22365623

Kaplan, J. D.; Ott, C. D.; Roberts, L. ^[1]; O'Connor, E. P. ^[2]; Kiuchi, K. ^[3]

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1. TAPIR, California Institute of Technology, Mailcode 350-17, Pasadena, CA 91125 (United States)
2. CITA, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)
3. Yukawa Institute for Theoretical Physics, University of Kyoto, Kyoto (Japan)

The merger of two neutron stars leaves behind a rapidly spinning hypermassive object whose survival is believed to depend on the maximum mass supported by the nuclear equation of state (EOS), angular momentum redistribution by (magneto-)rotational instabilities, and spindown by gravitational waves. The high temperatures (∼5-40 MeV) prevailing in the merger remnant may provide thermal pressure support that could increase its maximum mass and, thus, its life on a neutrino-cooling timescale. We investigate the role of thermal pressure support in hypermassive merger remnants by computing sequences of spherically symmetric and axisymmetric uniformly and differentially rotating equilibrium solutions to the general-relativistic stellar structure equations. Using a set of finite-temperature nuclear EOS, we find that hot maximum-mass critically spinning configurations generally do not support larger baryonic masses than their cold counterparts. However, subcritically spinning configurations with mean density of less than a few times nuclear saturation density yield a significantly thermally enhanced mass. Even without decreasing the maximum mass, cooling and other forms of energy loss can drive the remnant to an unstable state. We infer secular instability by identifying approximate energy turning points in equilibrium sequences of constant baryonic mass parameterized by maximum density. Energy loss carries the remnant along the direction of decreasing gravitational mass and higher density until instability triggers collapse. Since configurations with more thermal pressure support are less compact and thus begin their evolution at a lower maximum density, they remain stable for longer periods after merger.

• OSTI ID: 22365623
• Journal Information: Astrophysical Journal, Vol. 790, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ANGULAR MOMENTUM
APPROXIMATIONS
AXIAL SYMMETRY
COOLING
DENSITY
ENERGY DENSITY
ENERGY LOSSES
EQUATIONS OF STATE
EQUILIBRIUM
EVOLUTION
GRAVITATIONAL WAVES
INSTABILITY
MASS
MEV RANGE
NEUTRON STARS
NUCLEAR TEMPERATURE
RELATIVISTIC RANGE
SATURATION
SPHERICAL CONFIGURATION
SUPPORTS