Transcript Document
Calculating the moment of inertia of neutron stars Jacobus Diener Stellenbosch University, RSA Dr Alan Dzhioev and Prof Victor Voronov Bogoliubov Laboratory of Theoretical Physics, JINR Pulsar: Quantity of interest • Pulsars Rapidly rotating remnant star of massive star that exploded in core-collapse supernova Radius ~10 km Mass ~1.4 M (solar mass) Density ~1015 g/cm3 (few times nuclear density) Radio-emission from magnetic poles Sudden spin-ups in frequency (glitches) • Pulsars modelled as giant nuclei Constraining models proven difficult with observational data Models and constraints • Models for nuclear matter • Equation of state Mass-radius relationship for different models of nuclear matter. Observational constraints given by mass-radius relationship of EXO 0748-676 (purple) and General Relativity (black). Glitch models • Alpar et al. model glitch as two components differential rotating in the pulsar. • Outer crust spin downs faster than superfluid interior due to magnetic torques • Angular momentum transferred between two components resulting in spin-up of star. • Size of spin-up related to moment of inertia of different layers I res A I crust Calculating moment of inertia • Rapidly rotating ultra-dense fluid • Framework proved by General Relativity • General expression for moment of inertia 1 t I () drd dT (r , , , ) g (r , , ,) • Relativistic effects Rotation Breaking of spherical symmetry Frame dragging R ( ) 0 0 I () d 1 dr 2 2 e 2 e ( ) South African context • Hartebeesthoek Radio Astronomy Observatory 26 m radio-telescope Vela glitch data spanning 20 years • SA SKA/MeerKAT 26 m telescope at HartRAO Furthermore… • Presented a talk to students at the BLTP on the main aspects of my studies so far • Discussed possible nuclear matter calculations with Dr V. V. Burov using the Bethe-Salpeter approach Conclusion • Expression for moment of inertia derived • To be able to solve more study of rotating, axial symmetric relativistic fluid further study needs to be undertaken • Could provide publishable results when compared with long-term glitch data of the Vela pulsar from HartRAO Acknowledgements For organising and financing this visit thanks to the • National Research Foundation (South Africa) and • the Joint Institute for Nuclear Research. References • M.A. Alpar, H.F. Chau, K.S. Cheng & D. Pines, ApJ, 409, 345 (1993). • J.M. Lattimer & B.M. Schutz, ApJ, 629, 979 (2005). • B. Link, R.I. Epstein & J.M. Lattimer, Phys. Rev. Lett., 83, 3362 (1999). • F. Weber, Prog. Pat. Nucl. Phys. 54, 193 (2005).