| Abstract : | Pulsars are highly magnetized, fast rotating neutron stars and despite of regular rotation they exhibit irregularities in their spin down rate, and these irregularities can be called as timing noise. They also display switching between two integrated profiles called as mode changing, and the nulling is a extreme case of mode changing. During nulling and based on other modes, it has been observed that the slowing down rate of pulsars is different, so this is the basis of additional evidence in slow down rate of pulsars. We proposed a question regarding the amount of timing noise that can be accounted from the nulling behaviour of pulsars, if there exist any dependence of timing noise on nulling. The changing period derivatives of pulsars implies to the two state behaviour(normal and null state). We have performed simulations using a fortran code for changing period derivatives, and estimated the values of residuals. Results were encouraging as the values of the residuals that are obtained after the simulations are comparable to the actual values of timing noise parameter which has been estimated previously. The simulations have also helped us to appreciate the behaviour of timing noise parameter as the function of NF(nulling fraction) at the given value of null length. Hence, for nulling pulsars we can get timing noise when period derivatives changes which corresponds to the two different states(normal and null state). |
