A team of astronomers from Chile, the United Kingdom, and the Netherlands, has found a new, highly accurate way to measure the mass of young pulsars.
This artist’s concept depicts a pulsar called PSR B1257+12 and three exoplanets (discovered by Aleksander Wolszczan in 1992) orbiting around it. Image credit: NASA / JPL-Caltech.
Pulsars are rapidly rotating, very strongly magnetized neutron stars. They are known for their superb timing precision, although so-called ‘glitches’ can interrupt the regular timing behavior when the stars are young.
The leading theory is that these glitches arise as a rapidly spinning superfluid within the star transfers its rotational energy to the star’s crust.
“Imagine the pulsar as a bowl of soup, with the bowl spinning at one speed and the soup spinning faster,” said Prof. Nils Andersson of the University of Southampton, UK, senior author of the paper reporting the results in the journal Science Advances.
“Friction between the inside of the bowl and its contents, the soup, will cause the bowl to speed up. The more soup there is, the faster the bowl will be made to rotate.”
Prof. Andersson and his colleagues from the University of Amsterdam and the Pontificia Universidad Catolica de Chile have developed a novel technique for combining radio and X-ray data to measure the mass of pulsars that glitch. The idea relies on a detailed understanding of superfluidity.
The magnitude and frequency of the pulsar glitches depend on the amount of superfluid in the star and the mobility of the superfluid vortices within. By combining observational information with the involved nuclear physics, one can determine the mass of the star.
“All previous precise measurements of pulsar masses have been made for stars that orbit another object, using the same techniques that were used to measure the mass of the Earth or Moon, or discover the first extrasolar planets,” said co-author Dr Cristobal Espinoza of the Pontificia Universidad Catolica de Chile.
“Our technique is very different and can be used for pulsars in isolation,” he said.
Prof. Andersson added: “our results provide an exciting new link between the study of distant astronomical objects and laboratory work in both high-energy and low-temperature physics. It is a great example of interdisciplinary science.”
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Wynn C. G. Ho et al. 2015. Pinning down the superfluid and measuring masses using pulsar glitches. Science Advances, vol. 1, no. 9, e1500578; doi: 10.1126/sciadv.1500578
