http://arxiv.org/abs/2107.02946
Magnetic field may distort neutron stars (NSs), but the effect has not been robustly tested through gravitational-wave observation yet due to the absence of a fast rotating Galactic magnetar. The central objects of Gamma-ray bursts (GRBs) could be millisecond magnetars. Under the magnetar scenario on the X-ray plateaus of GRB afterglows,the spindown evolution modulated by the gravitational-wave radiation may be inferred from some special samples,so that the magnetically-induced distorting can be further estimated. According to two samples, GRB 060807 and GRB 070521, we found that the correlation between the effective ellipticity, $\varepsilon_{\rm B,eff}$, and effective magnetic field, $B_{\rm eff}$, is $\varepsilon_{\rm B,eff}\sim 10^{-4} (\frac{B_{\rm eff}}{10^{14}\;\rm G})^{2}$. This result demands that $B_{\rm eff}\sim 0.01 B_{\rm t}$ with $B_{\rm t}$ being the internal toroidal magnetic field strength of NSs. We suggested that the nonzero moment of force generated during few massive-star collapses may induce differential rotation between the interior and exterior of the proto-NS to amplify the internal toroidal field.
T. Lin, S. Du and R. Xu
Thu, 8 Jul 21
17/52
Comments: 8 pages, 3 figures