supernova remnant Cassiopeia A
portrait Vanessa Graber

Dr Vanessa Graber

Welcome to my website. I am a theoretical astrophysicist and I study neutron stars, some of the most exciting objects in our Universe.

night sky showing the milky way and a shooting star

Research

Neutron stars are stellar remnants that form in supernova explosions of massive stars. Each of these objects contains a mass comparable to the Sun's within a radius of about ten kilometres and exhibits high densities, fast rotation and large magnetic fields. Such conditions cannot be recreated on Earth, making neutron stars amazing cosmic laboratories to study matter under extreme conditions.

While I am interested in many aspects of neutron stars, my work can be broadly separated into two parts: The first focuses on the interface between astrophysics and condensed matter physics, while my second research area concerns the population synthesis of isolated neutron stars. More details can be found here:

night sky showing the milky way and a shooting star

Macroscopic Condensates

One of the most exciting aspects of neutron stars is that their interiors are strongly influenced by quantum mechanics. To better understand their behaviour, I study so-called superfluid and superconducting components.

Much like the Earth, neutron stars are composed of distinct layers. They have a solid crust and a fluid interior that contain neutrons, protons, electrons and possibly exotic particles. In terms of their high densities, neutron stars are very cold, giving the protons and neutrons the special ability to flow without friction: The charged protons form a superconductor, whereas the neutrons are referred to as a superfluid.

These two are exotic versions of quantum states that are observed in experiments on Earth. From their laboratory counterparts, we know that superconductors and superfluids create vortices that can be envisaged as tiny, rapidly rotating tornadoes. These small structures interact with their surroundings, affecting the large-scale dynamics of the star.

waterspout off the coast of Florida, 1969
Vortices can be envisaged as tiny, rapidly rotating tornadoes. Image credit: NOAA Photo Library

I research different approaches to include these small-scale effects into theoretical models of neutron stars. Using techniques that are well-known from standard magnetohydrodynamics, I have for example studied the evolution of the magnetic field in the interior of superconducting neutron stars. I have also presented novel ways that low-temperature laboratory experiments could be used to make progress in understanding neutron star astrophysics.

Furthermore, I have been analysing how coupling processes in the interior affect the star's response after a so-called glitch. These sudden spin-ups interrupt the regular spin-down of pulsars and are thought to be a macroscopic manifestation of superfluidity. By connecting the physics on different length scales, I developed a predictive model of the glitch rise showing that assumptions about the microphysics of vortices crucially affect the star's rotational behaviour. Comparing my predictions to the first pulse-to-pulse glitch observations, reported by Palfreyman et al. (2018), I derived constraints on the strength of the frictional mechanisms in the star's interior. An improved analysis of the data, revealing novel details about the internal components of the star, was recently published in Nature Astronomy.

Using techniques well-known from the studies of laboratory superconductors, so-called Ginzburg-Landau models, I have also been exploring the micro-scale characteristics of the superconducting protons in the neutron star core. Their properties are poorly understood but could have a significant impact on the stellar magnetism and are thus crucial to understand the macroscopic magnetic field properties of compact objects. By adapting the Ginzburg-Landau description to the neutron star interior and connecting it with realistic superfluid parameters and equations of state, my collaborators and I have constructed superconducting phase diagrams and found that the outer core of neutron stars exhibits so-called type-1.5 superconductivity, rather than type-II superconductivity as generally assumed.

More information can be found on my publication page.

night sky showing the milky way and a shooting star

Population Synthesis

In addition to focussing on the neutron star interior, I also investigate the global population of isolated neutron stars in our Milky Way.

Although about a billion neutron stars are expected to exist in our own galaxy, observational constraints limit us to only detecting a small fraction of them; we only know a few thousand of these compact objects to date. To overcome this gap, so-called population synthesis approaches are used to theoretically model the full population. Based on our current knowledge of input physics, these approaches focus on simulating a synthetic neutron star population. Once the simulated sample is created, we compare it to real observations to identify discrepancies and subsequently adjust our theoretical models. This kind of global study, thus, allows us to better constrain the input physics, i.e., learn more about neutron stars on an individual level.

I am personally interested in using new computational techniques, specifically machine learning, to perform the comparison between the synthetic sample and the observed characteristics. Machine learning is an implementation of artificial intelligence that gives systems the ability to automatically improve and learn from previous experiences without being explicitly told how to do so. These techniques have seen a lot of interest in the astronomy and astrophysics community, where it is often no longer possible to evaluate large amounts of data by hand.

Our aim is to use machine learning frameworks to improve our understanding of the physics of compact objects in the Milky Way, in particular a class of neutron stars with strong magnetic fields, so-called magnetars, of which we currently only know about a dozen.

artist impression of a neutron star
Artist impression of a neutron star and its magnetic field. Image credit: ESO/L.Calçada
library shelves filled with old books

Publications

A full list of papers can be found on the online databases ADSbeta logoADS, arXiv logoarXiv or ORCID iD iconORCID. Alternatively, a list of selected publications is given below.

  • M. Ronchi, V. Graber, A. Garcia-Garcia, J. A. Pons, and N. Rea, Analyzing the Galactic pulsar population with machine learning, (submitted to Monthly Notices of the Royal Astronomical Society) eprint arXiv:2101.06145
  • T. S. Wood, V. Graber, and W. G. Newton, Superconducting phases in a two-component microscale model of neutron star cores, (submitted to Physical Review C) eprint arXiv:2011.02873
  • P. Esposito, N. Rea, A. Borghese, F. Coti Zelati, D. Viganò, G. L. Israel, A. Tiengo, A. Ridolfi, A. Possenti, M. Burgay, D. Götz, F. Pintore, L. Stella, C. Dehman, M. Ronchi, S. Campana, A. Garcia-Garcia, V. Graber, S. Mereghetti, R. Perna, G. A. Rodríguez Castillo, R. Turolla, and S. Zane, A very young radio-loud magnetar, Astrophysical Journal Letters, vol. 896, L30 (2020)
  • G. Ashton, P. D. Lasky, V. Graber, and J. Palfreyman, Rotational evolution of the Vela pulsar during the 2016 glitch, Nature Astronomy, vol. 3, 1143 (2019)
  • V. Graber, A. Cumming, and N. Andersson, Glitch rises as a test for rapid superfluid coupling in neutron stars, Astrophysical Journal, vol. 865, 23 (2018)
  • V. Graber, Fluxtube dynamics in neutron star cores, Astronomische Nachrichten, vol. 338, 1090 (2017)
  • W. C. G. Ho, N. Andersson, and V. Graber, Dynamical onset of superconductivity and retention of magnetic fields in cooling neutron stars, Physical Review C, vol. 96, 065801 (2017)
  • V. Graber, N. Andersson, and M. Hogg, Neutron stars in the laboratory, International Journal of Modern Physics D, vol. 26, 1730015 (2017)
  • V. Graber, N. Andersson, K. Glampedakis, and S. K. Lander, Magnetic field evolution in superconducting neutron stars, Monthly Notices of the Royal Astronomical Society, vol. 453, 671 (2015)
  • A. Markowsky, A. Zare, V. Graber, and T. Dahm, Optimal thickness of rectangular superconducting microtraps for cold atomic gases, Physical Review A, vol. 86, 023412 (2012)
wooden chairs in a lecture hall

Talks

I have presented my research at many international conferences over the years as well as giving invited colloquia and seminars. Details are given below.

wooden chairs in a lecture hall

Talks 2021

Click on the folder icons to download the respective slides.

  • March 2021, Superconducting phases in neutron star interiors, Hadronic, Nuclear and Atomic Physics Group Seminar, University of Barcelona, Barcelona, Spain (online)
wooden chairs in a lecture hall

Talks 2019 - 2020

Click on the folder icons to download the respective slides.

  • November 2020, Superconducting phases in neutron star cores, Neutron Star Group Meeting, University of Southampton, Southampton, UK (online) folder icon
  • November 2020, The superfluid neutron star interior, Webinar, Fluids ECR Forum, University of Leeds, Leeds, UK (online) folder icon
  • November 2020, Neutron stars: Cosmic superfluids and superconductors, Pizza Seminar, Institute of Space Sciences (ICE-CSIC, IEEC), Barcelona, Spain (online)
  • November 2020, Neutron stars: Cosmic superfluids and superconductors, Seminar, Stony Brook University, Stony Brook, New York (online)
  • July 2020, Neutron stars: Cosmic superfluids, Colloquium, Research Training Group "Models of Gravity", Oldenburg, Germany (online) folder icon
  • June 2020, Neutron stars: Cosmic superfluids, Seminar, IRAP, Toulouse, France (online)
  • March 2020, Superconducting phases in a two-component microscale model of neutron star cores, Annual PHAROS Conference, Patras, Greece (cancelled due to Covid-19)
  • February 2020, Neutron stars as cosmic laboratories, Physics Colloquium, Texas A&M Commerce, Commerce, Texas
  • November 2019, Neutron stars: Macroscopic quantum systems, MAGNESIA Kick-Off Meeting, Institute of Space Sciences (ICE-CSIC, IEEC), Barcelona, Spain
  • April 2019, Crust superfluidity - Implications for macroscopic hydrodynamics, ICONS - Investigating crusts of neutron stars, JINA - CEE Workshop, University of Amsterdam, Amsterdam, Netherlands folder icon
  • April 2019, Probing neutron star physics in the laboratory, Quantum turbulence: cold atoms, heavy ions, and neutron stars, INT Workshop, University of Washington, Seattle, Washington
  • January 2019, Neutron stars as cosmic laboratories, Mini-Symposium, Goethe University, Frankfurt, Germany
wooden chairs in a lecture hall

Talks 2018

Click on the folder icons to download the respective slides.

  • November 2018, Neutron stars - Astrophysical superfluids, Astrophysics Colloquium, Swinburne University, Melbourne, Australia
  • November 2018, Neutron stars as cosmic laboratories, Astrophysics Colloquium, University of Melbourne, Melbourne, Australia folder icon
  • November 2018, Using neutron stars as cosmic laboratories, GW Group Meeting, Monash University, Melbourne, Australia
  • July 2018, Glitch rises as a test for rapid superfluid coupling, COSPAR 42nd Assembly, Pasadena, California folder icon
  • April 2018, Probing neutron star physics in the laboratory, Superfluid Seminar, Newcastle University, Newcastle, UK
  • April 2018, The superconducting state in neutron star interiors, MHD Seminar, Durham University, Durham, UK
  • April 2018, Rapid crust coupling and glitch rises in superfluid neutron stars, PHAROS WG2 Meeting, CAMK, Warsaw, Poland
  • March 2018, Modelling superfluid neutron stars, Astrophysics Seminar, McGill University, Montreal, Canada
  • January 2018, Mutual friction in superfluid neutron star crusts, Astrophysics Seminar, Newcastle University, Newcastle, UK
  • January 2018, Understanding the dynamics of superfluid and superconducting neutron stars, Gravity Seminar, University of Southampton, Southampton, UK
wooden chairs in a lecture hall

Talks pre 2018

Click on the folder icons to download the respective slides.

  • November 2017, Mutual friction in neutron star crusts, JINA - INT Workshop, University of Washington, Seattle, Washington folder icon
  • November 2017, Neutron stars in the laboratory, Condensed Matter & Astrophysics Seminar, Northwestern University, Evanston, Illinois folder icon
  • November 2017, Neutron stars in the laboratory, Physics Colloquium, Kent State University, Kent, Ohio
  • October 2017, Physics of superfluid neutron stars - Growth of the superconducting phase, New Perspectives on Neutron Star Interiors, ECT* Workshop, Trento, Italy folder icon
  • May 2017, Fluxtube dynamics in neutron star cores - Implications for magnetic field evolution, SMFNS2017 - 5th International Symposium on Strong Electromagnetic Fields and Neutron Stars, Havana, Cuba folder icon
  • June 2015, Magnetic field evolution in superconducting neutron stars, Annual NewCompStar Conference, Budapest, Hungary folder icon
  • April 2015, Magnetic field evolution in superconducting neutron stars, BritGrav 15, Birmingham, UK
  • January 2015, Magnetic field evolution in superconducting neutron stars, Observations & Theory in the Dynamics of Neutron Stars, ECT* Workshop, Trento, Italy
  • March 2014, Theoretical neutron star modelling - A closer look at vortex dynamics, BritGrav 14, Cambridge, UK
  • April 2012, Dynamics of superfluid neutron stars, GR & Relativistic Astrophysics Seminar, Eberhard Karls Universität, Tübingen, Germany
stack of folded old black and white newspapers

Press

Sometimes, scientists are lucky for their research to make it into the news. Find below links to a selection of articles covering research that I was involved with.

stack of folded old black and white newspapers

2019 - Vela glitch analysis

A selection of news articles, blog posts and videos about our Nature Astronomy article Rotational evolution of the Vela pulsar during the 2016 glitch:

stack of folded old black and white newspapers

2020 - Baby magnetar detection

A selection of news articles and blog posts about our Astrophysical Journal Letters article A Very Young Radioloud Magnetar :

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Teaching

'It is the supreme art of the teacher to awaken joy in creative expression and knowledge.' Albert Einstein

Lecture Notes

Summer Schools

three black camera lenses on gray surface

PHYS 434 Optics

I taught the undergraduate module PHYS 434 Optics during the winter term 2019 at McGill University. Below you can find general information on the course as well as the lecture notes, I created.

Classes started on Monday, January 7 and took place every Monday and Wednesday from 2:35pm to 3:55pm in Rutherford RPHYS 114. General information about the course, teaching assistants and an overview of the course content, prerequisites, evaluation and reading materials can be found in the syllabus folder icon. Individual lecture topics, assigned reading materials and important dates are given in the course calender folder icon. Note that both were subject to change throughout the term.

LECTURE NOTES:

PART I – Electromagnetism and Light Propagation folder icon folder icon
PART II – Geometric Optics folder icon folder icon
PART III – Superposition, Polarisation and Interference folder icon folder icon
PART IV – Diffraction, Fourier Optics and Modern Optics folder icon folder icon

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Guest Lectures

Below you can download the slides I created for a range of guest lectures or watch them online.

  • October 2020, Neutron stars - The strongest magnets in the Universe, as part of NASA's Universe of Learning program, USA (online) folder icon
  • July 2020, Neutron stars - Extraordinary cosmic laboratories, SEDS Celestia (Astronomy & Astrophysics Club, BITS Pilani - K. K. Birla Goa Campus), Goa, India (online) folder icon
  • October 2018, Supermassive black holes, compact binaries and accretion, PHYS 521 Astrophysics, McGill University, Montreal, Canada folder icon
  • March 2017, Superfluids and neutron stars, PHYS 432 Physics of Fluids, McGill University, Montreal, Canada folder icon
Quebec flag in front of cloudy sky

CRAQ 2019 Summer School

The Centre for Research in Astrophysics of Quebec (CRAQ) hosted its annual summer school in June, 2019 in Montreal. The 2019 topic was Stellar Astrophysics and I covered Neutron Stars during the Stellar Death section.

General information about the summer school can be found here. My presentation slides and a Jupyter notebook to calculate mass-radius relations for two simple neutron star model equation of state can be downloaded below.

Slides folder icon
Jupyter notebook folder icon

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Outreach

Communicating science and engaging the general public is one of our important responsibilities as scientists. Showing that science can be fun and relatable is a part of my work that I greatly enjoy.

progression of a solar eclipse

AstroMcGill

While working as a postdoctoral fellow at the McGill Space Institute in Montreal, I was part of the AstroMcGill outreach team. You can find information about past and upcoming events on facebook and twitter. We regularly hosted a Public AstroNight, a free monthly lecture typically attracting several hundred people, as well as Astronomy on Tap, a world-wide initiative combining your two favourite things: astronomy and beer. AstroMcGill usually runs several astronomy related games and short talks at the AoT events. In September 2017, I had fun talking about 'Neutron stars - a space oddity' folder icon.

In December 2018, I gave the public monthly lecture jointly organised by AstroMcGill and PhysicsMatters, the McGill Physics Outreach group. My Public AstroPhysicsNight talk was titled 'Neutron Stars: Extraordinary Cosmic Laboratories for Physicists' folder icon and provided a non-specialist introduction to my research (no equations, I promise). You can watch a recording of the lecture here.

picture of a partial eclipse on a Sunspotter telescope
Projection of the Sun during the partial solar eclipse using a Sunspotter telescope.

Besides its regular programme, AstroMcGill also organises and participates at special events. In August 2017, for example, we hosted several thousand people at the McGill University campus for a viewing party of the partial solar eclipse. Seeing so many people exciting about astronomy was an amazing experience.

crowd during the partial eclipse viewing on the McGill University campus
The crowd at our partial solar eclipse viewing event at the McGill University campus.
light bulbs illuminating a large hashtag sign

Blog posts

Besides participating at outreach events in person, I occasionally write for blogs that focus on different topics related to science and academia. You can, for example, read an interview with me about the importance of women in research here.

If you are interested in learning more about my experience at the 69th Nobel Laureate Meeting dedicated to Physics, which I participated at in the summer of 2019, you can read two posts I wrote here and here. One aspect of the Lindau Meeting is a poster exhibition, where a pre-selected group of thirty young scientists gets the chance to present their research. I was one of the lucky participants and my poster folder icon won the shared first prize, by public vote of all the meeting attendees.

crowd during the partial eclipse viewing on the McGill University campus
The Canadian delegation of young scientists at #LINO19 with the Canadian Nobel Laureates Arthur McDonald and Donna Strickland. Photo credit: Patrick Kunkel/Lindau Nobel Laureate Meetings.
smoke being trapped in a bottle that is held upside down

Hands-on demos

Demonstrations are an excellent way to get people of all ages interested in science. As a PhD student, I was involved in constructing simple hands-on experiments for open days and public events that help to illustrate complex physical concepts. A few examples that have proven particularly successful over the years:

striped lycra sheet deformed by a heavy mass and marbles rolling around
Visualising gravity using a lycra sheet and round objects of different masses.
  • Combining an old trampoline, striped lycra fabric and marbles of different masses provides a fantastic set-up to visualise the workings of gravity and the concept of space-time.
  • Wave propagation, reflection and interference can be playfully illustrated using a `jelly baby wave machine'. To build your own you need jelly babies, duck tape and kebab sticks. Idea first spotted here.
  • Following the first direct detection of gravitational waves, I constructed a table-top Michelson interferometer (my all-time favourite physics experiment) to visualise the concepts employed by interferometric gravitational wave detectors. I followed instructions provided by the LIGO outreach team.
person standing in front of an experiment explaining it to the audience
Explaining the concept of waves with a `jelly baby wave machine'.
standing microphone in front of orange background

Public talks

In December 2018, while working as a postdoctoral fellow at the McGill Space Institute in Montreal, I gave the public monthly lecture jointly organised by AstroMcGill and PhysicsMatters, the McGill Physics Outreach group. My Public AstroPhysicsNight talk was titled 'Neutron Stars: Extraordinary Cosmic Laboratories for Physicists' folder icon and provided a non-specialist introduction to my research (no equations, I promise). You can watch a recording of the lecture here.

In July 2020, I contributed to the Faszination Astronomie Online initiative organised by the Haus der Astronomie. The Haus der Astronomie, which literally translates to 'House of Astronomy', is a Centre for Astronomy Education and Outreach in Heidelberg, Germany, that runs events for the general public, as well as workshops for students, teachers, and science communicators. In response to the Covid-19 pandemic, the centre moved its German public talk series online and has been regularly streaming about fascinating astronomy topics on its own YouTube-channel. My thirty minute-long talk on pulsar glitches, titled 'Wenn Neutronensterne Schluckauf haben', can be viewed here.

In addition to making scientific content more accessible to the general public, I have also participated in events that aim to make scientists themselves more relatable. One great way of achieving this is via storytelling and in November 2018, I performed in front of an amazing audience at a Science Story Slam hosted by Broad Science and Confabulation.

colourful pencils in a box on top of a desk

School visits

In October 2018, I visited a secondary school in Tuttlingen, Germany, to tell the students about the wonders of the solar system and answer all their questions about what it means to be a scientist. We also played a game that the AstroMcGill outreach team has been using at their events. It's called 'Moon or Frying Pan' (idea first spotted here). Try it out! It's actually a lot harder than it seems, but the kids loved it.

two spherical pictures (one a frying pan the other one a moon) side by side on black background
Two examples from the game 'Moon or Frying Pan'. Image credit: Christopher Jonassen/NASA.

While working at the McGill Space Institute in Montreal, together with other AstroMcGill and PhysicsMatters members, I also volunteered for the Inquiry Institute. The project aims to connect physicists with Montreal school teachers to introduce the educators to simple experiments that can be repeated in the classroom and specifically highlight the importance of critical and structural thinking. We, for example, worked on a demonstration that combines a hula hoop with painted table tennis balls to illustrate the concepts of moon phases and solar eclipses; a set-up that has proven useful to explain how to encourage pupils to ask critical questions.

sailing boat on Lake Constance in the sunset

About

Or how to become a theoretical astrophysicist?

I am currently a senior postdoctoral researcher at the Institute of Space Sciences (ICE-CSIC) in Barcelona, Spain, working with Nanda Rea and others on the newly funded ERC project MAGNESIA that focuses on providing a census of galactic magnetars (a class of highly magnetised neutron stars). Further, I am a member of the European COST Action network PHAROS, which focuses on the multi-messenger physics and astrophysics of neutron stars and is a continuation of the NewCompStar network. I am also part of the Square Kilometre Array (SKA) Pulsar Working Group as well as the NSF Physics Frontiers Center JINA-CEE and the ​International Research Network for Nuclear Astrophysics (IReNA), which are dedicated to the study of nuclear astrophysics and the formation of elements.

Prior to my current position, I was a research fellow at the McGill Space Institute at McGill University in Montreal, Canada, where I worked with Andrew Cumming and Vicky Kaspi on a range of neutron star problems. Before moving to Canada I completed my PhD in the Gravity Group within Applied Mathematics at the University of Southampton, United Kingdom, under the supervision of Nils Andersson. Moreover, I have received a physics Diplom (MPhys) from the Eberhard Karls Universität Tübingen, Germany, where I was part of the Theoretical Astrophysics Group headed by Kostas Kokkotas.

The first 18 years of my life I was lucky enough to be living by Lake Constance in the South of Germany. Having seen many beautiful places over the years, I can say that the Swabian Sea (as the lake is often nicknamed) is one of the most magnificent spots I have been to and I try to go back as often as possible.

My full CV can be downloaded here folder icon.

old type writer in front of a white background

Contact

You can reach me in the following ways:

Mailing address:
Institute of Space Sciences (ICE-CSIC)
Campus UAB
Carrer de Can Magrans s/n
08193 Cerdanyola del Vallès
Barcelona
Spain

Email:
graber@ice.csic.es