THE SPINS-UK SEMINAR SERIES
We announce the launch of the new SPINS-UK seminar series, a monthly series of online talks about neutron star science. We hope that this will be a great tool to bring together the national neutron star community and to learn more about each other's activities, bringing to light new collaborations and discussions!
The seminars are held on Wednesdays, from 1-2pm UK time every 4 weeks. The inaugural talk took place on Wednesday 10th February.
For information on how to access the seminars online, please contact Lucy Oswald at lucy.oswald@physics.ox.ac.uk.
We are now inviting nominations and self-nominations for future speakers for this series. If you would like to propose a speaker to present a talk to the SPINS-UK community, please contact Lucy Oswald.
The seminars are held on Wednesdays, from 1-2pm UK time every 4 weeks. The inaugural talk took place on Wednesday 10th February.
For information on how to access the seminars online, please contact Lucy Oswald at lucy.oswald@physics.ox.ac.uk.
We are now inviting nominations and self-nominations for future speakers for this series. If you would like to propose a speaker to present a talk to the SPINS-UK community, please contact Lucy Oswald.
UPCOMING TALKS
Prof Nils Andersson
Date: Wednesday 30th June 2021
Time: 1pm UK time
Speaker: Prof Nils Andersson, Professor of Applied Mathematics, Head of General Relativity Group, University of Southampton
Time: 1pm UK time
Speaker: Prof Nils Andersson, Professor of Applied Mathematics, Head of General Relativity Group, University of Southampton
Neutron stars with mountains
A spinning neutron star will radiate continuous gravitational waves if it is deformed away from axial symmetry. Such signals are expected to be weak but this is (to some extent) compensated for by long integration times (as the detectability improves as the square-root to the observation time). While there have been many efforts to find signals from rotating neutron stars (both from targeted sources and through all-sky searches), the best we have at the moment are observational upper limits on the signal strength. In this talk, I will consider these results in the context of our theoretical understanding. I will argue that observations of both millisecond radio pulsars and accreting neutron stars in low-mass X-ray binaries hint at a gravitational-wave contribution to the spin evolution. I will summarise recent progress in the modelling of the neutron star "mountains" and discuss what has to be done if we want to make (further) progress on this problem.
A spinning neutron star will radiate continuous gravitational waves if it is deformed away from axial symmetry. Such signals are expected to be weak but this is (to some extent) compensated for by long integration times (as the detectability improves as the square-root to the observation time). While there have been many efforts to find signals from rotating neutron stars (both from targeted sources and through all-sky searches), the best we have at the moment are observational upper limits on the signal strength. In this talk, I will consider these results in the context of our theoretical understanding. I will argue that observations of both millisecond radio pulsars and accreting neutron stars in low-mass X-ray binaries hint at a gravitational-wave contribution to the spin evolution. I will summarise recent progress in the modelling of the neutron star "mountains" and discuss what has to be done if we want to make (further) progress on this problem.
PREVIOUS TALKS
Inaugural talk - Dr Sam Lander
Date: Wednesday 10th February 2021
Time: 1pm UK time
Speaker: Dr Sam Lander, Lecturer in Physics at UEA
Time: 1pm UK time
Speaker: Dr Sam Lander, Lecturer in Physics at UEA
The early life of a neutron star's magnetic field
Neutron stars host the strongest magnetic fields in the Universe, but we still do not have a clear picture of what makes them so strong, nor why the field strengths of young neutron stars vary over roughly four orders of magnitude. This talk will provide an overview of ideas about how dynamo processes might generate highly intense magnetic fields, discussing potential problems with different candidate mechanisms and asking whether any other physics could drive field amplification. After dynamo action has ceased, we present models for the kind of steady state to which the young star’s magnetic field might relax. We conclude by showing how the birth physics of neutron stars could be constrained through measurements of their magnetic inclination angles.
Neutron stars host the strongest magnetic fields in the Universe, but we still do not have a clear picture of what makes them so strong, nor why the field strengths of young neutron stars vary over roughly four orders of magnitude. This talk will provide an overview of ideas about how dynamo processes might generate highly intense magnetic fields, discussing potential problems with different candidate mechanisms and asking whether any other physics could drive field amplification. After dynamo action has ceased, we present models for the kind of steady state to which the young star’s magnetic field might relax. We conclude by showing how the birth physics of neutron stars could be constrained through measurements of their magnetic inclination angles.
Dr Andrei Igoshev
Date: Wednesday 10th March 2021
Time: 1pm UK time
Speaker: Dr Andrei Igoshev, Postdoctoral Fellow at the University of Leeds
Time: 1pm UK time
Speaker: Dr Andrei Igoshev, Postdoctoral Fellow at the University of Leeds
Sleeping beasts: magnetic fields shape observational manifestations of neutron stars
Neutron stars (NSs) are seen as radio pulsars, magnetars and central compact objects. Magnetars and central compact objects are bright, young NSs seen close to the centra of supernova remnants. Magnetars are extremely magnetised neutron stars which shows a variety of observational phenomena associated to their magnetic fields, such as burst and giant flashes. Both magnetars and central compact objects are much hotter than it is excepted even for very young neutron stars. We perform first three-dimensional simulations of the magneto-thermal evolution using a spectral MHD code. Our results show that presence of strong toroidal magnetic field in magnetars is necessary to explain their quiescent thermal emission, in particular a formation of a single hot spot. Using our thermal maps we are able to explain light curves of 10 out of 19 magnetars in quiescence.
In the case of the central compact objects, we test the configuration of magnetic field formed as a result of stochastic dynamo. Such a magnetic field consists of multiple randomly orientated loops of magnetic field. The global dipolar field slowly formed as a result of the Hall and Ohmic evolution. In our simulations we see 5-7% pulsed fraction, formation of a few compact hot regions and difference of two times in temperature between hot and cold regions typical for observations of the central compact objects.
Neutron stars (NSs) are seen as radio pulsars, magnetars and central compact objects. Magnetars and central compact objects are bright, young NSs seen close to the centra of supernova remnants. Magnetars are extremely magnetised neutron stars which shows a variety of observational phenomena associated to their magnetic fields, such as burst and giant flashes. Both magnetars and central compact objects are much hotter than it is excepted even for very young neutron stars. We perform first three-dimensional simulations of the magneto-thermal evolution using a spectral MHD code. Our results show that presence of strong toroidal magnetic field in magnetars is necessary to explain their quiescent thermal emission, in particular a formation of a single hot spot. Using our thermal maps we are able to explain light curves of 10 out of 19 magnetars in quiescence.
In the case of the central compact objects, we test the configuration of magnetic field formed as a result of stochastic dynamo. Such a magnetic field consists of multiple randomly orientated loops of magnetic field. The global dipolar field slowly formed as a result of the Hall and Ohmic evolution. In our simulations we see 5-7% pulsed fraction, formation of a few compact hot regions and difference of two times in temperature between hot and cold regions typical for observations of the central compact objects.
Dr Manisha Caleb
Date: Wednesday 7th April 2021
Time: 1pm UK time
Speaker: Dr Manisha Caleb, Postdoctoral Researcher at the University of Manchester
Time: 1pm UK time
Speaker: Dr Manisha Caleb, Postdoctoral Researcher at the University of Manchester
Fast radio bursts and their possible links to neutron stars
Fast radio bursts (FRBs) have a story which has been told and retold many times over the past few years as they have sparked excitement and controversy since the pioneering discovery in 2007. The FRB class encompasses a number of microsecond-millisecond duration pulses occurring at Galactic to cosmological distances with energies spanning over 5 orders of magnitude. While most FRBs have been observed as singular events, a small fraction of them have been observed to repeat over various timescales leading to an apparent dichotomy in the population. Though ~50 progenitor model theories have been proposed with the majority involving neutron stars, no consensus has emerged for their origin(s). However, with the discovery of an FRB-like pulse from the Galactic magnetar SGR J1935+2154, magnetar engine models appear to be the current leading favourite. In this talk, I will present an overview of the field of FRBs and the recent results from the MeerTRAP project at the MeerKAT radio telescope.
Fast radio bursts (FRBs) have a story which has been told and retold many times over the past few years as they have sparked excitement and controversy since the pioneering discovery in 2007. The FRB class encompasses a number of microsecond-millisecond duration pulses occurring at Galactic to cosmological distances with energies spanning over 5 orders of magnitude. While most FRBs have been observed as singular events, a small fraction of them have been observed to repeat over various timescales leading to an apparent dichotomy in the population. Though ~50 progenitor model theories have been proposed with the majority involving neutron stars, no consensus has emerged for their origin(s). However, with the discovery of an FRB-like pulse from the Galactic magnetar SGR J1935+2154, magnetar engine models appear to be the current leading favourite. In this talk, I will present an overview of the field of FRBs and the recent results from the MeerTRAP project at the MeerKAT radio telescope.
Dr Diego Altamirano
Date: Wednesday 5th May 2021
Time: 1pm UK time
Speaker: Dr Diego Altamirano, Principal Research Fellow at the Astronomy Group, School of Physics and Astronomy, University of Southampton
Time: 1pm UK time
Speaker: Dr Diego Altamirano, Principal Research Fellow at the Astronomy Group, School of Physics and Astronomy, University of Southampton
Marginally stable burning as a potential tool to constrain the EoS of NSs
Understanding the physics of thermonuclear burning of H/He on the neutron star surface is a fascinating area of research. In this talk I will first briefly review our current theoretical understanding of the different (thermonuclear) burning regimes we observe, and then focus on the so-called "marginally stable burning", a regime that occurs at the transition between stable and unstable burning. I will review the recent observational results and the current state of theoretical simulations that describe this regime. Finally, I will highlight and discuss why the observation of marginally stable burning has the potential to put constraints on the Equation of State of Neutron Stars.
Understanding the physics of thermonuclear burning of H/He on the neutron star surface is a fascinating area of research. In this talk I will first briefly review our current theoretical understanding of the different (thermonuclear) burning regimes we observe, and then focus on the so-called "marginally stable burning", a regime that occurs at the transition between stable and unstable burning. I will review the recent observational results and the current state of theoretical simulations that describe this regime. Finally, I will highlight and discuss why the observation of marginally stable burning has the potential to put constraints on the Equation of State of Neutron Stars.
Dr Matt Middleton
Date: Wednesday 2nd June 2021
Time: 1pm UK time
Speaker: Dr Matt Middleton, Associate Professor, School of Physics and Astronomy, University of Southampton
Time: 1pm UK time
Speaker: Dr Matt Middleton, Associate Professor, School of Physics and Astronomy, University of Southampton
Neutron star ULXs - magnetars or X-ray lighthouses?
Although it was long suspected that neutron stars and stellar mass black holes could be powering the extreme apparent X-ray luminosities of ultraluminous X-ray sources (ULXs), it wasn’t until 2014 -- when the first X-ray pulsations from a ULX were discovered -- that this paradigm was put beyond doubt. The mechanisms by which an accreting neutron star can appear at more than a hundred times its Eddington limit are well established in theory but depend sensitively on the dipole field strength and the accretion rate, both of which can be hard to infer. In this talk I will discuss some of the phenomenology of these enigmatic sources, the open questions still facing the field (such as the true nature of the population demographic) and how we can hope to obtain the answers.
Although it was long suspected that neutron stars and stellar mass black holes could be powering the extreme apparent X-ray luminosities of ultraluminous X-ray sources (ULXs), it wasn’t until 2014 -- when the first X-ray pulsations from a ULX were discovered -- that this paradigm was put beyond doubt. The mechanisms by which an accreting neutron star can appear at more than a hundred times its Eddington limit are well established in theory but depend sensitively on the dipole field strength and the accretion rate, both of which can be hard to infer. In this talk I will discuss some of the phenomenology of these enigmatic sources, the open questions still facing the field (such as the true nature of the population demographic) and how we can hope to obtain the answers.
