New observations of a very unusual star about 15,000 light-years from Earth have revealed a bizarre pattern of activity that astronomers have never seen before.
The star is named Swift J1818.0-1607 and was discovered just last year. It’s a so-called magnetar, a rare kind of neutron star that forms when supergiant stars don’t turn into supernovae but instead collapse into incredibly dense cores. However, unlike most neutron stars, magnetars are known for creating an extremely powerful magnetic field. Only about 30 of these strange objects have ever been detected in the Milky Way, but even among their strange type Swift J1818.0-1607 is an unusual phenomenon.
Among this exclusive group of “radio-loud” magnetars, none has ever pulsed like Swift J1818.0-1607, prompting some astrophysicists to speculate that this star might be some kind of “missing link” between magnetars and pulsars. A series of new observations by astronomers from the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav) confirm that Swift J1818.0-1607’s reputation as a freak is well deserved.
During eight observations with the Parkes CSIRO radio telescope over five months in 2020, researchers watched the magnetar’s radio pulses distinctly change in character – resembling pulsars and then changing to another form of faint shimmer before taking on a mysterious combination of pulsar-like and magnet-like radio pulses a few months later.
“Such bizarre behavior has never before been observed in any other radio magnetar. This raises a number of questions,” explains lead study author Marcus Lower.