An article published in “Astrophysical Journal Letters” describes a research, also presented recently at the meeting of the American Astronomical Society, about the pulsar known as PSR J1119-6127. Discovered over 16 years ago, recently it showed behaviors typical of a magnetar, a different type of neutron star. This oddity might help explain the link between pulsars and magnetars and the evolution of neutron stars.

Until a few years ago the nature of neutron stars appeared to be clear: they could be pulsars or magnetars. Neutron stars are what is left when a star reaches the end of its life, explodes in a supernova and the mass that remains is enough to make it collapse into an object smaller than a white dwarf.

Neutron stars have a magnetic field one hundred billion times more intense than the Earth’s. It causes the emission of electromagnetic radiation in regular pulses and for this reason these stars are called pulsars (PULSating STARs). However, there are neutron stars that have a magnetic field particularly strong even by the standards of the kind of stars that can be trillions of times stronger than the Earth’s. For this reason, these stars have been called magnetars (MAGNETic stARs).

In recent years things have become less and less clear and above all after a few decades the distinction between the two types of neutron stars has become much less clear. It’s one of the cases where advances in astronomical studies obtained thanks to new instruments such as space telescopes led to the discovery of many new neutron stars with peculiar characteristics.

Some years ago a neutron star with a split personality was discovered. A few months ago a research was published that focused on a very slow pulsar which is a magnetar. These are two of the cases, which are forcing astronomers to revise their models on neutron stars and to consider the idea that pulsars and agnetars are different stages in their evolution.

PSR J1119-6127 seemed another pulsar but after keeping a behavior normal for that type of object from 2000 to 2016 suddenly in July 2016 the Fermi and Siwft space telescopes detected two X-ray outbursts typical of magnetars and 10 other strong electromagnetic emissions at lower energies. In recent months, two studies on the strange behavior of this neutron star were already published in “Astrophysical Journal Letters”. One of them was also based on observations carried out by the NuSTAR (NUclear Spectroscopic Telescope Array) space telescope, an instrument specific for X-ray astronomy launched in June 2012.

Additional observations of PSR J1119-6127 were conducting using NASA Deep Space Network’s radio telescope in Canberra, Australia. The researchers found that the radio wave emissions had strong intensity fluctuations and this allowed them to quantify their evolution. In 10 days, something changed in the neutron star, which started behaving like a normal pulsar again.

Currently there are not enough data to provide an explanation of what happened to PSR J1119-6127 but only to speculate and those speculations are opposite. Some propose the hypothesis that these neutron stars are initially magnetars that eventually stop their X-rays and gamma outbursts and become pulsars. Others, however, suggest the opposite, that these neutron stars are born as pulsars and that in time their magnetic field becomes more and more powerful until they turn into magnetars.

If pulsars and magnetars really represent two stages of neutron stars’ evolution it’s plausible that one of the two phases is always the first though in these cases without evidence they can’t rule out anything. One of the key in the research might come from the discovery of other neutron stars like PSR J1119-6127, hoping that it’s a missing link between pulsars and magnetars. Discovering more of them could allow to see the transition in various stages, also to understand whether this is a common transformation or another type of phenomenon.