Understanding the spin-down rate changes of PSR B0919+06

Abstract

We study the spin-down properties of PSR B0919+06 based on almost 30 years of radio observations. We confirm that the time derivative of the rotational frequency $\dot{\nu }$ is modulated quasi-periodically and show that it exhibits a repeating double-peaked structure throughout the entire observation span. We model the $\dot{\nu }$ variation of the pulsar assuming two spin-down rates with sudden switches between them in time. Our results show that the double-peak structure in $\dot{\nu }$ has a repetition time of about 630 days until MJD 52000 (April 2001) and 550 days since then. During this cycle, the pulsar spin varies from the lower spin-down rate to the upper spin-down rate twice with different amounts of time spent in each state, resulting in a further quasi-stable secondary modulation of the two-state switching. This particular spin-down state switching is broadly consistent with free precession of the pulsar, however, a strong evidence linked with this mechanism is not clearly established. We also confirm that the pulsar occasionally emits groups of pulses which appear early in pulse phase, so-called "flares", and these events significantly contribute to the pulse profile shape. We find the $\dot{\nu }$ modulation and the pulse shape variations are correlated throughout the observations. However, the flare-state is not entirely responsible for this correlation. In addition to the flare-state, we detect flare-like events from the pulsar in single pulse observations. During these events, the shift in pulse phase is small compared to that of the main flare-state and clearly visible only in single pulse observations.

10 pages, 12 Figures, Accepted by MNRAS on 10 October 2014

References in corpus (6)

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• A periodically active pulsar giving insight into magnetospheric physics
• Pulsar Nulling and Mode Changing
• Detection of 107 glitches in 36 southern pulsars
• Radio and X-ray observations of the intermittent pulsar J1832+0029
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• Scattering study of Pulsars below 100 MHz using LWA1
• Long term radio and X-ray evolution of the magnetar Swift J1818.0-1607
• Discovery of state transition behaviors in PSR J1124--5916
• On the free-precession candidate PSR B1828-11: Evidence for increasing deformation
• Multi-frequency study of the peculiar pulsars PSR B0919+06 and PSR B1859+07
• Timing and emission variation of PSR J1733-3716
• Long-term rotational and emission variability of 17 radio pulsars