Cyclical Changes in the Timing Residuals from the Pulsar B0919+06

Abstract

We report the detection of a large glitch in the pulsar B0919+06 (J0922+0638). The glitch occurred in 2009 November 5 (MJD 55140) and was characterized by a fractional increase in the rotation frequency of Deltanu/nu=1.3x10^{-6}. A large glitch happens in the pulsar whose rotation has unstable character. We present the results of the analysis of the rotation behavior of this pulsar over the 30-year time span from 1979 to 2009. These results show that the pulsar's rotation frequency underwent continuous, slow oscillations which look like glitch-like events. During the 1991-2009 interval, the pulsar experienced a continuous sequence of 12 slow glitches with a fractional increase in the rotation frequency Deltanu/nu=1.5x10^{-9}. All the slow glitches observed have a similar signature related to a slow increase in the rotation frequency during 200 days and the subsequent relaxation back to the pre-glitch value during 400 days. We show that a continuous sequence of such slow glitches is characterized by practically identical amplitudes equal to Deltanu=3.5x10^{-9} Hz and identical time intervals between glitches of about 600 days and is well described by a periodic sawtooth-like function. The detection of two different phenomena, such as a large glitch and a sequence of slow glitches, indicates the presence of two types of discontinuities in the rotation frequency of the pulsar B0919+06. These discontinuities can be classified as normal and slow glitches.