MG15 - Talk detail

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Spinning collapsed objects like Kerr black holes or naked singularities would cause the spin axes of pulsars present in their vicinity to precess due to frame-dragging. We study whether and how these precession effects modify the observed pulse rate of such a pulsar in the strong gravitational field regime. In our recent work (arXiv:1711.04053), we report that the spin-precession rate, and hence the observed pulse rate, of such a pulsar moving on a circular orbit near an event horizon rises sharply as the orbit shrinks. This provides a new way to detect such a horizon, not only from a high observed pulse rate, but also from plausible detections of gravitational waves due to the increased pulsar spin. These effects could be observationally significant when considering pulsars inspiralling into supermassive black holes. Further, we note that a pulsar approaching an event horizon should eventually be disrupted causing a new astronomical phenomenon, which we call a spin-precessional disruption event (SPDE). We argue that a significant difference between the radioactive glow of an SPDE and that of a tidal disruption event of a pulsar near a naked singularity could distinguish such a singularity from a black hole. We also touch upon possibilities of finding new pulsars, understanding phenomena involving quasiperiodic oscillations and independent estimations of the spin of the central rotating compact object.

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