Magnetic fields in late-stage proto-neutron stars. Issue 1 (17th February 2021)

• Record Type: Journal Article
• Authors: Lander, S K; Haensel, P; Haskell, B; Zdunik, J L; Fortin, M
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 503:Issue 1(2021)
• Page Start: 875
• Page End: 895
• Publication Date: 2021-02-17
• Subjects: stars: evolution -- stars: interiors -- stars: neutron -- stars: magnetic fields -- stars: rotation; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab460
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We explore the thermal and magnetic field structure of a late-stage proto-neutron star (proto-NS). We find the dominant contribution to the entropy in different regions of the star, from which we build a simplified equation of state (EOS) for the hot neutron star (NS). With this, we numerically solve the stellar equilibrium equations to find a range of models, including magnetic fields and rotation up to Keplerian velocity. We approximate the EOS as a barotrope, and discuss the validity of this assumption. For fixed magnetic field strength, the induced ellipticity increases with temperature; we give quantitative formulae for this. The Keplerian velocity is considerably lower for hotter stars, which may set a de facto maximum rotation rate for non-recycled NSs well below 1 kHz. Magnetic fields stronger than around 10 14 G have qualitatively similar equilibrium states in both hot and cold NSs, with large-scale simple structure and the poloidal field component dominating over the toroidal one; we argue this result may be universal. We show that truncating magnetic field solutions at low multipoles leads to serious inaccuracies, especially for models with rapid rotation or a strong toroidal-field component.