Modelling pulsar timing noise

Lead Research Organisation: University of Southampton
Department Name: Sch of Mathematical Sciences

Abstract

Context: Pulsars - rotating neutron stars - are observed to gradually spin down, with the apparent loss in kinetic energy balancing a flux of electromagnetic and gravitational wave energy from the star. This spin down is smooth, but not perfectly so, with departures from a simple timing model being known as pulsar timing noise. The origin of this noise is not understood. The aim of this project is to develop mathematical models that describe this phenomenon.

Key objective and aims: the key objective is to build a model of a neutron star that incorporates the wide range of physical inputs that are likely to be important in this problem. The outputs of such a model would be compared against real timing noise and the model parameters adjusted so as to reproduce as accurately as possible the observed spin behaviour. In this way, the behaviour of fluids and solids in extremes of gravity, density and magnetic field would be probed, in a way that would simply not be possible in a terrestrial laboratory.

Novel methodology: the novel methodology lies in developing perturbation techniques to describe small departures from uniform rigid body spin-down, that include gravitational, elastic and magnetic forces. Then new numerical techniques to evolve the system on a computer would be developed, and used to explore the consequences of the model.

EPSRC research areas: The highly complex physics of neutron stars means that this project is relevant to multiple EPSRC research areas. Mathematical physics and Complexity science are the most obviously relevant areas, but there is also overlap with Cold atoms and molecules, Condensed matter: magnetism and magnetic materials, and Quantum fluids and solids.

Publications

10 25 50
publication icon
Yim G (2020) Transient gravitational waves from pulsar post-glitch recoveries in Monthly Notices of the Royal Astronomical Society

Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509747/1 01/10/2016 30/09/2021
1949172 Studentship EP/N509747/1 28/09/2017 31/03/2021 Garvin Yim
 
Description 1, Gravitational waves from transient mountains caused by pulsar glitches

A pulsar is a neutron star that spins rapidly, emitting a flash of radiation with each full revolution (just like how you see light from a lighthouse). Therefore, the rate of flashing tells us something about the how fast the NS is spinning. A pulsar glitch is an event where the NS's spin frequency abruptly increases and then typically recovers back to, but never quite reaches, the pre-glitch spin frequency. There are a few models to explain the glitch recovery but we propose a new model where at the moment of the glitch, a "mountain" is instantaneously formed which causes the NS's spin frequency to decrease (which explains the recovery). Additionally, the newly-formed mountain would theoretically emit gravitational waves. We take the optimistic view that the glitch recovery is solely due to a mountain and calculate the strength and detectability of the resultant gravitational waves. Our model predicts: gravitational waves from this model are marginally detectable with current 2nd-generation detectors; and gravitational waves from this model will be detectable in the 2030s with 3rd-generation detectors.

2, A physically-motivated model for timing noise

This part of the PhD project is still underway. Key findings will be reported at a more appropriate future date.
Exploitation Route 1, Gravitational waves from transient mountains caused by pulsar glitches

This research has created a new model that explains pulsar glitch recoveries and it can be independently tested with gravitational wave observations. We make predictions of the types of gravitational waves emitted and these can be searched for by gravitational wave detectors. There are indeed current efforts in trying to detect these predicted gravitational waves. If a detection is made, it would be the case of the first ever gravitational wave signal that does not come from the merger of two compact objects. If no detections are made, then further constraints could be placed on how much this model contributes to the observed glitch recovery.

2, A physically-motivated model for timing noise

Not yet applicable.
Sectors Other

URL https://arxiv.org/pdf/2007.05893.pdf
 
Description Contributed talk at SPINS-UK 2019 conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact I gave a talk on my work about "transient gravitational waves from pulsar post-glitch recoveries". It was well-received with many questions immediately afterwards and in the coffee break.
Year(s) Of Engagement Activity 2019
 
Description Invited talk to Continuous Waves Group at the Albert Einstein Institute 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I gave a talk about my work on "transient gravitational waves from pulsar post-glitch recoveries". It was well-received and many questions were asked afterwards. Certain questions helped inspire future work.
Year(s) Of Engagement Activity 2020
 
Description Invited talk to GrEAT Network with China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I gave a recorded talk about my work on "transient gravitational waves from pulsar post-glitch recoveries". This recording was translated and Chinese subtitles were added for the audience.
Year(s) Of Engagement Activity 2020
 
Description Invited talk to LIGO Continuous Waves Group 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact I gave a talk about my work on "transient gravitational waves from pulsar post-glitch recoveries". It was well-received and many questions were asked afterwards.
Year(s) Of Engagement Activity 2020
 
Description Seminar Talk to the Neutron Star Group at University of Southampton 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact I gave a seminar on my work about "transient gravitational waves from pulsar post-glitch recoveries". It was well received with many questions asked.
Year(s) Of Engagement Activity 2020
 
Description Southampton Science and Engineering Festival (SOTSEF) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Local people, mainly parents with children (5 - 16 years old), came to explore the University campus in an event to celebrate all things to do with science and engineering. My particular role was to help run a stall about neutron stars and their mergers (since GW170817 was still very topical at the time). We engaged with parents and children in an attempt to inspire them to go into science as a career. We showcased the research done at Southampton as well as provided lots of interactive games and information to participants.
Year(s) Of Engagement Activity 2019
URL https://www.sotsef.co.uk