Bhal Chandra Joshi

Pulsar studies:

A variety of investigation of pulsed radio emission from neutron stars, using the ORT and the GMRT as well as observations at optical and high energies, are carried out. Blind and targeted searches of pulsars, using the unique capabilities of GMRT, are ongoing with a view to increasing the sample of radio emitting pulsars. The newly discovered pulsars with the GMRT are followed up to determine precise timing solution to learn about the neutron star characteristics. Together with the imaging observations of neutron star environments with the GMRT, such observations are useful to constrain physics of pulsar wind and the resultant nebula. New pulsar discoveries have also uncovered new classes of neutron stars, such as intermittent pulsars and highly magnetized neutron stars along with exotic binary and millisecond pulsars.


Single pulse emission studies:

Another kind of study involves single pulse emission from radio pulsars, where a wide variety of single pulse phenomena such as pulse nulling, drifting and resultant mode-changing are observed. The GMRT and the ORT have been very useful in providing long simultaneous multi-frequency single-pulse observations, which are useful in constraining the pulsar magnetospheric physics and beam geometry. Extreme forms of unexplained emission in single pulses, such as isolated radio bursts from rotating radio transients (RRATs) and fast radio bursts (FRBs), are also studied as part of this program. Both telescopes have the capability to carry out low-frequency studies of the pulsed emission, which gets dispersed and scatter-broadened by the interstellar medium. Multiple frequency observations in these studies are useful in constraining the structure and the dynamics of the interstellar medium.


Precision timing studies:

Both the GMRT and the ORT are capable of high time resolution observations of pulse emission with precision timing. Observations of millisecond pulsars, which are very stable clocks, are therefore useful in constraining relativity theories and provide an ensemble of clocks, which could be used as a long baseline detector for stochastic gravitational background at nanohertz frequencies. Studies contributing to an international effort to detect such a background using these pulsar timing arrays is also currently ongoing. Both experimental and theoretical work in this direction is currently under way at NCRA-TIFR.


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