Astrophysics Colloquium - Probing Fundamental Physics using X-Ray and Radio Signals from a Magnetar

Abstract:  The last six years have witnessed a substantial number of new observational manifestations for magnetars, the most magnetic members of the neutron star family.  These encompass fast radio burst associations, the detection of giant flares in extragalactic magnetars, high cadence observations of glitch epochs, and new X-ray polarization information from IXPE.   Such discoveries have seeded a growth in understanding and a magnification of their mysterious character.  This talk summarizes some recent observational and theoretical advances pertaining to persistent surface X-ray emission.  Polarized magnetar signals are addressed in the context of atmosphere models that provide a benchmark for assessing key stellar geometrical parameters.  Characteristics from the sophisticated radiative transfer simulation MAGTHOMSCATT are presented, along with how light curves can be used to constrain the viewing and magnetic geometries.  Evolution of these light curves suggests dynamic changes in the field structure.  A core focus is on how the strong-field QED effect of vacuum birefringence impacts the emergent polarization signals detected in X rays by IXPE.  This culminates in a recent exposition on combined IXPE data and polarized radio observations for the magnetar 1E 1547.0-5408, which provide tantalizing suggestion of the action in Nature of this fundamental physics prediction.  

Short bio: Prof. Baring is a Professor at Rice University, Houston, Texas, in the Department of Physics and Astronomy.  He has been there twenty-five years, having graduated with a PhD from the University of Cambridge, United Kingdom, in theoretical astrophysics.  In the intervening time, he occupied positions at several prominent institutions in the US and Europe, including an eight-year stint at NASA's Goddard Space Flight Center in Greenbelt, Maryland, where he worked in the Laboratory for High Energy Astrophysics.  His career started with undergraduate studies in physics at the University of Melbourne in Australia, and has led him around the world in the pursuit of knowledge.  His research covers various sources of radiation in the cosmos, including remnants of supernovae, cosmic plasma shocks, gamma-ray bursts, jets of active galaxies, and pulsars, neutron stars and black holes.  Dr. Baring is  an Associate Scientist for the Large Area Telescope experiment on the Fermi Gamma-ray Space Telescope, an Associate Science Collaborator for the XL-Calibur balloon-borne X-ray polarimeter program, and a member of the AMEGO gamma-ray telescope consortium.  He served two terms as a Divisional Associate Editor for Physical Review Letters, a four-year stint as an Associate Editor for Astrophysical Journal Letters, and also spent four years as the Secretary-Treasurer of the High Energy Astrophysics Division of the American Astronomical Society.  He is the current President of Division D of the International Astronomical Union. He is the recipient of an Outstanding Referee Award from and a Fellow of the American Physical Society.