Letters of Intent received in 2015

LoI 2017-267
Pulsar Astrophysics - The next 50 years

Topics

Current and Next Generation Pulsar Surveys
Gravity tests with pulsars
Gravitational Wave science with pulsar timing arrays
Neutron Star Masses, Glitches and Equations of State
The Neutron Star Zoo
The multi-messenger view of Pulsars
Pulsar emission physics across the electromagnetic spectrum
Neutron Star Binaries
Constraining the magneto-ionic properties of the ISM using pulsars
The future of pulsar research and facilities

Rationale

2017 marks the 50th anniversary of the discovery of pulsars and is thus an excellent moment to reflect on what we have learnt from these remarkable physical laboratories and to cast our eyes forward to the exciting opportunities they provide for physical and astrophysical studies in the coming decades. This look forward to the future is essential as the continuous improvement of current facilities and building of superb new facilities like FAST, SKA, CTA, advanced gravitational wave detectors, E-Rosita, Astrosat, Astro-H, HMXT, Spektr-RG and NICER, promise decades of exciting (astro-)physics to follow.

Ever since the discovery in 1967 pulsars and neutron stars have provided an unprecedented opportunity to study the extremes of physics. This started with the very rapid identification of pulsars as rotating neutron stars with extremely strong magnetic fields and, selecting just a few highlights from the following decades, was followed by the discovery of the Hulse-Taylor binary, millisecond pulsars, the first pulsars in globular clusters, the pulsar planets and the double pulsar. In the last decade alone we have had some amazing discoveries and science with an impact across all astronomy: a pulsar in a triple system that promises to be the best test environment for the strong equivalence principle; a magnetar located in the Galactic Centre giving us a new view on these environs; more than 100 pulsars found to be emitting gamma-ray emission, including many millisecond pulsars, some of which seen exclusively at gamma-ray energies; pulsars which are transitioning on short timescales between being millisecond radio pulsars and low-mass X-ray binaries; sub-100-nanosecond timing precision achieved on a handful of pulsars; a 2 solar mass neutron star in a relativistic binary system which strongly constrains alternatives to the general theory of relativity and dense-matter equations of state. It is clear that the pulsar and neutron star world is thriving!

The discoveries are not going to stop there as almost every large radio telescope in the world is currently undertaking large-area surveys at radio frequencies ranging from 100 MHz up to 2 GHz and the Fermi gamma-ray mission is proving extremely effective in finding millisecond pulsars further fueling the exponential increase in pulsar discoveries. In, or near 2017, we will also have initial survey results from the next generation telescopes like MeerKAT and FAST which will also push our search horizons beyond the Galaxy and the Magellanic Clouds. These surveys, including the new view of the low frequency sky with LOFAR, LWA and MWA, and ongoing X-ray observations with XMM and Chandra are continuing to reveal new manifestations of neutron stars that challenge our understanding of their birth, evolution and death. These results push the boundaries of what is physically possible and they also affect our understanding of the supernova rate in our Galaxy.

An example are the many new black widow and redback systems that have been uncovered, violent binary systems in which the energetic neutron star is blowing its companion star apart providing unique laboratories for extreme physics and binary evolution. The discovery of the transitioning systems between millisecond radio pulsars and low-mass X-ray binaries state gives further insights in binary evolution and formation of millisecond pulsars.

The use of pulsars in a so-called pulsar timing array allows a direct detection of gravitational waves and incredible progress has been made in the last decade. The ever more stringent limits that are being placed on emission in the nanohertz frequency range already starts to affect models of the sources of a stochastic background such as binary supermassive black holes. With the international pulsar timing array (IPTA) project gathering pace, which brings together data from many radio telescopes to form the most sensitive data sets in existence, 2017 will be an ideal moment to bring together the community to present and discuss the most recent results, perhaps even a detection. It is also an ideal time to look ahead to the exciting possibilities with the SKA for gravitational wave detections.

The ever increasing timing precision required, and being achieved, for the gravitational wave searches is also having a revolutionary affect on our understanding of the interstellar medium, emission physics, binary evolution and tests of theories of gravity. This will allow many aspects of gravitation to be explored: tests of strong equivalence principles, gravitational dipole radiation, extra field components of gravitation, gravito-magnetism and space-time symmetries.

Not only are pulsars useful as detectors of gravitational wave emission, they may also themselves be a detectable source of gravitational waves. With the next generation of ground based gravitational wave detectors, Advanced LIGO and Advanced VIRGO, about to start taking data, by 2017 we will be at an ideal time to review the most recent results on both the gravitational wave emission from individual pulsars and neutron star-neutron star binary mergers.

The last decade has revolutionized our understanding of how pulsars operate. Ongoing monitoring of their spin in combination with very sensitive observations of their complex emission properties allow us for the first time ever to quantify the most fundamental physical properties of pulsar magnetospheres, giving valuable input to constrain the still relatively poorly understood physics under extreme conditions. Many further insights have been obtained by the more than an order of magnitude increase in the number of gamma-ray-emitting neutron stars and the addition of high-energy information in the TeV window from instruments like HESS, VERITAS and Magic.

With all the new instruments and telescopes, including CTA and GAIA, we can look forward to multiple new discoveries and physical insights. Across the electromagnetic and gravitational wave spectra we can expect synergies that will provide a better understanding of Galactic structure, extreme astrophysics and stellar evolution, nuclear physics and the strong interaction, and strong-field gravity. Some specific possibilities to discuss include the likelihood of detecting the first pulsar-black hole binary and pulsars orbiting SGR A* and how they will revolutionize our tests of general relativity and reveal properties of black holes. It is also an ideal time to reflect on the possibilities of discovering sub-millisecond pulsars, neutron stars with masses below 1.1 or above 2.5 M⊙ and what physics we can learn from them.

We propose to host the meeting at the Jodrell Bank Observatory, the site of the iconic Lovell Telescope, eMerlin and the SKA international headquarters and the award winning Jodrell Bank Discovery Centre. These elements make it an ideal site to host this anniversary meeting. The Lovell Telescope, the third largest steerable telescope in the world, has been observing pulsars for the entire 50 years and seamlessly connects the past, present and future of pulsar research having been involved in the field back to within just a few months of their discovery and still contributing to deliver cutting edge research like with the IPTA. The SKA HQ fully supports this application and having them on site connects directly to the strong future of radio pulsar studies and offers participants a chance to connect with this major international project. The Discovery Centre is an exceptionally strong and innovative outreach centre reaching more than 120,000 visitors a year. We will use their facilities for the meeting and we have already begun working with them to plan a number of events during our meeting but also throughout the year to celebrate the discovery of pulsars. The events during the meeting will include, e.g., “meet the expert” sessions for the public to engage with the scientists directly, public lectures, demonstrations and live pulsar observing.