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.
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.
Organisations
Publications
Yim G
(2022)
Gravitational radiation back-reaction from f-modes on neutron stars
in Monthly Notices of the Royal Astronomical Society
Yim G
(2020)
Transient gravitational waves from pulsar post-glitch recoveries
in Monthly Notices of the Royal Astronomical Society
Yim G
(2023)
Gravitational waves from small spin-up and spin-down events of neutron stars
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 | 01/10/2017 | 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 neutron star is spinning. A pulsar glitch is an event where the neutron star'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 creates a braking torque and causes the neutron star's spin frequency to decrease (hence, explaining 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 will be 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 neutron star oscillation model for timing noise Timing noise is the long-term (unlike, glitches which are short-term) unmodelled variation in the spin frequency of a neutron star. Currently, the true mechanism that causes timing noise is unknown so we take steps towards creating a model to explain it, with a key feature being that it can be tested with gravitational waves. We show that when certain oscillations are excited on the neutron star, which subsequently decay away, the neutron star either increases or decreases its spin frequency in a step-like way. The accumulation of these small frequency jumps, which may or may not be resolvable, could then give rise to the long-term variations in spin. With each jump in the spin frequency, we show that a burst of gravitational waves is emitted that lasts no longer than 0.1 s and has a frequency of 2000 Hz. We find that the gravitational waves given off will be detectable with 3rd generation detectors, but only when the gravitational wave signal from 4+ jumps are stacked together. |
| 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 neutron star oscillation model for timing noise The model created gives motivation for gravitational wave observers to continue their searches for burst gravitational waves. The detection of such gravitational waves would be the first of its kind. The model also provides a reason for small changes in spin frequency, which gives electromagnetic observers another understanding of how small jumps in frequency arise. The model is still fairly basic, but the inclusion of more physical processes could help us understand more about the interior of neutron stars, which is fascinating in itself. During the modelling, energy and angular momentum were conserved through careful calculation. This detailed calculation helps clarify some common misconceptions that exist in the field. In doing so, we were able to analytically prove the existence of a "gravitational wave back-reaction" where the excitation and decay of a prograde (retrograde) oscillation causes the neutron star to rotate in the retrograde (prograde) direction. |
| Sectors | Other |
| URL | https://arxiv.org/pdf/2007.05893.pdf |
| Description | NSFC Special Fund for Theoretical Physics |
| Amount | ¥180,000 (CNY) |
| Funding ID | 12247180 |
| Organisation | National Natural Science Foundation of China |
| Sector | Public |
| Country | China |
| Start | 01/2023 |
| End | 12/2023 |
| Description | Contributed talk at BritGrav21 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk on gravitational waves from f-mode oscillations. The talk was given virtually. |
| Year(s) Of Engagement Activity | 2021 |
| 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 | Contributed talk to BritGrav22 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "Gravitational waves from f-mode oscillations and their connection to small spin-ups and spin-downs of neutron stars". |
| Year(s) Of Engagement Activity | 2022 |
| URL | https://www.gla.ac.uk/events/conferences/britgrav22/schedule/# |
| Description | Contributed talk to GR23 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "Gravitational waves from small spin-ups and spin-downs of neutron stars". |
| Year(s) Of Engagement Activity | 2022 |
| URL | http://gr23beijing.com/article/type/666-1.html |
| Description | Contributed 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 "Modelling small glitch-like events as neutron star f-mode oscillations". |
| Year(s) Of Engagement Activity | 2021 |
| URL | https://www.youtube.com/watch?v=q9XruB1MRRU |
| Description | Contributed talk to KIAA Gravitational Wave Postdoc Workshop |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "Gravitational waves from pulsar timing irregularities". |
| Year(s) Of Engagement Activity | 2022 |
| URL | https://kiaa.pku.edu.cn/info/1026/8621.htm |
| Description | Contributed talk to LIGO Burst Group |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "Gravitational waves from small spin-up and spin-down events of neutron stars". |
| Year(s) Of Engagement Activity | 2022 |
| Description | Invited talk for NAOC Seminar (National Astronomical Observatories, Chinese Academy of Sciences) |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "Gravitational waves from pulsar timing irregularities". |
| Year(s) Of Engagement Activity | 2023 |
| Description | Invited talk for the KIAA-DoA Seminar of Peking University |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "Transient gravitational waves from pulsar post-glitch recoveries". |
| Year(s) Of Engagement Activity | 2022 |
| URL | https://kiaa.pku.edu.cn/info/1025/8590.htm |
| 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 | Poster presented at GWAECS |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Presented poster about my research. Won 1st prize for best poster. |
| Year(s) Of Engagement Activity | 2021 |
| Description | Poster presented at GWPAW Workshop 2022 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Presented a poster on "Gravitational waves from small spin-up and spin down events of neutron stars". |
| Year(s) Of Engagement Activity | 2022 |
| 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 | 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 | Gave a talk titled "A novel model for small glitches and anti-glitches". It was well received with plenty of questions. It was good practice for my PhD viva. |
| Year(s) Of Engagement Activity | 2021 |
| Description | Seminar Talk to the Peking University Astronomy/Pulsar Group |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "A novel model for small glitches and anti-glitches". |
| Year(s) Of Engagement Activity | 2022 |
| Description | Seminar talk to KIAA Gravity Association |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "Gravitational waves from pulsar timing irregularities". |
| Year(s) Of Engagement Activity | 2022 |
| URL | https://kiaagravity.github.io/activities/2022/11/13/Group-Meeting.html |
| Description | Seminar talk to KIAA Gravity Group |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "A model for magnetar glitches and antiglitches". |
| Year(s) Of Engagement Activity | 2023 |
| URL | https://kiaagravity.github.io/activities/2023/02/22/Group-Discussion.html |
| Description | Seminar talk to KIAA Gravity Group |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Professional Practitioners |
| Results and Impact | Gave a talk titled "A novel model for small glitches and anti-glitches". |
| Year(s) Of Engagement Activity | 2022 |
| URL | https://kiaagravity.github.io/activities/2022/10/07/Group-Meeting.html |
| 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 |