Magnetic fields: the key to understanding the physics of stellar evolution and exoplanetary systems

Lead Research Organisation: University of St Andrews
Department Name: Physics and Astronomy

Abstract

Some of the most intense solar fireworks have directly affected modern life on Earth. Rapid increases in solar activity send fluxes of charged particles towards our planet, disrupting satellite communications and generating spectacular aurorae. The sublime coloured lights flickering across the night sky arise from solar wind particles trapped in the large-scale magnetic field of the Earth. We are fortunate that this magnetic field protects our atmosphere, and us, from the harmful effects of the highest energy solar radiation. Yet however spectacular the events on our Sun may seem today, our middle-aged star is comparatively quiet and hides a much more violent past.

A few billion years ago the Sun was a contracting ball of hot gas, although it was still too cool within its core to fuse hydrogen into helium and shine as it does today. Young solar analogues, called T Tauri stars, are about a million times too faint to be seen with the naked eye. Space satellite observations, however, have shown that they are typically 1000 times more active in X-rays than the Sun is presently. They are surrounded by large dusty planet-forming discs, which are bombarded by X-rays arising from violent stellar magnetic events.

T Tauri stars are new-born stars which are still shrinking down under gravity to their adult proportions. As such stars collapse they should start to spin faster and faster, just like an ice-skater who pulls in their arms closer to their body. However, such stars are observed to be spinning slowly, an effect that has been attributed to how their strong magnetic fields interact with the gas and dust within the surrounding discs. T Tauri stars are embedded in a web of magnetic field which binds them to their discs, the eventual birthplace of planetary systems. It is expected that this magnetic web acts as a brake, allowing the star to remain spinning slowly. This process, however, is poorly understood.

Using a technique called Zeeman-Doppler imaging, which is analogous to methods used in medicine to produce 3D images of the internal organs of the body, I have been able to determine the structure of their magnetic webs. This newly available data signals the beginning of a fresh era of research into the formation of solar-like stars. My research will exploit information gained from the largest telescopes on Earth and from space satellites in order to investigate how forming stars interact with, and disrupt, their environments. The significant gains in observational results require corresponding development of state-of-the-art numerical models. Ultimately my research will provide insight into the formation of our own Sun, and Solar System, at a time when the planets were just beginning to form.

Roughly 500 planets, exoplanets, have now been found orbiting other stars with potentially thousands more awaiting discovery by the currently operating Kepler satellite. Some of the exoplanet host stars twinkle on the same timescale as it takes their planets to complete an orbit. This effect may be caused by the planets twisting the strands of the star's magnetic web; this process, if it can be understood, may provide a method of determining the magnetic properties of the exoplanets themselves. I will investigate star-planet interaction in detail during the STFC Ernest Rutherford Fellowship.

Publications

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Alencar S (2018) Inner disk structure of the classical T Tauri star LkCa 15 in Astronomy & Astrophysics

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Ardila D (2013) HOT GAS LINES IN T TAURI STARS in The Astrophysical Journal Supplement Series

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Ardila David R. (2013) Hot Gas Flows in T Tauri Stars in American Astronomical Society Meeting Abstracts #221

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Argiroffi C. (2014) V4046 Sgr: X-rays from accretion shock in Magnetic Fields throughout Stellar Evolution

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Davies C (2014) Accretion discs as regulators of stellar angular momentum evolution in the ONC and Taurus-Auriga in Monthly Notices of the Royal Astronomical Society

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Davies C. L. (2015) Observations of Accretion Disc-regulated Stellar Angular Momentum Evolution in Fully Convective Pre-main Sequence Stars in 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun

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Donati J (2017) The hot Jupiter of the magnetically active weak-line T Tauri star V830 Tau in Monthly Notices of the Royal Astronomical Society

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Donati J (2019) The magnetic propeller accretion regime of LkCa 15 in Monthly Notices of the Royal Astronomical Society: Letters

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Donati J (2013) Magnetospheric accretion on the fully convective classical T Tauri star DN Tau in Monthly Notices of the Royal Astronomical Society

 
Description New codes to understand the formation and evolution of young Sun-like stars as they evolve and interact with disks that are forming planets. New trends in how these stars evolve during the disk bearing phase and subsequently have been discovered. New models of how their high energy emission evolves with age have been developed. As stars develop solar-like interiors their large-scale magnetic fields increase in complexity and their high energy X-ray emission decays.
Exploitation Route Papers being citied and used by the community.
Sectors Education,Culture, Heritage, Museums and Collections,Other

 
Description Undergraduate Vacation Scholarship
Amount £1,300 (GBP)
Organisation Carnegie Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 06/2016 
End 07/2016
 
Title Data from stellar angular momentum paper (Davies et al 2014) 
Description Data from stellar angular momentum evolution paper, Davies, Gregory, Greaves (2014), NASA ADS bib code: 2014MNRAS.444.1157D VizieR catalog: J/MNRAS/444/1157 and NASA ADS bib code: 2015yCat..74441157D 
Type Of Material Database/Collection of data 
Year Produced 2014 
Provided To Others? Yes  
Impact Used a guidance / verification for theoretical models of Vasconcelos and Bouvier (2015), NASA ADS: 2015A&A...578A..89V 
URL http://vizier.cfa.harvard.edu/viz-bin/VizieR?-source=J/MNRAS/444/1157
 
Title Data from stellar magnetism paper (Vidotto et al 2014) 
Description Data used / derived in Vidotto, Gregory et al. (2014), NASA ADS bibcode: 2014MNRAS.441.2361V 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact Data is available publicly for anyone to use via VizieR, NASA ADS bib code: 2016yCat..74412361V VizieR catalog: J/MNRAS/441/2361 
URL http://vizier.cfa.harvard.edu/viz-bin/VizieR?-source=J/MNRAS/441/2361
 
Description (MaTYSSE) Magnetic Topologies of Young Stars and the Survival of close-in massive Exoplanets 
Organisation European Southern Observatory (ESO)
Country Germany 
Sector Charity/Non Profit 
PI Contribution Data interpretation and theoretical work.
Collaborator Contribution Data collection and reduction.
Impact Five journal papers so far, with several in preparation. NASA ADS bibliography codes: 2014MNRAS.444.3220D, 2015MNRAS.453.3706D, 2017MNRAS.465.3343D, 2017MNRAS.467.1342Y, and 2017MNRAS.472.1716H. The second paper (2015MNRAS.453.3706D) included a press release (UK: http://www.st-andrews.ac.uk/news/archive/2015/title,286569,en.php France: http://www.ast.obs-mip.fr/article1012.html ) with a resulting local radio interview (http://www-star.st-and.ac.uk/~sg64/interview_wave102_11Sept2015.m4a).
Start Year 2013
 
Description (MaTYSSE) Magnetic Topologies of Young Stars and the Survival of close-in massive Exoplanets 
Organisation Paul Sabatier University (University of Toulouse III)
Country France 
Sector Academic/University 
PI Contribution Data interpretation and theoretical work.
Collaborator Contribution Data collection and reduction.
Impact Five journal papers so far, with several in preparation. NASA ADS bibliography codes: 2014MNRAS.444.3220D, 2015MNRAS.453.3706D, 2017MNRAS.465.3343D, 2017MNRAS.467.1342Y, and 2017MNRAS.472.1716H. The second paper (2015MNRAS.453.3706D) included a press release (UK: http://www.st-andrews.ac.uk/news/archive/2015/title,286569,en.php France: http://www.ast.obs-mip.fr/article1012.html ) with a resulting local radio interview (http://www-star.st-and.ac.uk/~sg64/interview_wave102_11Sept2015.m4a).
Start Year 2013
 
Description BinaMIcS (Binarity and Magnetic Interactions in various classes of Stars) 
Organisation Observatory of Grenoble
Country France 
Sector Academic/University 
PI Contribution Producing 3D models of magnetospheric interaction in close (low-mass) binary stars (including accreting and non-accreting PMS tars) and providing input to the selection of observing targets. I am a member of the steering committee for the program.
Collaborator Contribution Data analysis and reductions; leading the observing programs. Models of massive stars magnetospheres and winds.
Impact NASA ADS bibliography codes: 2015csss...18..419H , 2015csss...18..509H.
Start Year 2012
 
Description ESA Athena satellite 
Organisation ESA - ESTEC
Country Netherlands 
Sector Public 
PI Contribution Providing scientific input, and feedback to ESA as required, through science working group 3.2 (star formation and evolution) as to the scientific requirements and goals of the future satellite mission.
Collaborator Contribution Leading the working groups.
Impact None as yet.
Start Year 2015
 
Description ESA Athena satellite 
Organisation National Institute for Astrophysics
Department Palermo Observatory
Country Italy 
Sector Public 
PI Contribution Providing scientific input, and feedback to ESA as required, through science working group 3.2 (star formation and evolution) as to the scientific requirements and goals of the future satellite mission.
Collaborator Contribution Leading the working groups.
Impact None as yet.
Start Year 2015
 
Description MaPP (Magnetic Protostars and Planets) program 
Organisation Paul Sabatier University (University of Toulouse III)
Country France 
Sector Academic/University 
PI Contribution I am the lead theory CoI in the program. Theoretical interpretation of the data, and construction of numerical models.
Collaborator Contribution Project leadership. Data analysis and observing program coordination.
Impact 4 conference paper, and 5 journal papers. NB: I am only counting publications for which my contributions were made when I was funded from STFC PI grants. There are multiple other publications associated with the project. NASA ADS bibliography codes: 2010MNRAS.402.1426D, 2010MNRAS.409.1347D, 2013MNRAS.436..881D, 2014MNRAS.437.3202J, 2014MNRAS.441.2361V, 2014IAUS..30240G, 2014IAUS..30244G, 2014EPJWC..6408009G, 2015IAUGA..2232877V.
Start Year 2008
 
Description SPIRou science team 
Organisation Paul Sabatier University (University of Toulouse III)
Country France 
Sector Academic/University 
PI Contribution Direct input to the SPIRou (a new nIR spectropolarimeter at the Canada-France-Hawaii telescope currently under going on-telescope tests; science operation begin in 2018B) Legacy Survey - target selection etc, and contributions to the science case. Contribution to the SPIRou Legacy Survey
Collaborator Contribution Design of the instrument, PI / lead roles within the Legacy Survey.
Impact None as yet (instrument has just been installed at the telescope).
Start Year 2015
 
Description Interview with Funding Insight magazine. 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Was interviews for a new e-magazine called Funding Insight, a spin off from Research Fortnight magazine, in January 2013. The article dealt with my experiences of applying for the STFC Ernest Rutherford fellowship, and tips for future applicants.

Greater awareness about the Ernest Rutherford fellowship scheme and insight into the application process.
Year(s) Of Engagement Activity 2013
 
Description Invited seminar - solar physics group, University of St Andrews, April 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other audiences
Results and Impact ~30 people attended an invited research seminar. Impact included detailed discussion and new ideas.
Year(s) Of Engagement Activity 2017
 
Description Invited seminar, AIP Potsdam, Germany, September 2017 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Invited seminar at an international institution. It generate discussion, new ideas, and new collaborations.
Year(s) Of Engagement Activity 2017
 
Description Invited seminar, Dublin Institute for Advanced Study, November 2014 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talk sparked discussion and questions.

Ensured that colleagues in a different country were aware some aspects of STFC funded research that was taking place in the UK.
Year(s) Of Engagement Activity 2014
 
Description Invited seminar, Dublin Institute for Advanced Study, November 2014 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Invited seminar, which sparked discussion and questions afterwards.
Year(s) Of Engagement Activity 2014
 
Description Invited seminar, Kiepenheuer Institute for Solar Physics, Freiburg, Germany, May 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact About 30 members of the department attended. There was significant discussion and several question afterwards.
Year(s) Of Engagement Activity 2015
 
Description Invited seminar, Rice University, Houston, TX, USA, February 2014 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talks sparked discussion and questions afterwards.

Ensured that colleagues in a different country were aware some aspects of STFC funded research that was taking place in the UK.
Year(s) Of Engagement Activity 2014
 
Description Invited seminar, University of Glasgow, October 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact About 40 members of the department attended, with lots of debate and questions afterwards.
Year(s) Of Engagement Activity 2015
 
Description Invited seminar, University of Sheffield, November 2016 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Invited seminar at a research institution. Discussion and questions were addressed afterwards.
Year(s) Of Engagement Activity 2016
 
Description Invited seminar, University of St Andrews solar physics group 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact Talk sparked discussion afterwards.

x
Year(s) Of Engagement Activity 2013
 
Description Press release and interview with Wave 102 local radio (Dundee, Tayside and Fife areas) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact A recorded interview with a local radio station, who picked up on a press release associated with a journal paper. Press release: http://www.st-andrews.ac.uk/news/archive/2015/title,286569,en.php and interview: http://www-star.st-and.ac.uk/~sg64/interview_wave102_11Sept2015.m4a
Year(s) Of Engagement Activity 2015
URL http://www.st-andrews.ac.uk/news/archive/2015/title,286569,en.php
 
Description University of St Andrews observatory open night 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Greater public understanding of science and of the work being undertaken by the University of St Andrews astronomy group.

Positive feedback received. Increased attendance year-on-year.
Year(s) Of Engagement Activity 2012,2013