Greek astronomer wins prestigious international award

A Greek astronomer shared the prestigious Shaw Prize for Astronomy 2021 for his contribution to our understanding of magnetars.

The prize was shared equally by Victoria M. Kaspi, professor of physics and director of the McGill Space Institute at McGill University in Canada and by the Greek Chryssa Kouveliotou, professor and chair of the physics department at George Washington University. , in the USA.

A magnetar is a type of neutron star believed to have an extremely strong magnetic field. The decay of the magnetic field fuels the emission of high energy electromagnetic radiation, especially X-rays and gamma rays. The theory concerning these objects was proposed in 1992 by Robert Duncan and Christopher Thompson.

Kouveliotou received his bachelor’s degree in physics from the National and Capodistrian University of Athens, Greece, in 1975, and received his master’s degree in science from the University of Sussex in England in 1977.

She obtained her doctorate in astrophysics in 1981 from the Technical University of Munich, Germany, under the supervision of Klaus Pinkau. She was a faculty member in the Department of Physics at the National and Capodistrian University of Athens before pursuing research work in the United States.

In 2012, she was selected as the recipient of the Dannie Heineman Prize for Astrophysics, which is awarded annually to recognize outstanding work in the field.

Kouveliotou was also an astrophysicist at NASA’s Marshall Space Flight Center in Huntsville, Alabama, and was the principal investigator of numerous research projects in the United States and Europe. She is also a founding member of several scientific collaborations around the world.

Thanks to the development of new precise observation techniques, the two winning astronomers of the Shaw Prize for Astronomy 2021 have confirmed the existence of neutron stars with ultra-strong magnetic fields and characterized their physical properties. Their work established magnetars as a new and important class of astrophysical objects.

Neutron stars are the ultra-compact remnants of stellar explosions. Most rotate rapidly with periods of a few milliseconds to seconds and emit powerful beams of electromagnetic radiation (seen as pulsars).

As such, they are precise “cosmic clocks” that allow fundamental physics testing in the presence of a gravitational field several billion times stronger than that of Earth. Reflecting their importance, the Nobel Prize in Physics has been awarded twice for work on pulsars (in 1974 and 1993).

Pulsars also have strong magnetic fields, because the progenitor star’s magnetic field lines are “frozen” in the stellar remnant when it collapses to become a neutron star. These magnetic fields burst into jets of particles along the magnetic poles, but classical radio pulsars are powered primarily by rotational energy and slow down slowly over their lifetimes.

Research by Greek astronomer shows extreme magnetic fields

The research carried out by Kaspi and Kouveliotou was motivated by the theoretical prediction that neutron stars with extreme magnetic fields up to a thousand times stronger than those of regular pulsars could form if the action of the dynamo was effective during first seconds after gravitational collapse in the core. of the supernova.

Such objects (called magnetars) would be powered by their large reservoirs of magnetic energy, rather than spinning, and would be expected to produce highly energetic bursts of gamma rays through the generation of pairs of highly energetic ionized particles at their centers.

From observations of a class of X / gamma ray sources called “soft gamma ray repeaters” (SGR), Chryssa Kouveliotou and her colleagues established the existence of magnetars and provided astonishing confirmation of the magnetar model. in 1998-1999.

By developing new techniques for synchronizing pulses at X-ray wavelengths and applying them to data from the Rossi X-ray synchronization satellite (RXTE), in 1998 Kouveliotou was able to detect X-ray pulses with a period of 7.5 seconds in the persistent X. – emission of rays of SGR 1806-20.

She then measured a spin-down rate for the pulsar and derived both the age of the pulsar and the strength of the dipolar magnetic field – which were within the range of values ​​predicted for magnetars, close to 1014 gauss. (1010 T). Spin-down measurements were extremely difficult due to the weak pulse signal and the need to correct the spin phase over several epochs.

The Shaw Prize 2021 recognizes the fundamental contributions of Victoria M. Kaspi and Chryssa Kouveliotou to understanding the enigmatic properties of magnetars, pulsars and gamma-ray bursts.