Extreme Physics with Pulsars and Radio Transients

点击翻译按钮获取中文摘要

Compact stellar objects such as neutron stars offer the opportunity to probe a wide range of fundamental physics problems. Many neutron stars emit lighthouse-like radio beams, which may hit the Earth once per rotation and cause us to label the star a pulsar. The fastest-spinning pulsars rotate several hundred times per second and can rival the stability of atomic clocks on short timescales. An array of these millisecond pulsars, spread across the sky, can be used to make a direct detection of gravitational waves passing near the Earth. The main sources of these gravitational waves is predicted to be pairs of supermassive black holes as the centres of galaxies that have recently undergone mergers, highly complementary to the stellar-mass black holes recently detected by the Laser Interferometric Gravitational-wave Observatory (LIGO). The pulsar timing array research proposed here will enhance the effectiveness of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), by improving the current data-reduction methods and by bringing in entirely new data which will address systematics due to variations in the interstellar medium. These data will come from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope under construction in Penticton, B.C. Simultaneously with its original cosmology mission, CHIME will provide daily data on the Northen NANOGrav pulsars, allowing us to model the variations in the interstellar medium in more detail than currently possible and providing corrections to the higher-frequency NANOGrav data. This project will accelerate the timeline for NANOGrav to make a detection of gravitational waves. CHIME will also provide dense data sets on numerous other interesting pulsars, including relativistic binaries, which are another long-term interest of this research group.******CHIME holds still more promise, for tackling the still-mysterious Fast Radio Bursts (FRBs). These are single spikes of radio emission, almost certainly extragalactic in origin, seen with some of the largest radio telescopes in existence. One of these sources has now been seen to repeat, but it is unclear at present whether there are two classes of source. What causes the bursts is still unknown-- in fact there are more published ideas than bursts at present -- but the inferred brightness and short timescale indicate that the involvement of a compact object such as a neutron star is likely. With a dedicated second instrument on CHIME, we expect to detect several tens of FRBs per day; the vastly improved statistics will constrain models and may help to localize the bursts well enough to identify host galaxies.