Stellar structures and the enigma of pulsars rotation frequency decay

37th Brazilian Meeting on Nuclear Physics

de OLIVEIRA, H.O.^1 ; Marinho, R.M.^1 ; Maglhaes, N.S.^1

Physics Dept., Technological Institute of Aeronautics, Vila das Accias, São José dos Campos, SP

12228-900, Brazil^1

关键词: Astrophysical objects;    Canonical modeling;    Dimensionless parameters;    Observational data;    Precise modeling;    Rotation frequencies;    Stellar structure;    Time derivative;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/630/1/012059/pdf
DOI  :  10.1088/1742-6596/630/1/012059

来源: IOP

【 摘 要 】

Pulsars are astrophysical objects normally modelled as compact neutron stars that originated from the collapse of another star. This model, that we name canonical, assumes that pulsars are described by spherical magnetized dipoles that rotate, usually with the magnetic axis misaligned to the rotation axis. This misalignment would be responsible for the observation of radiation emitted in well-defined time intervals in a certain direction (lighthouse effect), the typical observational characteristic of this kind of star. It has been noticed that the rotation frequency of pulsars is slowly decaying with time (spin down), implying a gradual decrease of the rotational angular velocity (Ω). Such decay can be quantified by a dimensionless parameter called "braking index" ("n"), given by n = ΩΩ/(Ω)2, where a dot indicates a time derivative. The canonical model predicts that this index has one only value for all pulsars, equal to three. However, observational data indicate that actual braking indices are less than three, representing an enigma. The main goal of this research is the exploration of a more precise model for pulsars' rotation frequency decay.