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The life cycle of magnetars: a novel approach to estimate their ages
High Energy Astrophysical Phenomena · Submitted 26 Apr 2021
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim For SGR 0418+5729, we obtain a dipolar $B$-field of $1.0\times10^{14}$ G, and a realistic age of $\sim18$ kyr, consistent within the magnetar paradigm.
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Anomalous X-ray pulsars and soft gamma repeaters are slowly rotating, young, and isolated neutron stars exhibiting sporadic outbursts and high X-ray quiescent luminosities. They are believed to be powered by ultrastrong magnetic fields, $B\sim10^{14}-10^{15}$ G, associated with `magnetars'. In the peculiar case of SGR 0418+5729, timing parameters imply a dipolar $B$-field of $6.1\times10^{12}$ G. This discovery has challenged the traditional picture of magnetars in terms of $B$-field strengths, evolutionary stages, and ages. Here we provide a novel approach to estimate a magnetar's age by considering the self-consistent time evolution of a plasma-filled oblique pulsar with the state-of-the-art magnetospheric particle acceleration gaps. The rotational period of magnetars increases over time due to angular momentum extraction by gravitational-wave radiations, magnetic dipole radiations, and particle winds. These torques also change the obliquity angle between the magnetic and rotation axes. For SGR 0418+5729, we obtain a dipolar $B$-field of $1.0\times10^{14}$ G, and a realistic age of $\sim18$ kyr, consistent within the magnetar paradigm.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Anomalous X-ray pulsars and soft gamma repeaters are slowly rotating, young, and isolated neutron stars exhibiting sporadic outbursts and high X-ray quiescent luminosities. | background 1.00 | 0.05 | 0.02 | asserted 1.00 |
| s1 | They are believed to be powered by ultrastrong magnetic fields, $B\sim10^{14}-10^{15}$ G, associated with `magnetars'. | background 1.00 | 0.05 | 0.03 | hedged possibility 0.93 |
| s2 | In the peculiar case of SGR 0418+5729, timing parameters imply a dipolar $B$-field of $6.1\times10^{12}$ G. | background 0.86 | 0.17 | 0.04 | asserted 0.75 |
| s3 | This discovery has challenged the traditional picture of magnetars in terms of $B$-field strengths, evolutionary stages, and ages. | background 0.56 | 0.07 | 0.05 | asserted 0.95 |
| s4 | Here we provide a novel approach to estimate a magnetar's age by considering the self-consistent time evolution of a plasma-filled oblique pulsar with the state-of-the-art magnetospheric particle acceleration gaps. | contribution 0.84 | 0.87 | 0.13 | asserted 0.99 |
| s5 | The rotational period of magnetars increases over time due to angular momentum extraction by gravitational-wave radiations, magnetic dipole radiations, and particle winds. | method 0.54 | 0.15 | 0.05 | asserted 1.00 |
| s6 | These torques also change the obliquity angle between the magnetic and rotation axes. | method 0.76 | 0.18 | 0.03 | asserted 1.00 |
| s7 | For SGR 0418+5729, we obtain a dipolar $B$-field of $1.0\times10^{14}$ G, and a realistic age of $\sim18$ kyr, consistent within the magnetar paradigm. | result 0.99 | 0.96 | 0.81 | asserted 0.82 |
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Original abstract
Anomalous X-ray pulsars and soft gamma repeaters are slowly rotating, young, and isolated neutron stars exhibiting sporadic outbursts and high X-ray quiescent luminosities. They are believed to be powered by ultrastrong magnetic fields, $B\sim10^{14}-10^{15}$ G, associated with `magnetars'. In the peculiar case of SGR 0418+5729, timing parameters imply a dipolar $B$-field of $6.1\times10^{12}$ G. This discovery has challenged the traditional picture of magnetars in terms of $B$-field strengths, evolutionary stages, and ages. Here we provide a novel approach to estimate a magnetar's age by considering the self-consistent time evolution of a plasma-filled oblique pulsar with the state-of-the-art magnetospheric particle acceleration gaps. The rotational period of magnetars increases over time due to angular momentum extraction by gravitational-wave radiations, magnetic dipole radiations, and particle winds. These torques also change the obliquity angle between the magnetic and rotation axes. For SGR 0418+5729, we obtain a dipolar $B$-field of $1.0\times10^{14}$ G, and a realistic age of $\sim18$ kyr, consistent within the magnetar paradigm.
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States a conflicting result 1 paper
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We show that the magneto-rotational properties of SGR 0418+5729 can be reproduced if this is an aged magnetar, $\approx 1\ {\rm Myr}$ old, which experienced substantial field decay.
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