CYCLICAL CHANGES IN THE TIMING RESIDUALS FROM THE PULSAR B0919+06

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 Delta nu/nu similar to 1.3 x 10(-6). A large glitch happens in the pulsar whose rotation has an 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 that resembled 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 of Delta nu/nu similar to 1.5 x 10(-9). All the slow glitches observed have similar signatures related to a slow increase in the rotation frequency for similar to 200 days and to the subsequent relaxation back to the pre-glitch value for similar to 400 days. We show that a continuous sequence of such slow glitches is characterized by practically identical amplitudes of Delta nu similar to 3.5 x 10(-9) Hz and identical time intervals between glitches of similar to 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, indicate 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.