#### IMSc Webinar

#### Probing Structural anOrbital Properties of Binary Pulsars (pre-synopsis seminar)

#### Dhruv Pathak

##### IMSc, HBNI

*Precision timing analysis of radio pulsars gives many interesting results and is expected to contribute further in many areas of fundamental physics in the future. In this connection, it is important to understand the external factors affecting the values of parameters estimated in the timing analysis. Among all these timing parameters, the measured values of the frequency derivatives are affected by the velocity, acceleration, and jerk of the pulsars. These effects are known as ‘dynamical contributions’. We explore these dynamical effects affecting the first as well as the second time-derivatives of the frequency (both spin and orbital). We point out the limitations of existing methods to calculate dynamical effects in the first derivative of frequency (or period) and argue the need for improved methods to extract these effects. We have devised such improved methods and argue that they should be used for pulsars located away from the solar system, especially when precise values of the periods derivatives are required. We introduce a package, ‘GalDynPsr’, that evaluates these different dynamical effects, following traditional as well as improved methods based on a well-known model of the Galactic potential. We also provide the formalism for deriving the analytical expressions for dynamical contributions in the second derivative of frequency (spin or orbital) of pulsars in terms of the Galactic coordinates, the proper motion, the pulsar distance, the radial velocity, and observed values of frequency and its derivatives. We compare these effects on the pulsars in the Galactic field with those near the Galactic Centre. We also perform simulations to study the effect of correction of the dynamical-effects using our formalism on the braking index as well as on the second derivative of the orbital frequency of simulated pulsars.*

google meet link: meet.google.com/oyv-dcmc-hgh

Done