Monotonic and cyclic components of radio pulsar spin-down

Biryukov, A.; Beskin, G.; Karpov, S.

Авторы: Biryukov A., Beskin G., Karpov S.
Журнал: Monthly Notices of the Royal Astronomical Society
Том: 420
Год издания: 2012
Издательство: Oxford Journals, Oxford University Press
Местоположение издательства: Oxford, UK, England
Первая страница: 103
Последняя страница: 117
DOI: 10.1111/j.1365-2966.2011.20005.x
Аннотация: In this article we revise the problem of anomalous values of pulsar braking indices n_obs and frequency second derivatives f2 arising in observations. The intrinsic evolutionary braking is buried deep under superimposed irregular processes, which prevent direct estimations of its parameters for themajority of pulsars.We re-analyse the distribution of ‘ordinary’ radio pulsars on f2 – f1, f2 – f0, f1 – f0 and n_obs–tau_ch diagrams assuming their spin-down to be the superposition of a ‘true’ monotonic term and a symmetric oscillatory term. We demonstrate that their effects may be clearly separated using simple ad hoc arguments. Using the maximum-likelihood estimator, we derive the parameters of both components. We find characteristic time-scales of such oscillations to be of the order of 1e3 – 1e4 yr, while their amplitudes are large enough to modulate the observed spin-down rate up to 0.5–5 times and completely dominate the second frequency derivatives. On the other hand, pulsar secular evolution is consistent with the classical magnetodipolar model with braking index n ≈ 3. Therefore, observed pulsar characteristic ages (and similar estimators that depend on the observed f1) are also affected by long-term cyclic processes and differ up to 0.5 – 5 times from their monotonic values. This fact naturally resolves the discrepancy of characteristic and independently estimated physical ages of several objects, as well as explaining the very large, up to 1e8 yr, characteristic ages of some pulsars. We discuss the possible physical connection of long-term oscillation with complex neutron star rotation relative to its magnetic axis due to the influence of the near-field part of the magnetodipolar torque.
Добавил в систему: Бирюков Антон Владимирович

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Monotonic and cyclic components of radio pulsar spin-downстатья